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 to idle ok around 700 or so and then starts stumbling anywhere from 950-600. I need to get it to idle correctly so I can finish balancing the TBs. In other words...the idle surges.

 

Surging is typically caused by being lean. The x-ram has a large plenum and a lot of surface area. I'd lock it in open loop and put a WB on it. Then try tuning from there. With a stock '8746 it isn't going to be easy.

RBob.

 

Thanks RBob. I did try doing that so it wouldn't go into closed loop and didn't help a whole lot, but I did gain a little ground that way. I'm working on getting a WB and using it to do some more tuning and also go to a heated O2. What do you mean by stock 8746? Thanks again.

 

Stock: slow ALDL data rate, limited data availability, small VE tables, limited AE tables, limited support of the IAT. The list is nearly endless.

A new 383, probably has a decent cam & heads, larger TBI units with larger injectors or more fuel pressure.

One item that can help is to get some heat in the intake manifold. This will help prevent puddling and help keep the fuel film under control.

RBob.

 

Ahhh...gotcha! Yeah your right, but a ton better than the stock 82 computer.

Did you by chance download my bin file and take a look at it?

Yep.... 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...

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!

 

check this out:
RBob says,
IDLE:

When in idle, the proportional gain and the proportional duration
use specific values. The prop gain is at: 0x2F9, and the prop duration
is at: 0x2F8. These replace the table lookups at: 0x4C7 and 0x4B5,
respectively.

For a rumpity-rump engine, it helps to set the idle prop term low.
This reduces/eliminates proportional action. This can have the effect
of smoothing the idle.

Also, do not forget about the O2 error bias value at: 0x2F7. This
value can be used to decrease the AFR at idle. Again, for a rumpity
engine, it can calm down the idle.

i made this change in my .bin. might be helpfull.

 

Thanks Ronny...Any chance I get download your bin and take a look at it and do a compare? Thanks.

 

Grumpy said:

An oscillating idle can be caused by:

Incorrect VE% table (flatten idle area).
Incorrect SA table (flatten idle area).
Too fast IAC reaction, increase (slightly) the delay values
at 0x5D7 through 0x5DA.
Stall saver set too high (it's kicking in).
Battery voltage varying.

too fast IAC action i believe is the throttle follower routines.

make sure not too lean in VE around idle cells. the XRAM idle A/F may be inconsistent due to design constraints. you may need to idle OL and giver it a rich commanded A/F. just my thought.

as far as my .bin sure i can email it to you. i just signed up for email(today) at my home. they are mailing a CD. office here will disallow sending a .bin. now that i think of it i dont think you can open it as it is a diff mask? maybe i can send you some tables of interest to you. i have only burned about 12 .bins since i adopted EBL so still a work in progress!

 

More good info, thanks a ton! I did flatten the VE/SA tables the other night and haven't really run it to see what the diff would make because it was late.

The rest of the info is great also, thanks again. If you have a web site, you can upload it there like I did for download of the bin.