Quote:
Originally Posted by humfrz
Wouldn't the "total mechanical resistance" be taken into account in the measurement of WHP .... ??
Maybe speedometers are off a bit ...... but, the speedometer on my FR-S reads within one MPH of what my GPS indicates (at about 60 MPH)..... 
This has been fun ......  |
WHP is most likely measured by clamping something to rear wheels. Even if it's a rolling road it does not account for drag from the front wheels etc.
Dyno's are notoriously diverse in there results anyway. I read an article where a journalist took the same car to 10 different performance shops and got ten different readings, the spread across the results was significant. I can't remember the actual figure but it was something like 12%.
Dyno's need to be calibrated carefully and often and most are not. Different performance shops are at different altitudes. Different weather / temperature etc make differences. The only useful Dyno results is when you switch some part of other and test on the same machine on the same day and even then the only reliable figure is the delta.
The fact that your speedo reads accurately does not mean the one in the mentioned video is reading accurately.