Forced Induction (FAQS)


You Better Come Correct!
Established Member
Sep 13, 2005
Destrehan, Louisiana
Greetings All Forced Induction Enthusiasts:

I would like to compile a thread concerning the various questions about forced induction. I will be constanly adding new information based upon testing and expirience in hopes it can be beneficial to the Blower Bistro and it's visitors for both the expirienced and inexpirienced. The common basis I will be touching grounds will be the following. (Dyno Testing, Detonation, Intercooler/Aftercooler, Various Supercharger Tests, FMUs, and other accessories based on expirience.)

Dyno Tuning

The first thing I would like a customer would be a datalog. If you can get a copy of your short pull datalogged, I'd like to take a look at it. I can almost guess what the problem is currently, but without the datalog information I can't tell you for sure. If you are familiar with datalogging and what it can do for you as a expirienced tuner will know, let me educate you a little on exactly what it does. As I have learend through my expirience of tuning:


What are they and why are they important? Because in order to have a complete stock like ECU after having the vehicle modified, you need to work like the stock ECU. You need to at least understand how the ECU works with open and closed loop operation.

Closed loop is when the ECU is set to feed off the factory O2 sensor. Its target is to get a perfect stoichiometric ratio of 14.7:1. Isn’t that too lean? For tuning WOT runs, yes. But in the real world, not necessarily. Ever since emissions testing came along, all vehicles were required to both run cleaner and still have good gas mileage. Look at the chart below.


As you can see, stoich is where HC and CO are both at minimal levels. Of course there’s not much you can do here about NOx, but as long as it’s not at its peak either. That’s what counts.

So how does stoich fall into good gas mileage. Well, think about it. If you had more air vs. fuel, then you would be using less fuel. Take for example a 9:1 a/f ratio vs. a 14.7:1 a/f ratio. A 9:1 means you are using 9 parts air to 1 part fuel. That’s a lot of fuel being used for just 9 parts of air. So when you use 14.7:1, you get more fuel economy. As a matter of fact, the leaner you run, the more fuel efficient your vehicle is. Hence Honda Imports are calling it's VTEC-E engines “Lean Burn” engines. They burn learner to get more gas mileage for each part fuel.

The downfall to burning lean is that you will create more NOx as can be seen in the chart above. NOx is directly related to heat. So the leaner your combustion, the hotter your engine burns. As a result, you get a lot more NOx pollutants out your tailpipe which is not good for emissions. Another reason why stoich is the ideal target ratio for gasoline powered engines. Its currently the best spot for gas mileage and emissions.

Okay so how does the ECU and O2 sensor work? The ECU constantly takes feedback from the O2 sensor to keep in the stoich range. The graph below is what our stock O2 sensor’s range is.


The O2 will constantly fluctuate back and forth between rich and lean. That’s just how it works. If you pull a waveform of the O2 over time, you will see that it’s a sine wave. That’s why many people see their Autometer A/F meter gauge fluctuate back and forth. The meter isn’t totally worthless. If anything, it’ll tell you if the O2 is not functioning right. Better yet, start calling it the O2 sensor gauge instead of the A/F mixture gauge. At least now you know your money wasn’t totally wasted.

So what does this all mean really? It means it’s important to have good gas mileage in a modified car. It means you can’t just forget about this part of the ECU when dyno tuning. Once we cover the open loop operation, then we’ll tie everything together.


Okay finally, we’re done with the emissions stuff and ready to handle the big power stuff everyone’s been waiting for. Open loop is when the ECU feeds off directly from preset fuel maps stored in the ECU. The ECU totally ignores the information sent to it from the stock O2 sensor. If you have the Autometer A/F gauge, this is where you will notice that it goes rich.

Okay so I lied, the Autometer does have a bit more use to it than just flashing bouncing lights. It reads your A/F in open loop operation, otherwise known as WOT (wide open throttle). Keep in mind though, its scale of accuracy is very little. And it can’t tell you how rich or how lean you are, just a direction of richer or leaner. When it comes to an engine, more precise info is needed.

This is as far as most people will go in terms of tuning. This is the tuning part we all talk about when you visit your local dyno tuner. Because all your dyno runs are done at WOT, this is the fuel map that your local tuner saves for you when you are satisfied with your results.

This method is preferred because you don’t want to be running the stock fuel maps when you are boosting or have cams that are beefier than stock. That stock fuel map just won’t do it for you. If you’ve gone this far, kudos for you because now you have made all those performance parts you put into your car worthwhile. It’s now actually doing some good than just taking up space.

So what about people who want dual setups? You know, that high boost drag strip map and then a street tune so it’s street able or drive able. You can, but that’s going to be quite hard. As a matter of fact, only a few setups can allow for that. Even then, it’s going to take some time to upload the new map for each time you switch from drag strip to street.

Originally Posted by [email protected]

This statement I see a lot :
"Is it ok for a daily driver at 7-10 psi and 13 at the track."

This is a NO NO someone tell me what's wrong with this statement ?

When you tune your tuning for what ? AFR ! Guess what....When you tune the car at 10psi and then head down to your local track and crank it up to 13psi !!! What do you think happens to your AFR ? You guessed it... It's not the same as 10psi !!! What does this mean ?
NOT SMART huh....DUH !

When you tune on a dyno and set your AFR and your at 10-psi, that's what your tuning is set at !!! PERIOD ! Crank that psi up and all the $$$ you just spent went down the drain because your NOT properly tuned anymore ! When you crank up the boost your pushing more air in the motor and this means your AFR = AIR FUEL RATIO has NOW CHANGED !!!= RISK ! HIGH RISK !! DANGER ! Not smart ! When you tune, your tuned ! LEAVE it alone or your NOT tuned anymore ! Now, now you stand alone guys read below...

Let me clarify a bit more on the tune for proper afr and set it and forget it...

What that means is you need to load another fuel map for that psi level if you were to crank up the boost from 10 to say 13-15psi.
If your running a stand alone system. But again keep this in mind.
You still need to tune proper!

I don’t think I can say it any better than that for multiple boost applications. Just pick what boost level you want and stay with it. Now your car runs like a champ… but sadly, only at WOT.

You soon realize that your gas mileage is poor. You worry about emissions because of all these performance parts on the car. What are you going to do when you have to take the sniffer test? Swap all those parts back out for stock? Heck no! Go one step further. Datalog that sucker!


What datalogging is what others may refer to as street tune. What street tuning does is allows the ECU to learn what the car needs at certain throttle/RPM/load through each gear. A laptop is NOT a must on any of these systems, its just an added feature to help tuning to a next level.

The most important thing you will need here for datalogging is a WBO2 (wideband O2) sensor and controller. In most cases, you’d want to get a gauge also. Otherwise, it would defeat the purpose of getting a WB kit in the first place.

The WBO2 sensor is practically the same size as the stock unit, but uses 7 wires instead of 4. Its also a 5V sensor compared to the 1V sensor that’s used with the stock setup. Here are some pictures of the WBO2 sensor and the factory sensor for comparison purposes.

Since the stock system is calibrated to feed off a 1v signal, using the 5v sensor is a bad idea. JUST DON’T DO IT. That’s where the WB controller comes in. You will need the WBO2 controller to make any use of the WBO2 sensor.

As I said before, when I started out there weren’t too many options. As a matter of fact, there was only the FJO unit, which many dyno tuners themselves used for well over $1k, and the TechEdge unit. So I opt for the TechEdge unit for cost. Today there are many other choices to choose from. PLX, Innovate Motorsports, Zeitronix, FJO, AEM, & Wideband Commander are among the many other choices out there. So look over all of them and choose which one best suits your needs and fits your budget.

With the WBO2 kit, you are now able to do another pat of tuning that many people can not get at a regular dyno tune (which only does WOT tuning, especially roller dyno's). I will not go into the datalogging technique myself because it’s different for each unit and standalone that you are using. What I will say though is that once you have it hooked up, drive around town with it. Do whatever you want. Make sure you get as many different possible driving conditions as possible.

Once you are done, you have to set the WBO2 to target 14.7:1 when you are in closed loop. Have the ECU set to ignore the 14.7:1 a/f ratio when in open loop so that it reads off the WOT fuel maps.

In essence what you are trying to do is what the manufacturer has done to the stock ECU. Have it target a particular a/f when in closed loop and have a designated fuel map to run off when in open loop. This way you can have both fuel economy and power in only one map. Now you won’t have to worry about adjusting for different fuel maps or boost levels at the drag strip and worrying about possible damage to your engine. With the functions of open and closed loop at the flip of your foot, you will have a stock like ECU built to match your setup.

Your car is already set up to do all these wonderful things. You just got to know how to take advantage of it. It’s all about open and closed loop operation. Once you understand that, you will be able to have max power at WOT runs and good fuel economy while driving regularly. Talk about a Jekyll & Hyde setup.

