9.4 Rotors in TII
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Joined: Sep 2002
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From: Pittsburgh,PA
9.4 Rotors in TII
Has anyone put 9.4 rotors in a TII, basically to make a cosmo motor, but not having to screw with the engine mounts or buying the block.
I have just beeing thinking about it while pulling my engine. Most engines die becuase of to much air and not enough fuel (detenation). But what about leaving the boost at almost stock levels, 5.5-8psi and use 9.4CR rotors. Although it might create aliitle more stress than running the same boost with 8.5CR or 9.0CR rotors, but nothing compared to running 12-15psi on the 8.5 or9.0 rotors...
Hmmmmm.....
I have just beeing thinking about it while pulling my engine. Most engines die becuase of to much air and not enough fuel (detenation). But what about leaving the boost at almost stock levels, 5.5-8psi and use 9.4CR rotors. Although it might create aliitle more stress than running the same boost with 8.5CR or 9.0CR rotors, but nothing compared to running 12-15psi on the 8.5 or9.0 rotors...
Hmmmmm.....
i had that thought too
i thought high compression + low boost = wide power band = good, but i am wrong
after i searched for a while i found out that was actually not a good idea
a couple people did that (may be more) : Bambam7 , kevin lander had that in his turbo vert ...
but if you do it , it has to boost at LOW psi, anything higher than ... 8 = good luck
may be you can get away if u got water injection
i thought high compression + low boost = wide power band = good, but i am wrong
after i searched for a while i found out that was actually not a good idea
a couple people did that (may be more) : Bambam7 , kevin lander had that in his turbo vert ...
but if you do it , it has to boost at LOW psi, anything higher than ... 8 = good luck
may be you can get away if u got water injection
Rotary Enthusiast
Joined: Dec 2002
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From: Darwin, NT, Australia
With the right tuning and a cool intake charge there is no reason you can't run MUCH higher boost than 8psi..
Hell even I was driving around with mine (9.4:1 rotors) at 10psi for about a week without probs.. that is on a stock S4 fuel system(with a microtech that wasnt tuned).
The difference in detonation potential between 9.4:1 and 9:1 rotors isnt that great at all, the difference between a stock TMIC and a half decent FMIC would give you a greater potential of detonation.
Hell even I was driving around with mine (9.4:1 rotors) at 10psi for about a week without probs.. that is on a stock S4 fuel system(with a microtech that wasnt tuned).
The difference in detonation potential between 9.4:1 and 9:1 rotors isnt that great at all, the difference between a stock TMIC and a half decent FMIC would give you a greater potential of detonation.
Thread Starter
Joined: Sep 2002
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From: Pittsburgh,PA
The cosmo engine has 9.0 rotors and much bigger ports.
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Banned. I got OWNED!!!
Joined: Jul 2001
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From: usa
I've done it before, and Im doing it now with my hybrid turbo motor in the convertible.
I used GSLSE rotors in the build, with 87 turbo irons and housings (massive streetport) and 89+ turbo externals, except 87 crappy turbo and manifold.
I had a couple guys suggest the SE rotors to me in the past, and I never gave it much thought. But, the more I thought about it, it made sense.
1) theyre already set up for 3mm seals, so no milling cost. I had several good stock corner seals around, and apex springs, and 3mm seals cost the same as 2mm seals, so the upgrade was basically free.
2) they're heavier. Not heavy enough to hurt the revving ability of the motor, or affect my redline (turbo engines are set up to run between 7-8k). But, heavy enough to give more torque and a better idle ability. Easier to get the heavy vert moving off the line, even when not racing. There is something to be said for letting the clutch out below 1000 rpm and having the engine not bog.
3) s5 and later turbo engines used 9.0:1 compression, and 9.4:1 isnt much more of a stretch. Keep the boost the same as you would an equally modified turbo II, run 93 octane at all times, add a walbro and set of secondary injectors, and you're good to go. I've taken mine to 15lb so far (rb exhaust, non ported s4 wastegate, custom intake/tid, big port) with no sign of detonation or lean conditions. The bitch is running real rich as a matter of fact, Ive been getting <15mpg on the HIGHWAY. Gotta pay to play though, so you wont hear me bitching.
4) NA 9.4 rotors are cheap and readily available, whether you decide to run SE or s4 rotors.
I used GSLSE rotors in the build, with 87 turbo irons and housings (massive streetport) and 89+ turbo externals, except 87 crappy turbo and manifold.
I had a couple guys suggest the SE rotors to me in the past, and I never gave it much thought. But, the more I thought about it, it made sense.
1) theyre already set up for 3mm seals, so no milling cost. I had several good stock corner seals around, and apex springs, and 3mm seals cost the same as 2mm seals, so the upgrade was basically free.
2) they're heavier. Not heavy enough to hurt the revving ability of the motor, or affect my redline (turbo engines are set up to run between 7-8k). But, heavy enough to give more torque and a better idle ability. Easier to get the heavy vert moving off the line, even when not racing. There is something to be said for letting the clutch out below 1000 rpm and having the engine not bog.
3) s5 and later turbo engines used 9.0:1 compression, and 9.4:1 isnt much more of a stretch. Keep the boost the same as you would an equally modified turbo II, run 93 octane at all times, add a walbro and set of secondary injectors, and you're good to go. I've taken mine to 15lb so far (rb exhaust, non ported s4 wastegate, custom intake/tid, big port) with no sign of detonation or lean conditions. The bitch is running real rich as a matter of fact, Ive been getting <15mpg on the HIGHWAY. Gotta pay to play though, so you wont hear me bitching.
4) NA 9.4 rotors are cheap and readily available, whether you decide to run SE or s4 rotors.
MMR bitch
Joined: Jan 2003
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From: Cookeville, TN
Originally posted by White_FC
That is just so incredibly wrong it is nearly funny.
That is just so incredibly wrong it is nearly funny.
The big difference tuning wise between using higher or lower compression rotors is going to be in the mount of timing advance used for each compression ratio. The lower the compression ratio the more timing you can run in relation to the higher compression engine at the same amount of boost. You will come to a certain point in the horsepower game where the timing retard will be so much on the high compression engine that the low compression engine is making more power at the same amount of boost. This point is still somewhere above 400 hp though. There is also more room for tuning error on the lower compression engine. You can't necessarily say that you are limited to only so much psi for any given ratio. It all depends on the tuning, how efficient your intercooler setup is, octane gas used, etc. Many variables. If you are just looking for 400 or so at the wheels then I say use whatever rotors you like. Just tune it properly. Nothing wrong with the 8.5:1 though but lowend drivability suffers a little.
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From: Darwin, NT, Australia
Thank you for taking the time to dig that up, I will agree with him that there is more headroom for tunning problems with lower comp rotors, but I will definatly disagree with the 400hp remark.
Thats my opinion, i've been known to be wrong all the time though.
Thats my opinion, i've been known to be wrong all the time though.
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