Which tables for cold start?

[CDeeZ]

Man I'm glad that you responded with your insight. Thank you so much!

I think that my AFR is actually leaner than what was stock. At least for the bin that I started with which I will post. It's a 350 4L80 bin.

Yes, good point about the fluctuating map causing AE during cranking and startup, I had not even thought of that.

I'm not sure why, but I have chased my tail with the IAC counts. The last time I set it with a fully warmed engine it was around 20 or so counts on the scanner..... I was shooting for 10 counts but I either coulnd't get it that low or it would go to 0 or near 0, or maybe 1, 2 counts IAC... Maybe that's what I ought to shoot for here?

Your 355 having a single plane intake is likely very similar to mine I have here, even though I'm $0E and you're $0D.....

The engine I have is a 355 with flattop pistons (no idea what the compression ratio is, I need to figure that out but I'm thinking about 9.5:1 maybe??) Lunati 20080660 cam, Weiand 7547 single plane intake, Summit SUM-162108 62cc chamber heads, long tube headers and a Holley 670 CFM throttle body running a Marine 28 PSI FPR spring and 61 PPH injectors.

Would you mind sharing your tune so that I can look at it?

[sturgillbd]

I'll have to get it posted tomorrow. I don't have it on this machine. Will try to post it before I head to work in the morning.

[sturgillbd]

Here is my bin...

[brian617]

I think that my AFR is actually leaner than what was stock. At least for the bin that I started with which I will post

Keep in mind if your VE tables arent accurate your commanded AFRs and actual AFRs wont match. With no O2 feed back in open loop the commanded AFR is being modified by temp and your VE as a baseline.

[CDeeZ]

Thanks sturgill & brian.

Sturgill, I'm wondering if I copy your Open Loop AFR VS Temp VS Vac table -AND- Open Loop Idle Lean Limit VS Temp table into my tune if that will solve at least some of the cold start overly rich problems I'm experiencing. Also, why are your two lowest MAP colums in the Open Throttle VE so much higher than the rest of the VE?


Brian, thank you for pointing that out. I've been using Dave W's spreadsheet to dial in the VE and it still needs work, but not sure how else to do it other than drive around and keep logging and adjusting the VE tables....

Questions for you guys:

Do you guys see any problem to setting the IAC to near 0 or at 0 while fully warmed up?


I know the LS guys (myself included) do not disable PE while tuning VE, I never disabled PE on my turbo LS while I was tuning the VE for it and it worked out fine. I have been taking the same approach here even though a lot of people think you should tune the VE for a TBI with the PE and AE disabled.... What do you guys think disable those for VE tuning or not?


I'd like to keep this TBI open loop, do we have any idea what other modifiers might need to be turned off for this?

And thanks again guys.

[brian617]

Brian, thank you for pointing that out. I've been using Dave W's spreadsheet to dial in the VE and it still needs work, but not sure how else to do it other than drive around and keep logging and adjusting the VE tables.....

Its really not that big of deal if your commanded and actual AFRs arent perfect, With a custom build and so many modifiers (tables) in the 427 PCM its tough to pull off. I think I remember cheating my cold AFR table to get the actual I wanted.

[CDeeZ]

Well my comment about the low MAP colums in the VE being weird. I was looking at your bin with the $0E XDF. Opened two instances of TunerPro and loaded your BIN with $0D and my BIN with $0E and the data isn't screwed up now when viewing yours with the wrong XDF. Oops.

Now let's see, where to go from here?

And we still don't know why GM had the Open Loop AFR table stupid rich in that stock 350 4L80 BIN I posted do we????

[CDeeZ]

Well this is revealing doing a side by side here. This has got to be the problem with it not wanting to start when cold and running soo poorly... The factory 350 4L80 bin is commanding a stupid rich AFR for some odd reason???

Check out these screenshots, one is comparing my bin after I leaned it out a bit to sturgills..... And the other one compares the stock 350 4L80 bin to a stock 350 4L60/700r4 bin.... Why in the world did they set up the AFR table so crazy rich in the 350 4L80 bin?????

