Moving target when VE tuning - What's the best approach?

[Markolc81]

Hi there, this is my first port, but I'm a long time lurker/researcher. I'm trying to dial in my VE table on my '99 C5 6-speed. The only mods are CAI and Long Tubed catted headers.

This is my first time tuning, and so far it's going well and I've learned a lot. I'm not trying to reinvent the wheel here with my VE table, this is more of a learning tune as it's still a stock motor and stock VE table. I followed all the steps to set myself up for a Open loop VE tune, targeting a 1.0 Eq.

My question is this - I hooked up my WB and went out logging one day recently it was chilly out about 50 degrees. Got a ton of nice date, and the fuel map was rich, between -12% and -4% all throughout. Great easy peasy.

I did not make any changes to the VE table, and went out logging the very next day to get some more data, now it was sunny and much warmer, almost 70 degrees. But I notice my IAT was much warmer 85+. Now the same VE Err table is showing 2-10% lean in all areas (my WB maxes at 1.09 EQ, so maybe leaner in some spots).

Now the only variable that changed was temperature.

Is this normal? How do you tune a moving target? I notice that stoplight to stop light, as my underhood temps creep at extended red lights, my EQ leans out, the richens back up after driving a bit.

Do I just set my IAT tables to read one temp (90?) while tuning VE? I haven't come across this type of situation in my study material.

I understand a load bearing dyno with underhood temps being steady is the ideal way to tune, but a street tune is what I'm after at my novice level.

I plan on tuning the MAF next, and when done going back to letting the PCM blend the two together.

Thanks for reading

[SiriusC1024]

Tune with the STFT and LTFT derived from the narrowbands instead of using the wideband.

[Markolc81]

So, only use my WB to tune 4,000RPM+ and WOT? Then go back to LTFT+STFT for part throttle?

Would this be the same direction for MAF tuning?

I'd like to know the reasoning behind this as I'm a novice and very curious.

Thank You.

[SiriusC1024]

You've got the right idea. I set PE enable MAP to 85kPa. Anything above that and pedal threshold will go into OL. You'll use the wideband wherever fuel trims, being CL, don't populate. The transition is automatic, and you don't have to worry about at what rpm it occurs.

Reasoning for using narrowbands:
https://forum.hptuners.com/showthrea...nd-vs-Wideband

Since you've got longtubes you may have to make adjustments to the O2 sensor PI settings. To what extent, if any, depends on what the O2 voltage traces look like. Should be a full width sweep when working correctly.

Don't be confused between O2's being stuck and O2's pegged rich/lean while fuel corrections are happening. At post #4 you can see it stuck lean, yet fuel trims aren't increasing there. It helps to get VE within 5% if you can. After that adjust O2 settings as required.

https://forum.hptuners.com/showthread.php?106787-Airflow-mode-LTFT-histogram&p=756115&viewfull=1#post756115

[Markolc81]

Currently I'm borrowing the O2 sensor bung from my Bank 1 header bung, and have disabled LTFT and STFT. I don't have a way to run both sets of O2s (NB and WB), unless I use a tailpipe adapter, or my post-cat O2 bungs. Removing my headers to weld in another bung is not in the cards for right now.

So for now since my WB is already attached, just focus on dialing in the fuel for WOT (85+KPa) VE table and MAF?

Thanks for the links - I'll be consuming that info tonight.

[SiriusC1024]

Well. Do the best you can. When you re-enable CL after tuning that'll reveal how far off the wideband was. You can make further corrections then.

I put my wideband in the y-pipe btw. Works fine being only 4 inches downstream of the collector. There are no-weld clamp kits for widebands, too.

[horsepowerguru427]

The no weld kits actually work very well. This is what i used with the first build i did and didn't have access to a welder at the time. Find an appropriate spot, drill a hole of applicable size and install the bung band with the provided sealer on the underside. I also second using the LTFT+STFT tuning up WOT/PE area. I used to use OL STFT but i tried LTFT+STFT after siriusC1024 kept harping on about it last year lol there was a very noticeable difference in power and drivability from what OL tuning had given me. And to answer your question, yes, you do the same thing with the MAF tuning. Log LTFT+STFT vs MAF hertz in a histogram and be sure to add MAF hertz to channels as well. Then just copy and paste special half into the MAF curve in the tune.

[ns158sl]

Honestly I almost prefer doing it that way if it is an aggressive setup. Itll be fine on yours too. Sometimes it seems using a WB gets you into the ballpark quicker and then wot is done so engine is "safeish" for those oh shit moments. Then go back and tighten it all up with NB's, especially with not adding a bung.

