All you ever wanted to know ... Yes they are more accurate

http://www.dyno.com.au/home.htm

 

the easiest way to caluculate FLYWHEEL HP.

Take your highest RWHP on the dyno and multiple it by 1.11 that will give you your flywhell HP

 

I think with that formula you are still estimating your drivetrain loss at 11%. But I guess that will get you close enough.


The only true way to know is to have your engine on an engine dyno. Just like Chris said:

 

drivetrain loss is NOT linear... Gregg E. will back me up on that one....

 

I think the 11% figure thrown about is probably right... for the transmission, when in third (direct) with the torque convertor locked. Any thing else the loss will be higher. As for overall drivetrain loss, 18 to 20% seems to be pretty well accepted figures. Most people use 18% for the corvette automatic drivetrain and it has IRS which eats more than a solid rear.

 

In the latest issue of Chevy High Performance (I know a lot of you get that mag) they measured the flywheel power of an engine and then installed it in a car to measure rear wheel on a dyno. They tested different trannys. I believe an automatic TH400 was like a 30% loss and a manual Muncie was 20%.

Of course these numbers have nothing to do with a Lightning but still are interesting, at least to me. The loss numbers are much higher than I ever heard people say to use before. I'm betting the actual loss of a Lightning would be higher than most think too.

 

I've seen half a dozen true back-to-back engine to chassis dyno comparisons. Superflow engine dyno to Dynojet chassis dyno. Three autos and three stick shifts. They all were dynoed with the same exhaust as would be in the car (or open exhaust in a few cases, just like in the car). The tuning was done on the engine dyno and the same tune was used on the chassis dyno with maybe slight blending of the fuel numbers. They all fell into a low of 20% to a high of about 28% loss.

Then again, depending on the engine dyno and chassis dyno used these numbers will probably change. These were also all 600+ rwhp cars.

Jody

 

as far as I can see, the advantage of the "eddy current" brake type systems is that they can measure at specific loads, not just full throttle.

this doesn't make them more accurate, but more useful for diagnostics and maybe street type/ part throttle or low speed tuning?