Dyno Reading.

[**RB2530**]

If you wanna put a "%" to it, its less than 10. Certainly not 15, and unlikely 10 given Paul (dirt) ran within i think 15kw @ 400rwkw/awkw

Yep...It may not be a percentage of power. It probably won't be purely a %..In the diff you have sliding friction (pinion to crown wheel) which 'will' be a percentage but the loss at the front tyres for example will be varied more by strap down load, tyre pressure, rubber compound etc etc. Even front wheel toe-in/toe-out will consume power as soon as it deviates from "0 deg".

It may be that with an average power output with an average front driveline, the number is 10% or there abouts.

Another point is that if the front driveline loss is 4%, and you assume that the rear driveline loss would be similar, the gearset loss is 20-25%. That is 'very high' when you consider the dyno run is done in 4th 1:1 ratio where the load goes straight through the g/box and bypassing the gears (although they are still spinning and would consume 'some' power).