Hi Chris,

As you know, the USDM EVO has less "mechanical stuff" between the flywheel and wheels and as far as I know, the actual drive train loss has never been measured accurately. The 15% to 24% (I like 24%) comes from DSM experience, comparison of trap speeds with other cars over the years, vendor gamesmanship, guessing and zero quality control relative to dyno's and testing methods here in the US. In other words, we don't have an answer either because the baselines from various dyno types and vendors are all over the map.

In the absence of a national standard for chassis dynamometers and testing methods, we will continue to bench race our Evo's and argue who has the fastest, quickest and most HP at a body velocity of zero... The problem occurs for owners who evaluate the best bang for the their buck. One vendor's dyno shows exhaust gains of 5hp while another claims 30hp and both accompanied by dyno plots. The buyer must look at other performance indicators and reputation and history. And again to answer your question, we don’t have a clue either.

Speedlimit...

PS Thank you for you well written technical contributions to this site.

 

Thanks Speedlimit. I agree that it would be great (but not for some) if we could have a common figure for all to use. I also think that the best method of testing the performance of an ENGINE is to sit the thing on an engine dyno and test it that way, just a bit of a pain I suppose. I also think that as long as you do back to back tests on the same rolling road then you will at least have an idea of the gain (admittedly only a %) over stock.

Thanks again Chris.

 

The majority (perhaps all?) of chassis AWD dyno's in the UK are dyno dynamics dynometers. These dyno's read very low compared to an inertial dyno (dynojet) or load type dyno that bolts to the hubs (dynapack). Take a look at this page:
http://www.vishnutuning.com/How_Big_...Horsepower.xls

It gives conversion factors for the various types of dyno. You input you "target flywheel HP" and it tells what "at the wheels" HP numbers you will get from the different types of dyno. If you do the inverse of the conversion factor listed and subtract that from 1 you get the % assumed drivetrain loss and it comes out to 28.5% on the dyno dynamics dynometer and 16% on the dynojet/dynapack dynos.

Hope that helps,

Keith

 

Nice calculator. I was using 24% as a EVO7 or EVO 8 with ACD and AYC and 20% for US Spec EVO8 and 15% for RWD.

This fixes the debate.