I have a 1987 S4 TII, and i have a really lean spike when accelerating from 3000 to 3500 rpm. It only happens under low load, not boost, which makes me thing its maybe injector staging. I had injector clinic 775 cc primaries, and 1050 secondaries. Attached is my msq and tune. I am positive it is not the grounds, as i went through and cleaned all them. I dont want to richen up with the ve in that area, because its where i am sitting while cruising on highway or interstate, and the afrs are good there.

 

well, checked all the grounds again, they are good. Checked the fuel system, it looks good, injectors are all clicking. I have another log that shows the issue even more, its attached. Dont think its staging anymore, as my primaries are not maxed out, and its at low load, so secondaries shouldnt even come on. if anyone has any ideas, shoot them my way.

 

If that was my car I would double-check datalogs to make sure the injector pulse or fuel pressure or ignition timing isn't changing. Then if all that checks out OK, I might try to adjust the injector phasing (firing angle, not pulsewidth). It doesn't make sense to spray fuel at just any angle, since the intake port will be shrouded by the rotor during part of the engine cycle. It's hard to predict the exact angle you should use since the fuel spends some time traveling between the injector and the intake port, but at low RPM when the injector pulse is small this should make a bigger difference. I would adjust the angle by at least 50 degrees at a time, if you make smaller adjustments it might not be noticeable. At low RPM the injector angle will affect the throttle response, the engine will feel somewhat lazy if it's wrong and somewhat eager if it's right.

 

I have an issue where the moment the secondary's came on there was a giant jerk. I am running NA so no boost involved

I got rid of it by just making the secondary's run at 1% at all times instead of 0%

I believe it is happening because their placement places them further up the intake runners then the primaries, so for a fraction of a second when they turn on, the primaries go down in fuel output, the secondaries take over, and there is a short length of tube that does not have fuel mixed in with the air supply, and it causes a momentary lean spike.

I am going to have to sit down one day and play with injector timing to see if there is some way to get rid of that stutter in power when they come on.