335i driver does test-drive with M3

[Redadair]

Originally Posted by swamp2

Red, you are really embarrasing yourself with your lack of understanding of the absolute basics of the behavior of a transmission. This is EXACTLY what gearing does - multiply torque. Why do you think a car accelerates better in 1st gear compared to 2nd gear? It is simply because the gear ratio in first mutliplies torque more to the wheels. I guess you have never heard the expression that a transmission is a "torque multiplier". The analogy is not perfect but a breaker bar or torque wrench does basically the same thing - the longer torque arm the more torque with the same input.

My other comment to folks is that speed, acceleration and jerk can all be quite decieving and we are very often misled by our senses. Bruce previsouly pointed out many factors that confound our "butt-o-meters" (although he came to the wrong conclusion from them). A classic example is the E46 M3 vs. E36 M3. In many ways the E36 M3 feels faster but is never is, under no circumstances. Ride, NVH, acoustics and shape of the torque/hp curves all contribute to this false observation. Numbers do not lie and a faster 0-60 time means a higher (average) acceleration over that interval.

Now let me put this into perspective.

Lets say you or I use our hands for this comparison. Lets take the drivetrain out of our test car and set it up on the ground. We will remove the engine and turn the pilot gear on the front of the transmission with our hand, this in turn will turn the rear wheels pushing our test drivetrain across our work shop.

Lets start the with the transmission in 6th gear. Nope, we can't turn that with our hand. Why? because the gearing is just too high. Now lets shift the transmission into 1st gear. Wow! look at that! we can actually turn the input shaft of the transmission, and while each revolution of the transmission does not equate one revolution of the rear wheels, the wheels are starting to turn. Pretty cool!

Why did this happen?

The transmission has 6 separate sized gears, with first being the largest gear. Turning this first input gear allows for the large gear to rotate easy, however the output gear only turns a small amount.

Questions:

Did the transmission increase the amount of torque our hands have, suddenly making us Supermen? No

Did the transmission work as a lever? Yes, allowing the lower gears to turn many revolutions to just one revolution of the rear out put shaft of the transmission is kind of like using a big lever bar to move something.

In no case did we increase the input straight, we only changed the distance that the input moved in relation to the output, and in doing so we allowed the same input power to move a larger output - object.

Another question:

Since these calculations are as you say always correct, how do you explain how a Diesel engine works? Seems to me I read where diesels make all their Enormous amounts of tuque at just off of idle, but then loose this power very quickly if the engine revs too high. So using your calculations a small gasoline engine that put out say 250hp with very low gearing would have greater overall power than say a 7 liter diesel engine that only put out 225hp. Amazing stuff?

Red