Rolling Roads

[BruceA]

Could anyone tell me, about power figures that are quoted using rolling roads.

Now - heres my question. In what gear are readings taken? To put it like this, if you took a reading in first gear, there would be more torque available to run the rollers, and hence a higher figure than in say 5th gear. Does the measurement program re-calculate the figures based on the gear ratios used?
Any ideas?

 

[Howard Jones]

I have limited experience I have with chassis dynos but I believe that the gear that is closest to 1:1 is the best choice. I have never seen anyone do it any other way. In most cars this will be 4th. This will provide data that doesn't require a ratio conversion factor.

For example, if you used 2nd and it was 2.00:1 then you would need to divide the resulting data by 2. On the other hand if you used 5th and it was 0.8:1 you would need to multiply by a factor of 1.2.

If I am wrong on this then I am sure you will see the correction posted very quickly.