When I was building and testing the dyno I messed around with different weights of flywheels..... I found that a lighter flywheel would allow some engines to reach really extreme high RPM's...but on the ground the engines didn't reach those RPMs....... then under the load of the heavier dyno flywheel the engine lost about 10 000 RPM....other engines will spin the same RPM under a heavy or light flywheel, it doesn't make a difference...the older OS VZB were a engine that spool very high under low load, bu would lose a pile of RPM once a heavier load was applied ( short stroke maybe ? ) ........... Compared to other dyno systems out there my dyno uses quite a large flywheel mass that I feel is very equally tuned to simulate the load of a truggy running on 100 % traction.....so if one of my engines pulls 40 000 RPM on the dyno its going to be able to pull that same 40 000 RPM under load, full traction in a Truggy.....