HP Tuners guru's needed!
08-29-2013, 10:00 PM
#1
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HP Tuners guru's needed! Finally got HP Tuners for the car and was able to pull the tune that was done on the car.
I'm looking for someones help on here who is familiar with HP Tuners and can just browse over my tune to see if there's anything that stands out. I feel that it runs way to rich at idle, but not sure that you can see the AFR's without logging a wideband through the serial port? Just looking for someone who can browse over the tune and a 2nd gear pull and see if there's anything that they can suggest or comment on.
Mods are in my signature.
I can email the tune, or upload them to my Google drive to be viewable.
Tune link: https://docs.google.com/file/d/0B1ih...it?usp=sharing
2nd Gear pull link: https://docs.google.com/file/d/0B1ih...it?usp=sharing
Thank you for the help.
I'm looking for someones help on here who is familiar with HP Tuners and can just browse over my tune to see if there's anything that stands out. I feel that it runs way to rich at idle, but not sure that you can see the AFR's without logging a wideband through the serial port? Just looking for someone who can browse over the tune and a 2nd gear pull and see if there's anything that they can suggest or comment on.
Mods are in my signature.
I can email the tune, or upload them to my Google drive to be viewable.
Tune link: https://docs.google.com/file/d/0B1ih...it?usp=sharing
2nd Gear pull link: https://docs.google.com/file/d/0B1ih...it?usp=sharing
Thank you for the help.
08-30-2013, 02:09 AM
#2
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Have you tried posting on the hptuners forums? There is alot of traffic over there with really good guys with real life experience. If you can't get a good answer here I would try there.
Every time I see someone tuning their car it reminds me how much I am lagging on tuning mine.
Every time I see someone tuning their car it reminds me how much I am lagging on tuning mine.
08-30-2013, 02:23 PM
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^^^ Thanks for the suggestion, I went ahead and posted up over there as well.
Also, thanks to DMM for taking a look over it. Waiting to hear back from him to see what he thinks about it.
Also, thanks to DMM for taking a look over it. Waiting to hear back from him to see what he thinks about it.
08-30-2013, 04:42 PM
#4
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Okay, some things are a little odd. I just did a cursory check to see what all was changed from stock using the "Compare" feature in the toolbar of the VCM Editor. I'll attatch the file (my 2004 stock CTS-V file) and you'll immediately know what's different b/c it shows up highlighted in green. When you open a map (MAF, VE, timing, what ever) on the top row of the toolbar within the map there will be a square with a blue star to the left, a red star to the right, and a square with both blue and red. The blue is the tune you are looking at, the red is the compare file, and the blue/red combo shows the differences between the two.
Some of the more serious problems:
"Fuel" (Open/Closed Loop Tab)
- Your Long Term Fuel Trims (LTFT) are completely disabled since the "MIN ECT" enable is set for 285*. The PCM can only add a limited amount of fuel with the feedback function (using O2 sensor data). Edit: I'm actually wondering if they did this to make it appear as if the tune is dead on, since someone using a scan tool waould always see "0" LTFT's. Hmm....
- "Closed Loop Enable" is set to 102*F instead of 131*...this is too soon to enter closed loop, although trivial since LTFT's have been disabled.
- "Airflow Mode" should be reset to stock settings
- Depending on your cam, enable the LTFT Idle
These are probably you single biggest contributing factor to the overly rich condition at idle that you are complaining about. Edit: The tunes shows that you have stock injectors, if that's not the case, they were never set up in the tune. Incorrect injector data is usually the single largest and most common contributor to the excessively rich idle complaint with modded and tuned cars.
Fuel "Power Enrich" Tab
This is the classic way to "PE Rape" a tune. At 1600 RPM you only need 33% throttle to enter PE, and at 2800 you only need 19%. To gauge this, 7%-10% is idle...meaning you're rocking PE all the time. Needs to be redone from scratch.
Airflow "General" Tab
- MAF Calibration has lower values than the original equipment LS6 tune across the board, meaning everything that was done (cam etc) actually moves less air (makes less power) than stock...or, they screwed the pooch on it.
- "Main VE" is stock save for low speed cells which have been changed using a standard deduction method (ie, they just used the same multiplier for every cell regardless of what was needed). This is wrong.
Here's the real problem with this...when your MAF and VE are not correct, the PE (power enrichment) will never be right since PE is a standard multiplier. The fuel trims (LTFT's and STFT's) will make adjustments under normal driving (not in your case b/c they turned them off, but you get the idea) and the stock tune only enables PE in the very upper RPM ranges. Your PE is set up for 12.31 AFR...if your base calibration is off (and it is off, I assure you) you will be running lean but you have the fuel trims (adjustment factor) to compensate. During PE, the actual AFR will be way lean since the base cal is incorrect. Hope that makes sense, LOL.
One last thing that I have never seen...they changed the Cyl Volume (displacement) in the tune (GENERAL TAB). The value should be 0.70821, they changed it to 0.71004 for some reason.
Without seeing the car I cannot comment on anything else b/c I don't know if the changes were actually required or not. I don't know if some things were done to mask other problems, such as the LTFT's. The tune does not appear to be overly unsafe, timing is only 4* higher than stock, and they did not zero out the retard, which are good things.
You're def going to need a wideband in order to get your MAF and VE correct. I can try to correct a few things and send it back to you, just can't do it right now. One thing you can do is to enable the LTFT's and see what you're running. Anything more than +/- 5 on the histogram requires adjustment, interested to see how far you're really off.
Some of the more serious problems:
"Fuel" (Open/Closed Loop Tab)
- Your Long Term Fuel Trims (LTFT) are completely disabled since the "MIN ECT" enable is set for 285*. The PCM can only add a limited amount of fuel with the feedback function (using O2 sensor data). Edit: I'm actually wondering if they did this to make it appear as if the tune is dead on, since someone using a scan tool waould always see "0" LTFT's. Hmm....
- "Closed Loop Enable" is set to 102*F instead of 131*...this is too soon to enter closed loop, although trivial since LTFT's have been disabled.
- "Airflow Mode" should be reset to stock settings
- Depending on your cam, enable the LTFT Idle
These are probably you single biggest contributing factor to the overly rich condition at idle that you are complaining about. Edit: The tunes shows that you have stock injectors, if that's not the case, they were never set up in the tune. Incorrect injector data is usually the single largest and most common contributor to the excessively rich idle complaint with modded and tuned cars.
Fuel "Power Enrich" Tab
This is the classic way to "PE Rape" a tune. At 1600 RPM you only need 33% throttle to enter PE, and at 2800 you only need 19%. To gauge this, 7%-10% is idle...meaning you're rocking PE all the time. Needs to be redone from scratch.
Airflow "General" Tab
- MAF Calibration has lower values than the original equipment LS6 tune across the board, meaning everything that was done (cam etc) actually moves less air (makes less power) than stock...or, they screwed the pooch on it.
- "Main VE" is stock save for low speed cells which have been changed using a standard deduction method (ie, they just used the same multiplier for every cell regardless of what was needed). This is wrong.
Here's the real problem with this...when your MAF and VE are not correct, the PE (power enrichment) will never be right since PE is a standard multiplier. The fuel trims (LTFT's and STFT's) will make adjustments under normal driving (not in your case b/c they turned them off, but you get the idea) and the stock tune only enables PE in the very upper RPM ranges. Your PE is set up for 12.31 AFR...if your base calibration is off (and it is off, I assure you) you will be running lean but you have the fuel trims (adjustment factor) to compensate. During PE, the actual AFR will be way lean since the base cal is incorrect. Hope that makes sense, LOL.
One last thing that I have never seen...they changed the Cyl Volume (displacement) in the tune (GENERAL TAB). The value should be 0.70821, they changed it to 0.71004 for some reason.
