MoTeC Global Forum

Hi,

Please does anyone have a maths channel formula to give a power (BHP or KW) graph based on speed, acceleration (pref calculated, or longitudinal g) and a mass constant.
Application is for comparison between cars, so looking for power at wheels or flywheel (gearing is the same on all cars).

An addition to the formula to include an aerodynamic component based on frontal area or drag coefficient would be great too.

Thanks very much,
Maelstrom

Yes I am working on this stuff, with the aim of migrating the MATLAB back into a maths channel or similar (.dll).

Some factors:
1) A run up to speed with a coast down in neutral can help to determine the rolling and aero resistance coefficients.

2) You need to know the entire mass

3) If you want chassis HP then it is easier (#2), if want to back it up to the flywheel, or engine, then you need to estimate the wheels and flywheels rotational mass.

4) With just chassis-HP (#3), then lighter wheels can give you HP, as can a lighter flywheel. This will make your power (at the same RPM) different in every gear. Where HP is really "acceleration HP" in low gears, but they are the same HP as you approach max velocity.

5) If the ground is not dead flat, then you might want to have GPS too, and there is a significant amount of energy used and gained going up and down hills. Not a huge amount if you have a high power to weight ratio, but enough that it might need to be considered.