What gear to use on a rolling road?

[Greenbat]

I sort of know the answer. 5th gear because it it is a 1:1 ratio.
However, how will the corrected power and torque vary from 4th gear to 5th gear.
Cheers
Greenbat

[jules78]

When we did the rolling road back in November the chap ran the cars in fourth to get the power !?! No idea why :roll:

[p 5ary]

you should never do a rolling road in fifth :!:
this is so bad for the car, no air resistance makes it possible to rev out which i believe should not happen in reality, also the fact the car is limited to 155 and peak power coming at peak revs it is not viable in fifth to get max bhp reading

[Cyclone]

It can also depend on which type of Rolling Road is used. For example, the rolling road that I use for my Cerbera at TCS in Chesterfield will run all Cerbs in 3rd gear, another place on a different set of rollers will use 4th gear.

What you have to consider is that a rolling road is calibrated to perform accurately at a given rate (or speed), a Cerbera running in 3rd gear at 7200rpm will be doing the equivelent of 115mph, in 4th this would be approx 160mph, in 5th it wouldbe 180mph+ :shock: , therefore if the rolling road is calibrated to run accurately at upto say 130mph then 3rd gear runs will be fine, however, if the same car is ran in fourth on the same rollers then once it has passed 130mph then the rolling road can no longer calculate the power efficiently and the power graph becomes exaggerated. I have tried this and in 3rd recorded 408/409 and 410bhp consistently (which is correct for the car), when ran in 4th I got 450bhp :shock: ....looks great on paper but is not the correct power for the car.

Hope this helps
Jules.