Discussion and questions related to the course EFI Tuning Fundamentals
A set of camshaft that has more aggressive than stock cam lobes usually idles better richer due to overlap, my question is, can this be addressed with adjustment of the cams via adjustable cam gears, even if it sacrifices a little horse power on top of the RPM band?
That is my question too
You can change the Overlap by advancing the intake and retarding the exhaust and vice versa. A lot of overlap at idle will cause intake reversion into the manifold and into the exhaust decreasing VE and causing a very erratic and variable intake of air and exiting of exhaust. This rough idle can be compensated through ignition timing and fuel delivery. Advancing the timing in the idle area can help as VE is lowered significantly at idle due to the reversion. Flame speed is decreased so it might help to advance the ignition timing to compensate for the lower flame speed. Depending if you’re working with a MAF or Speed Density based system, you can try to compensate for fuel delivery by changing the MAF scaling in the idle frequenices or changing the target afr table. With a Speed Density system you would have to obviously adjust the fueling as necessary. That way you can still maintain good idle characteristics without making that sacrifice.
Hope that helps.