Idle-EBL question - Third Generation F-Body Message Boards

Ronny · 10-31-2006, 10:06 AM

8746 with EBL.

i am idleing in "synch" per changes recently done to disallow asynch. open loop at idle.

previously i am of opinion that when it cycled synch-asynch-synch the surging idle was that transition. WB showed enleanment-enrichment with stall saver active. A/F OL idle was 13.5 to 14.0. 750-900 rpms. no IAC activity. zero counts.

now when i idle in synch i still have a pulsating idle. the pulse width moves from 1.3 to 1.6 or so and creates a surge. 500-800 rpms. on WB it shows a lean idle at 15.5-16.5/1-15.5 or so. A/F moves with surge. again open loop. stall saver is not IAC just the BPW increasing.

all i changed was to force synch?

it appears i need to enrichen IDLE-OL. and raise idle speed somewhat. i already moved that table Open Loop-AFR vs CTS & VAC @ 10% richer.

is that the table i idle off of on A/F OL?

is idle speed commanded off IAC-DRIVE and IAC PARK-NEUTRAL?

what is an IDLE CELL and where is it located in TP?

BLMs in CL under 2000 rpms 25-40 map show around 130-135.

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RBob · 10-31-2006, 11:24 AM

When the engine idles in open loop, both the VE table and the Open Loop-AFR vs CTS & VAC table is used.

The desired idle speed is from the IAC drive and park/neutral tables.

As you mentioned forcing the ECM to use sync injection mode helped quite a bit. This is a normal occurrence when running higher fuel pressures and small PW's. Down the road going to a VRFPR will additionally improve the idle.

Now to finish out the idle tune, set the forced idle open loop bit in the option word. Can't recall off hand which one it is, just check the calibration doc. Then start the engine and let it idle for a few minutes. This is to allow the after-start enrichment and SA to decay out.

Using the Prominator Pro you can make real-time changes. This makes idle tuning a piece of cake. Observe the RPM & MAP with the WUD, and note where the engine surges in RPM. That will be a lean area.

Increase the VE% in the cells of that area. Observe result, if better, then continue on. If worse, back out some of the changes. Once the idle settles down, change the desired idle RPM. And tune that area. Go up and down the RPM scale some until it is all good. You may also find some areas that are too rich. If so reduce the VE% is those areas.

Then return the idle speed setting to where the engine should idle. And take it for a drive. Note how the engine returns to idle when coming to a stop. If it doesn't return to idle smoothly take a data log of it. Look at that area and make further changes.

RBob.

Ronny · 11-01-2006, 10:36 AM

thank you for your help. the underlying VE-1 are lean. i narrowed down the cells it idles in and enrichened 10%. do to pulsing idle 850-600 rpms 30-50 MAP it covers a block of cells. so did all it sees. needs more enrichment still. idles 15.5/16.0 this morning at 185 F. will do that. due to cold intake manifold it appears it is needing more enrichment due to environmental temps. engine dies on deaccell to a stop. this is a manual trans remember. when heat soaked after 25 min drive it does not die but surges even more so.

pulse width is 1.1 to 1.6 "synch". iac is zero counts but sometimes will see 5 during event of surge. idle commanded to 825 in both park/neutral and drive for temps above and below 180F(+ - 15 deg).

i upped the iac stall saver rpms window to 600-750. is this right?

what is iac minimal idle steps? it is see it set at 13 at 180 deg yet my log show 0-5.

why cant the ECU lock the PW at say 1.6 and create an even flow of fuel. something is telling ECU to raise lower the fuel amount. is it the stall saver?

bottom line is i still may need to throw more gas at it.

comments please...

Dominic Sorresso · 11-01-2006, 01:41 PM

Ron,

The cam may be causing the VE to swing between cells. If those adjacent cells are too different than the other, you'll get a lean surge condition. Spark table may affect it the same way. The ECM is reacting the the MAP variations. Have you tried the idle state SA feature with EBL?

Ronny · 11-01-2006, 02:01 PM

the spark is the same in all cells it sees at idle. but will double check that. OK i did. 20-50 map at 1000 rpms spark is 23. 800 rpms is 21 across map. 600 is 20A.

i will now check the VE-1 table to be certain there are no cells that are mismatched so to speak. as follows:

20-25-30-35-40-45-50 map

1000 46-46-43-19-14-15-35
900 46-46-45-45-15-12-32
800 46-46-45-42-26-22-32
700 46-46-45-43-47-25-36
600 47-46-45-45-42-36-39

think the VE table needs smoothing. i will suggest some have been learned. maybe not?

