question on the relationship of torque and gear ratios to accelleration

[NSX_GTR_LM]

Is it a linear relationship for both? Here are a few examples.

If you double the final drive ratio, does your accelleration double in every gear?

Likewise, if you had double the torque and the same stock gear ratios, does that double your accelleration in every gear? Just trying to make a relationship to map shift points, thanx in advance.

[Griffin]

Gear reduction functions like a standard lever. If you have 2:1 reduction you will divide output RPMs by 2 and double torque by 2 (minus negligible losses for the gears themselves). So if in theory you double your gear ratio from 1:1 to 2:1 you would have twice the available power and half the available rotational speed. The problem is that this doesn't totally transfer to end result of doubling acceleration. The reason for this is mainly inadequate traction. The other problem is that this cuts the duration of your power band in half, and any time you make up will probably be lost again in the process of shifting. All in all the art of matchign gearing to drivign conditions is almost as much trial and error as brute science.

Griffin

[NSX_GTR_LM]

thanx for the confirmation. So basically a car that has twice the torque of another car, but the other one revs twice as high (hypothetically assuming the same dyno, just one is increased by magnitude) and are geared to top out at the same speed in each gear, they will be making identical power and should theoretically tie. I guess what I am asking is which is more efficient.

[t2000gts]

Originally posted by NSX_GTR_LM
thanx for the confirmation. So basically a car that has twice the torque of another car, but the other one revs twice as high (hypothetically assuming the same dyno, just one is increased by magnitude) and are geared to top out at the same speed in each gear, they will be making identical power and should theoretically tie. I guess what I am asking is which is more efficient.

well horsepower plays a definite role in how fast the car "revs".

two cars with same torque, geared for same mph/rpm in the same gears, but one has more hp, the one with more hp will start to walk away after they both get going.

as for the two examples, it really depends on if the torquey car makes good horsepower at the higher part of it's powerband, and the non-torquey car makes as much torque as it can while it's horsepower is peaking. in your example. they would be close, but i don't think they'd ever be 'even', one would always be pulling on the other, except they would alternate at every shift (torquey car pulls ahead at first, but the high rpm car shifts sooner, and spins its' wheels to a faster mph, won't let the other one get away)

[NSX_GTR_LM]

Originally posted by t2000gts


well horsepower plays a definite role in how fast the car "revs".

two cars with same torque, geared for same mph/rpm in the same gears, but one has more hp, the one with more hp will start to walk away after they both get going.

as for the two examples, it really depends on if the torquey car makes good horsepower at the higher part of it's powerband, and the non-torquey car makes as much torque as it can while it's horsepower is peaking. in your example. they would be close, but i don't think they'd ever be 'even', one would always be pulling on the other, except they would alternate at every shift (torquey car pulls ahead at first, but the high rpm car shifts sooner, and spins its' wheels to a faster mph, won't let the other one get away)

in my example, i meant similar torque curves (similar in the math sense that one is mearly a full magnitude to scale drawing of the other) so that both cars would have their peaks and valleys at the same SPEED (not rpm, since one revs twice as high as the other). I think I have solved the problem for myself, but if you guys want to add any more, please do. I am very open to learning more about this sheit.

[Chui]

"thanx for the confirmation. So basically a car that has twice the torque of another car, but the other one revs twice as high (hypothetically assuming the same dyno, just one is increased by magnitude) and are geared to top out at the same speed in each gear, they will be making identical power and should theoretically tie. I guess what I am asking is which is more efficient."

Depends on how you wish to define "efficiency". At one extreme we have the Ferrari 360 Modena, Honda S2000 and Honda Integra Type R. At the other end of the spectrum we have the GM Corvette Z06 and Dodge Viper.

If you're after a small, lightweight pkg then the small displacement, DOHC, VVT is the way to go. If you have no such restraints then the lower revving [better vehicle fuel economy] torquey engine is the way to go.

By the fact that we're owners of small, lightweight FF Platform cars I know which one you/I prefer... Besides, it requires skills at shifting to drive so there's more driver involvement if that means anything to you.