I'm working with a guy on the "tune" for his new build. He recently installed a 408 with a 24x/25x cam, LS3 intake, big tube headers, 6-speed manual car. He also bought 50 lb/hr FAST injectors
So we worked through a full VE and MAF tune and have pretty decent manners - all except for pulls through the 2,500 to 3,000 rpm range where it always spits and pops. Once above 3,000 it will pull cleanly (and strong) to 6,600.
Here is what we have experimented with, in an effort to eliminate the problem area:
- Using VCM Controls I manually added and subtracted timing - no change
- Using VCM Controls I manually added and subtracted AFR Control - no change
- Adjusted PE Throttle higher and lower - no change
- Disabled closed loop and all fuel trims - no change
- Adjusted transient "Fuel Boiling Time" and "Fuel to Wall Impact Factor" both up and down - want to say it may have affected some but the problem was still there
- Tried a crank sensor re-learn
- Used injector data for 50 lb/hr Deatsch Werks injectors - no change
- The owner replaced spark plugs and wires - no change
With stock misfire table settings I see lots of random misfire at idle and cruise but no smoking gun. We are fairly stumped. The car idles and cruises well and WOT feels crisp and strong. I personally don't fell like the problem area is a fuel or ignition timing issue. So I've about decided it is a fuel injector transition issue. The FAST injectors are supposedly made by Bosch but I have never found decent data for them. Unless someone comes up with a new great idea to try, my next step is to pick up some stock LS7 or LS9 injectors and swap them out.
I've attached the current tune, but I don't have a scan right now. There really isn't much to see in the scan though. Ignition timing is steady in the upper 20s and fuel trims <5 or 6%.. I know it's very difficult to remote trouble shoot, but figured I would at least toss this out and see what ya'll can come up with.
Clyde