Super Lean on Startup

[LMMKnight]

I'm seeing in the log of the VE table that I'm super lean on startup and then after driving around my VE is within 5%. Is there a way to control how much fuel goes in on startup? Cold it starts right up, warm it is taking two tries to start. Thanks for any help.

[Alvin]

I see the wideband put out a shaky signal for a bit but quickly gets in line.. Fuel trims are near zero on start up too.

I'm not sure what your talking about. It doesn't look lean at startup.

[LMMKnight]

Here's a picture of the histogram I'm using.

[Alvin]

Look at it in the line display. You can clearly see the wideband going off line specifically in that spot.

[LMMKnight]

Interesting. That table should be calculated off of the ((GMVE calculated by the computer) +- LTFT) % diff from the VVE and not off of the wideband. I guess I might be barking up the wrong tree then on the hard start issue.

[smokeshow]

What does the math parameter that histogram references look like?

Startup fueling also cannot just be plotted out on a histogram like regular fueling error. It's anything but steady state...so beyond a couple max/min metrics, the start data has to be evaluated manually.

[Cringer]

I'm seeing in the log of the VE table that I'm super lean on startup and then after driving around my VE is within 5%. Is there a way to control how much fuel goes in on startup? Cold it starts right up, warm it is taking two tries to start. Thanks for any help.

The main thing I see is that you are commanding around 6g/s of air at idle, but your start up air is around 3-4 g/s when hot! I changed a few things to help hot starts. Let me know how it goes...it might need more air for hot starts.

Also, how stable does it idle? Seems like it needs some tweaking.

2007 Suburban 6.0 4l70 DOD,AFM Delete, Honey Badger 2023-07-28-02 - cringer.hpt

[LMMKnight]

((DynAir+(DynAir*(STFT + LTFT)/100))-VVE)/VVE*100
(([2320.71]+([2320.71]*([50116.156]+[50114.156])/100))-[2311.71])/[2311.71]*100

[LMMKnight]

I changed the Cranking VE to 80 and my wife didn't have any more issues today. Thanks Cringer I'll take a look.

[Cringer]

((DynAir+(DynAir*(STFT + LTFT)/100))-VVE)/VVE*100
(([2320.71]+([2320.71]*([50116.156]+[50114.156])/100))-[2311.71])/[2311.71]*100

That is not going to work for start up. That is for steady state driving for dialing in the MAF/VVE.

[radjr]

@ Cringer
Hello, you posted the following: 2007 Suburban 6.0 4l70 DOD,AFM Delete, Honey Badger 2023-07-28-02 - cringer.hpt

Is that a base line tune that can be used for my 2007 Sub with an DOD/AFM delete using the L96 non DOD cam?

Thanks!

[Cringer]

@ Cringer
Hello, you posted the following: 2007 Suburban 6.0 4l70 DOD,AFM Delete, Honey Badger 2023-07-28-02 - cringer.hpt

Is that a base line tune that can be used for my 2007 Sub with an DOD/AFM delete using the L96 non DOD cam?

Thanks!

No.

[radjr]

No.

ok...

[ns158sl]

Ok I didn't want to start another thread pertaining to cranking fuel. How does a guy go about it? Im curious what is too rich/too lean? I have a feeling there is no answer, just actual time vs rpm rise? If even that would be it, is there a rule of thumb to go by without flashing then starting the car 300,000 times? Again, i know this is probably even dumb to ask because the other variables, well the ones we can control (FA fuel, Spark, Startup Airflow), let alone the ones we cant control (ECT, IAT, time off/evaporative fueling, heatsoak). Just curious what to even look for with numbers/scanner data. I let my WB heat up for a few minutes before starting and try different changes but cant quite get a handle on it. Finally figured out when adaptive timing becomes active, the ECM must be out of cranking mode, or i think atleast. Still trying to figure out the InjPW changes for the first little bit. Say it is 8ms then 4ms then 8ms again? I dont know what is affecting that and dont know what is affecting the ramp rate.I know there is a delay in WB and Commanded/InjPW, so i am not hung up on that by any means.

[blindsquirrel]

O2s don't give accurate data on a cold engine when combustion is poor. You will end up completely lost if you try using O2s, either NB or WB. A lot of the fuel remains in liquid form in a cold cylinder, only the stuff that's able to vaporize is able to be burned, so it needs a lot more because so much of it is wasted.

How did people ever tune carburetors back in the dark ages without all these fancy data collection tools and controls!?

[ns158sl]

Good point. Well I'll keep playing with fueling again.

[Alvin]

Also.. and not many people get this..

Cold OL fueling isn't mean to run at the AFR's it's commanding. Its meant to saturate the engine with fuel because only the fuel that is vaporized is burned. If you measure say 14.2-14.7 out the tail pipe of a cold engine even though OL is commanding 11:1 or even richer you are doing perfect. HOWEVER if you don't trim that out of your log or filter it out.. your AFR or EQ error will be all out of wack.


Think about it.. you start seeing black smoke as you go lower than 11:1.. A lot of OEM tunes are set to even 9:1 on startup.. none of them are black smoking on cold starts.