jackbombay said:
The question was very clear that car A had twice as much torque as car B yet TDIMeister, who is teaching automotive engineering classes in Germany, right?
Sorry to disappoint, but I'm studying it, not teaching.
Let me get this straight, if there were 2 identical 2002 TDIs that were both stock and one was driving in 3th gear at 1900 RPM and the other at 3500 RPM in 3th and both of them "floored it" you believe that the car that started at 1900 RPM would have a higher rate of acceleration?
Well this starts to become a more difficult question with more variables at play. I don't know exactly how fast a 2002 TDI is operating in 3rd gear @ 1900 RPM (too lazy to calculate it right now), but for the sake of the discussion I'll estimate it to be 30 MPH. At 3500 RPM, the second 2002 TDI, also in 3rd gear, would be running 84 percent faster, or 55 MPH from my initial guesstimate. The drag component at 55 MPH is about 3.4 times greater (1.84^2) than at 30 MPH. Now it is not clear which car will accelerate at the greater rate, because the demand to overcome drag is that much higher.
The most germane analogy to investigate is to have 2 TDIs travelling exactly side by side and at exactly the same speed at the initial point of interest. One car might be in 3rd gear riding near it's torque peak RPM. Another might be in second and hypothetically at the power peak RPM. IF AND ONLY IF at the very instant they both simultaneously gun the go-pedal, neglecting turbo lag, rotational inertia, etc., the car operating at peak power will have the acceleration edge.
BUT BUT BUT if both hold the same gear, moments after that the car already operating at the power peak loses it's lead and then at a predictable crossover point falls behind. Why? Because the power curve is already falling off from it's peak while the other car's power curve is still building up.
Moral of the illustration is that there are other factors to be considered (torque/power curves, etc.), but the
power available at the driving wheels for a given starting point of wheel rotational speed will govern the torque at the wheel and therefore the tractive force at the contact patch and therefore how quickly you accelerate.