Maybe a newbie question but please bear with me...

I was logging at idle yesterday and discovered something that puzzles me.
Shortly after it went into CL the BLM dropped to 108 (which should indicate rich right?) and the PW went down.
At the same time the WB O2 showed an increasing lean condition, it went from around AFR 14 up to AFR 17-18.
The NB O2 also showed a lean condition with low volt readings.
Commanded AFR was appr. 14,7

When I blipped the throttle the NB and WB showed rich as they should.
The BLM went up showing lean?

I canīt figure out how this corresponds to each other. I thought that the BLM should be around 128 or at least go up when the NB and WB shows lean?
It might show a little bit lean at idle because of cam overlap and therefore add fuel but BLM decreases fuel instead.

Any help is highly appreciated!
Maybe this is a correct behaviour of the BLM?

The engine is a 383 with HSR, Brodix heads, flat tops and XFI280 cam.
Iīm running a modified Arap-bin, MAF-system.

 

Hi..

At idle I think you should tune it in "Open loop". Tune it so It wont smell gas and has a good Idle, WB AFR could be 13 or 17.... ex my car idles at 17-18 AFR anything below that makes it smell gas.

WB vs NB O2-sensor, NB is depending on temp also and could be tricky to trust with a big cam.

BLM wont change with a blip on the throttle, its "long term" adjustment. And when you bllip on the throttle you activate AE and that should make it rich.

I turned off closed loop a few years when I started to tune current engine, never turned it on again

 

NB and WB read 02. If you are filthy rich it may be reading unburned 02. As stated do you smell rich at idle? Is it possible the tune is way off at idle? As stated I would try OL and see if you can get consistant A/F at 14.00/1 at idle by tuning...low load crusing may be a lot easier to get 14/1-15.0/1...

 

Thanks for the replies.
I will try OL and discard CL altogether. Itīs probably easier to get a decent tune that way.

BR
JWi