6 cylinders & 2 turbos, for now

[Matt D.]

The higher the compression, the smaller the "tuning window".
Meaning closer to the edge between being awesome and turning the engine into a pile of shrapnel.But is that still very true with e85?
I would assume so. E85 allows for more potential but the gap between a safe tune and dangerous tune is still narrowed because of the increased compression.

[Halon]

I agree with all the above statements, which is why I say higher compression is your friend "to a point".

My thoughts that I'll put out there one last time and leave it at that:

- Your stock compression ration is 8.5:1 (designed to run on premium). You are going to be running 9.5:1 (one more than stock, appx .5 more than a stock evo) and running E85. This isn't some new groundbreaking ungodly setup.

- How many 6-bolts are out there running greater than stock compression on e85, and what percentage of those turn to shrapnyl with the main cause being slightly higher CR?

- You'll have a full standalone with full control over ignition timing advance, and Shane tuning it. He can take a crap on the dyno, and find a way to hook up his Ostrich emulator to it, and tune it and make 500hp!

[Shane@DBPerformance]

ut there running greater than stock compression on e85, and what percentage of those turn to shrapnyl with the main cause being slightly higher CR?


This happened and still does happen a lot when guys put 2G piston or similar compression pistons into a 1G and then try to run the kind of timing a stock 1G ECU does with 7.8:1 compression and maps meant for 12psi of boost.

Just because an RSX or S2000 or Audi or Evo motor can run it's higher compression with boost doesn't mean it is quite as easy with some old tech/shitty headed DSM or Supra. It's definitely possible and doable, but don't expect to be able to run as much boost as a lower compression car can on the same gas. Read that last line again, and then also realize that just because someone else on the interwebz has done it doesn't mean your setup will or that you can duplicate what someone else who is an expert at it and has tried all kinds of exotic setup has done. Yes, you can and will run less ignition timing on a boosted higher compression motor to avoid detonation, but you often get to the point where you have to pull so much timing that the gains are not there with more boost, or where you actually make more power at less boost with more timing.

Most people, not all though, run less boost on high compression setups. You will make more power with less boost though with higher compression. If your gas is not limiting you then it is definitely beneficial to run more compression. Higher compression is most useful for guys trying to set record with a limited turbo. Say you want to make the Evo 8 stock turbo HP record and you know that you can't run enough boost or add enough timing to max out the octane on E85 or E98 or whatever, then it can help quite a bit to bump that compression up to 10:1 or whatever and run the same maxed out boost as before but make more power. It is also a power gainer for guys who are limited to a specific size compressor inducer size or restrictor in drag classes or rally racing, any time the turbo is maxes or limited in some way. Guys who want better throttle response out of boost like for street driving or autox also often run higher compression. Higher compression does not spool a turbo faster though.

If you have a turbo/setup that is very efficient and can run high boost AND you are octane limited by your fuel, then you often can make more power with less compression, just because of being able to run a lot more boost while still maintaining a decent amount of timing advance. There are so many variables though that go into each setup that it can be hard to predict how each car will respond. Little things like exhaust housing size can start to become a major factor in knock resistance when you start try to push a fuel or run high boost levels. Usually every month I get a car or two for tuning with a setup that just doesn't work. We can't run the boost they want because something is making it too prone to knock and if we pull out enough timing to make it not knock, then it either makes the car misfire from too little timing or just doesn't make any power. That's life, engines are not like computers, they don't do the exact same thing with exactly the same parts.

In the NA-T thread, I have personally done something that they THINK won't work. I have gone from the 1.3mm stock TT headgasket in an NA 2JZ to a thicker Cometic HG because we were not able to make the power the customer wanted due to excessive knock. The car had an AEM EMS on it, so we were able to fully control timing. With the decently thicker HG were were able to run more boost, run more timing and make more power. It was also a road race car, and you need usually need to run a decent amount of timing with a rich A/F and keep your boost under control on a road race car. If you try to pull even a moderate amount of timing, like you can on a street or drag car, then you run this risk of melting the turbo. This is a 3mm HG http://www.inlinepro.com/s1/p-52-inlinepro-headgaskets.aspx
that is commonly used in the S2000 motor to drop the compression down ALOT for boost applications. Its massively thick, weighs a surprising amount and it works perfectly.


Anywho, 9.5:1 should be fine, just don't expect to run 40psi with it on E70.

