Educate me on HP levels and pump gas

[RBB]

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.

Gotcha, so it's just to cover their ass, which is what I assumed from the get go. There's no real scientific reason to back down based off of a certain HP # if timing, boost, etc are all at safe levels for the octane. Maybe this is a recent thing they're doing with their tunes, as I've never heard any of the tuners say they won't tune over a certain amount of HP on a particular octane.

The last time I saw one of these motor combos dyno'd on 93 octane (I'm assuming) was @dale.baker 's thread from a couple years ago. If my memory serves me correctly he made a little over 800rwhp at only 12* of timing. He was still on the stock fuel pumps, and those were the limiting factor. If he wasn't running out of fuel they could've turned it up even more. So to say that we're going to dial it back to 750 just seemed a little unreasonable....ignition timing would have to be severely retarded to hit that #. Of course, I will do what the tuner wants....

 

[Catmonkey]

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 would 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?

What I'm saying is there isn't one from my standpoint, knowing your combination. By the same token your engine can rev much quicker than the knock sensors can pull timing. So with a load of bad gas, your knock sensors can come into play too late.

 

[Bad Company]

Can one of these engines produce over 750 RWHP on 93? Yes. Look at Shelby America with the SuperSnake with the 1000 Hp option and S-1000 cars. Now Shelby is rating this at flywheel Hp, so with a 15% power loss through the driveline that would net 850 RWHP.

There are many factors into how this can be achieved. The two biggest in my mind will be coolant temperatures and cylinder pressures, along with what engine RPM they occur while producing peak torque and Hp.

The tuner can play with both the timing and richness of the fuel mixture to combat detonation. The other thing that may have him concerned is when you swap between fuels. Depending on the race fuel you use it could carry extra oxygen. A blend of race fuel and pump gas could lend itself to creating a lean condition during the first fill of 93 pump gas if the race fuel is carrying extra oxygen in it. So he may want to limit the power for this too.

 

[RBB]

What I'm saying is there isn't one from my standpoint, knowing your combination. By the same token your engine can rev much quicker than the knock sensors can pull timing. So with a load of bad gas, your knock sensors can come into play too late.

Right, I couldn't think of a good reason either, but I'm not as well versed as some of you on some of the more technical aspects at play here. In my mind, if we're running a very safe calibration that hits 800rwhp, why the hell would we dial it back to hit 750? That just makes no sense to me.

 

[biminiLX]

I think it's a conversation best had in person while you're actually tuning. At least that's the way my relationship is with my tuner. We also go to the track together when possible. The point there is very few will commit to x power on a given fuel as a limit, you have to use the dyno and datalogging as a tool to discover what your combo will do.
It's also a bummer to be limited by 93, but you want to tune with what you have and how you'll use the car.
If we're just talking a dyno queen, no shame in that, some want to do dyno competitions. In that setting then you can push the envelope as it's a controlled environment (temps and potential octane boosters).
If talking the street, then tune for safety as you'll be unlikely to tell a difference between 750 and 850rwhp and there's too many variables including traction.
If on the track, why would you ever limit yourself to 93? For the rare times you race, get the best octane you can afford and tune it accordingly. On race days I'd maximize the potential of the parts you spent good money on.
Personally, I'm just thankful to have quality E85 as I can't imagine a better fuel for what I want from my car.
-J

 

[RBB]

I think it's a conversation best had in person while you're actually tuning. At least that's the way my relationship is with my tuner. We also go to the track together when possible. The point there is very few will commit to x power on a given fuel as a limit, you have to use the dyno and datalogging as a tool to discover what your combo will do.
It's also a bummer to be limited by 93, but you want to tune with what you have and how you'll use the car.
If we're just talking a dyno queen, no shame in that, some want to do dyno competitions. In that setting then you can push the envelope as it's a controlled environment (temps and potential octane boosters).
If talking the street, then tune for safety as you'll be unlikely to tell a difference between 750 and 850rwhp and there's too many variables including traction.
If on the track, why would you ever limit yourself to 93? For the rare times you race, get the best octane you can afford and tune it accordingly. On race days I'd maximize the potential of the parts you spent good money on.
Personally, I'm just thankful to have quality E85 as I can't imagine a better fuel for what I want from my car.
-J

I wish we had E85 around here....it's got to be coming soon I'd imagine. That's why I went ahead and did a return style system now. When the time comes I can drop in some new pumps and I'm good to go.

Of course I'll be running race fuel at the track. I'm not hung up on dyno numbers and I agree with you, 750 wheel is most likely more than enough for the street.

My issue was simply why are we limiting the car to some arbitrary HP # if we're already running a safe calibration for the octane? We're going to retard timing even further at that point just to not go over 750? After the conversation I had with them today it seems like yes, that's what will be done. I have never heard that from any of these tuners before and it still makes no logical sense to me....I suppose they're trying to cover their asses in some way.

