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Discussion Starter #1
I as just reading one of my mustangperformance books & saw something of interest. I've alwys been told that you lose 10 to 15% of your horse power in the drive line. Well at Mustang Magic in Deer Park, Ny they tested a stock 89 GT in this book from 1994. It even had the silencer box(stock). The car is to have 225 horse in the block, so ford says. Well the car dynoed 169.9 rwhp/242.5 ft-lbs torque to the ground (thats more than 30% lost from the flywheel to the tires). This same car had the timing tuned up from 10 to14 degress & the car then had 177.1rwhp/ 248.9 torque. Then the silencer box was pulled & got 179.5rwhp/253.3 torque. I see smal mods with NO cst & 10rwhp to play with. Noy bad info.
So do we lose 10 to 15% in the drive line or do you think 30%. This dyno info says 30%, but if some one can say the had there motor bench dynoed & then put it in the car for a dyno I would like to se the numbers. Also how much of that do you save by using a aluminium drive shaft or flywheel. I read in summit that 20% is lost in the drive shaft alone & with the aluminium you only lose 10%. Does any one have answers? I see what I read, but what I read is telling me two different things also.:confused:
 

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A percentage of loss is probably accurate for some power ratings in a narrow band. As opposed to a percentage, what if the drivetrain cost so many horses regardless of engine output? It would make sense that a given transmission and rear end would cost X amount of hp behind a 300 hp engine and the same behind a 500 hp engine.
 

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Discussion Starter #4
so then 225 to 190 is about 15% lose. What about the Professor Overdrive in Summit saying that you lose 20% in steel drive shaft & 10% with the aluminium. that must be wrong then also.
Thank you for your info
 

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10% more with aluminum? That's a crazy thing to say and they must know it. They must be pushing driveshafts this month.
Maybe if the old one had seized u-joints.
 

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Because the dyno is a measuerment of acceleration over time to calcualte torque/Hp. An aluminum drive shaft in reducing rotating mass will show a HP increase, maybe 1% at maximum though, as the larger diameter also slows the moment of inertia, and adds resistance to rotation. 10%... BS.

AUtomatics will show much higher Loss of HP through the drivetrain, as the torque converter is slipping and allowing torque to multiply, but drive wheel acceleration rate is reduced. SOOOOO it depends on the transmission and torque converter as to the amount of loss a chasis dyno will identify. On a typical manual transmission car its accepted that about 15% loss through the drive train is the norm.
 

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V8Mustang said:
A percentage of loss is probably accurate for some power ratings in a narrow band. As opposed to a percentage, what if the drivetrain cost so many horses regardless of engine output? It would make sense that a given transmission and rear end would cost X amount of hp behind a 300 hp engine and the same behind a 500 hp engine.
No, it's a more consistent percentage than you think, because as you increase the power (load) through the driveline, you increase the friction in proportion, so the loss percentage stays consistend and the loss value goes up with load. If that makes no sense, then consider this as a proof: The 225 hp engine loses 33 hp or so through the driveline. If that loss number was fixed then you wouldn't be able to turn the driveline with anything less than a 33-hp engine and frankly you could hook up a 5-hp lawnmower engine to the driveline and still move the car.

And to stave off further arguments do a search on "driveline loss" because this has all been hashed and rehashed.
 
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