Educate me on HP levels and pump gas

[RBB]

Question for some of you more educated guys on here. I've seen this topic briefly discussed before, but I've never really seen a straight answer, and it seems like opinions vary. I'm working on the initial base files with my tuner and today we discussed when the car is going on the rollers, expected numbers, etc. To make a long story short he tells me that they don't like tuning a car to make more than 700-750 HP on 93 octane. I'd imagine the timing in my street tune will have to be very low to achieve this.

This surprised me a little as I know I've seen cars running 93 pump tuned by this same tuner that are pushing more HP than that. I've also seen other tuners go 800-850 on 93 octane. I've always been under the assumption that you don't want to push more boost and timing than the octane can support (18psi, for instance, on 93), but I've never thought that you needed X amount of octane to support a particular HP level. Can anyone explain the reasoning behind this?

 

[GNBRETT]

u definitely need an X amount of octane to run that kinda number. it can be done with methanol for sure.

straight 93 is definitely pushing it past 750hp on pump gas unless u got some huge CI motor then u can make 1500+ hp on pump 93. but most tuners won't tune a 5.4 or Coyote setup past 750 hp without methanol just not enough CI/compression.

I come from the Turbo Buick world where routinely run 30 lbs of boost with methanol on 93 octane. without the alky no where near that on 93.

there are quite a bit of variables when determining if ur gonna make 800+ hp on pump gas. Cams, heads, valve train, type of forced induction ur running, timing and of course a stick car is gonna put down more HP to the wheels on the dyno then an auto where u lose 12-15% on average.

u can run all the boost u want as long as its not detonating. My combo will make a completely different HP number on pump 93 then yours will because I'm running a Turbo but I plan on making over 800 hp on straight 93 octane but I will be using Methanol as insurance just not fuel.

but seems like u got quite a set-up for sure but 850 hp aint happening without some extra octane from methanol imo.

 

[RBB]

u definitely need an X amount of octane to run that kinda number. it can be done with methanol for sure.

straight 93 is definitely pushing it past 750hp on pump gas unless u got some huge CI motor then u can make 1500+ hp on pump 93. but most tuners won't tune a 5.4 or Coyote setup past 750 hp without methanol just not enough CI/compression.

I come from the Turbo Buick world where routinely run 30 lbs of boost with methanol on 93 octane. without the alky no where near that on 93.

there are quite a bit of variables when determining if ur gonna make 800+ hp on pump gas. Cams, heads, valve train, type of forced induction ur running, timing and of course a stick car is gonna put down more HP to the wheels on the dyno then an auto where u lose 12-15% on average.

u can run all the boost u want as long as its not detonating. My combo will make a completely different HP number on pump 93 then yours will because I'm running a Turbo but I plan on making over 800 hp on straight 93 octane but I will be using Methanol as insurance just not fuel.

but seems like u got quite a set-up for sure but 850 hp aint happening without some extra octane from methanol imo.

Yeah, I'm just referring to the street tune here. Will be running race fuel at the track, so not worried about that. Just seems like I've seen plenty of GT500s pushing more than 750HP on 93 octane.

I really wish there was more E85 around here. I went ahead and did a return style system so it's only a matter of dropping in a new hat and wiring one pump when the time comes.

 

[GNBRETT]

well I think the more accurate question is were they making 850 hp at the track or on a dynojet or some other dyno other then a Mustang Dyno.

cause I haven't seen too many pump gas coyotes or 500's going that fast at the track on pump gas which would be about a 9.50 ET at probably 145 mph or so. its definitely possible with methanol but I have yet to ever see one go that fast.

Yeah, I'm just referring to the street tune here. Will be running race fuel at the track, so not worried about that. Just seems like I've seen plenty of GT500s pushing more than 750HP on 93 octane.

 

[RBB]

well I think the more accurate question is were they making 850 hp at the track or on a dynojet or some other dyno other then a Mustang Dyno.

cause I haven't seen too many pump gas coyotes or 500's going that fast at the track on pump gas which would be about a 9.50 ET at probably 145 mph or so. its definitely possible with methanol but I have yet to ever see one go that fast.

Seems like a dynojet usually. Never seen a GT500 run anything close to a 9.50 on 93 octane....not claiming to have ever seen that. I've seen quite a few dyno numbers bigger than 750 thrown around where I know the car was running 93.

