Rich on low rpm cruise
Changed my Target AFRs 1100 45kPa and 3000 45kPa from 14 to 14.4. Logged a cruise and got deviating (rich) AFRs from target. (Highlighted in DB31 excerpt.) I think the picture explains a lot. I've got the plugs under the primary throttle body pretty much dialed in now, but I have to figure out how to adjust the secondary throttle body so the plugs under them aren't over rich. Any idea how I do that?
https://www.dropbox.com/s/4wiybost7y8ahdn/Dashboard%2031%20Excerpt.xlsx?dl=0
https://www.dropbox.com/s/nzkbm9aoawp2kj7/IMG_4995.jpg?dl=0
As far as I know, there isn't a way to have individual injector tuning. In your case, a set of injectors. I'm assuming your linkage is opening both throttle bodies equally. Other than adjusting fuel, it could be distribution problem or throttle blades are not open enough. Check your secondary adjustment also.
Dual quads, and four barrel carburetors are new to me. Directions for 2x4 from FiTech are non-existent. How does one adjust a secondary? Is it the screw on the front left of the throttle bodies that adjust the blade opening? If so, tonight I loosened the linkage bar between the two and backed off this screw one turn on the front (dumb) TB, then retightened the linkage bar. I also backed out on the IAC screw on the front TB so the number of threads matches the rear (smart) TB IAC screw. Seems like there should be instructions somewhere for initial setup on FiTech 2x4's, as well as directions on adjusting the front (dumb) TB if it needs to match up to the rear (smart) one. Maybe FiTech takes for granted everyone knows how to tune dual quad carburetors and its done the same way with the FI ones. Reckon I'll try and call them tomorrow to see if they can give me some clues.
https://www.dropbox.com/s/j182gewtl0f4mux/DashBoard34.csv?dl=0
Please check my new idle log.
Readjusted Throttle bodies (the secondary's secondary was not shutting all the way, I think that may have been the problem.) Reset IAC learn. FiTech told me to make adjustments to both throttle bodies when setting IAC. Thanks
Your idle log is looking pretty good.
Excellent! Next time its dry and over 50F I'll get a cruise log. Thanks for all your help.
A cruise log doesn't tell us much unless you have an issue. Check your plugs and adjust your idle AFR accordingly. This will give you a base line to start with. Drive it and let learn. You will want to adjust Accel and Cranking as you go along.
Front and rear plugs are still not balanced. Rears are good, but the fronts, though better, are still rich. If I open up the rear TB and reset the link bar with the front TB a little more closed in relation, then reset TPS to zero will the system be able to reset its idle? I'd like to try that before I adjust the AFR so I don't starve the rears. I know I'll have to reset my IAC, but I can't think of another way to get them in synch. Could this work?
There must be a procedure to balance the throttle bodies. I'm not sure what that is. It would be similar to dual quad carbs, but different with the closed loop O2 sensing.
When you are checking plugs, are you looking at all 8 at Once?
Since I noticed the disparity front to back, Ive been checking all eight.
What exactly does the IAC do, and if front TB is squirting same fuel as back TB, will lack of air cause it to be rich? I think before I change linkage settings I'll try increasing airflow with IAC in front TB (screwing in IAC screw) while screwing out back TB in matching increments. So it would be half turn in front, half turn out back, warmup, check IAC step (10-15), 15 minute idle, check plugs. Repeat. if this works should balance out in just a few evolutions. I'll call FiTech and see if this could work.
Once we figure this out, I'll write up steps for tuning 2x4 FiTechs. Sad that FiTechs written information has almost nothing for the 2x4 systems.