 

[biminiLX]

I mean, if you're requesting more, they'll likely do it.
I'm assuming you'll have a safe street 93 tune and a much stronger race tune.
I personally would want it that way, but before I went E85 I always added a Torco like booster to my car before dyno, track, fun runs. Hell its a pleasure car and I ran it most of the time as I only put on 1500-2000 miles/year top.
-J

 

[RBB]

I mean, if you're requesting more, they'll likely do it.
I'm assuming you'll have a safe street 93 tune and a much stronger race tune.
I personally would want it that way, but before I went E85 I always added a Torco like booster to my car before dyno, track, fun runs. Hell its a pleasure car and I ran it most of the time as I only put on 1500-2000 miles/year top.
-J

I'm not necessarily requesting more, but if we're already running a safe conservative tune for the octane and the datalogs look great, I see no reason why we'd want to cut timing to make 750.

Yes, race tune will be turned all the way up.

 

[KEVINS]

I think you're reading more into what the tuner is saying about what's limiting the HP. A good tuner KNOWS the limit of common engine combos and unless given free reign to push it they won't do it. I'm sure certain tuners have a few vehicles that are pushed to those upper HP limits successfully and create forum chat-worthy numbers but those are probably the top 2%, not the norm and it's those 2% that get all the news. In other words the tuner knows/believes that 750hp on 93oct for your combo is a very safe tune for them/you that won't be pushing the fuel octane into the danger zone unless you tell him it's OK.

On a note concerning octane: If an engine isn't set up to hear knock with sensors then don't push it. My TT car was tuned to 720hp/720tq @ 18psi on 93oct before I bought it. Before I went into boost I chose to get a J&S Vampire knock detector just to give me a bit of piece of mind against knock. After installing it I had 91oct in the tank and lowered the boost to 7psi just to do some light testing. To my amazement the knock detector lit up like a friggen xmas tree @ 6psi of boost! Now, after having the detector on I have NO DOUBT that even tho it was tuned with 93oct @ 18psi the motor was detonating at that power level. The ONLY way to know is to have electronics listening for it.

I also have experience with meth injection and love it.. to a point. My GN was pushed to 30psi of boost on 91 oct/meth with no knock according to the detector. My TT Mustang also made 720hp on 91oct and meth inj. At these levels of HP with low octane fuel the meth becomes fuel not just octane. I was trying to make 900hp with 91oct/meth but due to spraying so much meth at the 700+ level I was getting fuel distribution issues. So I stopped at the 700hp level and switched to a standalone computer and incorporated a flex fuel system with tunes for E85 and 91oct/meth (haven't got the 91/meth tune done yet but it will be limited to 700hp) but has made 900+ on E85.

ks

 

[biminiLX]

You wouldn't in my opinion. You don't tune all 93 octane combos to 750rwhp. Your built 5.8 was different than my stock 5.8 at 750rwhp. Our s/c 5.8s are different from a turbo 2.0L or NA 600" Big block. All can make the same power, but all have different 93 pump limits.
Your tuner maybe talking his rule for our basic s/c 5.4/5.8 GT500s, and you're right it doesn't have to be detuned, but again variables on the street. If you're talking multiple street datalogs for your car on your fuel for the driving you do, then you'll be confident in a safe street tune.
-J

 

[biminiLX]

I think you're reading more into what the tuner is saying about what's limiting the HP. A good tuner KNOWS the limit of common engine combos and unless given free reign to push it they won't do it. I'm sure certain tuners have a few vehicles that are pushed to those upper HP limits successfully and create forum chat-worthy numbers but those are probably the top 2%, not the norm and it's those 2% that get all the news. In other words the tuner knows/believes that 750hp on 93oct for your combo is a very safe tune for them/you that won't be pushing the fuel octane into the danger zone unless you tell him it's OK.

On a note concerning octane: If an engine isn't set up to hear knock with sensors then don't push it. My TT car was tuned to 720hp/720tq @ 18psi on 93oct before I bought it. Before I went into boost I chose to get a J&S Vampire knock detector just to give me a bit of piece of mind against knock. After installing it I had 91oct in the tank and lowered the boost to 7psi just to do some light testing. To my amazement the knock detector lit up like a friggen xmas tree @ 6psi of boost! Now, after having the detector on I have NO DOUBT that even tho it was tuned with 93oct @ 18psi the motor was detonating at that power level. The ONLY way to know is to have electronics listening for it.

