Quote:
Originally Posted by gsxr
FYI... typical driveline loss is roughly 18% on a Mercedes with 722.3 transmission, give or take a percent or two, using stock wheels/tires on the chassis dyno. That means:
RWHP / 0.82 = crank HP (estimated)
Example: 261rwhp / 0.82 = 318hp at crank (estimated)
20% (or higher) loss estimates will result in artificially inflated crank HP numbers. If you want to be really conservative you can figure about 15% loss. Dunno what it might be with a manual trans, but maybe a percent or two less. (?)
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Not totally true.......
Depends on the type of dyno that you're doing your pulls on...
18% is typical on an inertia type whereas 30% is common on a eddy current load type dyno.
Inertia type like a DynoJet tests your vehicle's ability to accelerate the drum of inertia, which is about 2500 pounds, and does not add aerodynamic load to the equation. It uses a simple formula to calculate how much horsepower it takes to propel a given weight to a certain speed. To get get torque, the rpm is used to "calculate" it, from the HP calculation.
The load type like a Mustang add the difference between the weight of the drum, and your actual vehicle weight, add aerodynamic load, AND, also use a strain gage to DIRECTLY measure the torque, not calculate it.
The load type gives a more accurate RWP reading then the inertia type and you can better tune on a load type.
