[Diy_efi] BHP calculations

[Hugh Keir]

I am working on a spreadsheet to calculate BHP from datalogged information.

The basic formula I am working to is:

Engine BHP = acceleration BHP + wind drag BHP + transmission loss BHP.

I need help with the formula to calculate acceleration BHP.

I know the weight of the car and the change in engine RPM over time.

I can therefore use F=ma  ( force = mass * acceleration ).
Where I think F = lbs, mass = slugs ( 32.1 lbs each ) and acceleration =
ft/second change in speed, to calculate the acceleration BHP

Horsepower is 550ft lbs / second. I am not sure how you get BHP from F
above, do I just divide by 550 to get BHP?

I have used the wind drag calculations from
http://members.home.net/rck/phor/06-Speed.html which seem OK and will be
able to get some transmission loss figures from some rolling road runs.

Your help will be greatly appreciated.

I can copy the finished spreadsheet to anyone interested.

I have used a variable air density input to the spredsheet and hope to add
wind direction to normalise the readings.

Thanks

Hugh


_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi