cant get ltft to go down
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Staging Lane
Joined: Mar 2006
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From: rocky mount, va
cant get ltft to go down my ltft are at 16+ while at idle and also at low map pressure 35 and under. above 35kpa the ltft are 4. i tried retuning the car adding fuel to bring down the ltft but no matter how much fuel i add or even subtract th numbers remain the same. has any one run into this problem before? by the way, the car is in speed density mode.
The know it all's know it all
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Originally Posted by slow2000z28
my ltft are at 16+ while at idle and also at low map pressure 35 and under. above 35kpa the ltft are 4. i tried retuning the car adding fuel to bring down the ltft but no matter how much fuel i add or even subtract th numbers remain the same. has any one run into this problem before? by the way, the car is in speed density mode.
Thread Starter
Staging Lane
Joined: Mar 2006
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From: rocky mount, va
im running in sd mode so my Maf isnt hooked up, therefore the Maf table isnt an issue. i have a stock cam. havent tried to reset fuel trims yet, actually was afraid 2. not sure what happens when i hit reset. i dont have awideband yet so i am trying to do this w/ stock narrowband 02s. if anyone can tell me what will happen if i reset the ltfts that would be great.
Make sure you are tuning the seconday VE table. When the MAF is unplugged the PCM runs on the secondary table. If you have been tuning the primary table then you are really making no changes in SD.
On The Tree
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From: Satellite Beach, fl
[QUOTE= if anyone can tell me what will happen if i reset the ltfts that would be great.[/QUOTE]
Long term fuel trims are learned from STFT. They stay in memory for a baseline fuel correction, supplemented by STFT. If you erase/reset LTFT, STFT will take over and over a period of 50 miles will relearn LTFT. Basically by resetting LTFT you will speed up the tuning process when you alter your VE table.
Long term fuel trims are learned from STFT. They stay in memory for a baseline fuel correction, supplemented by STFT. If you erase/reset LTFT, STFT will take over and over a period of 50 miles will relearn LTFT. Basically by resetting LTFT you will speed up the tuning process when you alter your VE table.
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The know it all's know it all
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Originally Posted by slow2000z28
im running in sd mode so my Maf isnt hooked up, therefore the Maf table isnt an issue. i have a stock cam. havent tried to reset fuel trims yet, actually was afraid 2. not sure what happens when i hit reset. i dont have awideband yet so i am trying to do this w/ stock narrowband 02s. if anyone can tell me what will happen if i reset the ltfts that would be great.
Some people have modified the OS to run Sd but I have not seen the effectiveness of doing this as there are alot of Things in the OS that are dependent on the MAF.Secodnly there are large enough MAFS out there to cover the biggest NA motors i have seen. by the time your making 600hp NA then your into a whole new territory where the stock PCM is really a broken crutch.
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Verdad Gallardo On The Tree
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From: Satellite Beach, fl
SD mode is primarily used for VE table tuning, but some folks like it and leave it. Tuning objective is to get your fuel trims in the slightly negative area, then when you enter PE mode no extra fuel ie: LTFT from last table you were in before entering PE, will be added to the PE tables, making for unstable PE mode. Folks tune the VE and then optionally tune the MAF.
The know it all's know it all
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Originally Posted by Purrvert
SD mode is primarily used for VE table tuning, but some folks like it and leave it. Tuning objective is to get your fuel trims in the slightly negative area, then when you enter PE mode no extra fuel ie: LTFT from last table you were in before entering PE, will be added to the PE tables, making for unstable PE mode. Folks tune the VE and then optionally tune the MAF.
the logic loop is something like this roughy.
Montior TPS,
TPS change,
Calcilate Delta equal to or greater than last TPS or fix TPS change ovr time setup for MAF estimation.
If greater grab last known MAF value ,Look Up VE Muodifier MAP vs RPM table apply Modifier to Last and Current MAf reading Sum all 3 then divide by 3 use average.
Air per cylinder Calc based on engine size then final PW based on simultaeneous injector grs/sec vs Vac.
there is alot more conditioning going on but thats the heart of the dyna air calc.thats why you have to have the MAF to do VE table tunning. without it your not going to get close enough.
On The Tree
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From: Satellite Beach, fl
Originally Posted by CollinsAutomotive
Not really going to work since the VE table vaules are patially derived from the MAF input. You just have to log the car intensively and adjust the VE table based on feel, sound and aFR data. Yes the widebadn will be a touch bit behind but you can mentally match it up easily enough. big lean dip with TPS change and MAP increase.
the logic loop is something like this roughy.
Montior TPS,
TPS change,
Calcilate Delta equal to or greater than last TPS or fix TPS change ovr time setup for MAF estimation.
