L31MaxExpress
I'm Awesome
I have had an overly rich startup since the day one on the 97. Got a little better with the 0411 swap. I recently datalogged a startup with the coolant temp in the 50s and noticed that the 0411 post startup air fuel ratio was commanded at 3.5:1 and it stayed there for about 7 seconds before leaning out to the normal open loop air fuel ratio tables values. I downloaded 3 seperate 0411 van tunes including one from 2001 and two from 2002. One 2002 and the 2001 were 4L80Ee vans and the other 2002 a 4L60E van. I thought perhaps what I was looking at was non-GM tuning in the base file I had. Turns out it very much was how GM tuned the startup. From my experience with carbureted engines, it acted like the choke pull-off was not functioning. I set out to fix it. After reading the couple of posts I found with similar issues on cammed LS engines I had a little bit of direction to start on. I ended up multiplying both the After Start Decay Delay and the After Start Enrichment Multiplier by 0.25. I tested it out this morning after an overnight cool soak. The result is it now richens the mixture much less and only for about 1-2 seconds after the engine actually fires. It settles almost immediately to a commanded 10.8:1 air fuel ratio and the wideband closely matches. I hope this helps someone as it has always plagued me. The black box was so bad it would sometimes flood the engine on the first starting attempt. It would not start unless you pinned the throttle to the floor and cranked it over for 5-10 seconds. When that happened, it would generate a grey cloud of fuel smoke when it started.
After Start Enrichment Delay Stock
After Start Enrichment Delay Modified (Stock Multiplied by 0.25)
After Start Initial Adder Stock (The number gets added to the Open Loop Air/Fuel Ratio multiplier)
After Start Initial Adder Modified (Stock Multiplied by 0.25)
I data logged a cold start this morning with the wideband already pre-heated. Air Fuel ratio was about 0.72 lambda or about 10.15:1 immediately after it fired up.
After Start Enrichment Delay Stock
You must be registered for see images attach
After Start Enrichment Delay Modified (Stock Multiplied by 0.25)
You must be registered for see images attach
After Start Initial Adder Stock (The number gets added to the Open Loop Air/Fuel Ratio multiplier)
You must be registered for see images attach
After Start Initial Adder Modified (Stock Multiplied by 0.25)
You must be registered for see images attach
I data logged a cold start this morning with the wideband already pre-heated. Air Fuel ratio was about 0.72 lambda or about 10.15:1 immediately after it fired up.
xc_hide_links_from_guests_guests_error_hide_media