Originally Posted by
steveo
you have to wonder how much that has to do with the difficulties in nailing closed loop idle on this platform. the system starts kicking the crap out of each other pretty fast.
you have a cam with a bunch of surge, so you have fluttery MAP, your FPR fluctuates pressure, but the random waveform of afr alterations that produces doesn't really correspond to anything useful. then, every tiny change in afr that corrcl and int are making, the fpr is making its own jitter and confusing the hell out of it.
perhaps that's why when i was doing some just for fun 'how low can i go' idle testing, it would idle around 400rpm no problemo if i put a restrictor in the vac line to slow down the fluctuations, but without the restrictor it would almost die. i'm a bit different, though, my cam makes fairly high idle but unstable idle vacuum. unfortunately i couldn't leave it like that, it noticeably affected throttle response. instead of a blip of throttle instantly maxing out the FPR, it would lean out for a split second.