#11279, "RE: best compression for turbo?" In response to Reply # 0
The lower the compression, the bigger the combusion chamber. The bigger the combustion chamber, the more air you can cram in there. More air + more fuel = more power.
Perf: KYB AGX Struts Neuspeed Sport Springs 5 Strut Bars (2 F/U, F/L, R/U, R/L) Sprint Front Camber Kit $15 Rear Camber Kit Corbin's A/F Gauge MSD DIS-2 Ignition System Some Regrind Cams that need High Compression (which I don't have) Ported Intake Manifold Ported Throttle Body Nameless Cold Air Intake with a K&N Filter Custom 2 1/2 inch exhaust with Dual DTM Muffler Empty Catalytic Convertor Energy Suspension Motor Mount inserts Hurricane_GS Short Shifter Symborsky Shift Kit Clutchmasters Stage 3 Modular 225/50/16inch Wheels and Tires
Audio: Alpine CD Head Unit Alpine Flex4 25W X 4 for Fronts and Rears Alpine V-12 450W X 1 for Subs Infinity Reference Series 5 1/4 and 1 inch tweeter component systems for fronts and rears Blaupunkt 3 way 6x9's in the rears 3 MTX 5000 10" 12 ohm subs running 4 ohms mono
Flame Red SRT-4 GT40,8.5:1 Built Shortblock, Brian Crower Stage 2 Cams, etc etc etc...
#11281, "RE: best compression for turbo?" In response to Reply # 0
You've hit on a topic that many people have differing opinions on. Higher compression ratios make the turbo spool up faster and give you more off-boost power. I am of the opinion that there comes a point where you can't cram any more boost into a high-compression engine to make more power without having detonation. I believe that you should lower compression at that point if you want to build more power (of course you'll have to cram even more boost in). I think the problem arrives when you try to figure out at what point you have to lower compression ratio to start making more power (with higher boost) while avoiding detonation. I borrowed a textbook from my IC engines professor that is all about turbocharging. After I've read it cover to cover, I'll probably have a more educated opinion. I believe that OEM turbocharged engines have low compression ratios for a reason, not just tradition. It might be to avoid detonation when the bonehead driver puts in 87 octane.
#11282, "RE: best compression for turbo?" In response to Reply # 3
Has anyone here tried using a stand alone engine management system??? I know there was a miata in SCC and turbo a while ago that was pushing 400hp to the wheels on stock internals because he was able to tune the car perfectly with the tec-2
Toney '97 RS 5 Speed (totaled) 15.4606@88.42 Mph 96 Toyota Celica GT 88 Toyota Supra NA-T (w/ sports package) Got Boost?? Hell yeah I-6 turbo powah baby!
#11283, "RE: best compression for turbo?" In response to Reply # 4
I heard that too on a honda/acura site, they were running 27psi and pushing 350+HP on stock internals and how the hell does Stephan Papadakis run turbo on a high compressioned engine??? (and I know he is not low-compressioned)
#11286, "RE: best compression for turbo?" In response to Reply # 7
here's how i see the situation. the 4g63 is low balled at 7.9 prolly for what corbin said. remember this also allows them to get to 400 hp without a rebuild. hahn uses 8.8 in the same motor and car wehave and he's doin low elevens. so the question is what do you want to do with this turbo? if you wanna drag race and go as fast as possible in a straight line than drop the compression to just over 8 like 8.2ish and boost the hell outta it. if you wanna daily driven beast follow brad (super20g) and go 8.6 after all he's pacing and beating corvette's, how's that sound? as for me, i'm prolly gonna follow brad to an extent as far as compression and turbo. think i'm gonna go with an S-AFC instead of the big injectors though. i just love mitsu turbos can't help it. plus i enjoy taking turns so i'm gonna wana be able to stop pretty easy and swing into a turn without having to worry to much about breakin the fronts loose and drifting off the road
#11287, "RE: best compression for turbo?" In response to Reply # 8
that miata was making like 398hp to the rear wheels, thats like 450 to the flywheel with just bolt ons and the EMS. It runs 10 seconds in the quarter mile.
Toney '97 RS 5 Speed (totaled) 15.4606@88.42 Mph 96 Toyota Celica GT 88 Toyota Supra NA-T (w/ sports package) Got Boost?? Hell yeah I-6 turbo powah baby!
#11288, "RE: best compression for turbo?" In response to Reply # 0
Add me to the "Unusual" compression list. I have a 9.5:1 ratio. And no, it isn't a typo, that's a custom 9.5:1 with JE pistons. Why 9.5? I dunno, coz I didn't feel like 9.6:1. And as for pistonm clearance, well I tested my engine and it is still non-interference
Actually I wanted to avoid a lag risk.... I may be going up in life turbo-size wise.
Anyways, as someone noted if OEM turbo cars come 8.8:1 then, an engine can definitely take 9.5:1 I mean OEM specs are usually over-safe for dorks that do stupid stuff like fill the wrong type of gas (As Corbin already pointed out).
Also if you can somehow measure knock, you can ideally go to an insanely high compression as long as you are not harming the engine. Most Turbo 8 and 9 sec drag cars who don't declare their compresion ratios are *definitely* running higher than 9.. (I heard some Honda Unlimited class people run 11:1 with 20+lbs of boost).
As for 400hp on a "well tuned" stock-internal 420A car - sorry. It's not a matter of tuning here, it's a matter of physical capability. The stock internals can't handle it, I believe in this order: Rings, Rods, Pistons... Although any can go at any time (Blame Murphy & the laws of probability for that!) you definitely increase the chances of Major damage at that level.
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