Without seeing the car I cannot comment on anything else b/c I don't know if the changes were actually required or not. I don't know if some things were done to mask other problems, such as the LTFT's. The tune does not appear to be overly unsafe, timing is only 4* higher than stock, and they did not zero out the retard, which are good things.
You're def going to need a wideband in order to get your MAF and VE correct. I can try to correct a few things and send it back to you, just can't do it right now. One thing you can do is to enable the LTFT's and see what you're running. Anything more than +/- 5 on the histogram requires adjustment, interested to see how far you're really off.
Last edited by DMM; 08-30-2013 at 05:05 PM.
08-30-2013, 10:06 PM
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Hats off to DMM. Bravo my friend, bravo. If you PM me your paypal address or if it's the same one I sent the email to, I'll paypal over some beer money as a gift for your time.
If you don't mind correcting some of the things that you've pointed out, I'd really appreciate that. Of course, just when your schedule allows it. I'm still new to HP Tuners, but slowing catching on.
Going to adjust some of the things you've pointed out, atleast turn the LTFT's back on and get some values from that.
Thanks for your time spent man.
EDIT: If it's any easier, you can post of PM the values you'd change and what you'd change them back to.
Fuel - Opened and Closed Loop
Such as, MIN ECT from the 285 back to the stock 131?
Closed loop enable back to 102 to 131?
I don't see an "Airflow" setting, and if you're talking about 02 Rich/Lean vs. Airflow, they are the stock values. Wondering what to change here?
LTFT Idle is set to Disable TPS: 1.2% - 4.0 MPH (I don't think this works because it seems my TPS is at 7% at idle)
PE Table
Not sure what I need to change the values to inside either PE Throttle/Pedal - Hot or EQ Ratio or ADD vs. ECT.
Airflow - General Tab
Airflow vs. Frequency - Should I reset these back to the stock values?
Main VE - No clue what to change these values to.
Will also be changing back to the stock displacement figure.
Thank you for your help.
If you don't mind correcting some of the things that you've pointed out, I'd really appreciate that. Of course, just when your schedule allows it. I'm still new to HP Tuners, but slowing catching on.
Going to adjust some of the things you've pointed out, atleast turn the LTFT's back on and get some values from that.
Thanks for your time spent man.
EDIT: If it's any easier, you can post of PM the values you'd change and what you'd change them back to.
Fuel - Opened and Closed Loop
Such as, MIN ECT from the 285 back to the stock 131?
Closed loop enable back to 102 to 131?
I don't see an "Airflow" setting, and if you're talking about 02 Rich/Lean vs. Airflow, they are the stock values. Wondering what to change here?
LTFT Idle is set to Disable TPS: 1.2% - 4.0 MPH (I don't think this works because it seems my TPS is at 7% at idle)
PE Table
Not sure what I need to change the values to inside either PE Throttle/Pedal - Hot or EQ Ratio or ADD vs. ECT.
Airflow - General Tab
Airflow vs. Frequency - Should I reset these back to the stock values?
Main VE - No clue what to change these values to.
Will also be changing back to the stock displacement figure.
Thank you for your help.
Last edited by tmonttt; 08-30-2013 at 10:25 PM.
08-30-2013, 10:38 PM
#6
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No worries my man. I don't have a PayPal account, and besides, I have a debt to pay forward from another member, LOL. So if you get the opportunity and are in a position to do so, go ahead and pay it forward to the next guy.
I somehow got swindled into helping some friends move into their new house tomorrow (which I seriously do not remember agreeing to) so I may not be able to get something back to you until Sunday. I would go ahead and re-enable the LTFT's and see where you stand.
Also, do you know if you have the OE fuel injectors? I have some injector data, so if you know what injectors you have drop me a note and I'll try to set that up as well. If they're stock, never mind.
