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Originally posted by VTEC_boi
[b]But, question:
If a turbo Honda motor (say a B18C1 running moderate boost - 16psi) is still 'peaky' - y does tall-gearing have a positive affect? Since the motor still makes it's power in high RPM?
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Short gearing = large overall ratio = higher torque multiplication = better acceleration = worse top speed
Tall gearing aka Long gearing = small overall ratio = lower torque multiplication = worse acceleration = better top speed
This is true no matter what type of engine (1,2, or 3) you have.
But it does break down at two extreme points - 1) top speed - where aerodynamic drag is the limiting factor, there is no point in having more gear for a speed you cannot reach, so get a slightly shorter gear. 2) acceleration - where traction is a limiting factor, there is no point in having low gearing for torque that you can't put to the ground, so get a slightly taller gear.
For a drag car, it's generally pretty easy to calculate a good final drive ratio. If you want to cross the line at the top of fourth gear, estimate the speed you'll be going (say 130mph), then calculate what final drive ratio will have your car moving at 130 mph in fourth gear at redline. Then you'll have the tallest gear (most torque multiplication = best acceleration) possible that still won't limit the top speed you need to reach.
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Also, can you explain final drive ratios a little more in depth? Like, y does the USDM Integra Type-R have a 'bad' final drive?
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Final drive is just what every single transmission gear is multiplied by. You can adjust the entire range of the transmission just by adjusting the final drive. That's usually much faster, cheaper, and simpler than re-doing every single transmission gear. I haven't heard that the ITR has a 'bad' final drive. If so, is it either too short (good acceleration, poor top speed) or too tall (poor acceleration, good top speed)?
**edited 2:10p 12/7/01 - I had foolishly swapped 'tall' and 'short' - they are now correct! Thanks to texan**