Q&A Forum
Yesterday I had an engine of my own on the dyno to try the MOI wizard. Previously I had run short up and down sweeps to figure out the inertia factor. That worked well over the years with the Stuska/Quadrant Scientific setup and also with Yourdyno. I always did WOT sweeps, and with this engine and yourdyno the factor came out to be .52. Yesterday with the MOI wizard and part throttle sweeps it was kind of all over but more in the .3 range. I reran a RPM/Speed Curve profile I set up as an up and down sweep at WOT and and it was .52. So I'm wondering if the inertia factor is different at part throttle vs WOT?
Hi. The MOI relates to the physical rotating mass and is the same at all throttle positions. It may measure differently though, if the engine behaves differently when it ramps up vs when it ramps down. You can re-run the MOI wizard with the calculated MOI and change the MOI to 0.52 and re-run the again. Then check how well the power / torque overlaps going up/down, to see if the engine behaves differently, or if the calculation is wrong.
In the MOI wizard settings you can set the minimum and maximum RPM and the sweep rate to match what you did manually, then you can do a full power test.
I can login with you if you don't find the cause of the difference.