Lastly, I said all the above to say this: If your tuner isn't expirienced in the world of "custom tuning" then he's not going to be able to look at your datalog map and know how to adjust to your cars behavior. Your car may have some small issues. (exhaust leak, vacuum leak, wiring etc etc) But you cant be able to pinpoint these issue if your tuner can't give you an idea from your datalog map. He could have loaded a different fuel map to see how you car reacts, but I'm almost convinced he is only used to tweaking out the box tunes. He hasn't have the slightest idea what "custom tuning" is all about.


Turbo vs Supercharger

It's one of the most common questions we are asked - the answer to which is almost impossible to find
"What is better - a supercharger or a turbo?"

We only wish the answer were that simple, but unfortunately it is not. The simple answer is:
"It depends."
But don't worry, we'll go into more depth than that here. Both superchargers and turbos have distinct advantages and disadvantages. Selecting the right kind of forced induction for your vehicle will depend upon your particular vehicle, your driving habits, your power preferences, and your needs.

Clearing Up Confusion


According to Merriam-Webster's dictionary, a supercharger is defined as:
"a device (as a blower or compressor) for pressurizing the cabin of an airplane or for increasing the volume air charge of an internal combustion engine over that which would normally be drawn in through the pumping action of the pistons".
A turbocharger is defined as:
"a centrifugal blower driven by exhaust gas turbines and used to supercharge an engine".

According to Webster's, a turbocharger is included in the definition for superchargers - it is in fact a very specific type of supercharger - one that is driven by exhaust gasses. Other superchargers that do not fall into this category - the kind that we are all used to hearing about - are normally driven directly from the engine's crankshaft via a crank pulley. So in reality, it is not fair to compare all superchargers to turbochargers, because all turbochargers are also superchargers. For the purpose of this discussion, however, a supercharger will be considered all superchargers that are are not driven directly by the engine, while turbochargers will be considered all superchargers that are driven by engine exhaust gasses.



Both superchargers and turbochargers are forced induction systems and thus have the same objective - to compress air and force more air molecules into the engine's combustion chambers than would normally be allowed at atmospheric pressure here on Earth (14.7 psi at sea level). The benefit of forcing more air molecules into the combustion chambers is that it allows your engine to burn more fuel per power stroke. With an internal combustion engine, burning more fuel means that you convert more fuel into energy and power. For this reason, supercharged and turbocharged engines normally produce 40% to 100%+ more power (depending on the amount of boost - check out our horespower calculator) than normally aspirated engines.

How They Work


A supercharger is mounted to the engine and is driven by a pulley that is inline with the crank (or accessory) belt. Air is drawn into the supercharger and compressed by either an impeller (centrifugal-style supercharger), twin rotating screws (screw-type supercharger), or counter-rotating rotors (roots-type supercharger). The air is then discharged into the engine's intake. Faster crank speed (more engine rpm) spins the supercharger faster and allows the supercharger to produce more boost (normally 6 to 9 psi for a street vehicle). Typical peak operating speeds for a supercharger are around 15,000 rpm (screw-type and roots style superchargers) and 40,000 rpm (centrifugal-style superchargers).

A turbocharger operates in much the same way as a centrifugal (internal impeller) supercharger, except it is not driven by pulleys and belts attached to the engine's crank. A turbo is instead driven by exhaust gasses that have been expelled by the engine and are travelling through the exhaust manifold. The exhaust gas flows through one half of the turbocharger's turbine, which drives the impeller that compresses the air. Typical operating speeds of a turbocharger are between 75,000 and 150,000 rpm.

Head to Head Comparison


Now it's time to evaluate the turbocharger versus the supercharger according to several important factors.

The cost of supercharger and a turbocharger systems for the same engine are approximately the same, so cost is generally not a factor.

This is perhaps the biggest advantage that the supercharger enjoys over the tubo. Because a turbocharger is driven by exhaust gasses, the turbocharger's turbine must first spool up before it even begins to turn the compressor's impeller. This results in lag time which is the time needed for the turbine to reach its full throttle from an intermediate rotational speed state. During this lag time, the turbocharger is creating little to no boost, which means little to no power gains during this time. Smaller turbos spool up quicker, which eliminates some of this lag. Turbochargers thus utilize a wastegate, which allows the use of a smaller turbocharger to reduce lag while preventing it from spinning too quickly at high engine speeds. The wastegate is a valve that allows the exhaust to bypass the turbine blades. The wastegate senses boost pressure, and if it gets too high, it could be an indicator that the turbine is spinning too quickly, so the wastegate bypasses some of the exhaust around the turbine blades, allowing the blades to slow down..
A Supercharger, on the other hand, is connected directly to the crank, so there is no "lag". Superchargers are able to produce boost at a very low rpm, especially screw-type and roots type blowers.

This is the turbo's biggest advantage. The turbocharger is generally more economical to operate as it as it is driven primarily by potential energy in the exhaust gasses that would otherwise be lost out the exhaust, whereas a supercharger draws power from the crank, which can be used to turn the wheels. The turbocharger's impeller is also powered only under boost conditions, so there is less parasitic drag while the impeller is not spinning. The turbocharger, however, is not free of inefficiency as it does create additional exhaust backpressure and exhaust flow interruption.

Because the turbocharger is mounted to the exhaust manifold (which is very hot), turbocharger boost is subject to additional heating via the turbo's hot casing. Because hot air expands (the opposite goal of a turbo or supercharger), an intercooler becomes necessary on almost all turbocharged applications to cool the air charge before it is released into the engine. This increases the complexity of the installation. A centrifugal supercharger on the other hand creates a cooler air discharge, so an intercooler is often not necessary at boost levels below 10psi. That said, some superchargers (especially roots-type superchargers) create hotter discharge temperatures, which also make an intecooler necessary even on fairly low-boost applications.

Because a turbocharger first spools up before the boost is delivered to the engine, there is a surge of power that is delivered immediately when the wastegate opens (around 3000 rpm). This surge can be damaging to the engine and drivetrain, and can make the vehicle difficult to drive or lose traction.

Back Pressure
Because the supercharger eliminates the need to deal with the exhaust gas interruption created by inserting a turbocharger turbine into the exhaust flow, the supercharger creates no additional exhaust backpressure. The amount of power that is lost by a turbo's turbine reduces it's overall efficiency.

The turbocharger is generally quiter than the supercharger. Because the turbo's turbine is in the exhaust, the turbo can substantially reduce exhaust noise, making the engine run quieter. Some centrifugal superchargers are known to be noisy and whistley which, annoys some drivers (we, however, love it!)

In general, superchargers enjoy a substantial reliability advantage over the turbocharger. When a a turbo is shut off (i.e. when the engine is turned off), residual oil inside the turbo's bearings can be baked by stored engine heat. This, combined with the turbo's extremely high rpms (up to 150,000rpm) can cause problems with the turbo's internal bearings and can shorten the life of the turbocharger. In addition, many turbos require aftermarket exhaust manifolds, which are often far less reliable than stock manifolds.

Ease of Installation
Superchargers are substantially easier to install than a turbos because they have far fewer components and simpler devices. Turbos are complex and require manifold and exhaust modifications, intercoolers, extra oil lines, etc. - most of which is not needed with most superchargers. A novice home mechanic can easily install most supercharger systems, while a turbo installation should be left to a turbo expert.

Maximum Power Output
Turbos are known for their unique ability to spin to incredibly high rpms and make outrages peak boost figures (25psi+). While operating a turbocharger at very high levels of boost requires major modifications to the rest of the engine, the turbo is capable of producing more peak power than superchargers.

Turbochargers, because they are so complex and rely on exhaust pressure, are notoriously difficult to tune. Superchargers, on the other hand, require few fuel and ignition upgrades and normally require little or no engine tuning.



While the supercharger is generally considered to be a better method of forced induction for most street and race vehicles, the turbo will always have its place in a more specialized market. Superchargers generally provide a much broader powerband that most drivers are looking for with no "turbo lag". In addition, they are much easier to install and tune, making them more practical for a home or novice mechanic.

I hope you have found this discussion informative and unbiased. Sometimes when I explain this to people, they say that we are biased towards superchargers because that is all most shops carry. I remind those customers that a turbo is a kind of supercharger and that I truly hope to see turbochargers conquer superchargers someday.


Types of Superchargers:

When you begin to search for the best supercharger for your vehicle, the choices can sometimes seem overwhelming. With so many manufacturers, it's sometimes difficult to know where to start. This guide is designed to give you an overview of each supercharger manufacturer and will hopefully help you decide which brand is the best choice for you.

Often we are asked which supercharger is the best. This question is impossible to answer as each make of supercharger has its own set of characteristics (price, low end power, high end power, ease of installation, reliability, etc.) that make it unique. The combination of these characteristics may make a particular supercharger the "best" or the "worst" choice for your application depending on your requirements. With the help of this guide you will get a feel for which brand will most likely best suit your needs.