[07GTS]

there is prob more error from driving into a headwind compared to tailwind then just the temp swing cold to hot

[Markolc81]

So I'm going to attach two logs from earlier today. Tune 8 is my logged drive to work, tune 9 is my drive home. Stock VE table. PE set at 1.17. Both logs started when the car was at full operating temp. The only difference tune 8 was with my IAT logging actual temps (mostly 59 degrees). Tune 9 has my IAT table locked at 90 degrees.

What a difference 30 degrees makes in my VE EQ Err table.

Makes me not want to tune my car in this weather if by the summer I'm going to be super lean.

Even WOT shows quite the difference.

Do I just concentrate on the peaks and valleys and try to smooth the VE table as much as possible?

I saw somewhere while researching that Banish recommends tuning VE with IAT at 100 degrees on a steady state dyno. I'm gonna have to try to do this on the street.

[Markolc81]

Since I do not have the time to tune all in a one day session, and need to spread this out over several days. Would it be considered a terrible thing to lock my IAT table at say 90 degrees just to dial in my VE table?

Just for the sake of consistency?

I read of people that run on SD only tunes tying the IAT to the front bumper to avoid heat soak, I can't think that this is such a terrible idea.

But I'm new, so I must be missing something in my logic?

[SiriusC1024]

No don't mess with the IAT. SD airmass is calculated by PV=nRT. n (airmass in moles) = PV/RT. P=MAP, V=VE*displacement, R = constant, T=IAT/ECT combined in the Complex Temperature Model.

If you move IAT you'll have to adjust bias on the Complex Temperature Model. Minimize guesswork and get better results by keeping everything as close to stock as possible.
https://forum.hptuners.com/showthrea...l=1#post733666

When you enable CL later on it'll take care of any variance. That's specifically what it's for. This includes PE because LTFT's are carried over into OL.

Speaking of, I just looked at your logs. LTFT's are still baked in and causing error of almost 2%. You need to use VCM Scanner>Vehicle Controls & Special Functions to reset them.

[07GTS]

something has to be going on to get such a shift, something isnt right as IAT dosnt change fueling in the 10-20% swing range that just isnt possible there isnt that much more air getting into the engine to cause it from a temp shift, esp when ECT is part of the calc and that is more or less steady at operating temp, has tune file been posted yet ?

[SiriusC1024]

Alright look at the narrowband O2 trace for B2. It's still working, just no corrections. The fact that it's showing rich and lean means that you're pretty close to stoichiometric in BOTH logs despite what the wideband says. You're wasting time with that wideband.

Get trims kinda sorta close, like they are, then put the narrowbands back in. I mean really you don't need to do any wideband tuning with your build. You can tune the whole VE table with the narrowbands and CL. Graphically project the trends that are PE/OL on the VE table. Verify with wideband afterward.

[Markolc81]

Thank you for the tip on LTFT. I had forgotten to clear them! Also did not realize they would still effect the tune when LTFTs are disabled in the tune. Learn something new all the time!

Attached is my current Tune File.

And you're right, I really don't need to tune this with a WB. This is a safe stock tune, with a stock motor, aside from headers and CAI. I have upgraded to a LS3 card MAF (because I got it for next to nothing) and 42# injectors to support future mods. This is a learning/optimizing tune for me, and I know I will need to clean up the MAF tune due to the mods.

i have more mods planned later this year, and I'd love to be able to tune properly and reliably once the mods are performed.

I knew I would have a ton of questions along the way, and they sure pop up daily. The more I come across this now, the more informed I become. Thank you all who are providing feedback.

[SiriusC1024]

What's the part number on those injectors?

[Markolc81]

Bosch injector #0280155868

I imported this data for the injectors

[SiriusC1024]

Ok just making sure on the data.

If it was me I'd apply wideband error %-half, clean up the VE table, then switch to CL.

[Markolc81]

This goes back to my original question. Should I wait for a warmer day to do this, as 59 degrees has my motor running rich, and higher temps are closer to stoich?

I just don't want to be running lean and have my LTFTs add fueling in the summer to WOT.

[SiriusC1024]

Seriously it'll be fine. Don't worry about the weather. Factory cars run in Anchorage, Alaska and Death Valley, Utah. Run in CL. Tune in CL.

You want LTFT's adding fuel to WOT if required. LTFT's will adjust over time.