On an unrelated note, I just snapped in a USB mouse to the tuning laptop, wow what a difference, why didn't I do this a long time ago??? Using the touchpad is such a pain in the ass compared to a real mouse.

[sturgillbd]

My open loop afr table is not stock. I had to enrichen some because I was too lean.. My tune isn't perfect but the last 400 mile round trip I made in my Jeep, I got 19.5 mpg running 60-65 mph on the road and the M38A1 (cj5) is not exactly aerodynamic. I am running the Edelbrock Victor JR 2v Sportsman intake with EQ heads. I have the 1.6875 bore tbi (standard sbc size) and I start going into a vacuum after 4000 rpm. At 6000, my map reading is about 80kpa at WOT. You will have to just play with the values until you get it where you want it. As for a lean pop on cold throttle, the AE settings are easily overshot. I also run 61pph injectors at close to 30 psi. Im a little rich at idle but the pcm compensates decently. You were surprised at the settings difference between the 4L80 bin and mine. Now compare it to some of the CPI bins for the blazers and also look at say a 454 tbi bin like BMHK. Lots of tables that seem fudged just to get GM's desired effect.

[sturgillbd]

Thanks sturgill & brian.

Sturgill, I'm wondering if I copy your Open Loop AFR VS Temp VS Vac table -AND- Open Loop Idle Lean Limit VS Temp table into my tune if that will solve at least some of the cold start overly rich problems I'm experiencing. Also, why are your two lowest MAP colums in the Open Throttle VE so much higher than the rest of the VE?

]
You can try it and see if it works better for you. My base bin was BJYM. You can dowload that from here http://www.gearhead-efi.com/Fuel-Inj...2&d=1321320663

Questions for you guys:

Do you guys see any problem to setting the IAC to near 0 or at 0 while fully warmed up?

The only problem is if the idle is higher than commanded , you may set an IAC trouble code because the pcm cannot lower the idle any lower after the IAC goes to 0 counts. Usually you have the least IAC counts when engine is hot and the air entering the intake is warmer. To help cold driveability, it helps to have a thermac type air cleaner housing and it pulling warm air off the exhaust manifolds into the throttle body. You could fab a hot air tube off one of your headers.

I know the LS guys (myself included) do not disable PE while tuning VE, I never disabled PE on my turbo LS while I was tuning the VE for it and it worked out fine. I have been taking the same approach here even though a lot of people think you should tune the VE for a TBI with the PE and AE disabled.... What do you guys think disable those for VE tuning or not?


I'd like to keep this TBI open loop, do we have any idea what other modifiers might need to be turned off for this?

And[ thanks again guys.

I leave PE and AE enabled while tuning. I filter out both when doing normal VE tuning. For PE mode, I adjust the VE so it matches as close as I can to what I have set in the PE AFR vs RPM table. You can watch the INT during AE events and see whether you are lean or rich during AE. That is what is usually takes me the longest to get close. As for full time open loop, I have never tried it. I ran open loop idle for a while but now run closed loop. You could try to set the minimum temp for closed loop up to the max under closed loop qualifiers and that should make the PCM stay in open loop.

[CDeeZ]

Sturgill, will you post the XDF you are using? I'm using what I thought was the latest one for $0D while looking around at yours but I see a lot of things that are not defined. Cooling fan code perhaps?

[sturgillbd]

Yeah, I have the cooling fan patch and also made my bin display calculated airflow in the datastream to play with O2 switchpoints. Attached are the XDF's and adx I use for $0D

[CDeeZ]

Thanks much!

I still can't believe that the commanded AFR is a full 3 to 4 points RICHER in the lower temperature cells of the OL VS Temp Vs Vac table in the BJDR bin vs the BJYM... I mean, the only difference (on the surface anyways) is one bin is setup for a 4L60 and the other a 4L80.... Both are 350 TBIs etc etc. Like you said though, GM probably fudged it to get the deisred effect elsewhere. Here I though using the BJDR as a starting bin would be best since it was a 350 and 4L80 tune, which is what I have put in this truck... I guess that's what I get for blindly assuming everything else would also be "close enough"......

[brian617]

display calculated airflow in the datastream

I seem to remember you helping me with that, too bad I never used it LOL. Thanks anyway.