Since this is the craze these days heres how it done!
You will need a vehicle weight & E.T. to have a TRUE RWHP number because a chassis dyno does not replicate the RAM AIR affect etc...!
We will use my current setup for an example:
Horsepower = Vehicle Weight / (ET/5.825)3(cubed)
Example: 3700 lb(total w/driver) Challenger ET = 10.96
HP = 3700/(10.96/5.825) 3(cubed) 10.96/5.825 ='s 1.88
HP = 3700/1.88*1.88*1.88 = 3700/6.64 = 557 RWHP
