Heinz ... if you drove your car onto the rollers, ran it, and got the graph then that will be wheel horsepower and will already include the losses in the transmission ... so no more to subtract in your case.
To get crank horsepower a different type of engine dyno would be used .... or if you asked (for bar-room bragging rights or some such) then your dyno place might add some figure arrived at by a formula to give you a contrived 'crank horsepower' figure derived from your real-world wheel horsepower.
To me the only figure I've ever been interested in is wheel horsepower .... because that tells you what you have where it counts ... where the rubber meets the tarmac!! 🙂
K
