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mainline dyno rpm hold

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in many of your video you mention using the dyno to hold the car at a certain rpm, is this a setting on the mainline dyno?

I am able to hold the car at kph settings but cant find a way to use rpm to hold it.

Pete.. I would assume that the best way to achieve this is to hold the car at a certain speed, then adjust the speed accordingly to match the desired rpm.

I think my DynoDynamics dyno has an RPM hold function but I never use it, I use the speed function as well and just match it with the RPM area

thanks for the reply's. still getting to grips with the many functions of the dyno.


...but, in essence rpm and speed equals the same result in your target gear. All you want to do is to visit all relevant cells in steady state and tune the maps accordingly. Whether the reference input on the dyno is roller speed or engine RPM makes no difference.

In general context I'm referring to roller speed as this (almost) directly relates to engine speed. What you do tend to find on a rolling road dyno though is that as you apply more torque to the rollers, the tires will deform slightly so the engine rpm vs roller speed relationship tends to move around a little.

Mainline offer a function called Tacho Trim which allows the dyno to change the roller speed to target a specific engine rpm rather than roller speed. This requires an engine speed input to the dyno via CAn or a direct tacho input via the tacho pickup.

I've found this function still needs some work as particularly at light throttle/low load it tends to oscillate. If you enter the tach trim mode with a reasonable amount of load though it works exceptionally well.

Andre is right, as the tires deflect the tire diameter changes and the rpm does seem to drift, but I usually see this is really bad on wot pulls. The dyno uses derived rpm from the roller speed but if I do a pull to lets say 8k the graph might show on the derived rpm axis I revved to only 6900 or something like that. To have rock solid control and accurate read out you need the CAN or RPM tacho pickup. Without those you should use kph function for steady state. I only have the L series software so I dont have the MBT function so it takes little bit more effort to do load tuning but the dyno seems to handle it pretty well. Still learning mine as well!

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