Rich coasting condition on procharged silverado

[messerschmitt145]

Problem:
During a baseline dyno run the tech mentioned that the truck was coasting a bit rich and verified that my wideband was accurate (i had ignored it because the guy that tuned it said my wideband was wrong) . Started checking the tune and trying to resolve it myself but seems like no amount of changes will bring the afr in check during coasting.

Mods/setup:
This is a 01 silverado 2500 6.0L. The engine internals are all stock, i have a d1sc procharger, 80# seimens deka injectors, walbro 225 fuel pump, custom 3" exhaust with an H pipe and (unknown to me at the time) a 28" z bend 3" inlet to 2.5" outlet muffler for each pipe. The fuel rail does have the factory return line. The shop that tuned it did the 2 bar map upgrade, and set it up to run without the maf. I put a smaller pulley on the sc(4" to 3.8 IIRC), added a bigger intercooler, and recirculated the bypass valve since it was tuned.

Failed attempts:
so far ive tried tuning the ve table, the 15-25 kpa range the values are getting low enough that i don't feel comfortable with them(if low values like that are ok lmk), ive also been trying to tune the base idle airflow(cold starts are improving). The injector data that was in it from the shop was off from some resources i found and the data i found seems to improve its response to tuning. Today i tried changing short pulse limiter, short pulse adder, and minimum pulse but the rich condition persists making me think that this is not related to injector data.

Help:
1.Does the ve table that the shop made for me make sense, mainly it looks like it has been scaled to give a safe spot for a runaway turbo/wastegate scenario and im wondering if i should revisit that.
2.I know there is something im missing with the whole 12-10 afr while coasting any input is greatly appreciated
3.Why are the stft's able to lean it out while coasting but i can't seem to get it in check in olsd
4.Anything else look funky let me know

config
layout 3.Channels.xml

Graphs
layout 3 charts.Layout.xml

Log and file olsd (trying to get some response)
11-18-23 r77.hpl
David 2500 mod 11 r77 short pulse adder 5per red 11-18-23.hpt

Log and file stft's enabled
11-18-23 r80 stft enb.hpl
David 2500 mod 11 r80 ve table inj flow std 11-18-23.hpt

Original tune from shop (they were trying to make revisions for -10F cold starts)
David 2001 Silverado 2500 mod 8.hpt

Thank you.

[kingtal0n]

Theres a limit called min transient fuel or something and its a number that limits the minimum pulse 0.032 for example 3.2ms of fuel or something like that
there is also a minimum pulse table, and who knows maybe 10 other tables that limit minimum pulse, the damn injectors never seem to shut off
But it should go lean enough to -.- the wideband if done correctly


First you can try adjusting DFCO To meet the situation first, DFCO will send the wideband to lean -.- reading maximum oxygen at least the plugs wont be fouling as bad, if you want to shut off the fueling

If you just want to lean out the coasting so its reasonable 14's 15's 16's then the minimum pulse and min transient fuel numbers prolly need to be dropped down
and if its a turbo maybe consider getting rid of the maf and figure out which is used for the situation maf or map, generally we want to use a map sensor

[messerschmitt145]

Thanks for the quick reply, ill try the transient stuff. Im fairly new so im slow and cautious making corrections but ill try out some stuff either tomorrow or monday. as for dfco its disabled, the tuner didn't want it running, and there is no maf sensor so its all map right now.

Thanks again

[Matt Vardaman]

Your tune file has DFCO shut off. The enable temp is at 280. Go to fuel tab then cutoff/dfco change the enable temp for deceleration fuel cutoff to 104 which is what it should be factory. They must have turned it off while tuning and did not re-enable. That should fix your problem sir. Let us know how it goes.

[kingtal0n]

Well he said he is coasting rich. Which doesn't tell us whether he wants to coast engine (fuel) on or engine off. If he wants DFCO to shut off fuel the coasting will no longer be coasting, it will be a deep decel engine braking. So he needs to decide whether he wants coasting or engine braking. I personally never see any reason for coasting because if you lift from the throttle you want to slow down so I always use engine braking, so I always use DFCO. But there is still the decision to be made.

[SiriusC1024]

Correct about the transient limit. You take Min Injector Pulse and divide by 31.12. That value goes into Transient>Min Fuel Qual.

But..are you sure about the VE table? Those are really high numbers, especially at low MAP's. See, you shouldn't be running rich even with DFCO disabled. DFCO is disabled during tuning so that VE can be adjusted in those regions. Fueling should be on and it should be accurate. Afterward DFCO is re-enabled. Understand?

Could be the fuel injector data as well. That'll throw off VE a lot.

[Alvin]

This is going to be a problem with the min fuel in the transient section.

You can have a good running car without DFCO and without rich coast downs. I prefer no DFCO on most of my tunes in fact.

[messerschmitt145]

Thanks again for the replies, I got a chance on sunday to mess around with it a bit. One change on the Transient>Min Fuel Qual made a massive difference so im going to start trying to get the ve table dialed in better.

I have kept DFCO disabled because I was trying to tune the VE table and now its accepting changes

My goal with this was to get the commanded to match the actual afr and then enable DFCO at very least when I go for a drive in the mountains

As far as the injector data im fairly confident that I have the correct information in there now, When the shop put in the injector data they left the Short Pulse Limit at stock values and put in different values for Min Injector Pulse, Default Injector Pulse, Offset vs Volts vs VAC, and Short Pulse Adder. Actually I just realized that he was trying to use the injector data to help with cold starts. Anyway I got the injector data from this Siemens Deka 80lbs.hpt and even before the Transient changes it improved idle quality and startup.

Like I said for now ill work on getting the VE table dialed in more, with the changes i made after it was tuned and the corrections to the injector data im sure it needs it.

Thanks again for the guidance. Anything else that seems off let me know.

[Alvin]

There's honestly not a lot of "good" injector data for those injectors. They are kind of a old injector before everyone got on board with real data. You might be able to get something reasonable from FIC in GA.

[SiriusC1024]

That's Deka 80 Ford format that has been converted to GM format by Dsteck. It's an approximation, and that much can be seen just by looking at the offset table. Attached is the spreadsheet with the rest of the stuff, including Min Fuel and Fuel to Wall Impact.

If you're still having problems there's another set of Deka 80 data here at Post #26:
https://forum.hptuners.com/showthrea...pository/page2

And if you're having problems after that follow Alvin's advice. Deka 80's have a lot of variability I hear.

[messerschmitt145]

Thank you for the direction yall have been giving me. Im gonna take a few days to replace injector o-rings just to be sure thats not a variable, and take a good long look at all of the data both from the logs i have and the spread sheets and information you have helped me out with. Ill post updates when i have something to update.

Thanks again everyone

[messerschmitt145]

I tried out the data from those and they made a big improvement. The ve table is starting to smooth out and cold starts are the best they have been since it was tuned 2 years ago. 24F this morning and it fired right up. Also a throttle hesitation that I thought was a mechanical issue was fixed as well, nice and smooth taking off from stop signs now.

Yall are great, really appreciate all the help, ill most likely keep tinkering with it but for now its at a point where i feel i can jump in it and drive worry free.

[SiriusC1024]

Which data set did you use? Conversion sheet or FIC data from the other thread?

[messerschmitt145]

i used the conversion sheet you posted, most of the data was the same, the min fuel mg and fuel to wall transient data were things i hadnt seen yet. they made a massive difference, almost no spikes getting on or off the throttle and i almost have afr's matching commanded, but its running real smooth.

[SiriusC1024]

Sweet. A lot of people overlook those other parts. Glad you're back on track.