Results 1 to 13 of 13

Quick Long Term Fuel Trim Question

This is a discussion on Quick Long Term Fuel Trim Question within the Computer & Tuning forums, part of the LSx Technical Help Section category; When looking at long term fuel trim,,,and lets say for this discussion it's reading +2. I understand this as the ...

  1. #1
    Moderator Firebirdjones's Avatar
    Join Date
    May 2006
    Location
    Arizona
    Posts
    12,552

    Quick Long Term Fuel Trim Question

    When looking at long term fuel trim,,,and lets say for this discussion it's reading +2.
    I understand this as the car running lean and the computer is trying to add fuel,,,,so the tune would need to be fattened up a bit to bring that number back to 0.
    Do I understand that correctly?

  2. #2
    Senior Member mrr23's Avatar
    Join Date
    Jul 2005
    Location
    orlando, fl
    Posts
    7,134

    dark bowling green
    2000 corvette

    if you are within +/-4%, it is fine. but, yes you would need to fatten it up slightly. weather change can affect the LTFT numbers as well.

  3. #3
    Moderator Firebirdjones's Avatar
    Join Date
    May 2006
    Location
    Arizona
    Posts
    12,552
    Cool thanks,,,I wasn't sure if I was understanding that or not. Glad to know I am on the same page. Larry.

  4. #4
    Member
    Join Date
    Oct 2005
    Location
    calif.
    Posts
    213
    Remember---If you have a Negative LTFT number (rich) just before going to WOT the trims will lock on "0"--However if you have a Positive LTFT number(lean) just before going to WOT it will lock on that number-adding that % amount of fuel to your WOT fuel ratio.That is why it is always best to get the LTFT's either "0" or slightlt negative.

  5. #5
    Moderator Firebirdjones's Avatar
    Join Date
    May 2006
    Location
    Arizona
    Posts
    12,552
    Wow,,,now that is the kind of information that I need. This is the kind of important tuning info that is needed for everyone.
    Now if I hadn't known this before hand I would be beating my brains out wondering why I couldn't get the WOT air fuel ratio where I wanted it,,,,not knowing that the computer was adding fuel from the LTFT's and skewing the numbers.
    Thanks for that bit of info. Larry.

  6. #6
    Member
    Join Date
    Aug 2005
    Location
    Newport, Mi.
    Posts
    116

    red
    1999 Camaro SS

    I found it best to tune the LTFTs to between 0% and -5%, so that, no fuel correction factor is added to the WOT fueling. In this manner, its a bit easier to fine tune the "Power Enrichment RPM" table.
    Also, there are 22 Fuel trim cells (FTCs). 0 thru 15 are the cruising around cells, 17 thru 22 are specisl FTCs, with 22 being the WOT cell. FTCs 0 thru 15 are differentiated by engine RPM and MAP value, FTC 0 being low RPM (idle) and low MAP value, while FTC 15 is higher RPM and higher MAP. FTC 0 thru 15 are arranged in a 4x4 matrix, 0,1,2, and 3 are on the bottom row, while 12, 13, 14, and 15 are on the top row. Do a search, this FTC stuff is very well described on this board.
    When you jump from one of the normal driving cycle FTCs 0 thru 15, you jump into the Power Enrichment mode and FTC 22.
    Oh yeh, Each FTc has its own unique LTFT value and STFT value which get update when you are in each specific cell. And the LTFT values are available at startup (key on), while the STFTs are set back to 0% each time the engine is shut off.
    I apologize if you already know this stuff.
    Last edited by Doc99SS; 03-01-2007 at 06:05 PM.

  7. #7
    Moderator Firebirdjones's Avatar
    Join Date
    May 2006
    Location
    Arizona
    Posts
    12,552
    No I don't,,,but it hardly makes sense to me without having the program in front of me to look at what you are talking about. I am sure I will have tons of questions when I get this thing up and running.
    It would be nice if these programs come with a small booklet explaining what each area is for and what it affects. For what you pay for a tuning device I would think it could be included.
    It's just not a simple as a carb and distributor anymore,,,with way too many variables in a program where a guy can get completely lost. Larry.

  8. #8
    Senior Member mrr23's Avatar
    Join Date
    Jul 2005
    Location
    orlando, fl
    Posts
    7,134

    dark bowling green
    2000 corvette

    with HPtuners, when you mouse over a particular box, a brief description shows up at the bottom of the table or box. there are more in the help section. but no, there are no instructions on you do this and this is what happens type thing.

  9. #9
    Moderator Firebirdjones's Avatar
    Join Date
    May 2006
    Location
    Arizona
    Posts
    12,552
    Well it's been a week and it hasn't shown up yet. But I can't wait to get it up and running,,I am interested in what you said about gliding the mouse over the icons and brief descriptions coming up,,,this should at the very least give me some idea which is better than nothing.
    Please bear with me as soon I will bother people with questions I am sure. Larry.

  10. #10
    Senior Member mrr23's Avatar
    Join Date
    Jul 2005
    Location
    orlando, fl
    Posts
    7,134

    dark bowling green
    2000 corvette

    the descriptions tell you what it does, but you have to figure out what it means.

    figure on two weeks to get it.

    here's a screenshot from hptuners website. you'll notice the description at hte bottom of the box in gray.


  11. #11
    Senior Member mrr23's Avatar
    Join Date
    Jul 2005
    Location
    orlando, fl
    Posts
    7,134

    dark bowling green
    2000 corvette

    here, i did one better. this is three screenshots from my hptuners:

    VE primary table when moused over the button


    PE table when moused over the EQ Ratio vs RPM


    Idle when moused over the Idle Airflow button

  12. #12
    Moderator Firebirdjones's Avatar
    Join Date
    May 2006
    Location
    Arizona
    Posts
    12,552
    Thank you for that. I especially liked the description for the Power enrichment wide open throttle section,,,,it actually tells you what math is required to determin that number for your commanded AFR,,,,thats the kind of info that I need to know. This is very helpfull,,,many thanks. Larry.

  13. #13
    Member
    Join Date
    Aug 2005
    Location
    Newport, Mi.
    Posts
    116

    red
    1999 Camaro SS

    One piece of advice that I would like to give is to change only one table at a time and go out and check the results. Make only one change at a time.

    Also, purchase this book, its a great resource for you and your tuning efforts:
    "How to Understand, Service, and Modify Corvette Fuel Injection" by Charles O. Probst

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Help: Short term and long term fuel trim readings can ANYONE help?
    By DaytonaBlues in forum General Help
    Replies: 7
    Last Post: 10-20-2013, 05:21 PM
  2. Ressurecting Trans Am from Long Term Storage
    By Rhinohuey in forum General Help
    Replies: 12
    Last Post: 12-01-2012, 11:28 PM
  3. Question: Whistler Mod - long term durability?
    By davebowtie in forum Appearance Section
    Replies: 9
    Last Post: 07-06-2009, 09:55 PM
  4. rear o2's = long term fuel trim?
    By M-Ten in forum General Help
    Replies: 29
    Last Post: 01-27-2008, 03:45 PM
  5. Long term storage question
    By 02 HAWK in forum General Help
    Replies: 1
    Last Post: 10-23-2005, 04:55 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •