ZR-1 dyno question

[lt5vett]

Could any of you out there give me a reasonable % loss of horsepower from the crank to the rear wheels on a dyno run. Also, does it make a difference in what gear the dyno run is made in? If different gears are used then would the hp reading be read higher or lower? Thanks

[Ken]

I found this on a web site for Derrike Cope fans:
Question: What type of information do you get from chassis-dyno testing that is not available from the standard dynamometer test?
Derrike's Answer: The chassis-dyno gives the actual horsepower to the rear wheels. Typically, horsepower loss from the engine to the wheels through the drive train is about nine percent.

I suspect the readings won't be accurate until high gear is engaged.

Hope it helps ya.

[lt5vett]

Thanks, that is interesting and perhaps the lowest I have heard. I see #'s from people completely stock at 300 SAE corrected rwhp. If the car were rated at 375, that is nearly a 20% loss. Any ideas? Thanks. Nice looking car by the way. Bruce

[Ken]

Thanks for the compliment. :o

I was looking for a more definitive web site (rather than a "fan club") but I couldn't find one and I wanted to respond to your post before you got bored. :L

Ken

[twiget]

The number used for driveline loss on LT4 'Vettes seems to be 12-15%. I'm not sure if it's the same for other C4's though.

Jason

[Hib Halverson]

The "rul of thumb" for C4 parasitic driveline loss is 18% for manuals and 22% for automatics.

Understand this is an average and actual losses vary widely.

With ZR1s I've seen it as low as 15% and as high as 23%

[Jack]

Interesting Problem!
I DO NOT disagree with ANY of the numbers / ranges presented. But, perhaps there may be an explanation for DC's relatively low percent difference. I'm only guessing here so don't hold me to it ... and do please inform if there's additional factors ... or a hole in my hypothesis.

This comes to mind as I understand that cup teams have very deep pockets and their engines are not the only components optimized for a relatively short life. In contrast to street cars or weekend warriors or other roller-only chassis under $100K; I suggest that the NASCAR numbers MIGHT be relatively lower due to (a) straight-cut gears in tranny creating little or no load in-line w/ axis of main / countershaft ... rather than helical-cut AND (b) very light driveshaft AND (c) driveline bearings / bushings are setup w/ very loose tolerances. Again, just guessing!

What do you think?
JACK:gap

[Hib Halverson]

Originally posted by lt5vett
Thanks, that is interesting and perhaps the lowest I have heard. I see #'s from people completely stock at 300 SAE corrected rwhp. If the car were rated at 375, that is nearly a 20% loss. Any ideas? Thanks. Nice looking car by the way. Bruce

300 SAE corrected for a ZR1 with a two-bolt motor is a bit low. I'd say the engine in that car is not making the power it should be.

[ZR1Mike]

I've been told that ZR-1s lose about 18% at the rear wheels...