Originally posted by emosubaru
the above explination only works for the WRX(read: works for the werx) because of the torque curve.
some cars have a steadily increasing torque curve, and most likely you'd want to run those engines to redline, unless the gear was insanely tall and you'd be better off in another gear.
pretty much what matters is the last paragraph of my previous post...
if the torque/hp(it's all the same thing being measured, just like lenght and cm/in.) at this RPM that is being applied to the current gear makes the car accelerate at a greater rate than the matching torque/hp at the matching RPM in the next gear, it's not time to shift yet.
Yes, I made a generalization, gearing still has an enormous effect. This is why there is such thing as "Drag racing gears" and why Nascar cars do like 7.1 0-60 time but then still finish a quarter mile @ 130 mph(!)
but still, I'm looking at the dyno plots and the gear ratios:
1st - 3.454
2nd - 1.947
3rd - 1.366
4th - 0.972
5th - 0.738
So we're talking about a stock WRX.
notice 2/1 = .564, and * 7300 (fuel cutoff) = 4115 rpm.
Now for the shift for 1st to 2nd that's a huge difference TQ @ 4115 rpm is greater than the ratio between 2/1. (well just eyeballing the dynoplot it's pretty close).
But remember, lower gears also have less boost. 1st gear is like 9 psi on stock cars right? And dyno graphs are all in 3rd or 4th gear.
But looking at the other ratios:
3/2 = .702 = 5122 rpm
4/3 = .712 = 5194 rpm
5/4 probably irrelevant to racing.
Now I'm looking at the dyno of the Vishnu reflash on a stock car, and the ratio of TQ between redline at ~ 5200 rpm is about 120/160 = .75 and the ratio of HP is about 150/175, .86.
now the amount of TQ lower gear makes over higher gear (2, 3, 4 gears) is just about 1/.71, about 1.4. That' is still clearly edging out the higher gear EVEN on the Vishnu reflash, where the shift slaps you right into the MIDDLE of the TQ peak.
So this is a pretty rough, linear calculation but you can still see that it's pretty close.
Of course, modified wrx would be no question.