I put an LT4 HOT cam in my 5.7L TPI (7730 ECM). In trying to dial-in my VE tables, I'm ending up with about 40% VE for idle, at about 700-800 RPM, 60 kPa. I've richened it and leaned it out, but 37-39% VE is where it wants to be. BLM is about 135-140 at this combo. I've tried tuning it to get it closer to 128 and that only makes the idle quality worse, causes it to idle like crap. I've seen some threads posted indicating this might be the norm for this cam.

 

are you testing this while idling in closed loop?

IF you are closed loop, and IF you are generating crosscounts (i.e. the ECM is adjusting the BLM & INT to generate the proper injector pulsewidth which generates crosscounts), then adding a few percent to the VE should (after a few moments for things to settle out) result in a lowered BLM, the SAME injector pulsewidth, and the SAME engine idle quality (because same injector pulsewidth is the same amount of fuel).

If 38% VE results in 137 for the BLM, then your VE needs to be around 40.6% for a ~ 128 BLM at that rpm/MAP. Set it there, wait for the BLM to come down to ~128, and compare injector pulsewidths and idle quality. If the BLM is really slow to adjust/respond, and you are not getting a lot of crosscounts fairly rapidly, you may need a heated O2 sensor, especially since you're running headers. Bottom line is once the BLM has come down and the injector pulsewidths are the same, the idle quality should be the same.

Also, 60kPa is about 12" of vacuum. This seems a tad low to me for a HOT cam, as it's a pretty mild cam. it might be ok, but it might also be worth checking into to make sure you don't have a bit of a vacuum leak.

 

Thanks for those pointers. I'll check them out. This was for closed loop, and I am seeing some cross-counts. With my Prominator, it's a lot easier to try things out. thanks.