MAF and VE Tuning

[David-L]

I have done a lot of reading and watching videos about MAF and VE tuning and they all seem to say get a wideband sensor, turn off DFCO, PE, DOD, disable MAF to tune VE and vise versa, etc. That all makes sense and I will definitely do for WOT tuning. But for right now, I am only interested in part throttle cruise tuning and light acceleration. Please correct me if I am wrong, that is why I am asking, but I see no reason the stock narrowband sensors and LTFT could not be used to tune cruise and light acceleration without disabling DFCO and PE. DOD is of course disabled.

The only thing I am unsure of is tuning MAF and VE at the same time, without disabling one to tune the other. I am not sure how and when the two work and if that is even possible. My LTFTs all seem to be between -8 to -12, so it seems obvious it could use some adjusting. LTFTs have never been reset or disabled, at least not in the past 15,000 miles.

Vehicle is 2017 Silverado 1500 5.3L-L83 6L80E.

[kevin87turbot]

You can certainly run the stock narrow band sensors in order the dial in the part throttle fuel trims.
I actually prefer it on the late model applications.
Out of curiousity, what mods have you done to the truck?

[David-L]

Okay, that is reassuring that I'm not thinking just completely in left field. Do you know whether MAF and VE tables can be tuned at the same time or they must me done separately?

I haven't done anything major that would need a tune, just tires and rims, level kit, lights... just cosmetics pretty much. The entire reason I got HP tuners was basically because of the torque converter and transmission. I absolutely hated how it shifted and when the converter locked up. I've got all that pretty well dialed in where I like it and now I figured id see if any improvements could be made in the cruise area of the engine. Then I'll go back and tweak the transmission if I need to.

I thought I would be able to change stuff in the BCM also, but I didn't do enough reading to see that I cannot, but the transmission was still bothering the crap out of me. I'd love to be able to enable the cargo lights while driving forward and I would absolutely love to change the remote start cutoff delay from 10min to 15min. I cant tell you how many times I've gotten in my truck just for it to shut off as I'm putting the key in. But that's a topic for another day.

[kevin87turbot]

You can dial in the MAF and VVE tables at the same time. Check out Smokeshow's thread. It can be applied to Gen 4 and 5 applications.
https://forum.hptuners.com/showthrea...ight=smokeshow

That being said, your VVE tables shouldn't have to be reworked for your stock application.
Same for the MAF, unless you've added mods. If the fuel trims are off, you might check that the MAF is clean. I see a dirty MAF cause issues fairly often.

[David-L]

Okay, I'll check that out first then. Thanks for the tip!

[David-L]

If the fuel trims are off, you might check that the MAF is clean.

I haven't had a chance to clean the MAF sensor yet, planning that for Saturday. But I got to thinking, my truck doesn't have the flex fuel sensor so its locked in thinking the fuel is 10% ethanol. I know most pump gas you get not is pretty nearly exactly 10%, but some are lower. If the station I always go to has good gas with lower ethanol, could this throw off the LTFTs and explain the -8 to -12 values I'm seeing across the board?

[David-L]

So I actually was able to clean the MAF sensor like I planned Saturday. Reset the LTFTs and drove about 150miles so far. I'm seeing better percentages, but still seeing -6 to -10 on the LTFT values. They started out all close to 0 as I expected after resetting, spiked up to around -15 to -20 across the board the first 20 miles and seem to be settling back down around -6 to -10 across the board now after 150 miles.

[David-L]

So it's been a couple months now since I've changed anything in the tune and have done a ton of driving so the LTFTs should be well settled, I assume. The LTFT trims vary from -2.0 to -13.7, with the average in the cruising range being -8.4. Is it safe to assume that the VE and MAF tables could use some tweaking at this point?

Again, no mods done to the truck that I am aware of other than offroad tires and a level kit. Cleaned the MAF sensor and did a good tuneup (new filters, oil, plugs, fuel injector cleaner, etc) in December.

[Haans249]

With a completely stock setup, you do not need to touch the VVE. In fact, the VVE has very little effect on fueling when running closed loop. So, do not worry about the VVE unless you’re running a large cam. The VVE table is mostly used for torque calculations when you’re not running in SD (maf-less) mode.

For your MAF, I’d suggest making your fueling adjustments using your STFT and not LTFT. The STFT change constantly which are then incorporated into the LTFT. The STFT will allow you to adjust fueling throughout your MAF frequencies with more granularity and accuracy during part throttle (non PE) driving. Don’t forget to add the appropriate filters (ECT 190+, eq lambda less than 1.1 to filter out DFCO, even IAT if it varies widely in your application).

[David-L]

For your MAF, I’d suggest making your fueling adjustments using your STFT and not LTFT. The STFT change constantly which are then incorporated into the LTFT. The STFT will allow you to adjust fueling throughout your MAF frequencies with more granularity and accuracy during part throttle (non PE) driving.

That makes sense to me in a way and in another way it doesn't at all. I would think to use the LTFT because it should be a good average over a long time of what is happening. But I could see using STFT for the reasons you state. So I plotted another table of STFT vs MAF frequency and it was VERY different from the LTFT. The LTFT were all negative, ranging from -4.3 to -13.3... the STFT ranged anywhere from -3.7 to +9.2. Both tables showing averages with minimum of 100 cell hits. (don't really know if this is suitable or not, but sounded good). So why would the LTFTs be so vastly different from the STFTs?? I expected the STFTs to average out practically 0 if the LTFTs are well established. I assume that is saying the LTFT isn't as well established as I presumed? The STFT cells in the cruise range were between -2 to 2 percent.
Would it not be better still to take the sum of the LTFT and the STFT?