The feature that most separates the different brands of superchargers is the type of compressor that is used. There are three different types of supercharger compressors - centrifugal, twin-screw, and roots (click to learn more on each type of supercharger). It will be helpful to familiarize yourself with these three types of superchargers before deciding which supercharger is best for your application. In many cases you will find that there is only one type of supercharger available for your vehicle. In general, this indicates that there is one type of supercharger compressor that is clearly the best choice for your vehicle by most standards.

Roots vs. Centrifugal vs. Screw Type Supercharging

The most effective performance enhancement that you will ever do to your car or truck is definitely a supercharger. That is why it is very important that you choose the right type of supercharger to get the right kind of power for the type of conditions that you will put your vehicle through. This is a guide to help understand it's not just about forcing more air down the throat of your motor. There are different ways to get the air to the motor and these different ways create different type of power curves.


Centrifugal Type Supercharging
Centrifugal Supercharging compresses the air inside the case of the supercharger using an impeller. Then, discharges the air out of a scroll to the motor. This design is similar to turbo-charging except for centrifugal superchargers don't use the exhaust to build pressure, they use a belt, driven by the crank pulley to spin the impeller. Centrifugal supercharging is definitely one of the more user-friendly ways to supercharge your motor. The ability to change the impeller sizes and to spin the impeller at different speeds creates a more inexpensive way to have flexibility in your power curve. Centrifugal superchargers have become the standard for street use and light-duty racing and far outsell all other types of superchargers.

Recommended Usage:
Street Use - Commercial Use - Road Racing - Drag Racing

Positive Points:
1) Lots of Flexibility for Power Adjustments
2) Lower Discharge Temperatures
3) Great Reliability
4) Easy to install

Negative Points:
1) Not as much power at low RPMs as Roots or Screw type superchargers

Manufacturer Availability:
Paxton - Powerdyne - ProCharger - Vortech

Vortech's Centrifugal Type Supercharger


Roots Type Supercharging
The Roots Type Supercharger is the first style supercharger that was ever used and can be dated back to the 1880s when the Roots brothers designed it as an air conveyor for mine shafts. Roots blowers act like air pumps (not compressors), and In general, Roots blowers have a two or three lobe rotor design, depending on the size of the case. Roots blowers will give you positive pressure to your motor from just a crack of the throttle, and will give all that they have to offer at full throttle no matter what the rpm of the motor. Roots Type Superchargers may look awesome hanging out of the hood and are great for those looking for drastic power increases at lower RPMs. Roots blowers are also extremely reliable and require very little maintenance, which is why Ford, GM, Mercedes, Jaguar, and Austin Martin have all featured Roots blowers as original equipment on select high performance vehicles.

Recommended Usage:
Street Use - Towing - Extreme Drag Racing - Show Vehicles

Positive Points:
1) Boost throughout the entire RPM range, right off of idle
2) Highest Potential for Gain (A must-have for all-out drag racing)
3) Excellent Reliability
4) Great Appearance & Stature (Most common supercharger type for show vehicles)

Negative Points:
1) Sometimes Violent Throttle Response
2) Lower boost ratings at higher RPMs
3) Higher Than Normal Discharge Temperatures
4) Lengthy installation times

Manufacturer Availability:
Allen Engine Development - BDS - Magna Charger - B&M- Holley - Littlefield - Mooneyham - Weiand

Holley's Roots Type Supercharger

[B]Screw Type Supercharging[/B]
Screw type superchargers are derived from the Roots type concept but with vast improvements for street use. Although from the out side, screw type superchargers may look a lot like Roots type superchargers, on the inside you will find a twin-screw design that compresses air unlike Roots type superchargers which pump the air into the motor. Screw type superchargers have an axial-flow design that compresses the air as it moves between the screws to create positive pressure without creating the heat that Roots type superchargers can create. The Screw type supercharger's ability to produce a dramatic increase of power from idle and through out the rest of the power curve make them a great choice for heavy vehicles, towing or commercial use.

Recommended Usage:
Street Use - Towing - Road Racing - Drag Racing

Positive Points:
1) Great Power at Low RPMs (Great for Towing)
3) Factory Fit & Appearance
4) Great Reliability

Negative Points:
1) The Power Doesn't Keep Climbing in the High RPMs (Power curve is very flat)
2) Challenging To Achieve High Boost Levels or CFMs
3) Lengthy installation times

Manufacturer Availability:
Kenne Belle - Whipple

[B]Whipple's Screw Type Supercharger [/B]


Allen Engine Development
Supercharger Type: Roots (Eaton)

Overview: Allen Engine Development is a small manufacturer of a select few roots supercharger systems for the Ford 4.6L Mustang / Thunderbird engine.

• OEM quality
• Excellent power at lower rpms
• Very complete system - no additional modifications required
• Integrated intercooler system included with every system
• Self contained - no need to tap the oil pan for lubrication

• Kits available for few vehicles
• Kits are fairly expensive, but reasonably priced considering intercooler is included
• REV I kits have lengthy install times (new REV II kits are much easier)

Systems Available For:
• 4.6L GT Mustang
• 4.6L Thunderbird

Paxton Automotive
Supercharger Type: Centrifugal (Paxton)

Overview: Paxton Automotive is the first aftermarket automotive supercharger manufacturer. Paxton makes high-end centrifugal superchargers for a variety of Dodge, Ford, Lincoln, and GM vehicles.

• High quality compressor and components
• Very complete system - no additional modifications required
• High peak boost capabilities - great for racing
• Excellent installation instructions
• 100% maintenance free - no oil to change

• Not self contained - tapping the oil pan is required
• Little boost / small power gains below 3000 rpm

Systems Available For:
• Dodge Ram
• Plymouth Prowler
• Ford 4.6L Mustang and Cobra
• Ford 5.0L Mustang and Cobra
• Ford 6.8L Truck/SUV
• Ford F-Series Truck 4.6/5.4L
• Lincoln Navigator 5.4L
• GM Truck/SUV 4.8/5.3/6.0L
• GM Truck/SUV 7.4L

Powerdyne Automotive
Supercharger Type: Centrifugal (Powerdyne)

Overview: Powerdyne Automotive manufactures a complete line of centrifugal supercharger systems for many GM, Ford, and Dodge cars and trucks. Known for being one of the only self contained centrifugal superchargers and for being a low-cost leader, Powerdyne Automotive has proved itself to be a powerful player in this industry.

• Excellent value - low cost and good performance
• Very complete systems - no/few additional modifications required
• Super quiet "SilentDrive" belt driven internals make almost no noise
• Self contained - no need to tap the oil pan (except for XB-1A systems)

• Internal belt needs to be replaced every 50,000 miles (except for XB-1A systems) and must be sent to Powerdyne
• Installation instructions need improvement
• Not capable of high boost outputs above 12psi
• Little boost / small power gains below 3000 rpm

Systems Available For:
• Dodge Ram 5.2/5.9L
• Dodge Dakota 5.2/5.9L
• Dodge Durango 5.2/5.9L
• Ford 4.6L Mustang
• Ford 5.0L Mustang and Cobra
• Ford Explorer
• Ford F-Series Truck 4.6/5.4L
• Ford F-Series Truck 5.0/5.8L
• Ford Lightning
• GM Camaro / Firebird / TransAm
• GM 4.3L Truck / SUV
• GM 4.8/5.3/6.0L Truck / SUV
• GM 5.7L Truck / SUV

ATI ProCharger
Supercharger Type: Centrifugal (ATI)

Overview: ProCharger is known as a leading centrifugal supercharger brand and has established a reputation for its high quality intercooled supercharger systems that are capable of putting out incredibly high levels of boost. ProCharger is a strong believer in the benefits of intercooling and include an intercooler in almost every system they sell. Their P-1SC and D-1SC supercharger compressors are the only gear-driven centrifugal compressors available, and are very easy to install.

• Very high performance - cool (intercooled) discharge
• Self contained - no need to tap the oil pan (P-1SC and D-1SC only)
• Very upgradable - compressors capable of high boost outputs

• Lots of compressor noise (whine)
• Fairly expensive, but reasonable considering intercooler is included
• Little boost / small power gains below 3000 rpm

Systems Available For:
• Ford 4.6L Mustang
• Ford 4.6L Cobra
• Ford 5.0L Mustang
• Ford 5.0L Cobra
• Ford V6 Mustang
• Ford F-Series Truck 4.6/5.4L
• GM Corvette C5/ZO6
• GM LT1 Corvette
• GM TPI Corvette
• GM Camaro / Firebird / TransAm
• GM TPI Camaro / Firebird / TransAm
• GM Carbureted Big Block / Small Block
• GM 5.7L Truck / SUV EFI
• GM 5.7L Truck / SUV TBI
• GM 4.8/5.3/6.0L Truck / SUV
• GM 7.4L Truck / SUV

Vortech Engineering
Supercharger Type: Centrifugal (Vortech)

Overview: Vortech sets the industry standard with their huge line of automotive and truck superchargers. Vortech sells more superchargers than any other single manufacturer - and for good reason. Vortech quality is second-to-none and their impressive manufacturing plant is the best in the industry. Their high quality supercharger systems have enjoyed years of success on the race track and are capable of incredibly high boost output levels.

