when they say peak power at such and such rpm, does that mean ya should change gears at that rpm ?

like i seen somewhere peak power for my car is at 5500rpm, so wen racing is it best to change then or b4 then....

I reckon that depends on the shape of the power curve.. when you change gear you don't want to end up too far down the power curve.

Take two situations..

you're getting 120kW ATW at 5500rpm and you change up a gear which engages at 3500rpm and at that engine speed you're getting 100kW..

on the other hand you wait until 6000rpm when you're getting 110kW and you change up, engage at 4000rpm where you're getting, say, 105kW.

Let me bullsh!t my way through this for a minute.. say it takes 0.5 seconds for each 500rpm.. in the first example you increase power output from 100 to 120 in 2 seconds.. average 110kW. In the second you go from 105 to 120 in 1.5 seconds and 120 to 110 in 0.5 seconds.. giving you an average of 112.5 for the first 1.5 seconds and 115 for the last 0.5 seconds giving an all over average of 113.1 which has to be better, yeah?

I believe you're going to be better off aiming for the gear change window where your 'average' power is highest, even if that means going past the peak power point.

I am expecting many corrections, clarifications or arguments on this :|

The gearchange point changes depending on the two gear ratios you are going between.
Consider torque at the wheels. It drops off as you go higher in the rev range. The point at which you should change is when the torque curve at the wheels in the lower gear crosses the torque curve of the next gear.
This is a diagram I drew up for a different discussion, but it shows what I'm trying to say. The blue line is how you maximise the torque at the wheels. Shifting earlier than the crossing point is suboptimal and so is shifting later.

nice diagramatic drawings Mig...

yeah, i like the "blew up" part! :lol: :lol: :D

Hehem I'm glad someone noticed it and didn't take it seriously. :)

peak power at 5500, 1st change at 6000, revs drop to 4X00 then you are close to the peak power again in 2nd...

well done Mig... thats tops, you should be an artist!

Oi! My hands were stiff from being cold and shaky from coffee! Plus, I suck in the first place :lol:
Bah, I'm gonna be an engineer using CAD not an artist.