Anybody know the % loss in hp/trq numbers when the same motor is taken off the engine dyno and then ran in a car on the chassis dyno? Have seen a couple of ASCS motors with chassis dyno numbers, and wondering what that would relate to when the same motor would be on the stand.
Thanks for any knowledgeable information one may have or experienced.
Rob

Standard factors for engine power losses through the drivetrain (15-17 percent for manual transmissions and 20-25 percent for automatics are figures accepted by most tuners)

Thank you both, but I am wondering if it is less considering it is a direct drive application - no transmission ... ?

Thank you both, but I am wondering if it is less considering it is a direct drive application - no transmission ... ?

A motor on engine dyno hooked to the end of the crankshaft shows 500 HP
Same engine would show approximately 420 HP on a chassis dyno (using 16% loss factor) With manual transmission

With that in mind, a 603+Hp ascs motor on chassis dyno. would equate to approximately 718hp on the std dyno.

With no transmission they’re obviously no. Losses there but my guess is the quick change rear end would be more of a loss than a conventional rear…. I’d think something in the line of 10% would be close. From a very reputable hands on source the nascar teams strive for 1% loss at the wheels….. if it’s more they find out why

A direct drive situation, like a sprint car, is going to have considerably less loss of horsepower than a street car or drag car (which is what the blog is talking about). Through a standard transmission AND a differential, you’ll have slippage at the clutch as well as frictional losses in the gearbox and differential. With no clutch and no additional rotating gearing to deal with in a manual transmission, your drivetrain frictional losses will be limited to your quick change and your birdcage bearings. I don’t know specific figures, but I would be surprised if the losses were greater than 10%.

All that being said, none of that horsepower, at the crank or at the rear wheels, means anything if you don’t get it in the ground, and in dirt racing, that’s the proverbial $64,000 question.

As said above all the horsepower in the world does not mean a thing if it can’t be hooked up…. Probably something more important than all out horsepower is the drive ability of a motor. Especially on dirt. If the power hits hard making it hard to hook up there is a good chance the guy with 50-75 less horsepower is going to drive past