Calculating HP

[toyman]

I've wondered what my car is putting down to the rear wheels without the benefit of a dyno. The formula to calculate HP is:

HP= (Nc * injector rating * duty cycle)/ bsfc

Where Nc = Number of cylinders and bsfc = brake specific fuel consumption. The bsfc for a supercharged engine running at an AFR of 11.8 should be about .5.

Since I can data log my duty cycle and AFR the calculation for my setup is:

HP= (8 *42 * .7)/.5 = 470 which I assume is at the crank. With a 20% loss through the drive line the rwhp = 376. Does that look about right?

 

[ProKiller]

sounds low with that combo.

 

[moosetang408w]

That formula is quite general. It is assuming alot of different aspects! Probably get you in the ballpark though. I used Desktop Dyno Software to guestimate and even then I would only trust it within 15%.

I like to use the formula (money spent)/5=rwhp

 

[Dino Dino Bambino]

I've wondered what my car is putting down to the rear wheels without the benefit of a dyno. The formula to calculate HP is:

HP= (Nc * injector rating * duty cycle)/ bsfc

Where Nc = Number of cylinders and bsfc = brake specific fuel consumption. The bsfc for a supercharged engine running at an AFR of 11.8 should be about .5.

Since I can data log my duty cycle and AFR the calculation for my setup is:

HP= (8 *42 * .7)/.5 = 470 which I assume is at the crank. With a 20% loss through the drive line the rwhp = 376. Does that look about right?

With your combo you should be getting about 520 at the crank which would indicate a BSFC of 0.45. Very good for a blower combo and probably because the twin screw is efficient. Drivetrain loss will be ~23% so you're looking at an even 400rwhp.