996 Turbo / GT2Turbo discussion on previous model 2000-2004 Porsche 911 Twin Turbo and 911 GT2. Sponsored By Vivid Racing
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Cylinder pressure is cylinder pressure. Weather you archive more cylinder pressure with more timing and less boost or more boost and less timing, it doesn't matter. So far I have seen no indication why boost should be limited to 1.2 bar on pump gas....
Being too aggressive with boost or timing will cause the the same result....detonation. Detonation is what kills these engines....not boost.
If the DME is tuned properly, there is no reason why 1.3+ cant be run daily on pump gas.
Quoted for truth. When tuning cars, it is all give and take. There are far too many variables to just blindy decree that "x" amount of boost is too much for pump gas. It is all dependant on detonation. I gauruntee you that a very agressive timing map can kill a motor at relatively low boost levels. However, that surely doesn't mean that you can't have a tune that will live just fine with 24+ lb of boost on pump gas.
Cylinder pressure is cylinder pressure. Weather you archive more cylinder pressure with more timing and less boost or more boost and less timing, it doesn't matter. So far I have seen no indication why boost should be limited to 1.2 bar on pump gas....
Being too aggressive with boost or timing will cause the the same result....detonation. Detonation is what kills these engines....not boost.
If the DME is tuned properly, there is no reason why 1.3+ cant be run daily on pump gas.
Tony, why don't you weld the wastegates? After all, more timing and less boost or more boost and less timing, it doesn't matter. Right? Who needs Tial when there's a tune??
Scary.
If anyone is curious why this approach is dead wrong, we can go over the engineering. (hint, it ignores heat)
My bad......I should have said "1.4 bar on pump gas on a GIAC tune?" I know Tony is doing it but don't know of any others who are able to do it.......once.
many tuners know what they are doing. A GIAC off the shelf tune, I agree, but with a custom tune, should be ok. I am running 1.3 bar on stock injectors and 91 octane. I have easily done 200 hard runs since, not one cel, check engine or anything. No limp mode, etc. If you have the right tune it should be ok.
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many tuners know what they are doing. A GIAC off the shelf tune, I agree, but with a custom tune, should be ok. I am running 1.3 bar on stock injectors and 91 octane. I have easily done 200 hard runs since, not one cel, check engine or anything. No limp mode, etc. If you have the right tune it should be ok.
Tony, why don't you weld the wastegates? After all, more timing and less boost or more boost and less timing, it doesn't matter. Right? Who needs Tial when there's a tune??
Scary.
If anyone is curious why this approach is dead wrong, we can go over the engineering. (hint, it ignores heat)
I don't think he said you could run 50lbs of boost with 2deg of timing or vice versa, he just said you can run more than 1.2bar if tuned properly...I have been running way over 1.2 bar on pump for a long time now. Instead of being so cryptic, tell us why you believe this?
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no need. Everything is perfect. Full durametric of everything going shows all points are fine and that you are incorrect in your assesment and opinion
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Tony, why don't you weld the wastegates? After all, more timing and less boost or more boost and less timing, it doesn't matter. Right? Who needs Tial when there's a tune??
Scary.
If anyone is curious why this approach is dead wrong, we can go over the engineering. (hint, it ignores heat)
ok, fair enough. I didnt mentioning heat into the equation... but lets not go to extremes here, Im not talking about 2+ bar.
In fairness to my statement, do you know how EGTand IAT's are effected from 1.1 bar to 1.3.... I do . Exactly why I can comfortably say 1.3-1.4 with a proper tune isnt too much for pump gas.
I don't think he said you could run 50lbs of boost with 2deg of timing or vice versa, he just said you can run more than 1.2bar if tuned properly...I have been running way over 1.2 bar on pump for a long time now. Instead of being so cryptic, tell us why you believe this?
You're right. I took his argument to an extreme for an illustrative point.
I'd be very interested in a leak down and/or bore scope info from your or any motor that has been at these levels for extended periods (preferably 5k miles).
As far as my belief, it's all in the engineering. What you said earlier is right.. there are countless factors involved -- many of which few consider and cannot be measured by us mortals, e.g. combustion chamber shape and the flame front's propagation.
ok, fair enough. I didnt mentioning heat into the equation... but lets not go to extreams here.
In fairness to my statement, do you know how EGTand IAT's are effected from 1.1 bar to 1.3.... I do . Exactly why I can comfortably say 1.3-1.4 with a proper tune isnt too much for pump gas.
Tony, Nero trusts you and I have a ton of respect for him and Wes. Nero and I have been racing cars for a long time, so you have a lot of instant credibility in my eyes.
What I know in engineering and books, you augment with real world tests (as you have alluded to). So as I have asked others, do you have any leak down/pitting information from these cars long term? As we both know, factory ECUs can pull some incredible stunts to keep engines from catastrophic failure. The real question is the wear to the cylinder walls/rings/quench/valves and the accompanying blow by.
Tony, why don't you weld the wastegates? After all, more timing and less boost or more boost and less timing, it doesn't matter. Right? Who needs Tial when there's a tune??
Scary.
If anyone is curious why this approach is dead wrong, we can go over the engineering. (hint, it ignores heat)
I think everyone here knows that air heats when compressed, and we know that higher intake air temps can be a cuase for detonation. That is why the tune is important. If the motor is not knocking, there ins't going to any damage to the piston or the combustion chamber. Again, this is why the tune is important.
Of course there are limits, but you can kill a motor very easily at 1.0 bar with a bad tune. Does that mean that 14psi is too much for pump gas? I don't think so either.
You're right. I took his argument to an extreme for an illustrative point.
I'd be very interested in a leak down and/or bore scope info from your or any motor that has been at these levels for extended periods (preferably 5k miles).
As far as my belief, it's all in the engineering. What you said earlier is right.. there are countless factors involved -- many of which few consider and cannot be measured by us mortals, e.g. combustion chamber shape and the flame front's propagation.
This car has run for 2 years and 20k+ at 1.3 bar+ ... Less then 1% leakage across the board on the engine. It has been tracked with 91 octane numerous times. About half way through that time period, water injection was added and the boost was raised even more.
Its important to note that much of that 20k is track mileage.
BTW - We easily have 5 more stories similar to this one...this happens to be the most extream, as this car is primarily used as a track car and ALWAYS runs pump fuel.
I think everyone here knows that air heats when compressed, and we know that higher intake air temps can be a cuase for detonation. That is why the tune is important. If the motor is not knocking, there ins't going to any damage to the piston or the combustion chamber. Again, this is why the tune is important.
Of course there are limits, but you can kill a motor very easily at 1.0 bar with a bad tune. Does that mean that 14psi is too much for pump gas? I don't think so either.
Compression loads can damage the chamber, but I'm splitting hairs -- I get your point. And it's fair.
The elephant in the room is why didn't Porsche make the boost 19 PSI? There's an obvious quick answer: because the car had to be made for all conditions and every idiot owner imaginable. True. But we are talking about nearly doubling the factory boost. What do we know that their Ph.Ds with billions of dollars in R&D do not?
As Tony rightly mentioned, you can control pressure by retarding the timing. Pressure is pressure, no argument here. But, of course, the timing retard assumes a knock. I respectfully assert that there are two problems with this method. The first is obvious -- the car must knock first.
Second, and I believe far more problematic and illusive issue, is the engine's ability to reliably detect knock. Tony knows this, but for the benefit of everyone else, factory ECUs determine knocks by frequency. There are piezo-electric sensors in the block that measure the vibrations in the block. The ECU preforms a fast Fourier transform that looks for specific knock harmonic frequencies. These specific knock frequencies were determined at the factory by, you guessed it, knocking the engine.
As those familiar with harmonic resonance will appreciate, small changes in mass/shape can dampen or accentuate resonant frequencies. Thus, changes to the engine can change the knock harmonics. The degree to which this occurs depends on the engine and how waves propagate through the block and engines attachments/accessories. For most, this change may be negligible if not irrelevant. However, if the dampening of an engine is drastically changed, e.g. a lightened flywheel, these changes have been known to dramatically alter harmonics in some engines.
My point? Your mileage may vary. I think that it's dicey to rely on an ECU to always save the day. By running lower boost at a proper AFR, your ECU need not retard timing to save your pistons. And, for at least the reasons detailed above, that's not a fail safe that I feel is always consistent.
This car has run for 2 years and 20k+ at 1.3 bar+ ... Less then 1% leakage across the board on the engine. It has been tracked with 91 octane numerous times. About half way through that time period, water injection was added and the boost was raised even more.
Its important to note that much of that 20k is track mileage.
BTW - We easily have 5 more stories similar to this one...this happens to be the most extream, as this car is primarily used as a track car and ALWAYS runs pump fuel.
Tony,
Kick ass car.
What do you mean 1% leakage? Is that across the cylinders or total leak? I'd assume across the cylinders or that'd be one insanely tight engine.
Feel free to put the 1 bar sissy tune on mine. I'm hoping to order next week. Then I'm going to do fuel and run C16 24/7, at which point we'll eliminate the boost control.
At issue here is the potential for elevated EGT when still burning fuel exits the exhaust port having been ignited late in order to not spike cylinder pressures. Firing late causes the pressure to have to chase after the piston and could still be going when a valve opens. Tony doesn't seem to think this is an issue, his tune is on my car and I'm comfortable with it. The pressures run on my car, when the B/C works, are not so different from what I ran on my previous car. I've known guys who have taken this to extremes on other platforms and indeed they made power despite many screaming it was crazy <shrug> Those pressure levels were FAR higher than what Tony is speaking of here.
As for borescoping etc. - come on, just check the plugs for starters. This is like asking Tony to tear down a motor to check for corrosion after running meth despite it's use being just fine in many other platforms. Don't trust that what he is doing is sound then don't do it but if he, with experience at this, says it's okay then maybe bring evidence to the contrary rather than asking him to prove himself.
As for leaning on the knock sensor - I was recently having a discussion with someone that actually brought this out. Seems a tuner here told them that their tuning "detected race gas" and would raise octane to compensate and get more power. Huh?! In other words, they lean on the knock sensor, broaden it's range to advance timing, and if they don't see knock they advance. As pointed out here knock sensors detect KNOCK after the fact. So these guys are likely advancing timing, seeing knock, and falling back pretty regularly. If someone thinks they are doing something different I'm all ears but while there may be an alcohol sensor to my knowledge there's NO "octane sensor". That is the sort of tuning that worries me, Tony tuning for pump gas and "high" boost at 1.3 doesn't. Honestly I actually find it amusing that 1.3 is somehow considered high at all - I am used to 2BAR+ on race gas in Supra. (lol) I do happen to recall one Supra who's owner tuned a bunch of piggybacks attached to the OEM ECU. He was making pretty good power till one day his knock sensor FAILED. He found out quickly just how much he had been leaning on that specific sensor when he blew his motor. Given a choice I'd prefer timing that didn't lean on the knock sensor like a crutch...
. Exactly why I can comfortably say 1.3-1.4 with a proper tune isnt too much for pump gas.
) take can be found here:
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