VE tune changed drastically when MAF re-enabled?

[rel3rd]

Vehicle is 2002 Silverado 5.3.

Following one of the many similar suggestions online regarding VE tuning, I first set MAF fail frequency to 0, made HIGH and LOW octane timing tables reflect the same timing, then using VCM Controls RESET fuel trims.

I datalogged for roughly 30 minutes each time. (3 times so far).

After 3rd time of making tune changes and reflashing pcm, my LTFT's were all between 0 and 3, which I "thought" was great.

I then set MAF fail frequency back to stock 13500 Mhz (I believe it was), and reset fuel trims once more. Just for the heck of it, I datalogged another 20+ minute drive and a LOT of my LTFT's are now ranging anywhere from 8-18, averaging about 13 in most lower rpm cells.

Why did my LTFT's change so dramatically after putting the MAF back into the mix?

Did I miss something, or do something wrong?

Just when I thought I was finally getting somewhere, I got knocked back 3 steps, lol...

Thanks for any help, ideas, or insight.

[Texas_WS6]

I think after tuning the VE, you will also have to tune the MAF if you plan to reuse it. Is the cam stock?

[rel3rd]

I think after tuning the VE, you will also have to tune the MAF if you plan to reuse it. Is the cam stock?

Yes, cam is stock, and I am a dummy, lol.

Only mods to truck are listed in sig below.

[Texas_WS6]

Maybe a pro-tuner can chime in here, but I think you now need to tune the MAF for your VE changes.

[rel3rd]

I think you are right....don't mind me.

[jackedupcanyon]

No pro tuner here but yes you need to tune your MAF

[rel3rd]

Well....not having much luck...

I have been trying this:
http://www.hptuners.com/forum/attach...0&d=1228098301

and just can't seem to get in the ballpark. It runs great in OLSD. I keep logging and trying to get the MAF dialed in, but truck got to the point of having a serious "dead spot" off idle, and low rpm power, so I quit for the night...

[mowton]

Engine > Airflow > Dynamic Airflow> High RPM Disable -- set to 0 to enable MAF only. The put back to 4000 when done tuning the MAF.

[Blown]

Yeah what mowton said,
Then you will more than likely have to go back to the VE again for some fine tuning. As Russ K said once I think, wash, rinse ,repeat

[rel3rd]

Finally got her figured out today.

Guess yesterday was just too long of a day for me to be trying to do some technical work, lol.

All LTFT's are now 2 or less. Truck feels a little more responsive, or at least I think it does. Don't know if it's imagination or not.

Next up is a wideband to dial in the WOT fueling and then maybe I'll try a re-do of my car.


Thanks for the replies guys!

[RWTD]

Now that you're done tuning, disable VE and tell me if you feel any difference. My guess is no. LOL!

[blucreek]

Finally got her figured out today.

Guess yesterday was just too long of a day for me to be trying to do some technical work, lol.

All LTFT's are now 2 or less. Truck feels a little more responsive, or at least I think it does. Don't know if it's imagination or not.

Next up is a wideband to dial in the WOT fueling and then maybe I'll try a re-do of my car.


Thanks for the replies guys!

Use your Wideband to check to check your tune, I highly suggest applying the RTT with use of your wideband, you can locate and fix every deadspot you can find. Once you set it up it's really too easy!!

02 It wouldn't hurt to invest in a can of "CNC" MAF cleaner, available at your local parts store for about $7.

Log MAF with your wideband before cleaning, then without making any changes, clean the MAF then log. You'll be suprised
When you get MAF & VE afr error to +/- 1 , multiply by 1/2%. Should be able to feel it in your pedal by then.


chris

[rel3rd]

Now that you're done tuning, disable VE and tell me if you feel any difference. My guess is no. LOL!

Not sure what you are getting at? (or what the "LOL" is for?)

Feel any difference from what to what?

[rel3rd]

Use your Wideband to check to check your tune, I highly suggest applying the RTT with use of your wideband, you can locate and fix every deadspot you can find. Once you set it up it's really too easy!!

02 It wouldn't hurt to invest in a can of "CNC" MAF cleaner, available at your local parts store for about $7.

Log MAF with your wideband before cleaning, then without making any changes, clean the MAF then log. You'll be suprised
When you get MAF & VE afr error to +/- 1 , multiply by 1/2%. Should be able to feel it in your pedal by then.


chris

I still use the old "serial" version of HPT, but will be upgrading very soon to the MPVI Pro. Hopefully, will own a wideband at that time too.

[RWTD]

Not sure what you are getting at? (or what the "LOL" is for?)

Feel any difference from what to what?

Basically, what I was getting at is that you spent all that time dialing in the VE and MAF separately (I believe this is what you did, correct?), which is the GM method. However, I was asking you to disable the VE, and run solely on the MAF, and then tell me if you can feel any difference whatsoever in how your truck performs? My guess is no, you wouldn't, and/or it would run better, provided you have the MAF dialed in 100% properly. My point is that many could eliminate/disable the VE tuning altogether, and just run on and tune solely the MAF, and still have a perfect running vehicle.

[roberttimmons]

Basically, what I was getting at is that you spent all that time dialing in the VE and MAF separately (I believe this is what you did, correct?), which is the GM method. However, I was asking you to disable the VE, and run solely on the MAF, and then tell me if you can feel any difference whatsoever in how your truck performs? My guess is no, you wouldn't, and/or it would run better, provided you have the MAF dialed in 100% properly. My point is that many could eliminate/disable the VE tuning altogether, and just run on and tune solely the MAF, and still have a perfect running vehicle.

true story..

[rel3rd]

Basically, what I was getting at is that you spent all that time dialing in the VE and MAF separately (I believe this is what you did, correct?), which is the GM method. However, I was asking you to disable the VE, and run solely on the MAF, and then tell me if you can feel any difference whatsoever in how your truck performs? My guess is no, you wouldn't, and/or it would run better, provided you have the MAF dialed in 100% properly. My point is that many could eliminate/disable the VE tuning altogether, and just run on and tune solely the MAF, and still have a perfect running vehicle.

Thanks for that explanation. I was actually going to ask this same question.

To do that, would you just have to zero out the scale I attached below, and DISABLE LTFT's?
Then simply leave those two settings alone?


That's what I did when I tuned maf meter, and FWIW, both my car and my truck seemed to run better solely on the maf...once STFT's were dialed in.