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No set formula depends on your drive line loss. And there just like snowflakes

10% to 20% loss with 15% being used as a norm.
 

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What is the formula to convert rwhp to crank horsepower?
Not sure what “crank HP” is. Break HP is the ({torque measured at the flywheel} * RPM)/5252.

Probably not the question you were asking.
 

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Divide RWHP by .88 for manual and .85 for auto.
An example would be the 418 rwhp I used to have divided by .88 would be 475 at the crank.
Multiply and you get RWHP from the BHP :thumbsup:
Example
405hp X .88 = 356.4 at the wheels
 

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Then you would be right. I wasn't aware of such a calculation and its full meaning.

glad to see we have so many knowledgeable members:partyon:
 

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Then you would be right. I wasn't aware of such a calculation and its full meaning.

glad to see we have so many knowledgeable members:partyon:
I got that from one of the other members. I don't remember which one though :laughing:
DC is a great knowledge base :thumbsup:
 

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Keep in mind what Iburke posted - these approaches are just estimates. Also, if you make extensive modifications to your engine, then you probably shouldn't be using the same factor that you used when you calculated your baseline estimate.

The driveline will have a certain amount of fixed loss - say 20 HP or so, that won't vary based on the amount of torque provided by the motor. There will also be some variable losses based on torque (more stresses, higher heat buildup). Since we don't really know those components, I'd estimate crank HP as a range, settling on the numbers Spiderpat provided, and adding plus or minus 2% to each one.

Super_Jim - yes, he's asking about brake HP, measured at the engine crankshaft. Since the manufacturer's provide crank HP (like 345 HP on an LS1, or 400 on an LS2), then we can see how much loss there is in the driveline by measuring rear wheel HP (RWHP). Thus, the factors that folks are using to estimate back to crank HP.

Steven
 

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