IAT temp...howmuch does it affect??

[popeye55]

When I am doing my VE and MAf tuning. I am in open loop..correct? If so that means the truck is not compensating for changes in temp. I have been logging it just to see it's effect. Outside it reads 74 degrees"outside temp guage"....my IAT reads 100 roughly driving 55mph... when I stop to cut/paste..upload and start over on the tune I see my IAT from sitting has went to 125 degrees. DO i need to drive around till the temp comes back down to as close to the last logged temp....? Wouldn't the different IAT temps have a drastic effect on my logs since the truck VCM is not adjusting for it...thus making my logs vary lean or rich by x percent?

[popeye55]

I am having a hard time pinning down my VE. It seems to go from +/- 2 % from one log to the next even if I do not make any changes? I am using CPIG's tuning guide and no filters other then useally 50 plus cell hits. I fight the same thing on my MAF. I cannot seem to get them zeroed out!

[EC_Tune]

Read here. Marcin is on top of this one...

[popeye55]

I read that fast and honestly...I am not sure what I read

[popeye55]

I just cannot seem to get them zeroed out? Should I? Using my wideband LM1 correctly on a 4.3 which is in essence a LS1 computer, in my open loop VE tuning should I be able to get it less the +/- 1% or even 0%....same for the MAF ? When you "tuner GODS....you know who you are!" I guess I haven't really seen or been around a perfect or great tune to see what I need to be shooting for.

[mike01z]

I don't think they need to be exactly 0'd out cause even from day to night the air quality changes, I found the VE was hard to tune in but the MAF was pretty easy, you just gotta get it close and make sure you don't detonate by going too lean.

Also closed loop does a good job of keeping you around stoich once everything is back together.

[popeye55]

I have been tuning the VE till it is 0 to -2% then doing the Maf to the same trying to make sure all my tuning was done with close +/-10 degrees IAT. Once I enable everything it seems like my ltft's are about 3 to 4% positive. Is there a rough amount of time needed for the trims to settle in. I am not sure where I need to be looking...is there something I forgot..do they trims need more time? I reset them everytime when tuning which for VE and MAF I was in open loop.

[Braemerz28]

Had this same thing happen to me. Can't remember exactly which one it was, but I had a setting left on that was still adjusting some fuel for me. I chased 2% changes for about 1/2 tank of gas

You're trying to duplicate a steady state lab environment with a "real world" test set-up. You need to keep as many variables the same as possbile so trying to tune with IAT's in the same range as the last time you tuned and ECT's that have reached steady state is a good start.

You then need to go through every setting in the engine tab and turn off (or change settings so they don't take hold) anything that may be adjusting fuel above and beyond the base VE and MAF tables. These adjusters are in palce to account for the changes in the "real world" that your engine sees. Trouble is, you're trying to replicate that steady state lab envoronment so you don't want all those adjusters in play for right now. When you're done, turn them back on so your truck can adjust for that changing world for you. You're just trying to give it a better base to start adjusting from.

EGR, DFCO, Open Loop settings, closed loop enable temps, LTFT enable temps, power enrichment RPM, CAT overtemp, Piston Protection, are the ones that I believe I had turned off to do the speed density tune in addition to unplugging the MAF to make sure it wasn't doing anything.

Then I put the MAF back into play and adjusted that table with all of the other stuff still off.

I was able to get the VE and the MAF to less than 1% error all around this way. Then turned back on what I wanted on (left EGR off) and away we went with small STFT's and almost 0 LTFT's at that same IAT.

FYI - the same theory works for spark too. Make sure that if you are tuning your base spark table, you have the spark correctors all turned off or set to zero - like the EGR corrector table. Then when your tune is done, turn the EGR back on and copy in the stock EGR spark correction table again.

Hope this helps, I'm kind of tired, but it should give you some areas to look.

Later,

[WS6FirebirdTA00]

Large swings in IAT can cause large, incorrect fueling swings.

[y2konyxss]

Are there some changes that should be made when running a turbo system.

my system creates alot more IAT heat this must affect my cars fueling.