[mrtbolt64]

Trying to figure out how much "roughly" horsepower I am making at the crank.

These are two things I know. To run a 140mph it takes 670wrhp at 3230lbs.

By and online calculator it figures out to be 6% slippage at the torque converter.

So where does that put my at the crank? I always thought you used like 18% for drivetrain loss.

Tranny is C4 auto.


Thanks in advance

 

[stanginthe11s]

well if you know you have 670 hp and 6% loss then x-6%=670
personally i hate math lol. i believe to figure out drivetrain loss you need to go by constants such as tire size, gear and rpm at the end of the qtr. so say you have a 28" tire with a 4.10 gear and went through the traps at 7000 then you should be going 142 mph, based on that you could assume you made around 700hp in a 3200lb car. if you only went say 120 mph then you made 425 hp so the difference is 275 hp or about 39%. i know this because this is how realized i just toasted my trans lol. hope this helped. i may be wrong and theres probably an easy way but me and math dont get along lol.

 

[mrtbolt64]

Thanks

Rpm crossing is 6200, tire is 28" gear is a 3.55

 

[stanginthe11s]

that puts you around 9.30 @ 145mph and around 750 hp. these are just estimates of course. you can usually bank on being within 2 tenths and 2 mph from these figures. so if you went 140 then you can say you used about 670 hp or 89% of your estimated hp so theres a 11% loss. keep in mind there are alot of variables, and im only going by if you went 145mph. other than that i dont know how to get a better idea of slippage or loss, hopefully someone will know better than me.