HP Tuners LTFT
09-26-2009, 06:15 PM
#1
HP Tuners LTFT How are you tuning your LTFT in HP Tuners? I came across this method and am wondering if this is the simplest way to go about it?
"Normally, use your Injector Flow Rate (IFR) Table to adjust Long Term Fuel Trims (LTFT's.) Adjust IFR values downward to decrease LTFT; this tells the computer the injector is smaller than what it now believes. Hence, more fuel is added, which compensates for what the computer believes is a lean condition based on O2 Sensor readings, and brings the LTFT adjustment more negative.
So, adjust IFR's upward to increase LTFT (opposite of what I said for adjusting downward).
Try to maintain about 18% Throttle Position Angle (% TPA) when tuning LTFT's.)
The intent of the IFR table is to introduce a constant that coincides with the injector size and the Fuel Pressure.
Theoretically, if you haven't changed the injector or changed your Fuel Pressure, you should not modify this table. If your LTFT's are out of whack, you should first look for vacuum leaks and other abnormal situations. However, mod'ing the car can alter the LTFT's, so you may be justified in changing them if there are no problems that would induce such a shift.
The logic behind zeroing or negating LTFT's is that when you go WOT, LTFT's will be zeroed, meaning no additional fuel is going to be dumped into the engine at WOT, and tuning will be easier. It has been argued that if you can obtain positive LTFT's of a consistent value, this is just as good, as the value is predictable, and thus tunable. That argument seems to have merit to me. But, it has been my experience that when I make LTFT's zero or slightly negative, my car REALLY wakes up at WOT. It even seems more responsive at part throttle. But that is MY experience."
Is this the way to go about it?
"Normally, use your Injector Flow Rate (IFR) Table to adjust Long Term Fuel Trims (LTFT's.) Adjust IFR values downward to decrease LTFT; this tells the computer the injector is smaller than what it now believes. Hence, more fuel is added, which compensates for what the computer believes is a lean condition based on O2 Sensor readings, and brings the LTFT adjustment more negative.
So, adjust IFR's upward to increase LTFT (opposite of what I said for adjusting downward).
Try to maintain about 18% Throttle Position Angle (% TPA) when tuning LTFT's.)
The intent of the IFR table is to introduce a constant that coincides with the injector size and the Fuel Pressure.
Theoretically, if you haven't changed the injector or changed your Fuel Pressure, you should not modify this table. If your LTFT's are out of whack, you should first look for vacuum leaks and other abnormal situations. However, mod'ing the car can alter the LTFT's, so you may be justified in changing them if there are no problems that would induce such a shift.
The logic behind zeroing or negating LTFT's is that when you go WOT, LTFT's will be zeroed, meaning no additional fuel is going to be dumped into the engine at WOT, and tuning will be easier. It has been argued that if you can obtain positive LTFT's of a consistent value, this is just as good, as the value is predictable, and thus tunable. That argument seems to have merit to me. But, it has been my experience that when I make LTFT's zero or slightly negative, my car REALLY wakes up at WOT. It even seems more responsive at part throttle. But that is MY experience."
Is this the way to go about it?
Last edited by supercatxr7; 09-26-2009 at 07:36 PM.
09-27-2009, 12:33 AM
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.................There's a whole lot to it. Everybody has their own method of tuning. That whole 18% throttle position thing is BS, you should scan and log a whole range of throttle positions. To get better feedback, you might want to post your questions in the tuning section or on hptuners website.
With that being said......on a stock car, your fuel LTFT's should be 0 or close to however, that is not always the case. I.E. my buddies 07 gxp was dead nuts 0 and so was my 00 corvette. However, my cousins 06 gxp was way off, like +10%.
One a stock car I like to adjust the MAF to compensate for inaccurate fueling. Like I said, everybody has their own method but I'm sure many good tuners will agree that the MAF is the best place to tune fuel trims on a stock vehicle. I also like to keep the stock shape of the curve, nice and smooth.
You might want to start reading old posts and tuning books. Google Greg Banish, his book is excellent and should answer all of your questions.
With that being said......on a stock car, your fuel LTFT's should be 0 or close to however, that is not always the case. I.E. my buddies 07 gxp was dead nuts 0 and so was my 00 corvette. However, my cousins 06 gxp was way off, like +10%.