I also have experience with meth injection and love it.. to a point. My GN was pushed to 30psi of boost on 91 oct/meth with no knock according to the detector. My TT Mustang also made 720hp on 91oct and meth inj. At these levels of HP with low octane fuel the meth becomes fuel not just octane. I was trying to make 900hp with 91oct/meth but due to spraying so much meth at the 700+ level I was getting fuel distribution issues. So I stopped at the 700hp level and switched to a standalone computer and incorporated a flex fuel system with tunes for E85 and 91oct/meth (haven't got the 91/meth tune done yet but it will be limited to 700hp) but has made 900+ on E85.

ks

Last sentence tells all for guys that want big street power, run E85.
If you don't have it available, buy a corn farm
-J

 

[RedVenom48]

When in doubt, a can of Octanium is about 25 bucks. CHEAP insurance to safeguard your engine.

 

[Catmonkey]

I wish we had E85 around here....it's got to be coming soon I'd imagine.

I don't think there's a lot of incentive with $60/bbl. oil. Further south, it's like trying to find hen's teeth. It would really hamper your ability to travel.

 

[GNBRETT]

saving their ass and ur motor at the same time..... sounds like a win-win to me.

thats SOP for just about every decent tuner on the planet. their not there to give u a dyno queen number their there to tune it properly so it lives.

a dyno once again is a TUNING tool NOT a hp calculator. u want that go to the track and see what it MPH's. THAT is what will tell u how much power ur making NOT the dyno.

After the conversation I had with them today it seems like yes, that's what will be done. I have never heard that from any of these tuners before and it still makes no logical sense to me....I suppose they're trying to cover their asses in some way.

 

[StrayBullitt]

Last sentence tells all for guys that want big street power, run E85.
If you don't have it available, buy a corn farm
-J

haha.. I'd like to slowly work my way up to that point (w.out the farm) I see mention of return style fuel system all the time.. do we need to go return style on our cars? Or can we tap into the potential of E85 by upgrading pumps/injectors and adding BAP ?

 

[RBB]

Guys I know what a dyno is for, I understand tuners need to play it safe, etc. I, of course, want a safe calibration for my octane of choice on the street. This is all common sense, I don't need to be lectured on the these points and I'm not looking for a ridiculous tune that isn't safe for my motor.

My tuner has told me that even if the calibration is conservative and safe and the datalogs look good, timing will still be dialed back to keep me around 750rwhp. I found that statement unusual and was wondering if anyone had a technical explanation for it since I couldn't think of one. As far as I know that is not SOP for any tuner. From the responses I've gotten, there's no good technical reason for it, which is what I thought from the get go.

 

[KEVINS]

My tuner has told me that even if the calibration is conservative and safe and the datalogs look good, timing will still be dialed back to keep me around 750rwhp. I found that statement unusual and was wondering if anyone had a technical explanation for it since I couldn't think of one. As far as I know that is not SOP for any tuner. From the responses I've gotten, there's no good technical reason for it, which is what I thought from the get go.

Sounds like you better ask your tuner why he wants to limit the HP. I would like to hear the reason, too.

ks

 

[GNBRETT]

Technically ur forgetting the "LOAD" that ur car sees on the street that it doesn't see on the dyno.

ur car will be FASTER on the street then on the dyno which is why it makes sense to back it off a little on the dyno.

and its often why ppl who try to tune their car to MAX hp on the dyno often detonate on the street and melt their motors cause u simply make more power on the street!

That would be the "Technical" reason for it.

Guys I know what a dyno is for, I understand tuners need to play it safe, etc. I, of course, want a safe calibration for my octane of choice on the street. This is all common sense, I don't need to be lectured on the these points and I'm not looking for a ridiculous tune that isn't safe for my motor.

My tuner has told me that even if the calibration is conservative and safe and the datalogs look good, timing will still be dialed back to keep me around 750rwhp. I found that statement unusual and was wondering if anyone had a technical explanation for it since I couldn't think of one. As far as I know that is not SOP for any tuner. From the responses I've gotten, there's no good technical reason for it, which is what I thought from the get go.

 

[StrayBullitt]

Technically ur forgetting the "LOAD" that ur car sees on the street that it doesn't see on the dyno.

ur car will be FASTER on the street then on the dyno which is why it makes sense to back it off a little on the dyno.

and its often why ppl who try to tune their car to MAX hp on the dyno often detonate on the street and melt their motors cause u simply make more power on the street!

That would be the "Technical" reason for it.

This is a good point, I have heard this in some way shape or form before as well.

 

[RBB]

Technically ur forgetting the "LOAD" that ur car sees on the street that it doesn't see on the dyno.

ur car will be FASTER on the street then on the dyno which is why it makes sense to back it off a little on the dyno.

and its often why ppl who try to tune their car to MAX hp on the dyno often detonate on the street and melt their motors cause u simply make more power on the street!

That would be the "Technical" reason for it.

That is a good point, Brett. Hadn't thought of it that way.