I've noticed something I haven't seen before on mu 2015 ZL1. I just installed ID850 injectors and was doing a quick idle datalog to see how the trims are looking. Once warmed up the trims were 8-12% negative so I forced open loop to check what AFR (MAF failed) it was before pulling fuel out and it went leaner. Since in closed loop it has to remove 10% of fuel to maintain stoich, when going open loop it should be rich?
Short datalog attached where I switched to open loop and back..
69 Chevelle 418" LS3, 11.25:1,PRC 260 heads, TSP 235/239, Longtubes, dual 3", 4L80, 3.42
2010 Corvette Grand Sport A6, Heartbeat blower, 78mm pulley/10% lower, Kooks Long Tubes, 224/232 blower cam, ID1050x's, ECS stage 1 fuel system, alkycontrol meth system
Evap purge can also screw with fuel trims some
I'm curious whether you'll get the same results if the evap solenoid is unplugged
I can give it a try but would that be consistent and do it every time like this? I've never had to deal with emissions stuff when tuning, swaps into old cars are so much easier lol.
69 Chevelle 418" LS3, 11.25:1,PRC 260 heads, TSP 235/239, Longtubes, dual 3", 4L80, 3.42
2010 Corvette Grand Sport A6, Heartbeat blower, 78mm pulley/10% lower, Kooks Long Tubes, 224/232 blower cam, ID1050x's, ECS stage 1 fuel system, alkycontrol meth system
I dunno...
Honestly I wouldn't sweat it too terribly much. Maybe this will help though.
It could be the difference between tuning to the wideband and the PCM using the stock o2 sensors.
Rob
2017 Chevrolet SS 6mt LSA
Prior - 2015 Chevrolet SS 6MT LSA
Old - 1998 BMW 540I Supercharged 402 LS2/T-56 swap
Older - 1992 BMW 325i 402 LS2/T-56 swap
Very old - 1995 BMW M3/ 402 LS2/T-56 swap
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