I managed to get a short test drive and a data log. Question relates to EBL behaviour during deceleration from a steady cruise.
Engine 350TBI + 700R4 in 1975 C20.

Data log extract and narrative
(7:17 to 7:22) During steady cruise ECM is in close loop and 02 transitioning normally
(7:22 to 7:23) Deceleration started De = Y Cl=Y
(7:23 to 7:33) Continue to decelerate, but DE mode goes away! Why? TPS =1, Cl=2, NBO goes to 902mv!
(7:41) Close Loop is reestablished once speed is below 5 MPH

Time RPM MPH MAP BRO VAC VE% TPS CTS IAT I/C O2 G/S SA KnkCt sPW aPW DC% Ay Ae De Id Pe Dc Cl Ln Fn Ac Tc Cp Eg Cl INT BLM BPC IAC Fpsi AFR WB dTPS tpsAE dMAP mapAE aePW
0:07:17 1475 40 49 103 53 71 12 66 29 63 704 51 21 29944 2.563 0 12 N N N N N N Y Y N N Y Y N 1 128 123 135 42 0 14.7 0 0 0 0 0 0
0:07:22 1450 40 48 103 55 70 11 67 29 64 810 50 20 32869 2.533 0 12 N N N N N N Y Y N N Y Y N 1 131 123 135 43 0 14.7 0 0 0 0 0 0
0:07:22 1450 40 47 103 55 68 11 67 29 64 819 49 20 32929 2.38 0 11 N N Y N N N Y Y N N Y Y N 1 128 123 135 43 0 14.7 0 0 0 0 0 0
0:07:23 1275 40 35 103 68 62 5 67 29 65 903 37 21 32929 1.617 0 6 N N Y N N N Y Y N N Y Y N 1 128 123 135 38 0 14.7 0 0 0 0 0 0
0:07:23 1275 40 31 103 72 57 1 67 29 65 903 36 21 32929 1.343 0 5 N N Y N N N Y Y N N Y Y N 2 128 128 135 38 0 14.4 0 0 0 0 0 0
0:07:33 875 26 29 103 74 58 1 69 29 67 903 25 20 32929 1.526 0 4 N N N N N N N N N N N N N 2 128 128 135 21 0 14.4 0 0.4 0 0.3 0 0
0:07:41 625 4 38 103 64 52 1 70 29 69 894 16 18 32929 1.74 0 3 N N N N N N N N N N N N N 0 128 128 135 18 0 14.7 0 0.4 0 1.9 0 0

 

The reason DE goes away, is that the TPS and MAP have more or less stabilized. DE only occurs when you have a transient condition, like AE in reverse. If you want to rid your engine of fuel while coasting, that is the responsibility of DFCO or Deceleration Fuel Cut-Off

 

Fast355

Thank you for explanation regarding DE mode. Perhaps I have misstated my question - why ECM goes out of Close loop during coasting - perhaps DFCO operation requires OL (newb assumption on my part)??? Also, during prolong coasting DFCO flag in WhatsUp display was not active.. So - more questions (learning curve)

//RF

 

'Option word 3 - bit 5 - OpDcl' is probably set. This will put the ECM in open loop fueling during decel. Once un-set, you may experience surging during decel. If so it may be either the proportional gain at the gms/sec airflow is too high. Or the ECM is switching in and out of async fuel mode.

DFCO, to enter this the vehicle speed needs to be above the MPH parameters, and the RPM above the RPM parameters. This is usually for highway speeds on a thottle lift. Keeps the CAT(s) from melting.

RBob.

 

Rbob

Thank you - I should spend a bit more time reading documentation. In my application I have no CAT(s), but with old carburetor I used to get a lot off popping in exhaust during deceleration. Since I got EBL it is fascinating to see what ECM - engine are doing 'real time'. It runs very well, starts right-up and runs smoothly. Plenty of power to move 6000lb of Detroit iron down the road.

I am still dialling in my combo - the ESC module is way too sensitive or the engine is noisy - lots knock counts. Even though I do not hear classic load pinging - KS sensor is from pre-roller cammed 350. Like you said in your earlier post early ESC modules are less sensitive. Thanks again..

//RF

 

Sorry for the ressurection of the thread, but this is what is happeneing to me.

My car is switching in and out of asynch mode and I am getting a decel and very little throttle surge. I didn't always have, but about 20 or 30 bins ago it became more apparent, I dunno why. Is there a way to stop it from going into asynch during decel?

Thanks

 

Just set these two parameters to 0:

# INJ - Async Transition Hi
# INJ - Async Transition Lo

That will prevent the ECM from switching from sync to async mode from small PW's.

RBob.

 

Thank you RBob, I appreciate it. Gonna burn a new chip for the ride home and see if it gets rid of it. haha.