I've been tuning on an 1967 Super Sport w/ a BB 427 running a 730 ECM and have been having a tough time keeping it in closed loop long enough to log data. That being said, it seems that the more closed loop ECM learning the longer it will stay in closed loop. Here's the theory,

With a fresh burn, BLM's are set to 128. When the CL timer times out, the ECM will go CL. If the VE table is too far off, the BLM's aren't corrected fast enough to get the Os MV to cross over. Bang, the ECM switches back to OL. Shut the car off and restart. Timer times out again and ECM tries CL. BLM learned value is closer to being correct this time , so I'll get a few cross overs and the ECM stays in CL longer. Keep stopping and restarting and it seems to lock into closed loop better as the BLM's are learned. This is what I've observed. Am I smoking something here or have any of you seen this happen as well?


I'll throw the disclaimer in here for unsuspecting readers trying to solve problems. The information in this post is pure conjecture on my part. Please don't run with this as fact.

Thanks
Steve

 

What benefit, if any, is there to shutting the car off when it exits closed loop? I hope I am reading your post correctly. Is the tuning that far out that you can't just drive it and let it learn more and more? Or, in your case, will it not re-enter CL w/ out a restart?

Being that you're getting closer & closer, shouldn't you be tuning fuel curve to get it in the neighbourhood even further, speeding up the overall process?

Curiously, how long does it stay in CL?

Matthew

 

What software are you using that the engine needs to be in closed loop to datalog?.

I'd set the closed loop enable temp to 254, remove the O2 sensor and start dialing it in so that it at least runs half decent. then worry about fine tuning it. It sounds like your way off on where you're at. And you'r e fighting the ecm rather then letting it work for you.

 

Curiously, how long does it stay in CL?

Seems like it will only stay in CL for a few seconds then the O2 ready bit goes low and reverts back to OL. I was under the impression that the 730 would keep trying to go CL after a timer times out, and maybe mine is, but datamaster is not showing it.

The more time I get on the ECM the more it'l stay in closed loop.

I'm using Datamaster. Sure I can log OL data but I'm not sure what tuning can be accomplished when the ECM isn't correcting BLM's.

BTW, The car actually runs pretty darned good in both OL and CL. I've got the VE table in pretty good shape now and all BLM's are between 125 and 132. Not perfect but in the ballpark. Most of my problems now are some "tip in" flat spot from idle (maybe acceleration enrichment?) and it will also lay over pretty bad with a WOT stab at about 2500 RPM. I think the next step is a couple of WB dyno pulls to get the WOT enrichment in better shape.

Any one know how the Acceleration Enrichment table works? It looks kinda backward to me. Starts a factor of 1.00 at 0% delta tps then goes down to a factor of .25 as Delta TPS increases. Very Confusing! That being said, I keep telling myself that a Port Fuel Injected motor shouldn't even need a pump shot because the injector is right at the intake port.

Any insight would be appreciated.

Thanks for the posts guys

Steve

 

After weeks of frustration and second guessing my understanding of the 730 ECM, I finally found the reason this thing wouldn't stay in CL. Bad ECM! Through process of elimination it just got down to a bad ECM. Car didn't throw codes and ran well but just wouldn't stay in CL for more that 5 seconds at a shot. Swapped out the ECM with another one, and bang! Works like a champ! OK , now I can move on to some final tuning. What a way for a newbee to start. Oh well, I got a good education sorting out this mess.

Thanks for all who tried to post with some help

Steve