 

[GNBRETT]

I agree I hear their out there to but do u ever actually see any? I haven't for sure. I hear this guy has X amount of hp higher then anyone elses but their usually garage queens who got their dyno numbers with a Dynojet and never actually been to the track.

Don't get me wrong Dynojet is clearly the standard in Dyno's and is what most cars are dynoed on so its not like its BS that their car is reading that on a Dynojet. its pretty accurate I bet but the Mustang dyno to me is the more realistic to real world conditions vs. inflated or programmed ones.

my buddy owned a speed shop that worked on Turbo Buicks essentially and we had a dynojet there and thats what everything was tuned on including a few Mustangs with Turbos.

and the guys with Mustangs that had their cars tuned on a Mustang dyno would always come to the shop for a Dynojet pull and usually a tune as well cause that was his forte but the difference in HP/TQ was sometimes over a 100 hp and maybe 75 ft lbs of TQ.

Seems like a dynojet usually. Never seen a GT500 run anything close to a 9.50 on 93 octane....not claiming to have ever seen that. I've seen quite a few dyno numbers bigger than 750 thrown around where I know the car was running 93.

 

[biminiLX]

Lots of variables as stated, and remember the risk of detonation occurs at highest cylinder pressure, peak torque. Your cams will help this regard and it may tolerate more timing up top, as a higher rpm combo is usually is preferred if octane limited.
I made 750rwhp on 93 but always through in Torco for dyno or racing.
This is definitely an area to rely on your tuner and hope you have a good one.
-J

 

[Weather Man]

The reason good tuners don't push pump gas is that you are gambling that you are getting perfectly fresh true 93 octane gas every time you fill up. There are just to many ways to count for that true 93 to not, in fact, be 93. Built motors are not cheap, silly to risk that investment on "bubba" the substitute fuel delivery driver who drops a tank load of regular into the premium tank, or the 93 is old and stale, or the fuel is water contaminated, or, or, or.

Pay to play, set it up right for the power you want.

 

[RBB]

The reason good tuners don't push pump gas is that you are gambling that you are getting perfectly fresh true 93 octane gas every time you fill up. There are just to many ways to count for that true 93 to not, in fact, be 93. Built motors are not cheap, silly to risk that investment on "bubba" the substitute fuel delivery driver who drops a tank load of regular into the premium tank, or the 93 is old and stale, or the fuel is water contaminated, or, or, or.

Pay to play, set it up right for the power you want.

I agree with you, not arguing that it isn't good to play it safe due to human error at the pumps.

My question is more along the lines of why, mechanically speaking, there is a limit to how much HP you can make on a certain octane fuel? Of course there are many variables, but the main point I'm seeing is higher cylinder pressures as HP increases. It's just not a topic you see discussed much on the forums. What you always read is you need enough octane to support X boost and Y timing, no one ever really mentions HP limits as they pertain to octane.

 

[MastaAce03]

I agree with you, not arguing that it isn't good to play it safe due to human error at the pumps.

My question is more along the lines of why, mechanically speaking, there is a limit to how much HP you can make on a certain octane fuel? Of course there are many variables, but the main point I'm seeing is higher cylinder pressures as HP increases. It's just not a topic you see discussed much on the forums. What you always read is you need enough octane to support X boost and Y timing, no one ever really mentions HP limits as they pertain to octane.

The factory rods are the issue at that power level and above. Some have had issues with the rods with even less power.


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[RBB]

The factory rods are the issue at that power level and above. Some have had issues with the rods with even less power.


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No, I'm not talking about factory rods or other weak OEM components. We all are aware of those limitations. Fully built motor, good for 1,200HP....mechanically/scientifically speaking if you've got enough octane to run X boost and Y timing, why is HP output still limited by octane?

@biminiLX says cylinder pressures increase and I can get on board with that answer, makes sense. @Bad Company where are you at man? I know you will have a very detailed answer for me!

 

[MastaAce03]

No, I'm not talking about factory rods or other weak OEM components. We all are aware of those limitations. Fully built motor, good for 1,200HP....mechanically/scientifically speaking why is HP limited by octane?

Ahh, copy. In that case; the hp statement doesn’t make any sense. There’s a couple guys on here making mid 900s on straight pump 93. And I’m jealous.


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[RBB]

Ahh, copy. In that case; the hp statement doesn’t make any sense. There’s a couple guys on here making mid 900s on straight pump 93. And I’m jealous.


