Raptor drive train loss for Dyno numbers

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TXRaptor

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How much drive train loss on our Gen 2 trucks when looking at Dyno numbers vs at the crankshaft? I have heard 20-25% loss, but that is a big difference compared to other vehicles.

How much additional loss, if any, would you expect from 37" vs the factory 35" tires?

What are the other factors to consider when comparing dyno numbers on different trucks? Heat, humidity, elevation, tire/wheel weight, tire pressure ??

I know reading dyno numbers is an art vs science at some levels, I am just trying to get into the ball park.
 

1roadking

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Looks like about 20% is the norm. My guess is another 2 to 3 percent for the heavier tires, but that’s just a guess.
 
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TXRaptor

TXRaptor

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After doing some additional research, I came across an article which explains why it is not possible to correlate the numbers from a dyno to the SAE net HP numbers at the crank in any consistent way:

http://www.superstreetonline.com/how-to/engine/modp-1005-drivetrain-power-loss/

After much detailed explanation, his comment from the end of the article sums it up:

"So rather than attempting to convert your vehicle's dyno-measured wheel horsepower to a SAE net horsepower figure using a percentage or a fixed horsepower value, you're far better off accepting the fact that these two types of horsepower measurements aren't easily correlated and forego any attempt at doing so."
 

RivRaptor

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18% parasitic loss through the drive line in a 2 wheel drive truck is average so I was told by Heath Diesel's owner who dyno tunes 100's of trucks & H1's. I purchased a dyno developed tuned computer from him awhile back that he developed for H1's. I have a 96' H1. Food for thought...H1's have a 48% parasitic loss through the drive line! All wheel drive, geared hubs & 37's.
 
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