Inertia parasitic losses
Inertia parasitic losses
(OP)
Can anyone help me better understand just how much parasitic losses there are due to inertia of the reciprocation piston/rod mass assembly? Is there a way calculate these parasitic losses, as I already know how to calculated the inertia loads? Since inertia forces square themselves in proportion to RPM, does the rotating mass more than overcoming these reciprocating higher inertia mass loads or is there still a losses at any RPM?
Al1
Al1





RE: Inertia parasitic losses
RE: Inertia parasitic losses
Of course, if you're living in "tunerland" where parasitic loss is misconstrued to mean "a reduction in WOT vehicle acceleration," rather than a net loss in steady-state engine power output, then recip assy inertia does have an effect. Rotating assy inertia is more significant, of course.
For a reasonable estimate, add the entire "large end" mass of the conrod (if you split the rod at the cg) and 1/2 of the reciprocating assy mass (SE of rod + pin + piston + rings + bushes +etc) to the mass of each piston pin, and calculate the change in crankshaft "effective" inertia.
RE: Inertia parasitic losses
Al1
RE: Inertia parasitic losses
Your question suggests that perhaps you don't understand the "inertia energy" as well as you think you do. If you accelerate the piston up and down continuously in a frictionless engine, regardless of the acceleration rates up vs down, etc., whatever you put into the piston will have come out completely when it comes to a stop (top or bottom). The fact that there is a varying rate at which you put the energy in or take it out doesn't make a difference- the stopped piston hasn't accumulated any energy (where would it store it?).
If you consider friction, hysteresis, etc., then you can have energy losses, and the piston can get a little hotter.