[tpunx99GSX]

This happened and still does happen a lot when guys put 2G piston or similar compression pistons into a 1G and then try to run the kind of timing a stock 1G ECU does with 7.8:1 compression and maps meant for 12psi of boost.

Just because an RSX or S2000 or Audi or Evo motor can run it's higher compression with boost doesn't mean it is quite as easy with some old tech/shitty headed DSM or Supra. It's definitely possible and doable, but don't expect to be able to run as much boost as a lower compression car can on the same gas. Read that last line again, and then also realize that just because someone else on the interwebz has done it doesn't mean your setup will or that you can duplicate what someone else who is an expert at it and has tried all kinds of exotic setup has done. Yes, you can and will run less ignition timing on a boosted higher compression motor to avoid detonation, but you often get to the point where you have to pull so much timing that the gains are not there with more boost, or where you actually make more power at less boost with more timing.

Most people, not all though, run less boost on high compression setups. You will make more power with less boost though with higher compression. If your gas is not limiting you then it is definitely beneficial to run more compression. Higher compression is most useful for guys trying to set record with a limited turbo. Say you want to make the Evo 8 stock turbo HP record and you know that you can't run enough boost or add enough timing to max out the octane on E85 or E98 or whatever, then it can help quite a bit to bump that compression up to 10:1 or whatever and run the same maxed out boost as before but make more power. It is also a power gainer for guys who are limited to a specific size compressor inducer size or restrictor in drag classes or rally racing, any time the turbo is maxes or limited in some way. Guys who want better throttle response out of boost like for street driving or autox also often run higher compression. Higher compression does not spool a turbo faster though.

If you have a turbo/setup that is very efficient and can run high boost AND you are octane limited by your fuel, then you often can make more power with less compression, just because of being able to run a lot more boost while still maintaining a decent amount of timing advance. There are so many variables though that go into each setup that it can be hard to predict how each car will respond. Little things like exhaust housing size can start to become a major factor in knock resistance when you start try to push a fuel or run high boost levels. Usually every month I get a car or two for tuning with a setup that just doesn't work. We can't run the boost they want because something is making it too prone to knock and if we pull out enough timing to make it not knock, then it either makes the car misfire from too little timing or just doesn't make any power. That's life, engines are not like computers, they don't do the exact same thing with exactly the same parts.

In the NA-T thread, I have personally done something that they THINK won't work. I have gone from the 1.3mm stock TT headgasket in an NA 2JZ to a thicker Cometic HG because we were not able to make the power the customer wanted due to excessive knock. The car had an AEM EMS on it, so we were able to fully control timing. With the decently thicker HG were were able to run more boost, run more timing and make more power. It was also a road race car, and you need usually need to run a decent amount of timing with a rich A/F and keep your boost under control on a road race car. If you try to pull even a moderate amount of timing, like you can on a street or drag car, then you run this risk of melting the turbo. This is a 3mm HG http://www.inlinepro.com/s1/p-52-inlinepro-headgaskets.aspx
that is commonly used in the S2000 motor to drop the compression down ALOT for boost applications. Its massively thick, weighs a surprising amount and it works perfectly.


Anywho, 9.5:1 should be fine, just don't expect to run 40psi with it on E70.

Im pretty sure this is shanes longest post EVER.

[cmspaz]

Im pretty sure this is shanes longest post EVER.
I dunno, he had a pretty long drunk post from Brainerd this past summer...

[95talonracer]

No 40psi here. I just want to have a good street/strip car with better acceleration in and out of boost with a 6765 .96 housing billet turbo. I am guessing my choice of parts will work and I have been reading alot to make sure the parts I get will match what I want out of the car for power and drivability. Shane do you feel that coating the tops of the pistons and aftermarket better design valves will help with knock or being able to make better/safer power vs. stock head?

[Fran05]

I <3 Shane. He actually takes his time to explain things, his hard work gained knowledge with us. It is rare these days.

[Halon]

Definitely good info! Thanks for sharing Shane. My experience is very limited with this platform so all I can go off is what I read at this point. So the more I hear from the experts the more I learn! Thanks :)

[95talonracer]

Piston coating is done! Photos to be up tonight unless MAP beats me to it.

[goodhart]

I watched those videos on the Pro EFI you were telling me about on Sunday. The ones with the traction control and the flex fuel capabilities, that looks like one sweet tuning system. I can't wait to see this thing run now!