• Very high performance - capable of high outputs - aftercoolers available on some models
• Reliable, high quality compressor and components
• Very upgradable - compressors capable of high boost outputs
• SQ line of compressors are "Super Quiet"

• Tapping the oil pan is required
• Little boost / small power gains below 3000 rpm

Systems Available For:
• Ford 2.5L Contour
• Ford 4.6L Mustang
• Ford 4.6L Cobra
• Ford 5.0L Mustang
• Ford Lightning
• Ford 4.6/5.4L F-Series Truck / SUV
• Ford 5.0/5.8L F-Series Truck / SUV
• Ford 4.0L Truck / SUV
• Ford 6.8L Truck / SUV
• Ford 7.4L Truck / SUV
• Lincoln Navigator
• GM Camaro / Firebird / TransAm
• GM Corvette
• GM 4.3L Truck / SUV
• GM 4.8/5.3/6.0L Truck / SUV
• GM 5.7L Truck / SUV
• GM 7.4L Truck / SUV
• Dodge Durango
• Dodge Dakota
• Dodge Ram
• Honda Civic
• Honda S2000
• Acura Integra

Whipple Industries
Supercharger Type: Twin Screw (Lysholm)

Overview: Whipple Industries is rapidy emerging as a leading manufacturer of twin-screw supercharger systems for many truck and marine applications. Utilizing only the best quality Lysholm twin screw compressors, Whipple supercharger systems are completely self contained and provide amazing power gains even at very low engine rpms. Ideal for trucks and towing vehicles, these supercharger systems are truly a cut above.

• Excellent power at lower rpms and great for towing
• Very complete system - no additional modifications required
• Easy to install
• Self contained - no need to tap the oil pan for lubrication
• Very high quality

• Kits are fairly expensive
• Installation manuals need improvement

Systems Available For:
• GM 4.8/5.3/6.0L Truck / SUV
• GM 5.0/5.7L Truck / SUV
• GM 7.4L Truck / SUV
• GM 8.1L Truck / SUV
• Ford 6.8L Truck / SUV
• Chrysler 2.4L PT Cruiser
• Mercruiser Marine


How Your Drivetrain Handles Boost

The short answer to this question is both yes and no, so let's start with the basics. (See a comparison of supercharger types here!)

Drive train defined:
The system that transfers power from the engine to the wheels is known as the drive train or driveline. It includes the clutch or torque converter, the transmission, differential, ring and pinion gears, axles, and where applicable drive shaft(s) and transfer case, universal and/or CV-joints.

Power train defined:
The complete system of the engine and the drive train.

Understanding Factory Drive Train Limitations

The drive train in your car or truck is designed, by the manufacturer, to be strong enough to handle full engine power at the vehicle’s load and gross weight limits. Safety margins are factored into each component so that the entire powertrain will survive moments of particularly strenuous conditions. (ex: Shifting an automatic transmission into “Drive” and applying power while the vehicle is rolling in reverse). In some cases, the vehicle’s Powertrain Control Module (PCM) is programmed to identify stressful drive train conditions and take actions electronically to reduce them. One such example of this is where power is reduced during down or up shifting to extend the life of the transmission.

Many systems can also limit torque taking off from a stop. Abusive situations can also be identified by the PCM, such as a driver shifting back and forth between reverse and drive to create a rocking motion, or a high throttle position when putting the vehicle into gear - also known as “the drop shift.” The manufacturer knows exactly how much stress each component can handle under various conditions before it fails. The onboard computer (PCM) provides a way to extend the safety margins of the drive train without installing larger, heavier components. This contributes to higher fuel economy and lower cost.

Are Supercharger Kits Designed With Drive Train Limitations in Mind?

A Supercharger kit is the single best power upgrade you can make to your vehicle. Every supercharger manufacturer goes through extensive design, prototyping, testing, tuning, and qualification of each system before it can ever be brought to market. Most kits are tuned to be installed on otherwise factory-equipped engines. Power levels are specifically tuned not to exceed the critical thresholds of the OEM drive train components. An example of the Supercharger industry’s engineering confidence in their products' effect on powertrain lifespan is MagnaCharger’s 3-year/36,000 mile limited powertrain warranty.


What Affect Do Other Upgrades Have?

As explained, a supercharger kit installed to the manufacturers' specifications will not exceed the factory power train’s capacities. Problems will start to appear as other engine parts are upgraded to increase power even more. There are a few upgrades that will have an adverse affect on the drive train when combined with the supercharger. Here are some examples:

1. High-Stall torque converter. A torque converter multiplies torque from the engine to the transmission by a factor proportional to the rotational speed difference between them. Basically, a higher stall converter alone will cause the transmission to experience momentary input torque levels much higher than a stock converter would.

2. Boost Upgrade. Installing a smaller pulley on the supercharger is an easy way to get more power if detonation can be controlled. This extra power may be in excess of the drive train’s capabilities.

3. PCM Reprogramming. A popular performance modification to the PCM is to remove the Torque Management subroutines that reduce power in favor of drive train preservation.

4. Wider or larger diameter tires. From a drive train’s perspective, larger tires or wider high-traction tires have a similar effect when launching from a stop. Either tire upgrade will reduce wheel spin. Wheel spin actually reduces stress on the entire drive train once it begins. Increasing traction with a tire upgrade will increase driveline stress if the previous tires were able to break traction before.

These upgrades are so effective that together, with the supercharger, failure of a major drive train component is just about guaranteed to happen sooner or later if these components are not also upgraded to handle the additional torque.

Back to the Original Question:

In the never-ending quest for more power, it is this torque that ultimately dooms the weak link. Twin Screw and Roots superchargers make full boost right off idle when you jab the gas. At this instant, the engine may reach its torque peak just as the vehicle begins to move forward. The torque peak of a centrifugally supercharged engine would be seen in the higher end of the RPM range. Launching a centrifugal vs. twin-screw or roots with the same peak boost is therefore less stressful on the drive train and less likely to cause a failure for that reason.

It takes lots of torque to break parts, and twin-screws and roots superchargers make more of it. It is typical to see peak boost levels of centrifugal supercharger kits calibrated and tuned to one or two pounds greater than a roots or twin-screw kit for the same engine. The centrifugal supercharger kits do not have to be de-tuned to keep power levels manageable at low RPM.


Adding power, in excess of what the supercharger kit provides on a stock vehicle, is possible as long as attention is paid to the limitations of the transmission and the rest of the drive train components. If you’re building a torque-monster for towing and the best possible hole shots, driveline upgrades will be required.



As you probably have already figured out, detonation (aka "knock") is a big issue in the world of forced induction. You probably know that detonation is a bad thing, and that by adding a supercharger (or any forced induction power adder), you must take additional measures to avoid detonation, especially if your engine has other modifications. Normally the simple solution to stop detonation is to run higher octane fuel... but before we get ahead of ourselves, let's start from the beginning.

What is detonation / knock?

Under normal conditions, the combusting air and fuel mixture inside the combustion chamber ignites in a controlled manner. The mixture is ignited by the spark, normally in the center of the cylinder, and a flame front moves from the spark towards the outside of the cylinder in a contolled burn. Detonation occurs when air and fuel that is ahead of the flame front ignites before the flame front arrives because it becomes overheated. Under these conditions, the combustion becomes uncontrolled and sporadic and often produces a pinging noise, or a "knock" noise when the conditions become worse.

So far, detonation sounds cool... why is it bad?

Detonation is definitely not cool. Detonation causes sudden pressure changes in the cylinder, and extreme temperature spikes that can be very damaging on engine pistons, rings, rods, gaskets, bearings, and even the cylinder heads. Even the best engine components cannot withstand severe detonation for more than a few seconds at a time. More severe detonation obviously leads to more severe forms of engine damage. If there is enough heat and pressure in the combustion chamber, detonation can begin to occur before the spark plug even fires, which would normally initiate the combustion. Under these circumstances, known as "pre-ignition", the piston may be travelling up towards a wave of compressed, exploding gas. These are the worst kinds of detonation conditions, and can bend con-rods and destroy pistons.

What causes detonation?

Detonation occurs when several conditions / factors inside the combustion chamber exist at the same time. Increased compression, high temperatures, lean fuel/air mixture, advanced ignition timing, and lower octane fuels are all factors that PROMOTE detonation conditions. The good news is that, because there are so many factors in play, you can always find a way to eliminate detonation if it exists.

So, where do superchargers fit in?

