*READ* Gear Ratios, Final Drives, and Torque
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 integra 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)
Gaining power with a different transmission? They didn't teach us that at Import Tuner magazine school. This will of course not be shown on a dyno because they take the RPM signal and roller speed to correct down to a 1:1 ratio to get a clean measurement.
Here is a dyno chart comparing the torque curves of the 3 main stock Integra motors. Pretty much shows what we all know right? LS has the most low end power while the Type R has the most high end power and the GS-R is the middle ground.
This next chart compares the absolute gear ratios of each of the stock Integra transmissions.
Now look at the torque curves again with the torque multiplication of the gear ratios factored in. This example was corrected for 3rd gear, each gear would space the curves differently depending on the multiplication factors but 3rd gear shows a good average. Tells a very different story now doesn't it?
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 (~$450). 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.
Now look at what it does to the torque curve in 3rd gear for the GS-R, putting it much closer to the stock Type R.
The 4.785 final drive gives the GS-R a solid 58 lbs-ft torque gain throughout the powerband in 3rd gear for the GS-R.
Now put speed into the equation, and see the difference the final drive plays throughout the entire range of acceleration
I hope this has been an informative and helpful post! There's a lot more to our cars than intakes and exhausts...
From www.team-integra.net
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