Horsepower loss thru ZF

Dyno-testing an engine alone, then the car with the same engine on a chassis dyno, usually gives about a 15% drop in power, which includes trying to compare two different types of dynos on different days, tire slippage, clutch slip, trans, axle & u-joint losses, dyno factors etc. So no comparison of this type will be exact. IMHO, dynos are not good for verifying a horsepower number; they are comparison tools for tuning. You do a run on the dyno of choice, then make a change and immediately see what the effect was- up or down. You'll get a slightly different number if the same test is repeated a day, or a week later, on the same dyno.