There is no definitive answer to this question as it depends on a number of factors, such as the engine type and modifications made. However, there are some general steps that can be followed to convert HP crank to WHP.
Firstly, you need to determine the power output of your engine at the crankshaft. This can be done by measuring the torque and RPM of the engine using a dyno. Once you have this information, you can then use a calculation to convert this into horsepower.
Next, you need to take into account any losses that occur between the crankshaft and wheels. These losses can be due to factors such as friction or wind resistance. Again, there are various calculations that can be used to estimate these losses.
Finally, once you have taken all of these factors into account, you will be able to calculate an accurate figure for your car's WHP rating.