Quote:
Originally Posted by PencilGeek
Well, if you're looking for accurate results, I wouldn't use a roller dyno -- as they basically guess at horsepower based on the physics formula: F=M*A (Force = Mass * Acceleration). So they basically look at how fast you accelerate and the mass of the car, and basically guess -- or infer -- how much horsepower you've got. Once you throw in the inertial effects of the wheels, traction to the rollers, load put on the car by the straps, and the fact that I'll bet NOBODY actually weighs their car before the dyno -- you basically end up with useless results (with respect to accuracy).
So if you're looking for accuracy, the only choice you've got (short of pulling your motor out and putting it on a motor dyno), is to use a dyno that attaches directly to your hubs, places a hydraulic load on the motor, and measures torque exactly like a motor dyno does. Basically, you need a Dynapack or Rototest. I don't know which will be easier to find in Greece.
Now that I've said this, I predict the next 20 posts will be from people who swear by roller dynos, and will come up with all kinds of convoluted reasons why they're "good enough." Since you said you want accuracy, there's very little they can offer to give you what you want.
Click on my "Dyno Runs" link in my signature for a complete description and list of many tests I've already run on the M3.
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Well preached! I knew there was a lot of factors to consider getting a car dyno'd.
