This is going to be a long post so apologies to people with short attention spans.

Here's one from way out of left field that I have been considering for a while. There are a lot of threads on this site about how much hp=how fast, & how much better was the upgrade etc, but not many of us can justify heading for the dyno shop or drag strip every time we make a change to the car..... so here's what I'm thinking:

What you need:
1. Flat, straight road
2. Windless day
3. video camera, preferably digital.
4. A car with a tacho and the specs on its gear ratio's, diff ratio's & tyres, preferably a datto 1200 but anything will do.


Attach camera so it gets clear view of your tacho.

Drive car from 1500 rpm to redline in gears 1,2, 3 & possibly 4 if you have enough road (slowing back down to 1500 before each run)

Do a couple of replicates in each direction up the road to keep it scientific.

Possibly retard timing by 5 deg and do another run to test sensitivity of method. (that should drop a 10-20 hp depending on your car)


Back at the computer.

Time rpm in increments of 500 for each pull

Create graph of the pulls (gears 1,2,3 &4) and compare the shape of the curve. This is the torque curve at the rear wheels + the wind resistance for a given speed + the rolling resistance. (At this stage there are no units for torque)


Normalise the data by dividing the torque + resistance curve by the gear ratio.

After this step, the remaining difference between the torque curves is equal to the rolling resistance +the wind resistance


Create a graph of the combined rolling resistance & wind resistance and fit a curve.

Use the equation from that curve to remove roll+ wind from the data.

All three curves should look the same now.


Fom this, create a torque curve (at the rear wheels) using physics principles.

Calculate a power curve from that.


I am working on the basis that rolling resistance and wind resistance are the only 2 factors working against the power of the car, therefore you dont need to measure each individually, you can lump them together in a common equation.

would anyone be interested in a speradsheet that can do this if I put in the effort to work it all out?

Are there any maths or physics guru's out there who can check up on the work?

comments appreciated