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That's what I'm saying, I have seen big numbers thrown around on 93 octane. My tuner tells me today that they do not want to see more than 700-750 HP on 93....too much risk for the octane. First time I have ever heard that, there are too many GT500s to count that claim to make more HP than that.

This is a very reputable tuner, one of the big boys....many (most likely the majority) on this forum use them, and there's no doubt they know their stuff.

 

[RedVenom48]

Realistically, each car is unique. Many times not drastically, but unique none the less. The tuners are playing a game of "very safe". I suspect that most, if not all tuners have a contract or terms of service that specifically state in the event of catastrophic failure, they hold ZERO liability. Real world states that they can be sued, and they must defend themselves even with a liability waiver. So, like the OEMs, they wont dial up a tune to 100 potential.

Assume a stock long block with factory exhaust. The compression ratio, boost pressure and valve timing all will probably be within 5% or so of all units produced. At operating temp, with proper fuel delivery, all systems operating normally etc.

Remote tune sessions, remote dyno tune sessions, data log analysis and even in person tune sessions, the "real world" variables are something they cannot control. So even though they (the big boys) have at this point tuned a massive amount of cars, with massive volumes of proven data, the tuners must account for the worst scenarios. The scientific data on X octane fuel having a resistance to detonation given Y combustion chamber temp and Z cylinder pressure with A amount of ignition timing at moment of ignition is straight forward.

Now, add in real world factors beyond your control: inconsistent pump quality octane (single hose pumps, age of fuel, quality of storage, delivery to correct tanks). Things not in your control: component wear, carbon deposits, quality of parts used at the factory. Things in your control: regular maintenance to the engine, oil quality, air filter cleanliness, injector cleanliness based on quality brand fuel (detergents), ensuring proper working order etc. These variables all contribute to X octane resisting detonation.

In your case, with a wickedly bad ass build with strong components, the tuner still needs to cover his ass. With all the mechanical variables now fairly contained, pump gas is the biggest wild card.

E85 (verified by sampler every fill up), 100 octane unleaded pump race fuel (assuming proper storage), and actual race fuel from barrels are about the only real fuel consistency a tuner can rely on. It must be the only fuel the car is supplied with. No torco or octanium either! With 100+ octane available, your mechanical parts are now the weak link, but the tuner now has the biggest unknown fairly controlled.

The power level your tuner gave you wasnt the maximum power that 93 can support. Rather its a power output estimate based on a safe tune given all variable potentials. Id estimate that the OEMs are at about 70% total potential for a super safe margin of error combined with all the regulatory compliance they must deal with.

Other tuners trying to make a name for themselves or tuners with a SOLID liability waiver signed by the customer can push 93 as far as they dare. There is a scientific limit as to what it will withstand, and any tuner with knowledge of this can simply dial it up to that limit. The real world variables will ultimately decide how long that tune will keep the engine alive. Makes a quick buck, can draw a lot of potential customers in. But if their initial customers blow up their engines and take to the internet to rant, that company is finished.

They want happy customers, with their tunes being powerful but safe. Its a perfect example of cover your ass.

 

[Catmonkey]

My guess would be personal liability concerns. I think an engine like your could be tuned for more power output safely. That's not meant to say 800 rwhp is safe on the street. When you're operating beyond the limits of traction, things can happen quickly to both damage the engine or the car.... and worse.

 

[1 Alibi 2]

Sometimes you just have to listen to your tuner, even if you don't like the answer. He is looking out for your motor & his reputation, wants nothing to go wrong.
.
" This is a very reputable tuner, one of the big boys....many (most likely the majority) on this forum use them, and there's no doubt they know their stuff. "
.
Is your car @ the tuner's shop ?
If at the shop, is the tuning done on the street, then put on the dyno ?
A tuner will be less likely to stick his neck out on a canned or remote tune, than if he's doing the tuning in person.

 

[sleek98]

I think they are getting a little more conservative with their remote pump gas tunes. Which I dont blame them for wanting to cover their ass. I am wondering if they are starting to see more knock coming back in datalogs from less than stellar gas.

My first pump gas tune with them was on the ragged edge 20-21* on 93 with the TVS, the lastest one when I did the auto swap backed off 3* of timing. They also thought that going from a 2.4/stock lower to a 10%/2.6 was too much for pump gas and had me go up a pulley size.