If greater grab last known MAF value ,Look Up VE Muodifier MAP vs RPM table apply Modifier to Last and Current MAf reading Sum all 3 then divide by 3 use average.
Air per cylinder Calc based on engine size then final PW based on simultaeneous injector grs/sec vs Vac.
there is alot more conditioning going on but thats the heart of the dyna air calc.thats why you have to have the MAF to do VE table tunning. without it your not going to get close enough.
the logic loop is something like this roughy.
Montior TPS,
TPS change,
Calcilate Delta equal to or greater than last TPS or fix TPS change ovr time setup for MAF estimation.
If greater grab last known MAF value ,Look Up VE Muodifier MAP vs RPM table apply Modifier to Last and Current MAf reading Sum all 3 then divide by 3 use average.
Air per cylinder Calc based on engine size then final PW based on simultaeneous injector grs/sec vs Vac.
there is alot more conditioning going on but thats the heart of the dyna air calc.thats why you have to have the MAF to do VE table tunning. without it your not going to get close enough.
The know it all's know it all
Joined: Oct 2006
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Originally Posted by Purrvert
Interesting. VE tables are a fixed item, how does the MAF influence?
To answer you other question thee are 3 components in the VE table calculaiton.
Injector Size , MAF Airflow , Cylinder Size
On The Tree
Joined: Dec 2004
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From: Satellite Beach, fl
Originally Posted by CollinsAutomotive
Not really going to work since the VE table vaules are patially derived from the MAF input. You just have to log the car intensively and adjust the VE table based on feel, sound and aFR data. Yes the widebadn will be a touch bit behind but you can mentally match it up easily enough. big lean dip with TPS change and MAP increase.
the logic loop is something like this roughy.
Montior TPS,
TPS change,
Calcilate Delta equal to or greater than last TPS or fix TPS change ovr time setup for MAF estimation.
If greater grab last known MAF value ,Look Up VE Muodifier MAP vs RPM table apply Modifier to Last and Current MAf reading Sum all 3 then divide by 3 use average.
Air per cylinder Calc based on engine size then final PW based on simultaeneous injector grs/sec vs Vac.
there is alot more conditioning going on but thats the heart of the dyna air calc.thats why you have to have the MAF to do VE table tunning. without it your not going to get close enough.
the logic loop is something like this roughy.
Montior TPS,
TPS change,
Calcilate Delta equal to or greater than last TPS or fix TPS change ovr time setup for MAF estimation.
If greater grab last known MAF value ,Look Up VE Muodifier MAP vs RPM table apply Modifier to Last and Current MAf reading Sum all 3 then divide by 3 use average.
Air per cylinder Calc based on engine size then final PW based on simultaeneous injector grs/sec vs Vac.
there is alot more conditioning going on but thats the heart of the dyna air calc.thats why you have to have the MAF to do VE table tunning. without it your not going to get close enough.
"I'll give you a basic problem I ussually see.
The car is dyno tuned with a given fuel rate by mass air calc. and injector flow rates. L-terms pretty much stay 0 on the dyno and the WOT A/F is set on the dyno with timing adjustments for the best power.
Now you start driving down the street with the air filter getting a different velocity of air and the computer starts to adjusting the L-terms to maintain 14.7-1 A/F. When the L-terms go + it also adds fuel to the WOT part of the tune. So,you left the dyno at 13-1 A/F,then the engine added +8 fuel at cruise which dumped onto the WOT table and the car has an LEARNED A/F of 11.5-1."
That is the simple way to explain it."
Last edited by Purrvert; Nov 4, 2006 at 08:04 PM. Reason: spell
10 Second Club
Joined: Nov 2002
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From: Berkeley, California
Originally Posted by CollinsAutomotive
Why are you doing this ??? Put the MAF back on ... Flame Suit On
Originally Posted by CollinsAutomotive
I am not going to start pasting code snipets becuase i would be giving away proprietary information
There's been lots of discussion on what exactly the numbers in the VE table represent. One thing for sure, they don't represent volumetric efficiency solely.
Thread Starter
Staging Lane
Joined: Mar 2006
Posts: 57
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From: rocky mount, va
sorry its been so long since i looked in, (been putting a turbo on a friends h22 accord). im running w/o a maf b/c my maf is messed up. one sensor was hit when installing an intake and it has been off the charts since then. i bought the tunning software to tune the car w/o the maf anyways. that was what many of the people on here run, from the info i gathered when reasearching the software. why should i buy another maf when i can tune w/o it. some smoothe bellows and a tune and the car ran better than it ever did. i jsut reset my fuel trims then ran it and re tuned. car seems to be responding well. ive got a lm-1 wideband on the way so i can more effectively monitor things. thanks for all of the input u guys gave.