Flywheel and rwhp difference...

[DSR207]

Anyone with facts about the percentage of loss, I hear between 13% and 19%...

 

[Makara]

worms...


can...



open...

 

[SnakeEye]

worms...can...open...

LOL
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What I've noticed is about a 13-14% loss based on dynoing and published hp/tq.
Just my .02 cents, your mileage may vary.

 

[Chuck 98 RT/10]

LOL Drivetrain loss and "underated from the factory."

Who cares? Get the true performance at the track.

 

[SylvanSRT]

i dont think that using a percentage loss is accurate unless talking about stock vehicles. the driveline loss should be close even on a modded car(maybe alittle higher due to extra heat and possible friction losses). i would think that the drive train loss for a particular design should be relatively consistent across the board. I also think that most of the people using a percentage are the tuners and or parts sellers that try to explain why mods wont make the hp they claim when sold to someone. If the SRT is quoted at 500 hp and makes 430 rwhp then the loss would be 70 hp and a modded car w/ 600 crank should be near 530 at rwhp.

 

[Cris]

Silvan that really is not true. The loss, as measured on a Dynojet or similar transient dyno, is impacted by straight frictional losses (the linear portion), frictional losses (those that are force related such as gears), fluid losses (square of the engine or driveline speed), and inertial losses (driveline, wheel, tire, etc - note this only affects transient dynos like Dynojets). The end result is a loss curve with a constant, a linear and a exponential portion.

For most vehicles in the 200-300 hp range this ends up being around 15% at the peak horsepower speed. As you increase the power the tendency is for the loss percentage to go down. However the actual loss continues to climb and does not stay contant. for a 500 hp car like the Viper a 12% loss would be a reasonable estimate.

 

[Viper X]

Most computer programs on this subject use 18%. I doubt that the Viper's loss is that high. !2 to 15% seems closer.

 

[CHAD]

12-13% seems the most realistic, IMO. I agree there is probably a constant component as well as a linear component but difficult to figure to say the least. On big power cars, I'm not sure the dyno is very accurate anyway (probably reads a little high).

 

[womsterr]

I think 18% more of an avg for autos, not standard.

12-13 sounds about right for a stick.

 

[Dave T (BADVENM)]

i had woodhouse do some mods on my '01. first dyno (mustang) was about 25% while the 2nd one they used (first one was down) was closer to 18%. makes for confusing calculations on improvements.