Greetings, Marquis,
Just the man I have been looking for! On many published torque curves for V8s I see in magazines and many of the torque curves I generate with the commercial DynoSim program, there is a noticable dip in the 2500-3200 RPM range. I have adjusted most of the variables in the DynoSim program without causing the dip to smooth out.
Most of these are performance engines, with larger porting and longer cam timing, but still street engines. Some of the dips remain even when switching from NA to supercharged, so it isn't primpary pipe length on the V8s. Where should I look for the causes?
thnx, jv.
Hi, youll have to excuse the brevity of my answer as Im currently on Christmas break in Finland!
Is it a Volumetric Efficiency dip or torque curve dip?
Just for understanding and examining sensitivities- what if you tried to shorten cam duration or minimise the amount of overlap?
I wonder if there is some "anti tuning" going on from the exhaust manifold/down pipe side which is hindering good cylinder filling via the overlap?
I also think it unusual that the phenonemon is present on the boosted variant- which is why I asked if it is there on the VE curves and/or torque curves.
In boosted engines the "boost driver" be it a Roots blower, centrifugal blower, turbo charger etc etc is what predomaiantly drives the Vol. Eff curve and hence torque curve shape. This can be the dynamics of the boosting system be it waste gate, the supercharger pulley ratio driving off a particular area of the adiabatic isolines of the isentropic efficiency map. Im not saying conventional tuning effects arent important just much less apparent