When LTFT are positive, do I add to VE ??
Thread Starter
TECH Resident
Joined: Aug 2004
Posts: 875
Likes: 2
From: Portland Oregon
When LTFT are positive, do I add to VE ?? 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.
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.
Originally Posted by 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
Thanks
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.
Thread Starter
TECH Resident
Joined: Aug 2004
Posts: 875
Likes: 2
From: Portland Oregon
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.
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.
Originally Posted by racecar
How do I filter the decel and DFCO for the log???
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.
Last edited by muncie21; Aug 3, 2006 at 01:10 AM.
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Originally Posted by muncie21
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.
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.
I just did this and no numbers post at all. What does that mean?
Originally Posted by marthastewart
I just did this and no numbers post at all. What does that mean?