A supercharger increases the amount of air inside the combustion chamber (see "Bye Bye 14.7 psi"), which in turn increases the compression inside the combustion chamber. Along with increased compression comes higher temperatures and higher pressures, which as we know, tend to increase the chances that some form of detonation will occur. In order to compensate for the increased compression and heat, we must change one or more of the other factors / conditions to move us away from our detonation threshhold. Tuning the supercharger system to the engine in this way for maximum performance without detonation is something that supercharger manufactuers do so, chances are, you won't have to worry about it unless you do other modifications to your engine that place you closer to your detonation threshhold.

How do I get rid of it?

The two most common tricks used by supercharger manufactuers and engine tuners looking to obtain maximum performance without detonation is 1. use higher octane fuel, and 2. retard the ignition timing.

Higher octane fuel burns more controllably and is not as likely to combust before the flame front. This is why racing engines use 100+ octane gasoline. The ONLY benefit of racing gasoline is that it moves you away from the detonation threshhold, which allows you to be more aggressive with power producing factors - i.e. raise compression, advance timing, etc. This is why you'll be disappointed if you put racing gasoline in your mom's bone-stock '82 Toyota Cressida thinking you'll turn it into a race car. If you don't have detonation, the increased octane will do you no good. For cars designed for daily street driving, you obviously won't want to fill up with 100+ octane fuel every week at the tune of 5 bucks a gallon. This is why supercharger manufactuers tune their supercharger systems to run properly without detonation on 91 octane fuel - aka "premium" at your local gas station (in some states premium gasoline is around 93 octane).

Retarding the ignition timing will delay the timing of the spark, which also moves you away from your detonation threshhold. Most popular "power programmers" or "chips" increase engine power by advancing the ignition timing, and requiring you to run a higher octane fuel to avoid detonation. These work great, except the advanced ignition timing is NOT compatible with most superchargers, unless you're happy to run 100 octane fuel. In fact, many supercharger systems include an "ignition boost retard" that retards the ignition timing when it senses boost from the supercharger. This allows you to maintain stock performance while not under boost, yet still remain safe while the supercharger is making its boost (and power).

Another way to avoid detonation is to cool the incoming air charge to lower the temperature inside the combustion chamber. On a supercharged application, this task can be handled by an intercooler (see "Let's Talk Intercoolers") or by a water injection system (less common). The intercooler takes the incoming air charge and passes it over a series of air-cooled or water-cooled fins and ducts, thus cooling the air in the same way that a radiator cools your engine's coolant. Intercoolers are thus very popular in higher output supercharger systems, where detonation becomes more of a problem. Often times, the intercooler allows you to run more boost and also allows you to eliminate the ignition boost retard, meaning you'll notice increased performance, and still experience no detonation. Another way to lower the temperature of the combusting air and fuel is to run cooler heat range spark plugs. Many supercharger manufacturers will recommend cooler plugs for you supercharged engine.

Because lean condition (fuel starvation) also contributes to detonation, it is important to make sure that the fuel system (pump, injectors, etc.) is capable of delivering the increased fuel requirements of the supercharged engine. Often times, an otherwise perfectly tuned engine will experience detonation just because the fuel pump can't deliver enough fuel to the engine. Upgrading certain fuel components is almost always necessary when supercharging an engine. Most supercharger systems normally include the upgraded fuel components if they are necessary. If you are installing a supercharger on an engine with other modifications, make sure you consider the additional fuel requirements and compensate with larger injectors and / or a bigger fuel pump.

Some modern vehicles come with "knock sensors" that listen for detonation, and automatically retard the ignition timing to eliminate detonation. Although these devices are effective in preventing engine damage, they are not tuned for performance, so you should not rely on the knock sensors and expect your engine to run its best.


Altough detonation can be potentially damaging to an engine, a simple understanding of what it is, and what causes it, will help you stay away from your detonation threshhold. Pay attention to "knock" and pinging noises that come from your engine becuase they could indicate detonation inside the combustion chamber and should be dealt with immediately. If you're looking for a new supercharger system, don't worry too much about detonation - the manufacturers have designed the system for use on your stock engine, and if you follow the manufactuer's fuel recommendations, you will not have a detonation problem. If you ever do notice detonation, perhaps from bad (low octane) gasoline or extremely high air temperatures, just drive with a light foot until you are able to resolve the cause of the problem.


What is an FMU?

Horsepower is a result of two key components: air and fuel. The supercharger itself, whether a centrifugal, roots, or twin screw, really only provides one of the two major ingredients for making more power. Each supercharger kit is a complete system that increases both air and fuel flow into the engine. A supplemental fuel system upgrade must complete the package.
The FMU Explained

There are several methods used by various supercharger kit manufacturers to deliver supplemental fuel to the engine under boost. An FMU, or “Fuel Management Unit”, is the chief component used for one of these methods. An FMU is often referred to as a boost-dependant fuel pressure regulator. The FMU is essentially a variable fuel-pressure regulator that automatically raises fuel pressure as boost rises.

Depending on the capabilities of the stock fuel pump, a booster pump may be used in conjunction with the FMU. The FMU is downstream (after) of the stock regulator. As boost pressure begins to rise, the FMU starts restricting the flow of fuel returning to the gas tank. Like a garden hose, if the flow is restricted, the pressure increases. The increase in restriction results in an increase in the pressure of the fuel being delivered to the factory fuel injectors. Higher fuel rail pressure enables the fuel injectors to deliver more fuel in the same amount of time than they do at the static stock fuel pressure.


The FMU is calibrated precisely for each supercharger system - a rise in fuel pressure equals a directly proportional rise in boost. The ingenious simplicity of the system means that no computer recalibration is required. Without the FMU, the stock fuel system would not be able to maintain an air-to-fuel ratio low enough to prevent a lean condition. FMU-based systems are the most popular with supercharger kit manufactures.

Other Types of Supplemental Fuel Systems Used With Supercharger Kits

Some supercharger kits take a different approach to supplemental fuel supply. One of these alternate methods, to an FMU-based approach, uses an auxiliary EFI computer. This computer is connected to one or more separate fuel injector(s) installed just before the intake manifold. The auxiliary injector(s) work like a TBI to provide additional fuel to all cylinders. These systems do not require an increase in fuel pressure over stock and, therefore, the fuel flowing through the factory injectors is not increased.

On most supercharger systems, booster pumps are not needed unless the supercharger kit manufacture determines (through testing) that the stock fuel pump is not able to provide enough volume to supply both the factory and auxiliary injectors. These kits do not require recalibration of the factory computer.

The most effective way of compensating for the additional fuel required under boost is to replace all of the factory fuel injectors with higher-flowing ones. This method requires recalibration, or replacement, of the factory computer with a new fuel map appropriate for the new injectors. Replacing all of the fuel injectors is expensive and labor intensive, thus making this fuel system upgrade the least popular among supercharger kit manufacturers.


It should also be noted that some engines are designed with proprietary fuel injection that makes swapping out injectors impossible. Just like the others, supercharger kits getting this fuel system treatment may require a booster pump or replacement of the stock pump depending on the application.

For specific information about which fuel system upgrade is included with each kit, start with our Shop by Brand page and select an application.


So, that's the bare-bones of an FMU. In the next installment, we'll get into more the more detailed and technical aspect of this darling of the Fuel Management program - the FMU.

Getting Technical

The FMU, also know as a “boost dependant fuel pressure regulator,” only increases fuel rail pressure when boost is applied to the reference port on the FMU. This regulator is in the return fuel line and is downstream of the static fuel pressure regulator. The FMU is a simple mechanical device that can be calibrated by changing the internal ring and spacer. Inside an FMU is a piston. The boost pressure comes from the manifold to a fitting on the FMU and applies pressure to a washer sitting on the piston. The larger the washer, the more pressure it applies on the piston. The piston pressure blocks the flow of fuel down the return line. This backup creates a higher line pressure because the fuel cannot freely pass through.

As explained in the previous article, there are two key ingredients to making horsepower: fuel and air. We are going to discuss the most popular methods of increasing the quantity of fuel, to support the air entering the motor under boost, and its relationship to the amount of power you are trying to make.

3 Steps to Delivering More Fuel

Traditionally, there are three most common ways to deliver more fuel to your engine. They are:

Upgrade Your Injector Scenario
Utilize the Power of the FMU w/ Existing Injectors
Use a Computer Programmer to Regulate Fuel Management With Upgraded Injectors
Upgrade Your Injector Scenario

To get more fuel, you can run larger injectors, increase the pressure to the injectors you already have, or add an auxiliary set of injectors. The auxiliary set of injectors usually squirts fuel into the manifold and requires a secondary injector driver to tell the injectors when to fire and for how long. This method is effective for street cars because it lets the car run like normal with smaller injectors. It is also good for cruising because it prevents the motor from overloading with fuel and stumbling. It then allows the second set of larger injectors to give more fuel when you are trying to make power. The major downside is that this method is very expensive because of the additional components required. Furthermore, it can be very difficult to tune because of the wide adjustment range of a completely separate set of injectors. This common dilemma led to the eventual creation of the FMU.