After talking with them and realizing that a new motors going to be 15-20k all done, I would like to go up another pulley size for pump gas as its not going to make a huge difference on the street if I am at 700 or 650 whp. Its going to be a spin fest either way. Dump in E85/race gas and swap pulleys to add another 100-125 hp at the track.

 

[RBB]

Realistically, each car is unique. Many times not drastically, but unique none the less. The tuners are playing a game of "very safe". I suspect that most, if not all tuners have a contract or terms of service that specifically state in the event of catastrophic failure, they hold ZERO liability. Real world states that they can be sued, and they must defend themselves even with a liability waiver. So, like the OEMs, they wont dial up a tune to 100 potential.

Assume a stock long block with factory exhaust. The compression ratio, boost pressure and valve timing all will probably be within 5% or so of all units produced. At operating temp, with proper fuel delivery, all systems operating normally etc.

Remote tune sessions, remote dyno tune sessions, data log analysis and even in person tune sessions, the "real world" variables are something they cannot control. So even though they (the big boys) have at this point tuned a massive amount of cars, with massive volumes of proven data, the tuners must account for the worst scenarios. The scientific data on X octane fuel having a resistance to detonation given Y combustion chamber temp and Z cylinder pressure with A amount of ignition timing at moment of ignition is straight forward.

Now, add in real world factors beyond your control: inconsistent pump quality octane (single hose pumps, age of fuel, quality of storage, delivery to correct tanks). Things not in your control: component wear, carbon deposits, quality of parts used at the factory. Things in your control: regular maintenance to the engine, oil quality, air filter cleanliness, injector cleanliness based on quality brand fuel (detergents), ensuring proper working order etc. These variables all contribute to X octane resisting detonation.

In your case, with a wickedly bad ass build with strong components, the tuner still needs to cover his ass. With all the mechanical variables now fairly contained, pump gas is the biggest wild card.

E85 (verified by sampler every fill up), 100 octane unleaded pump race fuel (assuming proper storage), and actual race fuel from barrels are about the only real fuel consistency a tuner can rely on. It must be the only fuel the car is supplied with. No torco or octanium either! With 100+ octane available, your mechanical parts are now the weak link, but the tuner now has the biggest unknown fairly controlled.

The power level your tuner gave you wasnt the maximum power that 93 can support. Rather its a power output estimate based on a safe tune given all variable potentials. Id estimate that the OEMs are at about 70% total potential for a super safe margin of error combined with all the regulatory compliance they must deal with.

Other tuners trying to make a name for themselves or tuners with a SOLID liability waiver signed by the customer can push 93 as far as they dare. There is a scientific limit as to what it will withstand, and any tuner with knowledge of this can simply dial it up to that limit. The real world variables will ultimately decide how long that tune will keep the engine alive. Makes a quick buck, can draw a lot of potential customers in. But if their initial customers blow up their engines and take to the internet to rant, that company is finished.

They want happy customers, with their tunes being powerful but safe. Its a perfect example of cover your ass.

My guess would be personal liability concerns. I think an engine like your could be tuned for more power output safely. That's not meant to say 800 rwhp is safe on the street. When you're operating beyond the limits of traction, things can happen quickly to both damage the engine or the car.... and worse.

I understand all of the outside variables, of course I don't have a problem with that, I even requested a very safe tune for the street....don't need to go crazy with the timing, etc. I've just never heard a tuner say we don't want to see any more than X HP on a certain octane. If you have enough octane to safely run Y boost and Z timing, it seems like HP wouldn't be limited by the octane. Of course Y boost and Z timing will create X amount of HP on a particular engine/blower combo, so you can give someone a general idea of what kind of power it will make.

The way I took what he was telling me yesterday (and this is pretty much word for word from our email) is that even if the tune is good and we're well within the safe timing and boost limits for 93 octane, the timing will still be dialed way back if we go over 750HP. Just seemed odd to me as I have never seen this discussed on the forums before. Also, I know there are many GT500s running well over 750 rwhp on 93 octane, many which, I believe, are tuned by him. Don't get me wrong, I'm not complaining, as 750 at the wheels is more than enough for the street....I will have a race gas tune for the strip. All of the outside factors excluded (batch of bad gas, etc), I just wanted an explanation as to why we would dial the tune back based solely on a HP # if we're running a known safe calibration for timing and boost.

