Jeep Strokers

Start by going backwards.

My OBD2 swap is well underway. Much of the harness has been completed and will be ready install soon.

Question.........

On the current OBD1 set up the ECM does a good job of keeping the mix at around 14.7. In fact perhaps a little too good. Using an Autometer WB with it`s own bung 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 ?

The JTEC is much faster acting so I suspect my AFR`s will come in sooner then what I am seeing in SBEC. In the mean time I am still curious what you folks read and how quickly the ECM reacts to part and WOT conditions.

Having not seen SBEC cal I am speculating at best. But as far as I can remember, early JTEC did not have much OL transition delays, either rpm , MAP, time based. Later models did. I would be curious to see if SBEC did.

Many widebands will not catch the fluctuations in AFR found in closed loop, this is why I use and swear on Innovate products.

I think Dino has OBDI. You may want to compare notes with him.

Was hoping he might chime in.

I had to unhook my factory o2 sensor and adjust my hesco f/p regulator to get any place close on my fuel trim. I now have it in the 13-14 range under normal driving and 12.2-12.5 under hard acceleration. I just leave the o2 unhooked all the time.

jsawduste wrote:Start by going backwards.

My OBD2 swap is well underway. Much of the harness has been completed and will be ready install soon.

Question.........

On the current OBD1 set up the ECM does a good job of keeping the mix at around 14.7. In fact perhaps a little too good. Using an Autometer WB with it`s own bung 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 ?

The JTEC is much faster acting so I suspect my AFR`s will come in sooner then what I am seeing in SBEC. In the mean time I am still curious what you folks read and how quickly the ECM reacts to part and WOT conditions.

Sorry I only just noticed the thread.
Yes I do indeed have OBD I but my Jeep is an export model without O2 sensor feedback control and no cat so it's permanently in open loop mode.
However my ECU behaves similarly and I think this was by design from the factory to optimize fuel economy. Under part throttle acceleration the AFR stays at 14.7 until the engine hits 3000rpm, and then it's as if a small N2O shot kicks in as it goes rich with a sudden surge of extra power. When I plant the pedal to the metal the ECU does respond quickly and the AFR goes rich almost immediately but only when I'm past ~2000rpm.

Thanks Dino, it would seem that our ECM`s are behaving similarly. Not exactly as my transition to open loop is slow compared to what you are describing.

This again is one of the reason I am looking forward to the OBD2 swap. A much faster processing of input data.

jsawduste wrote:This again is one of the reason I am looking forward to the OBD2 swap. A much faster processing of input data.

Yeah, it's a bit like going from Windows 95 to XP.