Utilize the Power of the FMU

The FMU is great because it allows the car to run normally on a small injector, but can also increase the rail pressure under boost which, in turn, forces more fuel through the same size orifice. The fuel that the FMU adds has a direct relationship to the boost pressure. The proportionality is usually stated in a ratio, for example 12:1. This means that the FMU will add 12psi of fuel for every psi of boost. (For example, 10psi of boost will add 120psi of fuel pressure.) When all is said and done, this could net a total of about 140psi of fuel pressure which is often too much for a little injector to handle. It is also the reason most people opt for a combination of larger injector and lower ratio of FMU. This is an ideal setup because it allows the same quantity of fuel but at a lower pressure which is more constant for tuning and less fatiguing on the injectors.

Computer Programs and Fuel Management

The third most popular method of increasing fuel is to add larger injectors and use a computer chip to calibrate and control them. This often can cause the car to run great under boost. However, it is often harder to mange when the car is a daily driver or when cold started. Even this method only can supply enough fuel to support a given amount of pressure. Eventually it, too, requires an injector so large that it would not be suitable for any type of street driving - just racing.

This is why the FMU has become so popular. It offers great versatility for street and strip use. You get the ability to support horsepower and still have the street ability of a daily driver. It is also mechanical and not very complex, so there is little chance of having any reliability issues. The final attribute of an FMU, that has make it popular, is its ability to be easily recalibrated (for a relatively low cost) to match the injector choices you make.


The Mystery of Octane

What is octane? The concept of octane is peculiar to many people, including myself. I can't see it, I can't hold it, I can't buy it by itself, but I know I know I pay extra for it if I want more than 87 of it in my gas. Today we take an in-depth look at what octane is, and what significance a gasoline's octane rating has with regards to a supercharged engine.

The Simple Definition

An octane rating (87 vs. 89 vs 92, etc.) is a measure of a gasoline's ability to resist detonation, which manifests itself in a pinging or "knocking" noise. Higher numbers indicate that the fuel can be compressed to a higher level before detonation / knock occurs in an engine, which occurs when. As described in "Detonation, Knock, and Pre-Ignition 101", detonation / knock occurs when air and fuel that is ahead of the combustion flame front ignites before the flame front arrives.

The Complicated Definition

Octane is actually more than just a rating - it is a hydrocarbon just like methane (single carbon atom), propane (three carbon atoms), butane (five carbon atoms), and heptane (seven carbon atoms). Octane (C8H18) is a hydrocarbon with eight carbon atoms and eighteen hydrogen atoms. 100% octane fuel is remarkably resilient to compression (i.e. it does not combust when compressed) and is thus resilient to detonation / knock. This resilience is derived from the branching of octane's carbon chain (see figure). Because of the nature of octane as being resilient to detonation, all fuels are compared to 100% octane as a benchmark fuel, from which an "octane rating"can be obtained. Heptane, a hydrocarbon with seven carbon atoms, compresses very poorly and spontaneously combusts even under small amounts of compression. In other words, Heptane's behavior when compressed is diametrically opposed to Octane's behavior under the same conditions. For this reason, Heptane (which has an octane rating of zero) is the other benchmark fuel used in the octane rating system to determine a fuel's octane rating. A fuel that spontaneously combusts (knocks) under the same amount of compression as a fuel composed of 87% octane and 13% Heptane would have an octane rating of 87. This is not to say that 87 octane gasoline is made up of 87% octane and 13% heptane, rather that the 87 octane gasoline "knocks" in a laboratory knock engine at the same compression ratio as a fuel composed of 87% octane and 13% heptane.


The coomposition of an octane hydrocarbon.

Unfortunately, it gets even more complicated. Because various fuels respond differently under varying engine loads, a gasoline may get a different octane rating on a free running engine and one under load. For this reason, the octane rating label that we see at the pump (monitored by the U.S. Cost of Living Council) is actually an average of two octane ratings - the motor method rating (where the engine is run under a load) and a research method rating (where the engine is run freely). The formula used to get the CLC Octane number on gas pumps in the United States is thus: (Motor Octane Number + Research Octane Number) / 2.

What's the benefit of higher octane?

Higher octane fuel has only one beneficial feature - it allows an engine to run at higher temperatures with more advanced ignition timing under higher levels of compression witout detonating / knocking. Higher octane fuel does NOT have more potential energy and will not make an engine perform better unless that engine is knocking. On modern engines with knock sensors, higher octane fuel may make the engine run better if the knock sensors are retarding the ignition timing, which hinders performance. High octane fuel does not burn cleaner, it does not clean your engine, it does not increase horsepower or torque (unless you are experiencing knock), it does not smell better, it does not increase fuel economy (unless you are experiencing knock) and is not better for the environment. If you buy higher octane fuels for any of the above reasons, STOP!

When should I switch to a higher octane fuel?

First off, never run lower octane fuel than is recommended by the vehicle's manufacturer. If the vehicle manufacturer recommends 89 octane gasoline, this means that the engine has been tuned to perform optimally without detonation on 89 octane fuel. Once you've done some modifications to your engine, the manufacturer's recommended gasoline may no longer suffice. Obviously, if you can hear detonation inside your engine in the form of pinging or "knocking", try a higher octane fuel. You will also need to run a premium grade fuel (91+ octane) if you have a supercharger, turbocharger, or if you have an ignition programmer that advances your ignition timing.

Why is higher octane fuel more expensive?

Higher octane fuels are more expensive because they must go through more refining steps that increases the octane rating. These additional steps do not make the fuel better in any other way.

How is it possible to have 100+ octane gasoline?

There are some fuels that are even more resilient to compression than 100% octane. Some additives, like tetraethyl lead, increase the gasoline's ability to operate without knock. Some racing and airplane fuels have octane ratings of 110+!

That's all the time I have for now I will be adding more information as I have time to post in depth. Thanks for reading and I hope this was beneficial to your needs for understanding the complex world of forced induction.

Last edited:


killer cobra
Established Member
May 10, 2005
DFW, Texas
A lot of great information and answered many of my questions.
Thanks for posting Chip... :beer:
This needs to be a sticky!!


You Better Come Correct!
Established Member
Sep 13, 2005
Destrehan, Louisiana
newbreed77 said:
A lot of great information and answered many of my questions.
Thanks for posting Chip... :beer:
This needs to be a sticky!!
Would be my goal. I'd like to provide alot of sticky worthy information for everyone. Maybe I could mod Blower Bistro :) Send vote to LL! :)


New Member
May 5, 2005
The Unknown
Thanks alot chip for the great info, this should be a sticky in the blower bistro.
can we vote a mod? who is the current mod in this section?


You Better Come Correct!
Established Member
Sep 13, 2005
Destrehan, Louisiana
Thanks, I will keep the information coming as more testing is done. Also Don (Gr8white) is the current mod but he hasn''t really been around for a few months. I think this forum could certainly use a few mods.


You Better Come Correct!
Established Member
Sep 13, 2005
Destrehan, Louisiana
newbreed77 said:
Chip could you throw in some info. on octane boosters (Torco, NOS booster, etc...) :beer:

Sure Neil!


Q: How are racing fuels made?

A: All gasoline contains the same general family of hydrocarbons; low test, high test, racing gas and aviation gas. General refiners are set up to make a large volume of gasoline, hundreds of thousands of gallons per day to satisfy their retail market.

Making a racing gas goes like this: you start with a blending stock of gas, then you add your own additives to end up with whatever octane level you're after. A blending gas is a raw, basic gasoline, with no additives or detergents.

Iso-octane is an example of one that can be used. You have to calculate what you want in a racing gas before you start adding things to a blending stock, or even what kind of blending stock you start with.

For example, for the fuel that we make, we want to end up with an octane of approximately 108 research method, with a motor octane that will blend back to about right at 103-104 RM-over2. That's an average of research and motor methods of testing octane and is the most commonly accepted rating.

We add lead, lead scavengers, various aromatics, napthanics and light-end hydrocarbons to get the correct Read Vapor Pressure to control vapor lock. You have to change gasoline from a liquid to a vapor to get it into a proper state for an air/fuel mixture ratio, so the spark plug can ignite it. A carburetor does this job of turning the liquid into a vapor.

Q: We see ads all the time, this gas has 102 octane, this gas has 115 octane, or another with 118. What do we need? Let's say you have an engine with 8.5 to 1 compression ratio. How much octane does it require?

A: That's a tough question. It has a lot to do with the combustion chamber shape, location of the spark plug, condition of the combustion chamber, the air/fuel ratio you enter into it, a huge number of factors including the air temperature and the load the engine is put under.

What we're talking about is trying to defeat detonation; that's the real problem. I can give you some approximate guidelines. If you're using a 10 to 1 engine and over, you need racing fuel. On a 9:1 engine, you're probably in the 98 octane area, and there are a lot of good strong 9 to 1 engines out there.

There is no real linear type of relationship between compression ratio and the octane requirements. You can have an engine with extremely high compression and really have a low octane requirement. I know people who have had engines in the 13, 14 or 15 to 1 compression ratio range and have used 103 to 104 octane fuel with no problems.


