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      04-22-2007, 01:53 PM   #26

Drives: e92 335i
Join Date: Nov 2006
Location: Helsinki

iTrader: (0)

Originally Posted by needforspeed View Post
Frictional resistance (air and road) is obviously a factor and it's effect does increase (roughly) to the square of speed. However, a vehicle will accelerate most when wheel torque is greatest.

If you work out the torque at the wheels (multiplying by gear ratios and final drive ratio) then you will see that it is massively higher in 1st gear than 5th or 6th.

There are several small light vehicles which can accelerate to 60 mph very quickly. They are often powered by high revving engines with relatively low levels of torque.

To continue to accelerate as swiftly in the upper gears you need the ability to generate lots of torque at high revs.
When it comes to how engine affects acceleration, power during the acceleration defines how fast the car accelerates.

You are kind of right saying that one needs torque at high revs. Torque is power multiplied by time. Thus, you need power x time at high revs (revs is measured as 1/time (revs per time)) -> power x time / time (power multiplied by time divided by time -> power. So torque at high revs is power.

Power is defined as how fast the work is done. The work can be e.g. getting car to 100 mph. How fast this work is done (ceteris paribus) depends on the average power during the acceleration.

You can't avoid having high torque if you have high power as it is closely related to power. However, average power is the measure affecting the acceleration. Power means performance. Torque is luxory and stress to transmission components.