Making Sense of John Passini's Book
Posted: Sat Sep 17, 2005 5:44 pm
Whew! Reread the Mainjet section were he generally describes the behavior of a large main and air jets paired together and their mixture pattern going lean at high rpms versus small pairs and discovered I had misinterupted what he stated. He is right on the money actually saying they are opposites. The only source to do so so far that I've found which has confirmed my observations with the AFM exactly. Too bad he didn't have the same tool to work with! Would have really blown my socks off if he'd mentioned two-phase flow but it was not to be.
The only major point he made that I have my doubts about is the accelerator pump circuit contributing lots of fuel at full song. Maybe if the engine revs above 6500 would it then suck hard enough for some fuel to flow through there but below that I got none as far as I can tell. With the standard Lotus jets I had it leaning out to the 20 to 1 range at full song at my 6500 redline. If the accelerator pump circuit is contributing any at all it's only a trickle.
That's why I'm running much smaller jets to get the mixture to 12 to 1 and have it steady through out the whole rpm range.
The only major point he made that I have my doubts about is the accelerator pump circuit contributing lots of fuel at full song. Maybe if the engine revs above 6500 would it then suck hard enough for some fuel to flow through there but below that I got none as far as I can tell. With the standard Lotus jets I had it leaning out to the 20 to 1 range at full song at my 6500 redline. If the accelerator pump circuit is contributing any at all it's only a trickle.
That's why I'm running much smaller jets to get the mixture to 12 to 1 and have it steady through out the whole rpm range.