Don’t forget to add the appropriate filters (ECT 190+, eq lambda less than 1.1 to filter out DFCO, even IAT if it varies widely in your application).

Excellent point... to be sure i set this up correctly, does this appear to be the correct way to type it into the Filtering Function box? "[50010.242]>190,[68.238]<1.1"

[Haans249]

Using LTFT's to make adjustments to your MAF is not going to be as accurate as using STFTs

1) The LTFTs are already and average of STFT, so by using LTFT you end up averaging an average number
2) The STFTs are instantaneous adjustments compared to LTFTs. So as you're hitting different MAF frequencies, the same adjustment from LTFT (say -10%) would be applied to a broader range of frequencies, when compared to STFTs which would be more specific to each frequency hit.

Here are my filters:
[50090.156.slope(1000)]<5 AND [50090.156.slope(-1000)]<5 and [50010.242]>190 and [50127.238]<1.1

So for yours, you need to have it setup like so: [50010.242]>190 and [68.238]<1.1

Oh, and I forgot to mention, you will need to disable your LTFTs in your tune while you go through this process as those will impact your fueling as well. So, disable the LTFTs, then use the STFTs to adjust your MAF.

[David-L]

Thanks for the insight Haans249. And especially thanks for the filters advice. I wouldn't have figured that out.

I didn't exactly follow your advice though, I left the LTFTs enabled and added more to the filters to filter out any transients, shifts, idle, etc.:
[50010.242]>180 and [2517.161.avg(1500)]=0 and [50091.156]>0.5 and [2517.161.avg(-200)]=0 and (abs([50090.156.slope(1500)])+abs([50090.156.slope(-500)]))<2 and ([6310]=9 OR [6310]=14 OR [6310]=15)=0

I took the sum of the LT and STFT vs MAF Frequency, copied it to excel and smoothed it out, multiply the MAF table by %1/2 and did some more smoothing. Made a few logs and the MAF table seems to be spot on now. Values -2.5 to +1% where as it was -8 to -14%. Only messed with the cruising range too, didn't go close to WOT or PE cells. Haven't messed with VVE tables yet.

[Dominatorstang]

I too have LTFT in my calc, but I end up disabling the LTFT's on the scanner side when logging that like Haans249 side I do not like how LTFT skew readings. Leaving them in the calc does not hurt anything though. Quick and easy to disable in scanner too, just have to remember to do it.

[David-L]

What do you mean by disabling the LTFTs on the scanner side when logging? I don't quite follow. How can it be in your calcs if it is disabled?

[Dominatorstang]

On the scanner side you would go into the green button next to the engine button for pulling DTC's. In there you will see a button to disable LTFT's.

Years ago when I first started I was thinking like you probably are. I figured I did not need to take the time to log the STFT's and find the average when I could just drive around and let the LTFT's do that for me and then just do a quick log trying to hit the different cells to pull in those learned LTFT numbers. Later I started to realize the LTFT's do not work that way. The ECM does not have a cell for each spot you see on the graph that it is learning for, it shares learned values for many different cells which is what creates the problem with using LTFT's.

I have since been able to disable the LTFT's on my 2017 Sierra L86 in the tune. Not sure why it did not before, but it does now. The thing about leaving the LTFT in my calculation is that when the LTFT is 0 (disabled and reset) then it has no effect in my values. But if a value is there, then it will take it into account. Makes it more universal this way, but is not needed if disabling LTFT's

In the end to turn off LTFT, I used the exact below values. I originally threw in some values that I figured should work to disable, but it did not. The below is something I ran across on another post or tune and worked.
LTFT disable.jpg

[David-L]

Years ago when I first started I was thinking like you probably are. I figured I did not need to take the time to log the STFT's and find the average when I could just drive around and let the LTFT's do that for me and then just do a quick log trying to hit the different cells to pull in those learned LTFT numbers.

Bingo... that is exactly what I was thinking I could do. I have read all over the place not to do that, but there was never a clear explanation as to why. You clearly explained what is happening and why it does not work. Thank you! I'm not one to just do as someone says, I need an explanation why to or not to haha.

And the disabling LTFT in the scanner makes sense now too. Thank you again. I didn't understand what exactly that did before. So, in the attached screenshot, I would hit LTFT Learn OFF? Would I then need to hit LTFT Reset to clear the LTFT so it wouldn't affect the calculation?

[Dominatorstang]

Yes, that is how you will turn off LTFT and you would need to reset them. Something else that may help to understand the LTFT learning is to be logging "fuel trim cell" on the scanner. It will give you a number, so you will then see where all cells are shared. You can probably see these in the tune file, but I have not looked into it enough to say.

Something else you may have already come across is that you can leave PE on with LTFT's disabled and tune using STFT's. Do not take this wrong though, you do not get to tune PE this way, also STFT's will go to 0 and start pulling cells in that area towards 0 unless you filter out OL which you may already be doing that. Leaving PE on just makes me more comfortable honestly. In the past I had done the old school way of tuning PE using the narrow band voltages, but tuning PE with a wideband is totally worth it.

I know you are not as worried about WOT and such right now, but check into the PE tuning on these trucks. Some pretty good gains can come from PE adjustments which then lets you add some time once you have PE kicked in.

[David-L]

I am logging Fuel Trim Cell actually and it never seems to match up to anything that I have seen. It has only ever been 0,8,14,or 15 with the majority of my driving being 0 and most of the rest being 15. I've tried to look in the editor and see what areas of the VE the FTC correlates to, but noting adds up. And Engine>Fuel>Oxygen Sensors>LTFT Boundaries>Airflow Mode is all set to 64. So i'm totally confused on that one.