I've been struggling with this for days trying to make sense of a rpm vs torque chart I've seen recently.

The chart states the engine load was measured 100% 70% 40% 0% and at 1000 2000 3000 4000 rpm. How is this done if using a chasis dyno?

I attached the chart for reference.

That's my question, but below I'll elaborate on my thinking and hopefully there will be a clear error in my understanding...

I think part of my problem is that I'm unsure what the throttle is doing when these charts are produced using the dyno.

Am I right in thinking that to get the 100% load points over each rpm, the test is started with the engine idling then pushing the throttle to 100%? The RPM will increase rapidly up to redline and the engine torque at each RPM can be estimated working back from wheel RPM and transmission ratio etc. They measure at 4 discrete RPM though, suggesting they might have control over the dyno resistive force?

Engine Load vs RPM

  • 2
    $\begingroup$ Not all dynos work by inertia. In fact, absorption dynos, which provide a braking force are preferable for controlled, precise data collection. These devices provide a controlled braking torque to cause the engine to stabilize at a particular operating speed. That gets you torque vs. rpm data points without mucking around with transients. $\endgroup$
    – Dan
    Jul 26 '15 at 19:58

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