BLACK10 said:
Bone
I have know Idea about open or closed loops ..all I know is every time I put the pedal all the way to the floor my A/F drops to 10
First off, do you have a stand alone wideband gauge you are seeing this with? My W.B. Gauge reads a little richer than a dyno pull for whatever reason. I am still researching it.
A mode of operation in our PCM that occurs after a cold start. During open loop, the computer provides a fixed air/fuel ratio that is richer than normal to improve cold derivability until the engine warms up. So one thing to do is make sure the engine is warmed up prior to a good SC pull.
However, I have seen both the flash (not SC flash) and the VEC go into Open Loop for 0.3 seconds during dyno pulls. I do remember some debate on how long the engine goes into Open loop (VEC vs Flash). Nevertheless, not to start too much trouble, and Boomer deserves a reply, but on my truck I witnessed OPEN Loop (after truck was warmed up) with the VEC alone, the Flash alone, and both VEC and Flash together, not for a huge time but long enought to be a concern, approximately 0.3 seconds. NBT was present during the multiple pulls on the dyno. I'm not bashing either system, just pointing out it is an issue to deal with in our trucks.
I now can also monitor it daily with the Scan Gauge II.
http://www.vtcoa.com/forums/showthread.php?t=1549&highlight=scan+gauge
However, I am no expert on SCs and would have to ask DC, Boomer, and Sean. It may just be the tune? At least you are safe and it's not 17+! Throw a 125 shot on there and it would probably bring it to 12.5 AF !