OK, feeling dumb today as it is a Bank Holiday!

How do different rolling roads calibrate your cars RPM to the rollers for torque and peak power calculations?

I have only been on one set of rollers where they used a 'clamp' device on an ignition lead to, I presume, check rpm.

Using standard gearing tables does not work as you get tyre size error - on my car at the moment the tyres are 'slightly' undersize and so using a speed measure would be incorrect, for example.

Any thoughts anyone - in my experience different rollers have give me very different, torque, peak torque rpm and peak power rpm (out by up to 500rpm) for the same state of modification.

Rannoch

 

The problem on early cars is that you can't get a pick up for the sensor due to the coil packs (no leads)
On the MAHA at Star, the operator watches the engine RPM on the tacho, runs up the car on the rollers and presses a button on the handset telling the dyno that the engine is running at 2000 rpm.
From this the calcs can be done.
OEM tacho's are not the most accurate bits of kit, hence the errors

Andy

 

I believe at PE the operator enters the engine RPM at 60mph on the rollers speed readout

 

The only problem with this is that the rev counter is inaccurate. This is something that I've seen with EVERY single car I've adjusted the ECU in... what you see on the telemetry does not correllate with what's on the rev coutner, sometimes the error can be up to 500 RPM! Last few times on the rollers @ PE we calibrated them using the telemetry data

Cheers,

Pat.

 

The really BIG variable in the figures is the atmospheric pressure and temperature compensation.
Some rolling road set ups do not compensate some do it automatically (Star/PS and G force) and some the operator can enter whatever figure he wants (PE & WL ? ) adding or subtracting anything up to 15% of the power as desired !!