Gear ratios for FI
Thread Starter
Joined: Oct 2007
Posts: 604
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From: Gainesville FL
Gear ratios for FI What are u all running rear gear wise with a t56 and a centrifugal ssupercharger ? What are your trap speed and mph ? What is your hp and tq . Debating on changing out my 4.11s out of my S60 rear to gain some traction .
I ran 4:10's & changed out to 3:42's . I like it. 1st gear is still useless but I now get traction if I roll into second. It holds pretty well.
I never tracked it so no trap time. We toned it back so now I'm at 780 / 770 TQ. I can say that when it hits about 650 lbs TQ ( 3700 rpm) its a crap shoot of whether or not its going to get sketchy in second gear ( a little pedal & back in the action) . Third gear is good to go once the tires are heated up.
What I immediately noticed was that the violent hit & rise of the RPM range ( which would blow off the tires) was tamed. The lower gears allow for me to stretch out the TQ range for a bit longer time frame. A nice steady pull was the result.
Note: My suspension is stiff & low. I'm sure all the traction issues can be mitigated with enough travel & spring rate. Presently sitting on R888R 315's
I never tracked it so no trap time. We toned it back so now I'm at 780 / 770 TQ. I can say that when it hits about 650 lbs TQ ( 3700 rpm) its a crap shoot of whether or not its going to get sketchy in second gear ( a little pedal & back in the action) . Third gear is good to go once the tires are heated up.
What I immediately noticed was that the violent hit & rise of the RPM range ( which would blow off the tires) was tamed. The lower gears allow for me to stretch out the TQ range for a bit longer time frame. A nice steady pull was the result.
Note: My suspension is stiff & low. I'm sure all the traction issues can be mitigated with enough travel & spring rate. Presently sitting on R888R 315's
Hey Chris, I would probably reach out to Bob @ Brute. If you talk to him I'm pretty sure he can take you in the right direction. He originally told me to go with 3.90 gears; however, I have a S-60 strac and that gear ratio is not available. Therefore; I went with 3.73 and I have been very happy. I'm using 28" rear tires to help. Car is somewhere in the 600's. No track data yet.
Blowers aren't load dependent just RPM so just go to an online calculator for trap speed and gear ratios and RPM. Spec a gear ratio that puts you crossing the finishing line in the gear of your choice at max RPM.
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Joined: Nov 2003
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From: Norn Iron
4.11 is very short.
More importantly than what others have...is what do you have ? what power, what sort of rpm's ? overall gearing/tyre size ? What trap speed do you anticipate for the track, if that's your intended usage ?
More importantly than what others have...is what do you have ? what power, what sort of rpm's ? overall gearing/tyre size ? What trap speed do you anticipate for the track, if that's your intended usage ?
Thread Starter
Joined: Oct 2007
Posts: 604
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From: Gainesville FL
I have a built 408 with a novi 2200x . It has a built tr6060 out of a 15 ZL1 in a t56 housing and tail shaft for a fbody . The tear end is a S60 with 4.10 or 4.11 with a spool with a set of toyos 305 35 18 .
9 Second Club
Joined: Nov 2003
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From: Norn Iron
I'd say something in the 3.5-3.6 range would be a good starting point. Certainly nothing shorter than that. That should easily see 150+ at say 7k in 4th.
Although a brief look online seems to suggest tallest available for an S60 is 3.54...so that's the only realistic option
Although a brief look online seems to suggest tallest available for an S60 is 3.54...so that's the only realistic option
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On The Tree
Joined: Dec 2011
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From: Houston Tx
My Procharged c5z got faster at the track going from 342 to 390. As long as traction is there and it doesn't make you have to grab another shift....you damn near always go faster with a steeper gear. For roll racing it is really hard for someone to catch you in a bad spot too.
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I understand people say that but it makes no sense to me. If you do not have a load on a turbo because the numerical gear is too high, it is because the throttle is not fully open because you are blowing the rear tires off so it makes sense to get a shallower gear to help with top end and can help with traction at the start and can reduce the number of gear changes required if you are drag racing.
I understand people say that but it makes no sense to me. If you do not have a load on a turbo because the numerical gear is too high, it is because the throttle is not fully open because you are blowing the rear tires off so it makes sense to get a shallower gear to help with top end and can help with traction at the start and can reduce the number of gear changes required if you are drag racing.