WHATS THE DIFFERENCES BETWEEN PROP-SHAFT AND CRANKSHAFT HORSEPOWER? WHICH IS MORE ACCURATE?
Either method of measuring power is fine, as long as you do not mix the two. On a power head crankshaft dynamometer you don’t have to worry about things like the style of gears affecting the results. Prop-shaft dynamometers are much more convenient and test the entire engine assembly. Also, comparisons between different models and brands can be made with far fewer changes. At any rate, if you gain 10% at the crankshaft you will gain 10% at the wheel. If you need to evaluate exhaust changes, a prop-shaft dynamometer (with a torque transducer to actually measure shaft torque) is the way to go. Actual power losses through the drive train are in the neighborhood of 5%-10% (this will vary slightly with the style of gearing used). This is NOT counting exhaust restriction losses (which can be eliminated by modifying the stock driveshaft housing). Backpressure from a non-relieved stock exhaust system will reduce a STOCK power head’s output by 0%-5% and MUCH more on a radically ported power hea
