racecar

My scan of LTFT's are running from +2 to +25, with a lot of +25 in the lower MAP. Most of the others are +6 to +15. All LTFT are positive. I added 50% of the LTFT number to the VE table cell, e.g. VE cell =75, LTFT for that cell = 12, I added 6 to the cell = 81. Ran it 30 minutes then scanned for 20. The LTFT's are higher. Did I go the wrong direction? What am I missing here.

SSpdDmon

iTrader: (10)

If you are still running with the MAF enabled, it will do a majority of the fueling calculations. VE is only referenced somewhat in low airflow conditions (idle/light throttle) and in speed density mode (no MAF). But yes, if you see positive fuel trims you increase the VE table or the MAF table to increase fueling. Just remember, fuel trims are a percentage. If you want to increase a cell in the VE to reduce the LTFT's, you need to multiply as a percentage. In other words, if you have a +12 LTFT and you want to do a 50% correction, you multiply the affected cell by 1.06. If you add 6 to that cell, it could be way more than you needed. Say the value in the cell was 42 and you add 6. You then have 48, which is a 14.3% increase. If you only wanted a 6% increase, the new number should be 44.52.

RedWS6 00

Remember to reset your fuel trims after every time to change the VE table.

racecar

When I download a new program does that reset the trims?? Or do I need to reset them?? How do I reset them in HPTuners?
Thanks

muncie21

iTrader: (14)

Downloading a new tune doesn't reset the fuel trims. You need to do that through HPT. Go to VCM Controls and then Fuel&Spark--> there's a button that says 'reset fuel trims'.

BTW, when you are logging, make sure you filter out decel and DFCO in your LTFT histogram, or it will throw your VE values off. Oh and un-plug the MAF.

racecar

I will reset the LTFT's and try another scan.
How do I filter the decel and DFCO for the log??? That would make a difference because I am driving through some small hills and coasting sometimes.

muncie21

iTrader: (14)

Go to the setup screen for your VE/LTFT histogram. There's a entry field labeled 'plot filtering', press the "?" to look up the PID in question (in this case it's PID.6310) and create a logical expression to include or exclude certain parameters.

To ignore coasting/idle or WOT fuel trim cells, setup a filter that excludes these values. Your expression should look something like this:

PID.6310>0 AND PID.6310<17
I believe FTC 0 is coasting and greater than 18 are idle and WOT.

It's also a good idea to set the 'cell hits required' field to 20 or 25 to exclude errant values.

FYI- PID.6310 is the PID for the Fuel Trim Cell (FTC). There's a posting of what all the FTCs are, but in general 1-16 is normal driving, 0 is coast or decel and 17-21 is Open loop, WOT, and some other stuff.

markp03

iTrader: (4)

tag... good info.

racecar

Excellent info on the decel PID. I would have never found that one.

marthastewart

iTrader: (1)

I just did this and no numbers post at all. What does that mean?

muncie21

iTrader: (14)

You may not be logging one or more of the values in your formula. Check in the scanner to see if any values come up.