One a stock car I like to adjust the MAF to compensate for inaccurate fueling. Like I said, everybody has their own method but I'm sure many good tuners will agree that the MAF is the best place to tune fuel trims on a stock vehicle. I also like to keep the stock shape of the curve, nice and smooth.
You might want to start reading old posts and tuning books. Google Greg Banish, his book is excellent and should answer all of your questions.
09-27-2009, 08:40 PM
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would you be referring to your car? If so, I wouldn't recommend fiddling with it until you read up, you could easily blow it up if you're not careful. Post a scan. Do you have a wideband?
09-27-2009, 09:04 PM
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using hptuners is relatively simple and it just comes with time. Its the principles of tuning that you need to learn. That book by greg banish is excellent you really need to check it out.
Thats good that you have a wideband hooked up. Are you going to post a copy of a scan or what?
Thats good that you have a wideband hooked up. Are you going to post a copy of a scan or what?
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09-27-2009, 09:54 PM
#8
using hptuners is relatively simple and it just comes with time. Its the principles of tuning that you need to learn. That book by greg banish is excellent you really need to check it out.
Thats good that you have a wideband hooked up. Are you going to post a copy of a scan or what?
Thats good that you have a wideband hooked up. Are you going to post a copy of a scan or what?
Attached.
09-27-2009, 11:07 PM
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I'll take a look at it asap. I have to get hptuners on my girlfriend's laptop, mine broke the other day and I don't have the money at the moment to get it fixed. So bear with me.
In fact, post your scan in the tuning section and/ or on the hptuners website, there will be others there that will help you as well.
BTW, what state are you in?
In fact, post your scan in the tuning section and/ or on the hptuners website, there will be others there that will help you as well.
BTW, what state are you in?
Last edited by JDMC5; 09-30-2009 at 02:51 AM.
09-30-2009, 02:48 AM
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Your PM box is full.
I just got done looking at your tune. I need more info. Why didn't you log MAP pressure? Does the commanded a/f ratio correlate to what you are getting on the wideband? If so that's pretty rich. Your long/ short term trims aren't working with the histogram and I'm too sleepy to figure out why.
How long has it been since you reset your fuel trims before this scan? Is doesn't look like they aren't "learned" yet. Make sure you drive around for a few days before taking the scan at face value.
I just got done looking at your tune. I need more info. Why didn't you log MAP pressure? Does the commanded a/f ratio correlate to what you are getting on the wideband? If so that's pretty rich. Your long/ short term trims aren't working with the histogram and I'm too sleepy to figure out why.
How long has it been since you reset your fuel trims before this scan? Is doesn't look like they aren't "learned" yet. Make sure you drive around for a few days before taking the scan at face value.
09-30-2009, 08:05 AM
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Don't adjust your IFR to deal with LTFT's - that tuning methodology is a pure hack. All airflow/RPM values will be adjusted by the same amount, but the reality is that the LTFT will be different values for different values of airflow.
IFR is dependent only on Fuel Pressure, injector size and manifold vacuum. The proper way to tune using LTFT's is to adjust the MAF curve and/or VE table by the LTFT number. There's some animated tutorials and tuning guides on the HPTuners forum that will explain things in more depth.
IFR is dependent only on Fuel Pressure, injector size and manifold vacuum. The proper way to tune using LTFT's is to adjust the MAF curve and/or VE table by the LTFT number. There's some animated tutorials and tuning guides on the HPTuners forum that will explain things in more depth.
09-30-2009, 01:52 PM
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Don't adjust your IFR to deal with LTFT's - that tuning methodology is a pure hack. All airflow/RPM values will be adjusted by the same amount, but the reality is that the LTFT will be different values for different values of airflow.
IFR is dependent only on Fuel Pressure, injector size and manifold vacuum. The proper way to tune using LTFT's is to adjust the MAF curve and/or VE table by the LTFT number. There's some animated tutorials and tuning guides on the HPTuners forum that will explain things in more depth.
IFR is dependent only on Fuel Pressure, injector size and manifold vacuum. The proper way to tune using LTFT's is to adjust the MAF curve and/or VE table by the LTFT number. There's some animated tutorials and tuning guides on the HPTuners forum that will explain things in more depth.
agreed, that pretty much backs up what I was saying. First lets start with a good scan. One, more time.....read Greg Banish's book haha