I somehow got swindled into helping some friends move into their new house tomorrow (which I seriously do not remember agreeing to) so I may not be able to get something back to you until Sunday. I would go ahead and re-enable the LTFT's and see where you stand.
Also, do you know if you have the OE fuel injectors? I have some injector data, so if you know what injectors you have drop me a note and I'll try to set that up as well. If they're stock, never mind.
08-30-2013, 11:14 PM
#7
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Fuel - Opened and Closed Loop
- LTFT Enable should be the stock 131
- Closed loop enable should be the stock 131
- Disregard the "Airflow Mode" (Mode vs. Airflow) - the thing shows green but has the OE values. May have been changed and changed back, but it's okay. My bad.
- LTFT Idle is set to Disable TPS: 1.2% - 4.0 MPH (I don't think this works because it seems my TPS is at 7% at idle) You can play with this, won't hurt anything to extend the values to see what it does for you. I am kind of at a loss as to whether this will help or not b/c of your cam and the MAF and VE not being correct, only one way to know if it helps or not!
PE Table
This is really up to you and should be tailored to your driving habits. I don't know how often you're looking for max power at 1500 RPM, so I usually data log to see where TPS is during normal driving and set the PE/Throttle Pedal accordingly. You have no idea how light 30% throttle feels. Look at the data while you're driving (normal street driving) and let that be your guide.
In your current tune, MAP is the only thing that keeps you out of PE, I usually set throttle higher in the area's where normal "cruising" is done and then taper down to 18% as RPM's get higher. The reason I do this is that manifold vacuum (MAP) can change with load (going up hill, etc) not necessarily when intended. If you set the throttle to your driving habits, you'll only actually get PE when you're looking for it.
Coincidentally, this is why I originally tuned my old Maggie setup. The hack that tuned it (John B. of BEHE) raped the PE and it felt like it had a broken motor mount on tip in cruising at around 2k RPM. Turns out, on tip in (PE was set to 18% throttle across the board) it was entering PE and slamming to 11.5 AFR under high load and light throttle, exactly when it was not needed.
I'll set this and you can see how you like it, but it really helps to tailor it to your driving style.
Airflow - General Tab
- Airflow vs. Frequency - You can copy the OE values back in but they still won't be correct until you tune with a wideband.
Main VE - I would not attempt changes without a wideband or previous experience
- LTFT Enable should be the stock 131
- Closed loop enable should be the stock 131
- Disregard the "Airflow Mode" (Mode vs. Airflow) - the thing shows green but has the OE values. May have been changed and changed back, but it's okay. My bad.
- LTFT Idle is set to Disable TPS: 1.2% - 4.0 MPH (I don't think this works because it seems my TPS is at 7% at idle) You can play with this, won't hurt anything to extend the values to see what it does for you. I am kind of at a loss as to whether this will help or not b/c of your cam and the MAF and VE not being correct, only one way to know if it helps or not!
PE Table
This is really up to you and should be tailored to your driving habits. I don't know how often you're looking for max power at 1500 RPM, so I usually data log to see where TPS is during normal driving and set the PE/Throttle Pedal accordingly. You have no idea how light 30% throttle feels. Look at the data while you're driving (normal street driving) and let that be your guide.
In your current tune, MAP is the only thing that keeps you out of PE, I usually set throttle higher in the area's where normal "cruising" is done and then taper down to 18% as RPM's get higher. The reason I do this is that manifold vacuum (MAP) can change with load (going up hill, etc) not necessarily when intended. If you set the throttle to your driving habits, you'll only actually get PE when you're looking for it.
Coincidentally, this is why I originally tuned my old Maggie setup. The hack that tuned it (John B. of BEHE) raped the PE and it felt like it had a broken motor mount on tip in cruising at around 2k RPM. Turns out, on tip in (PE was set to 18% throttle across the board) it was entering PE and slamming to 11.5 AFR under high load and light throttle, exactly when it was not needed.
I'll set this and you can see how you like it, but it really helps to tailor it to your driving style.
