How accurate is the horsepower results on ElanScan?

[XiPHiAS]

How accurate is the horsepower results on ElanScan?
Anyone did (already) some tests in combination with a dyno?

I will run a ElanScan when I am on the dyno within some weeks.

[GeoffSmith]

The power is a prediction based on rate of change of speed (acceleration) and weight of the car (I don't think it includes rolling or air resistance). I don't think ESM or John managed to do any ES runs when they were developing the mountain range, so some ES runs and dyno results would be very very interesting indeed.

Make sure you check your base timing before doing the dyno runs.

[ESM]

We have ElanScan runs from dyno runs but obviously the ES power calculation becomes meaningless in that situation because the mass of the car isn't being accelerated by the engine - the dyno is.

The power value is very approximate, wheel spin fools it completely, the calibration of the VSS is assumed to be correct, the VSS is noisy enough to make filtering of the data a requirement to get anything other than nonsense, the road is assumed to be flat, wind resistance isn't factored in. If you plot power against engine speed and squint you can get an idea of power curve.... If you use a bit of imagination.