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OBD1 SBEC Engine Controller ??

864 Views 1 Reply 2 Participants Last post by  ironmangq
Posted this question on jeepstrokers but didn't get much response. Running a 4.9 stroker in a YJ

On the current OBD1 set up the ECM does a good job of keeping the AFR at around 14.7. In fact perhaps a little too good.

I am using an Autometer WB with it`s own bung/sensor installed close to the ECM O2 sensor.

Closed loop operation.
Slight acceleration but still within closed loop parameter the AFR stays at around 14.7. Shouldn't the ECM momentarily richen the mixture a bit for the added airflow/load then stabilize itself back to 14.7 ? Mine stays at 14.7 even with a speed or load increase.

Open loop WOT
Again the AFR stays at 14.7 for 3-4 seconds. The ECM finally sees the open loop condition then starts dumping fuel for a high 12.x AFR.

Sustained 70% ish throttle.
ECM stabilized to throttle opening. At this point you can toggle the AFR back and forth between 14.7 and high 12`s by dipping in and out of closed/open loop.

It would seem that my ECM is not richening the AFR during closed loop and is slow to respond to open loop unless it has had a chance to "stabilize" itself for x amount of throttle opening. Is this common or do I have a lazy ECM ?

In process of finishing up a XJ harness to convert to OBD2/JTEC but am still curious about the OBD1 operation.

The JTEC is much faster acting so I suspect my AFR`s will come in sooner then what I am seeing in SBEC. What do you folks read during the above described conditions and how quickly does the ECM react to part and WOT conditions ?
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Is it reading the TPS sensor properly? you might have a lazy TPS so the ECM isn't seeing the quick change in throttle position and going into "acceleration enrichment" mode. Or your MAP sensor is lazy or not working right, It could be that the stroker engine is pulling enough vacuum at part throttle that it won't fall into the enrichment tables in the tuning, why the WOT run takes that long to enrich is beyond me other than the ECM not seeing the WOT throttle condition on the TPS sensor.
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