Treacle wrote:
Darryl - read Diceman's post above and see if you still think that. The at the wheels figures will be different on different dynos as the losses that are calculated also include the losses of the dyno itself etc. so at the wheels figures are also meaningless for comparison unless try are done on the same dyno.
Edd, my engineering science project was on power lost in various stages of gearboxes, drive shafts and chain & sprockets.
Go read some simple physics stuff, and then you will realise all these dynos are using ... F=ma namely the drum / rollers the car is resting on. And a simple counter of its rpm. Throw in time and you've got acceleration. The drum is a known weight. The rest is easy, use a few know sae correction factors and you are good to go.
The dyno run the other day ( somewhere near bristol wasn't it ? ) first thing wrong with the runs that day...... Phil's chart showed 20 degree C temp. Wasn't everyone saying how cold it was in that room that day ?
Irrespective of whatever tyre pressure was used in each car that day, or how heavy the car was, the drum was measured nothing else.... The force to speed up that drum at the actual rate achieved on each dyno run for each car gives you the force available at the wheels. Ie. The last (lowest ) value left of what the engine produced from its crankshaft is what was used to turn the drum. Assuming the drums bearing system didn't degrade over the course of the day. The wheel figures are fact. Now maybe the dyno software "adjusted" the measured power shown on the screen or prinout, but from one car to another it shouldn't of changed.
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Darryl