Gearing Explained

Gearing plays a much bigger
role in your car's performance than most people realize. Everyone
focuses on engine horsepower (peak horsepower at that) and never really
pays attention to what gearing can do for your motor. In alot of cases,
proper gearing will effect your car's accelerational ability much
better than any bolt-on motor modification can.

Why do
cars have gears? The major and often overlooked reason is torque
multiplication. Most people don't even think about this yet it's one of
the most important aspects of making your car go faster with better
gearing.

How much torque does a stock GS-R motor put to
the ground? About 110 lbs-ft max (estimation). Think of how much force
that is. If you have enough leverage you can torque 110lbs-ft on a
torque wrench by yourself with your arms. Can you move a car by
yourself using that much force? Sure you can, but it's not going to
move very fast and it's going to put a heck of a lot of stress on your
body.

Your motor is the same way. You could have a silly
drag race of two guys pushing one car and another other car that was
being powered by it's 110 lbs-ft motor and 1:1 absolute gear ratio and
the car that was being pushed would win.

So how do we
make a car that has a motor putting out such weak torque faster? That's
when gears come in. Gears will multiply the torque by certain factors
depending on their size/teeth count. Take a GS-R in first gear (3.23),
when the motor spins 3.23 times, the driveshaft will turn once. And for
every 4.4 turns of the driveshaft, the differential (final drive, 4.4)
will turn once. That is directly connected to the axles which turn the
wheels. You can simply multiply 3.23*4.4 to get an absolute gear ratio
of 14.212:1. This means for every 14.212 turns of the motor the wheels
will turn once. So if the motor gets to turn 14.212 times in order to
only turn the wheels once, the amount of torque the motor is applying
to the wheels gets multiplied that many times.

Multiply
it out, 14.212 * 110 lbs-ft = 1,563 lbs-ft of torque to the wheels. Now
does that look better? Yes I think we can accelerate a car decently
with that amount of torque.

Different gearing then would
have obvious affects on your torque output. Take 3rd gear in a GS-R,
and put different trannies on it.

Stock GS-R at 110 lbs-ft max torque in 3rd gear.

Applied torque to the wheels:

GS-R tranny, 1.36*4.4*110= 658 lbs-ft

LS tranny, 1.269*4.266*110= 595 lbs-ft (63 lbs-ft power loss)

Type R tranny, 1.458*4.4*110= 706 lbs-ft (48 lbs-ft power gain)


The final drive modification

A cost effective and completely painless upgrade for both a GS-R and Type
R would be to install the JDM ITR 4.785 final drive kit. There
are of course even shorter final drive kits so it will depend on your
budget and how short you really want your gears to be. But the 4.785
will put the GS-R at a very close level to the stock ITR gearing, as
you can see from this chart comparing their absolute gear ratios.

Ya the gears play really important role in the car's performance.Thanks for the details.



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