jeepguy553

Been doing some tuning...here's what I have so far. Bill-usn1 told me I might have a little trouble with this because of the difference in engine size. I believe him now. 1.) Moved IAC Steps in Park back to OEM setting of 160. 2.) Moved lowest 4 points in VE1 down a bit 3.) Moved entire VE2 table down by 10% 4.) Moved IAC steps vs CTS up a little (@44.6F->162 steps and @60.8F->151) I am still getting a little smoke when the engine is in "choke". I also managed to notice a couple of other things I can change. 1.) (Table) Choke AFR vs CTS (0x34D to 0x35D). This one has a OEM setting of 1.80 ($12). What does this do? Does it change IAC steps? It seems to want to add a little more air to the mix, but I am probably dead wrong. 2.) Idle AFR vs VAC. Location 0x233. OEM setting of 1.80 ($12). What is this? Does this actually figure the idle AFR at a given idle MAP? TIA!

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1980 Jeep CJ-7 with a GM-fueled AMC V8, Accel 300+ ignition...GM 1-ton axles front and back...still sort of under construction

Z69

The minimum air setting would should preclude the need to raise this. As others have said, this is a CC air leak. It leans out the mixture. Check the recent IAC posts.

See above.

I haven't looked at $12, but by your title Ch AFR vs CTS meaning coolant temp sensor. It should change the amount of fuel added to the base fuel map based on CTS. So it should be lower.

My impression is you've got it backwards or write it that way. Not being a smart a$$.

Grumpy, I'm sure you will correct me. I'm probably AFU :hail:

Grumpy

Opening the IAC means you need to supply a large slug of fuel during crank. BTW, it can take awhile for the *slug* to burn off.
You've got to balance the commanded AFR, to IAC to commanded idle. And you want to get the decay AFR right.

Opening the IAC, and richening up the cold AFR is just going to use more and more fuel. I've been having good luck with closing the IAC down some, and then leaning the cold AFR. IMO, having the engine fire up and run cleanly cold at 900 RPM is a goal.

If you have to open the IAC up, then that might be an indication that your too rich.

jeepguy553

Not taken as a smart a$$ comment at all. It is exactly what I was asking for. If I wrote it backwards, then that means I understood it backwards and that is now corrected. I guess I was under the impression that i would change AFR by moving the IAC...now I know better...I think...
Best idea, don't fk with that one for now.

jeepguy553

Absolutely! Thank you Grumpy!
Now the question is...where to pull fuel from. The VE1% table? The BPC (BPW) location $241? Right now it is set to 120 ($78). I am afraid to give it anymore in fear that I might get even more fuel. The OEM setting was 128 ($80). I took it down a seemingly reasonable amount in an attempt to lean out the mixture some. I am wary of taking anymore out of the main table.
GRRRR!!! The engine SOUNDS really strong...but it still has a little case of the sniffles. I wish I could figure out how to post a sound byte of the engine at idle. AMC engines don't purr...they grumble.

Z69

Did you get the Autoprom?

This is a carb trick for idle setting, but pull fuel out until you get the highest vacuum/lowest map reading. This may be difficult since the engine will be warming up and the ECM will start pulling fuel out based on CTS.
You could make a few cells in the CH AFR vs CTS the same so it won't pull fuel out though.
As an EFI Novice, this is something I would try.

Are you using a 454 bin or a mix and match of a 350 and 454? (So I can learn too)

jeepguy553

Yes, I did get the Autoprom...and I love it. I have had a few problems logging data, but they weren't related to the Autoprom...it was my Mickey Mouse computer setup. I now have a PackardBell 486DX66 machine running Win98 for the emulation and the datalogging...in the garage. I have no idea what I am gonna do for mobile logging. I hope my Jeep buddy here can come up with a better laptop/notebook so that I can get some good data runs once I get the idle ironed out right.
My bin is the "cop car" bin. I should probably look into another base bin and use what I have for this one as preliminary settings for it.

JPrevost

If you're using TunerPro and my ecu file then it should have the comment about how that AFR vs CTS choke is used. Basically it is SUBTRACTED from desired open loop AFR. The open loop AFR table is derived from 2 arrays. One is based on vacuum and temp, the other is rpm and temp. From that you get an open loop map that can be tuned relatively well (for only having 2 arrays). Then there is the choke AFR which is subtracted from this.
I believe off the top of my head that you start with the RPM vs CTS open loop AFR lookup, then add the vacuum vs CTS open loop AFR lookup, then subtrace the choke AFR constant. The Choke then goes away slowely based on cold start CTS, does it, I forget. In any case you can tune how fast you want the choke to go away, etc.
For cold start, like Grumpy said, you might be too rich if you need a lot of IAC. I know from the factory they run really but I don't know why. Maybe it's to heat up the CAT quickly. I know there wasn't much cold start emissions testing back then so honestly I don't know why they do what they do.
In anycase, I would lean out the open loop AFR tables and if you're starting with the ANLU table you might want to look at getting the desired AFR to 14.5 and like 13.8 under no vacuum (high load). I've found this to be best. The stock open loop AFR map is really odd, it even has areas above 15.4 which suprised me.
I'm still working on it but I have some tuning software I wrote that combines charts to make 3d maps, I might release it once I get all the bugs worked out. It's really nice because it does a 3d plot of the whole open loop AFR and then you can click a button to add the choke and watch it decay. I haven't figured out the timing of decay but it's just some eye candy to help visualize. Another table that my software does is combine the 2 VE tables into 1 plot. I've finished a new feature that I find useful, it's called "smooth." It's really good for getting a table quickly mapped out nice and smooth. Just pick a strip of data and it'll interpolate between the points.
I think before I release this software I'm going to try and get the romulator to hookup right and aldl stream data. That would be useful for quickly getting a VE table mapped out . Let's hope I keep the c3 ecm for a little bit longer and don't loose interest.