Quote: idle state SA feature with EBL?

what does that offer?

Dominic Sorresso · 11-01-2006, 02:15 PM

Ron,

If I'm reading this right, why are the decel areas in the VE table so rich? I can see why a surge between 700 and 900 rpm.
The Idle State SA is an Option Word. You check it and then set the Desired Idle SA. It will maintain that Spark Advance while the car is in idle with none of the variation you would get from using the Main SA tables.

Ronny · 11-01-2006, 02:29 PM

you think i overenriched at 20 map. did so since when deaccellerating(DE not functional) the A/F on WB pegged very lean. and i believe it was CL when i saw BLM's read extremely high during this event. so i added fuel and now with prolonged accelleration BLM's are in line when i see 20 map at all rpms. keeps manifold wet and i dont see the harm.

as i stated my A/F in OL idle is 16.0/1. that is probably related to surge(lean). i fattenned up all those cells this morning and this post is current value.

i will suggest 850 rpms at 40 map is where i should idle for my motor.

i see SA-Idle state SA. it reads 20. idle SA bit is checked.

Dominic Sorresso · 11-01-2006, 10:18 PM

You want the AFR in the decel area of the VE table to be lean. Mine goes to 21:1. The injectors are shut off. I don't want fuel in on decel unless I want the exhaust to crackle and pop. As for where your idle should be, it'll be where it will be. Mine is at 875-925 at 46-50 kPa. Depends on your cam.
If the Idle State SA is checked then idle is using 20d.

Ronny · 11-02-2006, 11:49 AM

OK. the option word is checked and log shows idle at 20 deg A steady.

i am now thinking it may be a clogged fuel filter??? i keep throwing fuel at those cells i am surging accros rpm/map and cannot get idle A/F enrichened? i added more fuel to VE1 last night to no avail. the values i posted are current and it is still idleing at 16.0-16.5/1. i also added globally 10% more fuel to the Open Loop-AFR vs CTS & VAC as stated in post.

seems this issue manifested when i forced synch-idle. in CL it is right at 14.7/1 ???

not sure if this is related but you will recall to get VE2 under 100 at 2400-3000-40-50 map area i needed to fudge the BPC. last i checked VE2 i had a max value about 93 in a couple cells but my BPC which should be about 80 is currently 120. good news is the WOT A/F is now 12.7 as commanded. was over 13/1 before i upped FP to 24. WB has new sensor properly calibrated.

should i add fuel to those cells that are under 30 down here?

1000 46-46-43-19-14-15-35
900 46-46-45-45-15-12-32
800 46-46-45-42-26-22-32
700 46-46-45-43-47-25-36
600 47-46-45-45-42-36-39

seems getting idle squared away should not be this difficult.

RBob · 11-02-2006, 01:05 PM

I reformatted the VE chart for an easier view:

Code:

      20  25  30  35  40  45  50 map

1000  46  46  43  19  14  15  35
 900  46  46  45  45  15  12  32
 800  46  46  45  42  26  22  32
 700  46  46  45  43  47  25  36
 600  47  46  45  45  42  36  39

For your question about the low cell values, yes, I would just bump them up. The ones that are 12, 14, & 15 set to 24, then the one at 19 to 30. First need to get the surging to stop, even if it means to be on the rich side. Can then adjust the VE for the best idle.

The values at 46 at 20-25 KPa are most likely never be used. It is rare for a cam'd engine to reach that low a MAP value at such low RPM.

As for the fuel filter, I believe there is something not right about the fuel delivery. IIRC you went to a BPC of 140, with fuel pressure at 24 psi. That doesn't really add up. When you get a chance email your current BIn to me (thanks).

RBob.

Ronny · 11-02-2006, 01:15 PM

i will send it tonight. you asked for the old pre EBL 7747 also and i dumped all those. however one is still sitting on a chip so will get that to you as well this weekend.

hopefull that will do the trick. will know tomorrow.

just a dumb question? if we can lock the SA idle at a set adv (20) why cant we lock the fueling at a set PW? that assumes the rpm and the map will hold steady. in essense i guees that is what we are doing in making the VE transitional cells similar in fueling.