ok, I have 550cc prim. and 1600cc sec. and a T-78. The secondary injectors have resistors on them for the PFC. The car is not fully tuned yet but we did work on this spot and it is in the 3300-3700 rpm range. The A/F is smooth and does not lean out through the whole rpm range except for this spot. To me it would make sense that when the turbo begins to spool (typically in the 3300-3700 rpm range) the secondary injectors begin adding fuel (switching from 550 to 1600cc). At this point there is a big lean spot, it goes from nice and rich to very lean and I feel the car bog down a little bit. Now like I said we have been working on this and it has gotten better, but can this ever be fully removed, or will having such a difference in injectors will this always be there when the second cycle of fuel comes in? Also would this be best worked out on street tuning (what we have been doing) or dyno tuning (load bearing dyno)?

 

That's weird. My car goes from normal to very rich because the 1600's begin to dump fuel. Are you sure its not a rich spot? I assume your running a wideband so i would think not. We worked mine out on the street. There is now only a slight stumble on light throttle tip-in when cruising around. Never any prblems @ WOT.

 

yeah, it seems like it would become very rich, but its almost like right in that spot the 550cc's are still running when it begins to boost, causing the lean spot, then the 1600cc's come on brinning it back to rich. When I am crusing around at a little over average throtle, is when I feel/see it but at WOT and taking it easy, it is'nt really there, so its always hard to spot and correct. who tuned your car? and yours is smooth now? thanks for the info too btw

 

A couple of questions/comments...

Did you wire up the 1600 injectors yourself?
What resistors did you use (Ohms and Watts)?
Are ya sure you got them wired the right way
When the 1600s were put in, did you make sure that the pintle in the middle of the injector wasn't stuck?
What is your fuel pressure (at idle or at 0 manifold pressure)

This spot is always troublesome to fix, but usually I think it's the opposite problem - going rich. I spent many hours working on my 550/1600 and it's very smooth now.