They might be able to provide that info and yes, if they had that and you had two very accurate pulls 300rpm/sec and 600rpm/sec you could calculate the total MOI then subtract the dyno components and you'd have the engine MOI, but in reality would be inaccurate due to accuarcy of the dyno.randy331 wrote:Wouldn't Superflow be able to provide the inertia factor for their dynos?
Using that info, and the two different dyno pulls at different acceleration rates, couldn't you calculate the inertia factor for the engine? Then take bobweight reductions, and the stroke length (distance from center of rotation) and the weight removal needed to rebalance, and calculate the increase in available power.
That sounds correct to me.randy331 wrote: If you have two engines of equal power, when dynoed on a steady state pull (not accelerated) the only difference is one has a heavier rotating assembly. Then you pull both engines on an accelerated pull, the lighter assembly would now show more power than the heavy one. (correct?) Although both would now show less power than before, because some power is now consumed accelerating the mass of the rotating assembly.
Definitely No and probably not.randy331 wrote: Question; We have an engine that we have dyno info on. We now take the engine apart replace the 100 gram wrist pins with 200 gram wrist pins, and we drill the rod throws just enough that when we put our new heavier bobweight on and spin it on the balancer, no weight needs removed from or added to the counterweights.(it remained in balance.) In other words, all we did is move weight from rotating to reciprocating.
Assuming no additional crank flex, cylinder loading etc,
Would this engine show a power gain on a steady state pull?
Would this engine show a power gain on an accelerated pull?
If what you're getting at is how does reciprocating weight affect the power required to rotate the engine components the answer is it acts like rotating weight. I am not sure that the value would be exactly half like the bobweight would be, but lighter reciprocating components would show power gain on accellerating dyno pulls only and show no gain on a steady state pull.
Thats how I see it anyway.
Rick