dyno results and questions

[freshstart]

I've never seen a chassis dyno, but isn't it mechanically simple in that the car is anchored to the fixed frame of the dyno, then the (rear in my M3 case) tires contact rollers and are allowed to rev against them? Then I'm guessing that the dyno puts a load on the rollers and that's what measures torque and or hp?

Also, wouldn't you have to take into account the drive ratio of each vehicle and which gear the car is in? All these questions are leading to this...

If you have two identical vehicles, the only difference being the weight of the wheels or flywheel or driveline or anything else downstream of the crank, would this rotating weight difference affect the hp or torque output results? It has to doesn't it? The vehicle with the heavier wheels requires more energy to turn the extra weight, but then once the weight is moving (rotating inertia), it would take more to stop it right?

So here's my thinking that I want people who know what the hell they're talking about (as I'm obviously sketchy here) to respond to...

The car with the heavier wheels would show less hp but more torque, am I right?

If this is true then you could effect the output readings from a chassis dyno by modifying the rotating weight. So to judge engine hp and torque based on chassis dyno results can be misleading because of all the possible variables between the tire contact patch (which is what the dyno is reading) and the crank.

A chassis dyno reports "wheel hp" or "wheel torque" right? ...and people quote those numbers to gauge the true effective results of the modifications they've made to their engines. But if you can change your wheels and get a different hp or torque result then isn't it more accurate to think of it as "tire contact patch hp or torque"? I know that's getting picky but as I'm here looking at my dyno results I have to wonder about these things. Ok, the math geek will shup now.

Barker

[bimmerdremer]

sick car, i think i saw it in washington on a trailer.

[freshstart]

if you did see it, it was last july when it was on it's way from Virginia to Oregon.