Sometimes you just have to listen to your tuner, even if you don't like the answer. He is looking out for your motor & his reputation, wants nothing to go wrong.
.
" This is a very reputable tuner, one of the big boys....many (most likely the majority) on this forum use them, and there's no doubt they know their stuff. "
.
Is your car @ the tuner's shop ?
If at the shop, is the tuning done on the street, then put on the dyno ?
A tuner will be less likely to stick his neck out on a canned or remote tune, than if he's doing the tuning in person.

I have no problem with the tuner, and of course I'll listen to and go with what he thinks is best. I was just curious as to why we'd dial a tune back based solely on a HP # if we're running a safe calibration for the timing and boost level. Not at the shop, it will be a remote tune session on the dyno. Still going through initial revisions on idle/cruise logs right now.

I think some of you guys are taking this question the wrong way. I'm curious, I like to learn about the mechanics of things. I don't care if this is what he thinks is safe and this is how we're going to do it, no problems from me there. I don't care about the tuner protecting his rep, of course I understand that, that is also a given and I have no problem with it. I'm also not interested in the fact that we could get a batch of bad gas, etc.....that is a given on any day....I'm not interested in discussing that either.

I only want to discuss this question from a mechanical/scientific viewpoint....all this other stuff is inconsequential to me and a given. Why would you dial a tune back if it's making over X amount of HP when you're running a known and safe calibration that can support the amount of boost and timing you're making on a particular octane?

 

[StrayBullitt]

No, I'm not talking about factory rods or other weak OEM components. We all are aware of those limitations. Fully built motor, good for 1,200HP....mechanically/scientifically speaking if you've got enough octane to run X boost and Y timing, why is HP output still limited by octane?
@biminiLX says cylinder pressures increase and I can get on board with that answer, makes sense. @Bad Company where are you at man? I know you will have a very detailed answer for me!

I have always been taught that Octane is a quality of or say a measurement of resistance to detonation. Detonation (knock, pre-ignition, whatever you want to call it) especially at our power levels is not safe, this is when hard parts/internals can be damaged and you cannot safely and reliably run the Engine under all conditions.

So with that said I don't know if I would try and wrap my head around a certain horsepower level as the limitation for a given octane, but rather at what point on a specific Engine is the combustion event no longer stable with said octane and at what point is the threshold for resistance to detonation with said octane in that Engine being reached. There will be a ton of mitigating factors that go into that equation, your hard parts and supporting mods will be a factor in that, even ambient conditions.

X boost and Y timing will create a given environment for which the fuel is introduced and in that environment can the fuel sustain a controlled burn, not pre-ignite, not vaporize, I guess generally be able to maintain it's properties. You can play with one or the other (boost/timing) increase/decrease one or the other, however ultimately you will reach a point of diminishing returns, you can only increase boost so much before you start pushing limits of efficiency with your power adder and pushing hot air that is losing density. You can only back off timing so much because the Engine has a range of timing at which it performs best at and you need to start the combustion event for a proper burn throughout all of the RPM range.

So I will say that once you have reached this point of diminishing returns trying to combat or control detonation, then that is your Max Horsepower.( On your specific Engine with your specific fuel ).

 

[RedVenom48]

A rated torque output probably has a specific energy requirement that must be met to get to said output. Given the nature of automotive reciprocating piston power, rapid compression and ignition of pressurized air and fuel is inherently an inefficient way to harness energy.

Direct injection offers engineers and tuners a much more stable fuel system to control detonation. Injecting fuel into the combustion chamber literally milliseconds prior to ignition via spark allows for far higher boost pressure on pump fuel. Youre pressurizing LIQUID fuel in the fuel rails and injecting it, and not exposing fuel VAPOR to compression with air on the compression stroke. Youre nowhere near at risk for detonation compared to a port fuel injection setup if the fuel goes in effectively, at the timing point of ignition. Of course, a direct only setup has a ton of drawbacks real world.

Scientifically, there is no reason x octane at its max spec Y cylinder pressure with max spec Z timing at T temperature would need to be backed off. You wouldn't dial it back if the fuel's known quality was 93. Regulated intake air temp, regulated coolant temp etc would also be needed. You would take it to its limit with the known power breaking point of your engine mechanicals.

What we are saying is real world, its never always 93, air temp is always varying, youre still compressing air AND fuel at the same time. Boost pressure could be off and parts rated for 800lbs reliably could have a bad day, develop micro fractures in their structure and at 743 lb of generated torque fail. Cover ass mode engage. Thats literally the reason reputable tuners are stating power figures with pump fuel that seem lower than what possible.