Q: What makes a good racing gasoline? Any secrets you'd like to give away?

A: We buy a blending stock from two different companies? There are two different stocks and we co-mingle those. Now this is important: these stocks are sold by an ASTM specification and it means they'll be the same quality and molecular weight each time.

We try to control the variables as tightly as possible, by buying the same group of chemicals, time after time, with the same chemical characteristics. What we end up doing is giving you a base fuel that you can tune with and use, and it doesn't change.

It has the same chemical components, the same chemical characteristics, the same specific gravity and all of this is very important for consistency. A racer doesn't want to change the variables. And fuel is one of them.

We've done our own testing, and without naming names, I can tell you some startling facts. We've sent samples of certain racing fuels to the lab for testing, and one time it's 114 octane, and a month later the same brand of fuel tests out to be 108. It's got a specific gravity of .76 one time and the next batch tests out at .73. You splash it in the motor one time and it runs great. The next time, the specific gravity of the fuel is different and it flows differently. Different specific gravity fuels flow through the carburetor jets at different flow rates.

By just changing the fuel, you can richen or lean your engine out. Let's say a major refiner wants to make an 86 octane fuel and they want it blended as economically as possible. The building blocks used to make a higher octane fuel are expensive! The benzenes, toluenes, xylene complexes - or the BTX complexes - they want to use as little of these as possible. That's why lead was always so effective; because they could splash a lot of lead in it and bring the octane way up, and do it really cheap. These major refineries are only making a cent, two cents or three cents a gallon profit once the smoke clears. They have to keep production costs down.

You're not under that restriction with racing fuel, because these fuels usually cost three dollars a gallon or more and the profit potential is greater, at least on a per-gallon basis.

With this in mind, you should be able to make a good fuel, with repeatable characteristics, time after time. This is the single most important thing to look for in a racing fuel, I feel.

More important than high octane numbers?

A: Absolutely! Look, if you had a bike where you used a dozen pipes during testing, and all of them were different, you wouldn't know where you were at! You couldn't time the motor... you couldn't jet it.

Take a drag racer, for example. He might go through three or four sets of pistons in a race. If each piston had a different compression ratio, how would they know what to do? They'd be lost. So the important thing in any racing situation, is to have the same kind of fuel, day after day, time after time, year after year.


Q: So the real expense for racing fuel is in the quality control, the assurance that it's consistent all the time. Why can't this be done with pump gas?

A: For a major refiner to make racing fuel is out of the question; he's not going to touch it. It's a pain in the butt to make; there's a lot of quality control that has to be done and there has to be a level of cleanliness you're not going to find in volume production.

Q: How can we, the consumers, tell a good racing fuel from one of lesser quality?

A: Given that they all can provide you with an octane, say 103, it may be just window dressing. A lot of people think that by buying a higher octane, it'll make your bike get to the finish line quicker and you may do better.

As to usability in a motor, ultra-high numbers are questionable. Octane will make up for some sins that an engine builder might have built into the motor, but an engine only needs what it needs... not a bit more.

What makes a fuel better? Our fuel has been identical for 15 years ... same specific gravity, same Read Vapor Pressure, same octane, whether it be research or motor method of rating. Some people advertise outrageously high octane readings, which makes it particularly attractive to people who don't understand what they need.


Right now in the racing fuel business, there's a race to market the highest octane fuel that you can make. People relate the highest octane to "my motor is making more power." That couldn't be further from the truth.

One of the downsides to building a fuel with ultra-high octane is adding components that really slow down the flame front in the combustion process. You can get the flame front so slow, that the engine is now running in a too-rich condition. This takes away horsepower. So here you are, slowing down the flame front and getting rid of detonation, at the expense of losing horsepower.

I see this all the time at the track. I see engines running "heavy"; they're trying to tune it to lean it out, when actually the flame front is causing the problem.

Q: Are there good ways to get the good octane numbers and are there bad ways? I guess our question is, are there shortcuts?

A: I've seen some fuels with compositions of 25 to 30 percent aromatic content. Aromatics are a reliable, correct way to build octane, but people tend to think that if a little bit is good, then more ought to be better and a whole lot is just great!

If you run reliable lab tests on octane and incrementally increase the aromatic content, most lab people feel that if you get up above the 10 to 15 percent aromatic content, your octane falls off.

What the engine does is start making more heat, which requires more octane, which makes more heat: a real vicious cycle. It's like a dog chasing its own tail.

The bottom line is this: let's say your motor needs 92 octane to run correctly and you fill up with 125 octane wonder gas. You will not run any faster. In fact, you might end up running slower because of a radically slowed flame front.


Q: Let's say that we have a racer on a budget. He's got a lightly modified engine and would like to run racing gas, but can't afford it. Can he mix race gas with pump gas and, if so, what ratios?

A: On a stock motor, I don't think the racer would need to run racing gas, except during the summer when it's very hot. Here, you stand a very real chance of vapor lock with pump gas. I'd recommend that the racer start out with a good stock major brand gasoline of at least 92 octane rating, then go out and test.

If the engine runs fine and doesn't ping or detonate, that's fine. You can use that gas. Just make sure you buy it at a very busy corner with a high volume turnover. This way you stand a better chance of getting fresh gas, and no substitute gas.

If you do have some pinging and detonation, try one gallon of racing fuel to three gallons of pump gas. In a stock motor, this should do it. Test it again under the same circumstances to check it out. You're going to have to check this regularly, because the variables in the street gasoline WILL CHANGE, while the variables in a good racing fuel will not.

The combination of 92 octane street gas and 103 octane racing gas will kick up the actual octane two or three points. There's no real chart you can draw... it's not a linear thing. But that's all it might take to make the motor happy.

Here's something startling, and I almost hesitate to say it. You don't get any increase in the performance with racing fuel. Not a bit. Not any racing gas. Good racing fuel allows you to run your timing more radical, to extract more horsepower out of what you've got.

I can take any racing fuel made - including ours - and make the engine hammer and detonate by have the timing set too far out. Timing lead is critical. You want to make the engine ping? Easy, just add too much lead. Conversely, running the timing closer to top dead center will cool things down. Remember the TT bikes of ten years ago? They ran so much lead, they could not be kick started. They had to be push started.


I would not buy any racing gas, or pump gas, with alcohol in it. That's the first thing I'd ask ... "Does it have any alcohol?" It's not that you can't use alcohol. Ethyl alcohol is a good additive; it can be used up to ten percent in most cars.

Alcohol really offers a different fuel/air ratio than gasoline. Racers who do run alcohol have to use enormous jets and really drink the stuff through the carb.

Make sure that the fuel does not have MTBE in it. It's a very effective new additive, but it may be illegal in your organization, as it is in many. It's an oxygen or nitrogen bearing com-pound.

Probably the single best option is to test with a hydrometer several containers of the racing gas you're considering buying. This will give you the specific gravity of the fuel, and if it varies from container to container, it will tell you a very sad story about quality control.

You can buy a gas testing hydrometer for about four or five bucks. All savvy tuners test with them BEFORE they start tuning, or if they cannot use their regular gas.


Q: What about using AV, or aviation, gas?

A: There's an old wives' tale about AV gas out of World War II and I don't know who started this, but it says that if you put AV gas in your car, you'll burn the valves. There's no doubt that aviation fuel can be used in any internal combustion engine that's driven up and down the highway at cruising speeds.

It doesn't make much sense to use it for that since it goes for something like $1.75 or $1.85 in this area, and is not easily obtainable.

A motorcycle and an airplane really live in two different environments. An airplane generally takes off, climbs to its altitude and the general outside temperature is at or below zero. Even in the summertime, it maxes out at 10 or 20 degrees above. And an air-plane does not turn high rpm. A typical prop job loafs along at two to three thousand rpm. Of course, there are some high perfor-mance exceptions. The engine just drones along at low power settings, except for take-offs.

Here are some more food for thought:

It all comes down to fuel. You can build the hottest, most throw-down thumpin’ big block that ever existed, but it’s gotta have good gas.

What is good gas anyway? What separates the killer stuff for your NMCA Pro-Streeter from the slag your lawnmower barely runs on? After consulting experts in the field, we decided to check into the various street fuels available, various types and grades of octane booster, aviation gasoline (AvGas), and racing fuels. By comparing the different options available to you, it may be easier to choose the best grade for your ride.

What is octane anyway? Octane is a measurement of a fuel’s resistance to ignition. Ideally, the air/fuel mixture will ignite at the proper time and burn smoothly through the power stroke. The idea is, one powerful combustion of better than several. randomly-ignited small flame fronts. When you can precisely control the point at which the fuel will ignite, maximum performance of the engine can be achieved, and power-robbing knock and ping will be eliminated. Knock and ping are a result of abnormal ignition, or multiple flame fronts colliding within the combustion chamber during the compression stroke.

