OK, thought I understood some of this stuff. Here’s the problem I can’t solve – At idle while cold and warming up in open loop, Cell 4 INT = 128 and BLM = 114. This BLM would indicate it’s rich and can smell gas fumes for a mile. So as a rough shot at leaning idle while emulating with AutoProm and monitoring with TunerPro RT, select VE table rpm cells 400-600 for all KPAs 20-100 and multiply by .9 and idle on that. Can hear the engine change slightly but BLM does not change. Multiply by .9 again and can hear idle change more radically and it runs rough and nearly dies, but again no change in BLM.

So perhaps some stupid questions:
1. How (specifically) do you lean (or richen) $8D Speed Density open loop idle before it goes into closed loop, and
2. Then how do you see the effect of your changes?
3. Granted the ECM is in open loop and not in learn mode, but why are the VE table changes not reported in BLM?
4. And if they are not going to be reported, then were back to the 2nd question – How do you see the effect of your changes?

Details:
· 7730 ECM, $8d Mask, Speed Density, basically stock AUJP (EGR delete, VATS disabled)
· VE Tables are unchanged from stock AUJP
· TPI Using 22# injectors with Injector Flow rate set at 22.98, which gives BLMs of 125-129 in all BLM cells --- except for idle (cell 4)
· Idle set at 650 RPM in ECM and that’s right where it idles (650-675 RPM) steady

Help please. Thanks!

 

I will help you w/#2, #3 & #4, other members will answer better for #1- ie. give you directions to finding your open loop AFR tables, idle lean limit afr, IAC settings...

#2: I observe OL changes with wideband o2.

#3 OL fueling is independent of & does not affect BLM, thus no change.

#4 As you said, see #2.

My last bit of advice is, don't snap at the boss when he tries to help you.

Nice Car!

 

Xch3no2, Thanks. – Don’t have wideband O2, only single wire. I know you didn’t address question #1; but without wideband, does that mean that I can’t correct an overly rich OL idle. Rather just have to accept what he ECM gives and wait for closed loop?

And by the way, who have I snapped at?

 

No not at all, you can raise the AFR in the lower rpm v kpa of the open loop table, balance w/IAC & throttle stop setting & maybe raise max lean idle AFR.
But,
My first move would be to determine why (if the engine is stock) is the idle rich. Give a good hard look @ IAC steps/activity & physical condition, maybe an aging CTS? Has the timing been inadvertently altered? PCV unrestricted & proper part? Injector leaking?


BTW when using text, bold means loud, italic means insistent, you used both & it came across very snotty. The man you were addressing is one of the most knowledgeable you will ever have the opportunity to engage. I suggest that you do it with respect.

 

I'm thinking there is a basic misunderstanding of when those BLM tables get looked at. Maybe I'm the one who misunderstands.

I was under the impression (Boys, PLEASE correct me if wrong!) that if the ECM is still in warm up, it is in "open loop" at that point, and not looking at those tables yet. That would explain why your changes have so little effect, as the ECM hasn't begun to look at them until it gets to "closed loop", which will be after warm up, not during.

I offer my preemptive apologies if I am wrong.


Dave

 

Thanks again. I’ve given thought to all the questions you posed, especially why rich at OL idle when everything else seems reasonable, but cannot come to any solutions or conclusions. Here’s some more info you addressed that may help; hopefully, it’s not TMI:

Engine not stock, but not radical either. Has less than 1000 miles on it and trying to get thing right: 350 +.060, 52mm TB w/airfoil, mild hydraulic cam, headers w/Flowmasters, ported & polished heads and matched ported & polished TPI intake, Accel ignition components. Everything is basically new. No vacuum leaks. Passes all fuel pressure/injector checks per GM shop manual. New CTS, TPS and refurb TB (no shaft wobble, leaks or vac leaks). CTS temps being reported appear accurate. Have 2 PCV valves and both new and active. IAC & TPS set via proper procedure (idles steady at 650rpm with approx 30-35 IAC counts (this may be deemed to be too high, but repeated settings & resettings always cause it to settle in at this level), TPS slightly high at .59v – excellent throttle response). IAC activity during datalogging appears right in that it moves up with higher rpms and drops as they decline. KPAs also 40-ish at idle and increases as rpm rises. Timing set with wire pulled at 6* BTDC and that setting is in ECM. In closed loop, for all but cell 4 idle, BLM’s are slightly rich to 128 and require some VE table tweaking. That’ll be done once the OL idle issue is solved. CL Idle is averaging 116 BLM so it is also rich. But I can change that in the VE tables and can see the effect of those changes in INT and BLM.

After writing all that, I reflected back on something you said in your first post: “#3 OL fueling is independent of & does not affect BLM, thus no change”

So sorry to beat this point to death, but if the results of raising the AFR in the OL lower kpa .vs. rpm table, etc., will not be reflected in BLM in OL, then I’m back to my original issue – What do I look at when datalogging/emulating to determine the effect of any OL fuel changes? It seems I have to have WB O2 to do this if there will be no change in OL BLM. This is what I can’t seem to get a grip on. Thanks for your patience. I’ve read hundreds of post and articles but this matter has just not registered with me.

 

I think that you are soon to be the very happy owner of a WB o2 setup.

Your engine configuration is improved enough to require the stock bins be altered to match.

I'm using Innovates LC-1 controller & have found it to be a priceless tuning aid.

 

How does the engine run, this is what to look for. If it is better when a bit richer, then that is what the engine wants. If better when a tad leaner, then that is correct.

Tuning is not giving the engine what we think it wants. It is giving the engine what it wants.

RBob.

 

running 2 PCV valves will cause problems if the motor does not have a vent of some kind to pull fresh air in.
all you really need is 1 PCV valve in 1 valve cover with a filtered vent in the other VC.

have you cleared the ECM memory? not just clearing codes with TunerPro, but killing power to the ECM by disconnecting the battery.
the computer uses learned values at startup.
when im working on my tune, i hook the constant power memory wire to a switched ignition source to clear the ECM every time i turn the motor off.
like that my ECM is always at 128/128 at startup, cold or hot.

 

Lakeffect2 – You’re talking my language. Like you, also believe that both INT and BLM are locked at 128 until closed loop is entered. As stated by xch3no2, apparently the only way to monitor idle fueling in open loop (or any other fueling issues in OL for that matter) is with a WB O2. If that's wrong, I too offer apologies and would welcome an understanding of how it’s done. Maybe someone could just say it directly or offer an alternative.

RBob, no disagreement that we should give the engine what it wants, but without a way to monitor the effect of what it eats in OL, we’re flying blind – which is what I thought datalogging capabilities sought to eliminate. Raced cars before computers for many years in a prior life and that leads me to believe my car’s rich in OL idle, but am reluctant to start changing OL parameters without understanding (seeing) the effect of those changes. That’s why I’m searching for an answer. If it’s WB O2, then so be it.

DENN_SHAH, thanks for the reminder about clearing the ECM before each logging session. Had forgotten to do that. Actually have a hidden toggle switch across the hot lead to the 2 ECM connectors (B1 and C16 I believe) that I just forget to use. I'm correcting the PCV valve issue. Thanks.

 

84Elky, Yes the only way you will get good, hard number, reference in OL is to install a WBo2.

With that said, be aware that your own sense of hearing, feeling, even smelling the engines operation are not to be disregarded. In fact the WB is there to confirm & quantify what all these years of wrenching have taught us. It can just as easily misguide or lie to you.

When or if you rely only any one aspect of observation, there will surely be something sneek up behind you & plant one across your backside.

 

Thanks, and Amen!