Ok, I just started doing the ECM tweaking on my 8746 with the Prominator on a new 383 with twin TBs on an X-Ram manifold. The problem I'm having is that it won't idle right. The motor starts and idles ok in open loop, then in closed loop the idle ok around 700 750 or so and then starts stumbling anywhere from 950-600 off and on. I need to get it to idle correctly so I can finish balancing the TBs. In other words...the idle surges intermittantly. The timing is at 10* now as well.

Cam, .520-.515, 224-231, 113. Dart Pro1 heads 180cc, 64cc. 2" TB with 80lbhr injectors @20psi. headers, X-ram version IV top plates, the list goes on and on...

If someone with lots of bin experience could point me in the right direction or would like to take a look at the .bin I'm using, you can download it at:http://members.***.net/buccaneer95\Tom 383.bin BTW: you have to copy the entire link and then paste it into your browser instead of just clicking on it to download the .bin. Sorry about that!

Thanks for any and all help.

 

i had that same issue with my prior 7747 and pre EBL. what i saw was the CL idle falling into "asynch" due to the larger inj's not able to idle CL at 800 rpms. i run 23 lbs FP to fuel adequately WOT. that FP too affects idle quality. "asynch" flag shows in my datalog as this occurs. with idle falling into asynch the fuel is being cut off and engine dies and is caught by stall saver and IAC opens brings up idle speed and IAC returns to zero steps causing the surge to repeat. there is info regarding this on "throttle follower" also if you search. i believe the IAC routines can be tamed a little so as not to over react. also search "proportional gains". i believe it too addresses the surge issue. i am now idleing OL with EBL. seems the conversion to EBL improved my idle quality.

 

Buccaneer,

Your bin shows that you have disabled asynch which is fine. Your surging may very well be a lean surge at idle. I would add some Injector Bias. You have none now which could mean that by the time the injector can open, its also supposed to close. I use 770msec. Think of it as timing advance for the injectors. I think your TB's are too small for a 383 but that isn't the problem.
I would also get the EBL ECM. VE and SA tables much more granular for better control over fueling a cammed motor.

 

Thanks a ton guys, I really appreciate any and all info concerning this issue and a way to correct it. A friend of mine has the EBL and loves it and suggested that I move in that direction. His 383 is fairly close to mine except he is running 2.13" TBs and 90lbhr injectors. If I make some changes, would you take another look at the bin? Thanks again!!

 

Dominic, I changed the Bias to 770usec and no change in idle. Then I tried several other variations of that, like 360usec 150 etc...Still with no real change. So I set it back to zero. i know this will probably take a while, but I'd like to get it closer faster. any suggestions?

 

consider OL idle?

 

Thanks Ronny. I sent you a PM.

 

Just leave it at 770 and start tuning. There's no "silver bullet".

 

Ok, after a few hours of playing and asking a lt of questions. It was found out tonight that I have a bad 8746 ecm. I swapped in a 7747 from a friends vette with a known good 383 bin and fired it up and it idled pretty good with no surging in OL or CL. No glowing tubes at CL etc... After datalogging for six minutes, the numbers looked fairly good with all things considerd. I'll be getting a new ecm with an Ostrich and EBL this time. Its always something, but at least I'm making progress and hopefully get the beast running great.

Thanks for all your help and support.