Rear end ratio calculator for hp/torque?

[Confederate1969]

Having watched a lot of car shows in the last couple of years, I have seen the two types of dyno's people can use - one for power at the flywheel and the other for power at the rear wheels. Since a rear end ratio change out is one of the quickest ways to multiply power to the wheels, I am curious if you all know of any cheap and quick calculators online for determining rear wheel power if you have the flywheel hp and the rear gear ratio available.

 

[RoadRunnerJD]

Never heard of such a calculator. You can't change the horsepower of the engine by changing the rear ratio. The average loss of HP between the flywheel and rear wheels is 20%. I think by lowering the rear ratio, you can reduce the HP loss between the flywheel and rear wheels. You could measure the diff before and after on a dyno...but I don't know that it can be calculated.

 

[george68hemirr]

http://www.moparts.org/Tech/tech/index.html

 

[RoadRunnerJD]

You need to have your mph in the 1/4 mile and the weight of the car to calculate your HP but it won't help to know your flywheel HP and rear gear ratio. For my 2013 Charger R/T, I used the formula above and with a 99.05 mph and a 4500 pound car, my rear wheel HP is 333 vs a factory rating of 370