jeepguy553

This is being printed and saved for tomorrow's tuning adventures.
If you want a C3 ecm to play with, PM me with a shipping address. I have a 7747 I will give you (no PROM) if you want it to fool around with.
Where (mathematically) is it subtracted? That's really what is throwing me for a loop. For example, intuitively, if I had a 14.7 AFR and the table tells the ECM ot subtract 3.0 from that, it would leave me with 11.7 AFR...right? I know this is nit-picky, but I really want to understand this so I am not robotically changing settings.
Thnx, Jon.

kevm14

Then here's my question. I have a 6965 ($62) and I believe it works the exact same way. But why couldn't GM have worked the choke AFR functionality into the AFR vs CTS array? Why two arrays for essentially the same thing? Is it possible that the choke array is still used in closed loop? I have been reading Grumpy's posts about his 454 pickup and I tried some of those things. I reduced the cold start closed loop timer and decreased the closed loop coolant temp threshold and for the first time, I've seen BLMs in colder coolant temps. And they are mostly pretty low, 109 at one point. Could I use the choke array to adjust for this?

Also, I have tried to add fuel at high load areas via the AFR vs vacuum array (open loop) and what I got was very unexpected. The engine fell on its face and the O2 actually went to zero, indicating to me to be a very lean condition. I asked tunercat about this and he has no idea why it would do this. Does anybody else?

RBob

The choke AFR functionality and the AFR vs CTS array have two different purposes. The choke AFR adjustment decays out quickly. It is only intended to help prevent stalling during initial startup. There is choke SA involved in this also.

The AFR vs CTS array is intended to adjust the AFR for best running. A cold engine requires a richer AFR in order to run properly.

RBob.

kevm14

This is my stock table:


Also, Tunercat says of this table in the $42 help file:
"This cold engine AFR vs. coolant temperature table is used to control engine AFR after the ECM has gone into “closed loop” and prior to reaching normal (or near normal) operating temperatures."

So is it used in closed loop? I don't see any other way to dial in my lower coolant temp BLMs other than this table. Am I missing something?

jeepguy553

Just a thought...what would happen if you:
1.) Bumped the CTS Threshold for Closed Loop up a little...OR
2.) Looked at the O/L tables and tuned them before the engine goes into C/L...maybe look at #1 to stay in O/L for a little longer

RBob

No, the AFR vs coolant and the AFR vs vacuum ($42 mask) tables are added together and only used during open loop. Closed loop AFR (stock w/gasoline) is 14.7:1.

If you are trying to dial in BLM's then the ECM is closed loop. In what way does the $62 mask use an IAT?

RBob.

kevm14

Tunercat shows launch mode SA multiplier settings and a BPC multiplier.

Problem is, the BPC vs IAT table looks like this:


This does me absolutely zero good for tuning colder CTS closed loop BLMs to 128. This is why I thought the choke table might somehow affect the ECM's closed loop fueling, not in terms of deviating from 14.7:1, but getting the BLMs to 128. In other words, it's just another term in the grand equation to calculate injector PW. Besides, TC's help file says it's used in closed loop. Maybe I'll e-mail him and ask. Then again, I'll probably just play with it and see; that's the best way to learn.

I realize this, but we're talking about the "Air Fuel Ratio at Startup Vs. Coolant Temp. (Choke)" table, which tunercat's $42 help file says is used in closed loop. I'm just trying to turn my 109 BLM at, say, 120*F coolant to 128...

kevm14

I recently lowered the threshold for closed loop just so I could get some O2 data at these never-before-seen coolant temps (in closed loop). And I've tried tuning with the open loop arrays. I can't seem to dial it in right, AND when I play with the vacuum AFR table (specifically, add fuel at high loads) the drivability gets all messed up and there is a severely lean condition, even with small changes to the table. I've asked Tunercat to look his $62 over but he says it looks right, so I have left the vacuum table stock...

RBob

Ah yes, the "IAT is getting a tad hot so add some fuel to cool the engine table". If not running a thermovac preheat aircleaner can patch the code to expand the table. And yes, probably used in closed loop.

As far as the "Air Fuel Ratio at Startup Vs. Coolant Temp. (Choke)" table, it may be in effect during closed loop, but I am hard pressed to see how. By the time the O2 starts switching, the coolant is up to threshold temperature and the closed loop delay timers expire, the choke AFR would have decayed out.

With the problems you are having it almost sounds like something else is going on. Once up too operating temperature how does it drive?

RBob.

kevm14

It tends to drive pretty well, but to be honest, I think I should dial in my VE a little better. For the most part, my [regular operating temp] BLMs are 125 to 128 but I have caught a few 120s at light load recently, so maybe I should turn those into 128s before complaining about cold temp BLMs.

I'm not running the heat riser from the manifold to the air intake, but does anybody have a clue about 6965 code? I mean I know it's still an HC11...I have used Tunercat's decompiler before to look at the code, because I wanted to turn my speed limiter into a rev limiter, but my variable names aren't the same as the $61's.