i have an 87 mk3, 7mge, and right now it is running 12:1 compression would it be a bad idea to turbo it at some point? and how hard would it be?
12:1 compression bad idea for boost?
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12:1? First off, what kind of fuel are you running to support that kind of compression. Did you or someone else have that motor built? If so what kind of pistons? To answer your question, no. With a cr that high you would be out of your mind to even attempt to cram boost into the system. That cr would have to come waaayy down, if your compression is truely that high.
I could see 10.5:1 but 12:1 seems a bit much for boost. Your going to be doing more damage than good to that engine man if you dont have your tune down to the molecule basically. Id say do not boost it. And make sure it is infact 12:1
i bought it off of a guy and he just had the motor rebuilt by a shop in Akron and he told me it was running 12:1 compression and i am wanting to bring it down so i can boost it. i couldn't tell you what fuel he has been running in it i am still waiting on it to get back from the shop from having the valves re-adjusted.
Wouldn't be unheard of, but you don't see many Supra engines with compression ratios that high. If you had direct injection, I see nothing wrong with high CR and boost, but on our engines? I'd be a little wary.
However... what is your compression ratio when you're cramming 12-15psi into the engine? Someone correct me if I'm wrong here, but wouldn't your compression ratio be higher because of boost, above and beyond what your static compression is?
However... what is your compression ratio when you're cramming 12-15psi into the engine? Someone correct me if I'm wrong here, but wouldn't your compression ratio be higher because of boost, above and beyond what your static compression is?
Well, I calculate an effective compression ratio at 15 PSI boost (Which most people think is fairly safe on a reasonably built 7M-GTE with pump gas) of about 17:1 (16.9something)
I get about the same (Or a smidgen lower) effective compression ratio calculated for 6PSI on 12:1 static compression, so that could probably be managed on pump gas.
I had worked it out before that if you started with a stock 7M-GE bottom end, with 9.2:1 compression you could run 12 lbs of boost (Like, the limits of the CT-26) on premium pump gas and should not have detonation problems, provided adequate fuel delivery.
Edit: Before doing ANYTHING though, be absolutely sure of what you've got. 12:1 would require custom pistons at the very least.
I get about the same (Or a smidgen lower) effective compression ratio calculated for 6PSI on 12:1 static compression, so that could probably be managed on pump gas.
I had worked it out before that if you started with a stock 7M-GE bottom end, with 9.2:1 compression you could run 12 lbs of boost (Like, the limits of the CT-26) on premium pump gas and should not have detonation problems, provided adequate fuel delivery.
Edit: Before doing ANYTHING though, be absolutely sure of what you've got. 12:1 would require custom pistons at the very least.
Its simple .....running boost with that kind of compression is infeasible. Definitely verify that compression.
Here's my thought on the subject:
-Lower CR requires more boost to make XXX hp.
-Higher CR requires less boost to make same hp level.
Which one of these two is going to have better response, spool time, and power curve? If anyone can steer me in another direction if my thoughts are off base, let me know, because the idea seems perfectly feasible to me. Worst case scenario, run some water-methanol mixture...
-Lower CR requires more boost to make XXX hp.
-Higher CR requires less boost to make same hp level.
Which one of these two is going to have better response, spool time, and power curve? If anyone can steer me in another direction if my thoughts are off base, let me know, because the idea seems perfectly feasible to me. Worst case scenario, run some water-methanol mixture...
Nick M;1837931 said:
But not pump gas, I believe that mixture is about 85% Toluene.
http://en.wikipedia.org/wiki/Toluene
"Toluene at 86% by volume fueled all the turbo Formula 1 teams in the 1980s, first pioneered by the Honda team. The remaining 14% was a "filler" of n-heptane, to reduce the octane to meet Formula 1 fuel restrictions."
I doubt very much you're actually running 12:1. Very, very much.
How does that shop claim to have achieved that level of compression?
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How does that shop claim to have achieved that level of compression?
Sent from my ADR6400L using Tapatalk 2
te72;1837886 said:
Good point, I have 10.5 cr pistons and my compression reads 190, I believe that is close to 11.0 and I've been toying with the idea of turboing it for a few years now.
I thought I'd probably have to change the headgasket to drop compression some, still might be a good idea.
2jz88mk3;1838001 said:
Of course it isn't. The engine had to last 500 miles or so. Gas has too much thermal energy and lights very easy.
Hi Comp/Low boost makes for a very drivable package in a street car but you'll always be fuel/knock limited, that and you need to pull timing to make it survive thus lowering the HP potential, modern engines have active knock sensing and can mix and match a couple of predefined knock tables to find a happy medium (think MoTeC SKM built it)
The guy i bought it off of told me 12:1 compression and to run it on 93 fuel. I just feel like that is going to be a bad idea if i even try to boost it.
So, run as high of octane as you can afford, and set it up to inject the water/methanol at anything over say... 5-8psi? Sounds like it would be a blast on the street...IJ.;1838019 said:
Guy I bought my car from said it had 1200hp and was powered by unicorn farts. Guess you can't believe everything someone selling you a car tells you, huh? :nono:Function>Form;1838583 said:
Get a compression tester and learn to use it (search on here, I know it's been asked before), let us know the results!
