I've been reading the post "tuning closed loop idle" and had a thought that no one has commented on so I thought I would make a seperate thread. In the above thread someone posted that tuning closed loop idle is nearly impossible due to the overlap of large cams giving the O2 sensors a false lean condition from the oxygen and fuel be thrown out the exhaust suring overlap. My question is, how would a waste spark ignition like Delteq affect this? Would there be enough fuel and air to ignite and burn off the "overlap mixture"? Would this pose any serious problems if a large amount of "overlap mixture" is present?

 

I have thought of this myself, although now possible to tune closed loop idle thanks to the new tuner cat revision as you do not let the o2's correct at idle, I have to say that no matter what you do, you will still throw fresh o2 and raw fuel out the tail pipe, my guess is that a waste spark ignition coupled with an ignition box or maybe those crazy Nology wires can acctually hurt the performance on big cammed cars. It is my understanding that the wate spark ignition fire the other cylinder at its exhaust stroke, now is it wrong to assume that the spark would occur late in the exhaust event? Now with a big cam the main reason for the extra fuel/o2 comming out is because on the exhaust stroke the intake starts to open and fuel/air comes in and accidentally escapes past the exhaust? So generally with a narrow overlap and huge durration this WASTE spark could occur while the intake value is still open causing major reversion back into the intake if it lights the fuel exiting correct? This would not be a good thing. If you want to make sure all the o2 fuel is burnt off, I would say the best thing to do is to lower the spark advance causing the mixture to keep on burning while exiting the exhaust, loosing all power but the pipes would glow and most of the mixture would be burnt off which escapes durring the intake/exhaust overlap, and also may cause burning of the intake value cuz with big cams the intake value stays open longer and opens sooner with narrower LSA, not something I would suggest.

 

So would deltq be a bad idea for big cammed cars? Reason I asked is I was thinking about buying delteq especially after this weekend at the dyno where my factory iginition started breaking up after 5500 or so rpms. Should I just go with an MSD of some type?

Also would a larger LSA reduce this false lean due to there not being as much overlap?

 

I'm not sure, I would think so however.