Need help with VE tuning

[PurplePiss]

I can't figure out what's happening. This is my process.

I upload a VE tune, let it warm up to 175* ECT, reset fuel trims, then log. I log for 20-30 mins, then filter so I have cells with 15 or more hits. I take that the VE % error AFR info and paste it into excel. I delete all -1, -2, and -3's. If I have 0's, I make them +1. I then take that and do a paste special multiply by half which should move everything very slowely.

I usually log to work in the morning when the IAT is 85-95. I work on the tune at lunch, then upload and go through the whole process in the afternoon on the way home when the IAT is 100-110. I end up being really lean in the afternoon.

1ve.jpg is the afternoon, and 2ve.jpg is this morning.

How do you tune the upper load/rpm ve, a bunch of WOT runs?

[PurplePiss]

Anyone?

[EC_Tune]

You're pretty close. maybe bump the higher MAP regions 1-2% then get to tuning that MAF...
VE just needs to be close if you are using the MAF.

BTW: I actually like to have positive (+1 @~30 kpa to +4 @~15 Kpa) LTFT's at 15-30 Kpa MAP. Helps fuel economy and you're near DFCO anyway. And I like near 0 at 35-55 Kpa 55+ I like to run up to -4 LTFT near the higher MAP zones.

[PurplePiss]

Is ambient doing that to my trims?

[EC_Tune]

IAT will "adjust" your VE somewhat as GM is a *bit* over agressive on how much the IAT contributes to the overall mixture.

Look over Cylinder Charge Temperature Bias table in the Airflow tab. The closer to 1.0 you get the more evenly divided the airflow calc is placed between engine coolant temp and IAT. Look over this THREAD for more info.

EC

[PurplePiss]

Hmm.. ok. I got rid of IAT affecting spark until 120+ degrees, but I guess its still using IAT to monkey with the calcs for fuel.

So in the new version we have cylinder charge temperature Bias and Filter tables. Which do I change to 1's across the board?

If I do this, should I jack the VE by 1.12 so that I am not +20's on fuel trims?

With the IAT potentiometer mod, does that really give you the ability to essentially run 15.5 AFR cruising (lean cruise)? Or will the computer keep trying to correct? I have a long trip to Norwalk in August, and would love to play with this. Does the VCM control for AFR do the same thing?

One more question. Should I set the timing to stock to do VE tuning or should I run the +1 - +3 timing tables I was using when just playing with timing? I read that timing affects AFR, so I figure I should run more timing to tune, but I'm afraid since I will be lean in the initial tuning, that more timing might be dangerous. :boom:

[Tim05GTO]

When it comes to VE I never multiply by half. I've never seen overshoot with the VE table. The MAF is another story and I will adjust the multplier (0.0 - 1.0) in my spreadsheet depending on how far off things are.

Tim

[PurplePiss]

Thanks Tim. I think my problem is IAT. After reading the other thread I think I will be setting the bias to 1 so its more dependent on ECT and less on IAT. I think for tuning I will also fix the IAT with a potentiometer. I just can't figure out which table to modify. They have small values in both right now and I just want to make sure I'm doing it right. Also, I want to know about timing and how it relates to tuning ve before I do anything.

[PurplePiss]

Two questions guys. Should I quit ve tuning and hit the MAF, even though I haven't really touched anything over 4k?

Two, when I switch over to a bias of 1, what do you do to the VE table to make sure the car isn't waaaaay lean the first time out?

[SMOKINV8]

As far as the 4k+ VE tuning vs just MAF tuning, think about what you're asking. You know and we know that dialing it in with a wideband would be ideal. Should you do it? That's up to you.

If you don't, you can compensate for any VE errors in the MAF tuning, so you should be fine. I would still recommend guestimating the higher range of your VE table at the least though.

[PurplePiss]

I wouldn't even know where to begin to guesstimate. I only have like 10 hits in a cell or 2.

I was trying to tune VE again today and I'm seeing freakin 134* IAT if I sit at a light. When I started the car, the ambient was 90 and it read 95 due to sun. start driving and it hovers around 110. Ok fine. Then I sit at a light and it heat soakes and then its all over. It will not come back down unless you do 55+ for more than 3 minutes.

1.) Do you guys really think that the air is that hot?

The car consumes like 10 cubic feet per second at WOT, I doubt it has time to absorb heat. That's why I'm thinking of either fixing it with a resistor or a pot. I am also thinking about getting that fast reacting brass IAT sensor, but I wouldn't know where to mount it.

I really think I need to play with the bias at 1 thing, but I want to know what to do to the VE table initially so I'm not 20% lean. I figure if I reduce the dependency on IAT and try and improve the reaction time, that will be the ticket.

2.)Can anyone comment?