All reputable fuel manufacturers determine the octane rating of their gasoline in the research lab using a special, dedicated single cylinder engine. Comparing the gasoline to a series of standard reference fuels in the test engine results in either a research octane number (RON) or a motor octane number (MON) depending on a set of operating conditions. The RON is determined with the test engine operating at 600rpm, at standard barometric pressure, and the intake air temperature set at 125 degrees Fahrenheit. RON is primarily used to address part-throttle knock and ping problems. The MON addresses wide open throttle operation and is determined with the test engine spinning at 900rpm, also at standard barometric pressure, and the intake air temperature pumped up to 300 degrees.

The best predictor of a fuel’s performance in a street/strip machine is the Anti-Knock Index (AKI). This is simply the average of the RON and MON numbers, or (RON+MON)/2. Most all octane ratings posted at the pumps are determined by this AKI formula, and are the minimum values you could expect to see. The minimum octane requirement of your engine is determined by several variables besides the compression ratio. The engine and cylinder head configuration, air/fuel mixture, timing, coolant temperature, atmospheric pressure, relative humidity, and ambient air temperature will also affect the octane required to make your mill produce maximum power.

The burn rate of a fuel is a measurement of the time required for complete combustion of the air/fuel mixture. The notion that octane ratings affect the burn rate of fuel is about 180-degrees from reality. Burn rate is a function of several variables, and the two are completely independent, although there is generally a correlation between octane ratings and burn rates.

To give you a good example of this, we contacted Jim Wurth from Sunoco Race Fuels. He explains, "A perfect example is Sunoco Maximal, which is our fastest burning fuel, and coincidentally one of Sunoco’s highest octane fuels at 116 (R+M)/2. A lot of Pro Stock teams rely on Maximal for those sub-seven second runs. When they are turning 9,000rpm or more, the fuel has to burn pretty quickly to achieve complete combustion."

Octane boosters offer little help in the quest for higher octane. Most popular street-legal octane boosters claim increases in octane ratings up to five points, and those boosters intended for off-road use only claim up to seven points. That’s a lot of octane to hope for simply by pouring an additive in a tank. Sunoco told us that before they launched their GT-100 Unleaded retail pilot program, they wanted to be sure that a 100 (R+M)/2 octane street-legal fuel would be of value, and that enthusiasts would not be able to get the same (or better) results using an octane booster. Nine of the most popular retail octane boosters were put through a series of tests to determine where the consumer could get the most bang for the buck. The test results were verified by an independent testing facility, using several brands of regular unleaded and premium gasolines, just to make sure everything was legit.

According to Mark Borosky, Vehicle Test Engineer for Sunoco, "Of the nine octane boosters tested, none showed a significant increase, and one actually lowered the octane number of the test gasolines." Testing repeatedly showed a maximum increase in octane of 3.5 points by only two of the six street-legal octane boosters when the recommended treatment rate was blended with lower base 87-octane gasoline. The best the remaining four products could muster was less than a one point increase. "While clearly no one would actually use an octane booster in a low base octane fuel, we wanted to give the manufacturers the benefit of the doubt relative to their claims of five-to-seven point increases" explained Borosky.

When tests were performed using 98 and 94-octane fuel, even the two best products from the previous tests produced a disappointing 1.5 to 2 point maximum increase. The remaining four street-legal octane boosters showed less than a .5 point increase. Those products designated for off-road use only didn’t fare any better than the street-legal products. Subsequent tests where the dosage of octane booster was doubled, tripled, and even quadrupled produced only minimal improvements in octane, regardless of the base octane hum-ber of the test gas. In fact, quadrupling the treatment rate of the most powerful additive produced only a 3.5 point increase in octane when added to 98 premium, resulting in a cost of $3.25 a gallon.

An alternative path to octane euphoria is to blend gasolines of different octane levels yourself. It’s easier than you may think, safe, and the results are predictable. The formula for mixing gasolines of the same type is pretty straightforward. When you mix a 50/50 blend of two unleaded fuels, simply average the two octane ratings to determine what’s in the tank. If you mix 94 and 100, you get 97. The same generally holds true for leaded gasolines, assuming the lead content is nearly equal.

Blending a leaded fuel with unleaded, however, pushes the octane up a bit more than the math would suggest, due to the effect of the lead. Just a gram or two of lead blended into the unleaded fuel will raise the octane number significantly. Commercial leaded racing fuels contain anywhere from a trace to six grams of lead per gallon. If you were to mix 50 percent 110 octane leaded fuel with 100 octane unleaded, you would actually end up with an octane number around 106 to 107. Keep in mind that even the smallest amount of lead or leaded gasoline with unleaded, could spell the end of your catalytic converter or oxygen sensor. The same holds true for using octane boosters intended for off-road use only. A word to the wise, check for any lead content in all the additives you might mix with your unleaded gasoline. And check with your state emissions regulations for street use.

We asked Sunoco’s Wurth about using aviation fuel in an automobile engine. He was emphatic when he said, "Don’t do it. Even though Sunoco is a major producer of aviation fuel, this fuel is specifically blended for aircraft engines. Aircraft operate under very different conditions than automobiles, and the fuel requirements are quite different as well. Aircraft engines generally use very small pistons and run within a very narrow rpm range. There’s no need for transient throttle response in an airplane because after the pilot does the initial engine run-up, the throttle is set in one position and the rpm doesn’t normally change until landing. Also, airplanes fly where the air is cold and thin, and the atmospheric pressure is low. These are not even close to the conditions your street machine will see on the ground. Also, since most piston-driven aircraft cruise at 3,000rpm or so, the burn rate of aviation gas is much too slow for any high-performance automotive applications."

What is it that makes race gas so different? What’s it made of? Sunoco tells us their GT PLUS 104 octane unleaded race gas is only 15-20 percent traditional gasoline, and about 85 percent additives! Actually there are about 120 different chemicals in GT PLUS. One reason it isn’t street legal is the high oxygen content. The EPA requires that the oxygen content of a street legal fuel cannot exceed 2.9 percent. GT PLUS is about 3.5 percent oxygen. This fuel is light in weight at only 6.14 1bs-per-gallon. The high oxygen content improves the octane, and when the induction system is properly calibrated, this fuel will help make additional horsepower. The high oxygen content has a supercharging effect, since 3.5 percent oxygen is the equivalent to about 17 percent more air. Different fuels can actually alter horsepower 5-to-10 percent or more.

We wanted to know more about the different types of race gas Sunoco had, and didn’t realize there were five different types of racing fuel alone.

GT-100 Unleaded, is a clear fuel with a pump octane of 100, and will handle compression ratios of up to 12:1, and is street legal in all 50 states.

GT PLUS, is also unleaded, and is rated at 104 octane. It is suitable for compression ratios up to 14:1 and is colored light blue. It will not harm oxygen sensors or knock sensors in computer controlled engines. It is not street legal.

STANDARD, is a leaded fuel rated at 110 octane, is colored purple and is intended for drag racing, road racing, and race boats.

SUPREME, also a leaded fuel, rated at 112 octane, is dark blue. It was developed to help resist vapor lock and meet the demands of sportsman, modifieds, offshore powerboats, and endurance racing where engines regularly run in excess of 7,000rpm.

MAXIMAL, we mentioned earlier, is colored red, has 116 octane, and is leaded. It is intended for exceptionally high performance applications, like Pro Stock, where extremely high cylinder pressures are common. Its extremely fast burn rate is satisfactory where rpm exceeds 10,000.

Now that you’re an expert on gasolines, you probably would like to know where to buy and store the stuff. If you are fortunate enough to live in the mid-Atlantic states, you can take advantage of Sunoco’s GT-100 Unleaded retail pilot program and get 100-octane race fuel at pumps located at select service stations. The rest of us have to purchase from local speed shops, at race tracks, or directly from Sunoco distributors.

When you plan on buying fuel in quantity, say a 55-gallon drum, you’ll be happy to know that racing fuel has a shelf life of about a year, if you store it properly. The container must conform to all safety standards, and should be made from metal or polymer. Make sure the container is opaque and solid in color. The white plastic jugs we see at the track should be used for short-term storage only. They let in sunlight, which will affect the fuel The lead in leaded fuel and other chemicals in unleaded fuel are photosensitive, and will dissipate if they are exposed to the sun. Keep any container tightly sealed to prevent evaporation.
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Oct 23, 2006
Here is some more info for the Roots section..


Check out the efficiency maps

A simple explanation of the isentropic efficiency maps:

During compression, air heats up. Theoretically it should increase temperature by a set amount. The Isentropic efficiency states how close this temperature gets to the ideal temperature.

Since SAE defines standard conditions of 14.35psi and 77 F, The 100% efficent temperatures relative to boost are:

6psi = 134 F
12psi = 179 F
18psi = 217 F
24psi = 252 F

Now you can see why intercoolers are very important. Even with a 100% thermally efficient Supercharger/Turbocharger an intercooler will help!
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