Airflow - General Tab
- Airflow vs. Frequency - You can copy the OE values back in but they still won't be correct until you tune with a wideband.
Main VE - I would not attempt changes without a wideband or previous experience
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08-31-2013, 12:27 PM
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Again, thanks DMM.
I am still on stock injectors so don't worry about that portion of it.
Just tailor the PE table to something you would consider for yourself, I'm not an overly aggressive driver, but I can always play with the values after you provide me with the updated tune that you put together.
Airflow vs. Frequency, I will reset those back to stock values for now.
VE Table - I will just leave this be for the time being until I get a wideband in the car. I don't have the knowledge to mess with it.
Again, thanks for all the help, going to make the adjustments that you've stated today and see how the car runs. Take your time and just send me a copy of the tune you put together when you have time.
Thanks bud!
I am still on stock injectors so don't worry about that portion of it.
Just tailor the PE table to something you would consider for yourself, I'm not an overly aggressive driver, but I can always play with the values after you provide me with the updated tune that you put together.
Airflow vs. Frequency, I will reset those back to stock values for now.
VE Table - I will just leave this be for the time being until I get a wideband in the car. I don't have the knowledge to mess with it.
Again, thanks for all the help, going to make the adjustments that you've stated today and see how the car runs. Take your time and just send me a copy of the tune you put together when you have time.
Thanks bud!
08-31-2013, 03:58 PM
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Here's a quick update; I've gone in an adjusted the values that DMM shared to change and I've noticed improvement. I no longer have the extreme unburnt fuel smell at idle. It doesn't back fire in between shifts anymore and seems to run a bit better throughout the RPM band.
DMM; I'll email you the new tune that I put on it this morning as well as a log of it idling, and some cruising with a 2nd gear WOT pull in it. I'll still wait for you to adjust the PE table and the other things you were going to adjust, but you've definitely put me on the right track.
Here's the files for those who want to look at the new tune/log.
Tune: https://docs.google.com/file/d/0B1ih...it?usp=sharing
Log: https://docs.google.com/file/d/0B1ih...it?usp=sharing
Thanks again for the help, DMM especially.
DMM; I'll email you the new tune that I put on it this morning as well as a log of it idling, and some cruising with a 2nd gear WOT pull in it. I'll still wait for you to adjust the PE table and the other things you were going to adjust, but you've definitely put me on the right track.
Here's the files for those who want to look at the new tune/log.
Tune: https://docs.google.com/file/d/0B1ih...it?usp=sharing
Log: https://docs.google.com/file/d/0B1ih...it?usp=sharing
Thanks again for the help, DMM especially.
09-01-2013, 12:31 PM
#11
Just a note:
I will never use LTFT's when a tune is done. Run CL using STFT's only. This protects adjustments that would otherwise be made to the (PE) portion of the tune.
The reason is, is over time LTFTs will taint your perfectly dialed in VE / MAF when in PE.
Please note, 'dialed in'.
I will never use LTFT's when a tune is done. Run CL using STFT's only. This protects adjustments that would otherwise be made to the (PE) portion of the tune.
The reason is, is over time LTFTs will taint your perfectly dialed in VE / MAF when in PE.
Please note, 'dialed in'.
09-01-2013, 10:08 PM
#12
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Just a note:
I will never use LTFT's when a tune is done. Run CL using STFT's only. This protects adjustments that would otherwise be made to the (PE) portion of the tune.
The reason is, is over time LTFTs will taint your perfectly dialed in VE / MAF when in PE.
Please note, 'dialed in'.
I will never use LTFT's when a tune is done. Run CL using STFT's only. This protects adjustments that would otherwise be made to the (PE) portion of the tune.
The reason is, is over time LTFTs will taint your perfectly dialed in VE / MAF when in PE.
Please note, 'dialed in'.
