I was curious to see where on-board dyno technology has gone from the days of the old school GTECH. I downloaded an app from PerfExpert (it was $6) and figured I'd give it a shot since all the reviews are positive.

There is a pretty extensive setup in which you have to calibrate the motion/accelerometer in your smart phone, you have to fill out a ton of parameters on the vehicle you are testing down to your weight, how much fuel, frontal area * Cd, etc and you also have to follow a pretty strict procedure as far as ensuring the phone stays very still during testing.

Long story short, I tried it out last night, and it measures engine horsepower/torque but gives a roundabout estimation of wheel horsepower based on some standard driveline loss percentage, and I got the following results:

425hp @ 5919 rpm, 426.2tq @ 4710 rpm which calculating around a 12% drivetrain loss on a C5Z puts me at 374/375 at the wheels respectively.

The car (an '01 Z) has a vararam intake, carbon air bridge, XS power long tubes (off road), Ti bypass exhaust, and a diablosport tune. Seems like those numbers are pretty darn close to where I should be for my mods, and the reviews I've read from guys who have actually had their car on a dyno say the numbers are within just a couple hp.

Anyway, I am in no way affiliated with this app, (which is why I'm not posting any links) I just thought it was pretty cool, and maybe some of the other members who were curious would want to give it a shot. It could be a useful tuning tool as it will measure differences in hp (or 0-60, 1/8th mile, and 1/4 mile ET) so you will know if you made a positive change. Pretty cool app and thought others may like a heads up.

 

I have always heard DT loss is a bit more ~15% for manuals
~17% for automatics

to get crank HP, take RWHP and divide by .85 (manauls) or .83 (autos)

but in any case interesting app

 

Drivetrain loss is always fuzzy; and I don't think it should be a percentage anyway. The power eaten up by the clutch, trans, rear, axles, etc doesn't increase as the engine becomes more powerful (if that makes sense) so in a way, a bone stock Z06 should be dyno'ed and see what it makes vs. the advertised crank hp number, and if there is a 50hp difference for example, the statement should be "A Z06 loses 50hp through drivetrain losses."

A bone stock 02-04Z typically dynos 355-360rwhp (if memory serves me correctly) which is around a 12% loss from 405; or roughly 50-ish hp.

That is essentially the method to my madness in coming up with my calculated rwhp numbers vs. the measured crank hp numbers, whether I am right or wrong

 

Does the App have a setup for 2001 zo6?

If not, care to share the parameters you are using?

 

It lists our year cars but the year separation didn't make much sense so I chose to build my own parameters to make it more accurate.

I used the following:

Weight: 3049 pounds
Displacement: 5.665L
Fuel Capacity: 60.6L
Drag coefficient * frontal area (in m^2): 0.63
Pitch: 3 degrees/G
Gearbox ratios: 2nd 2.07 3rd 1.43 4th 1.00

I left a few fields out as they are either specific to your personal car (tire size, rear end gears, and such) or plainly obvious.

 

I always thought this should be the case too as it seems logical to me, but pretty much every magazine article or book I've ever read that gives both net (crank) hp and rwhp numbers for a given car doesn't seem to bear this out. The more hp at the crank, the more hp is lost through the drivetrain. Never understood why.

 

Ive run dynolicious for 5+ years. Seems to be very similar. It was always real close when I had slower vehicles, but with the vette it is never consistent. Roughness of the road messes with it too because that throws off the accelerometers on the phone.

 

You loose more when making more power because you still multiply with 15% for the drivetrain loss. No matter how much power you make the friction of moving parts it is still the same. Meaning that each moving part has a certain friction coefficient.
For example when you push your couch accross the wooden floor is a lot easier than accross the carpet. That is beacuse wood has a different friction coefficient vs the carpet. Now whether its you by yourself or 5 people pushing the couch across the carpet, it doesnt change the friction coefficient of the surface. It will move the couch quicker but the carpet still hold its strong friction surface. Then you have all kinds of dynamic frictions, but the most known ones are kinetic and static.