Taking it one step further, the PCM will look at all of the enrichment tables (PE, BE, and even the Open Loop tables) and will only apply its fueling values from whichever is richer: The OLFA table (x-referenced by ECT & MAP) or PE (x-referenced by RPM) or BE (x-referenced by MAP). I have my OLFA table set to all 1.00's from 160* ECT on up, that way WOT always gets it fueling from PE or BE.
I never understood why someone would disable LTFT's unless they had a huge cam that would suck for daily driving anyhow. LTFT's enable the PCM to attain the desired AFR despite fuel quality etc. and only serve to maintain drivabilty by ensuring the correct AFR in closed loop. By disabling LTFT's but enabling STFT's, you're taking the PCM and tying one arm behind its back.
09-02-2013, 05:27 PM
#13
Sorry man, your theory of operation is wrong. All enrichment tables such as Power Enrichment (PE) or Boost Enrichment (BE) are open loop. When you data log you will see both LTFT's and STFT's flat line to "0" whenever these tables are active since they're open loop. The PCM does not look to the O2 sensor data during PE or BE which is why having accurate MAF and VE tables are essential.
Taking it one step further, the PCM will look at all of the enrichment tables (PE, BE, and even the Open Loop tables) and will only apply its fueling values from whichever is richer: The OLFA table (x-referenced by ECT & MAP) or PE (x-referenced by RPM) or BE (x-referenced by MAP). I have my OLFA table set to all 1.00's from 160* ECT on up, that way WOT always gets it fueling from PE or BE.
I never understood why someone would disable LTFT's unless they had a huge cam that would suck for daily driving anyhow. LTFT's enable the PCM to attain the desired AFR despite fuel quality etc. and only serve to maintain drivabilty by ensuring the correct AFR in closed loop. By disabling LTFT's but enabling STFT's, you're taking the PCM and tying one arm behind its back.
Taking it one step further, the PCM will look at all of the enrichment tables (PE, BE, and even the Open Loop tables) and will only apply its fueling values from whichever is richer: The OLFA table (x-referenced by ECT & MAP) or PE (x-referenced by RPM) or BE (x-referenced by MAP). I have my OLFA table set to all 1.00's from 160* ECT on up, that way WOT always gets it fueling from PE or BE.
I never understood why someone would disable LTFT's unless they had a huge cam that would suck for daily driving anyhow. LTFT's enable the PCM to attain the desired AFR despite fuel quality etc. and only serve to maintain drivabilty by ensuring the correct AFR in closed loop. By disabling LTFT's but enabling STFT's, you're taking the PCM and tying one arm behind its back.
Nothing to do with the LTFT or STFT on what you log - fully aware these are zeroed out in OL.
If I remember correctly, it a Positive only scenario thing as well. (PE + LTFT additional fuel) when in OL...
As far as I know, LTFT still play a role in OL if your LTFTs are wanting to add fuel.
Search "Disabling LTFT for good".
There are also other mentioned reasons to disable LTFT, especially using LT headers.
"Another example why I don't like LTFT, if you get an o2 to rail (which is common on aftermarket headers) it can get way off quick."
"By "rail" do you mean they stick at a certain MV instead of oscillate up and down? Cause that is exactly what I'm getting. The Trims would get "perfect" and suddenly the O2's will stick to 886mv for a few seconds and blamo! My LTFT's are diving to +/-10."
As for the one hand behind the back analogy - I disagree for the most part.
I good tuned car doesn't need LTFT what so ever and I still believe it mucks up ones VE table in the WOT area over time.
STFT enabled to keep CL and those short *NOW fuel adjustments is sufficient.
Last edited by vmapper; 09-02-2013 at 05:49 PM.
09-02-2013, 10:56 PM
#14
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Okay - I see where you are going with this. Didn't mean to seem like a dick, I misinterpreted what you were trying to convey. As I eluded to earlier, an all out race car with nasty cam etc. by all means, disable them. However, for a vehicle that sees 95%+ street duty, I still disagree...but I'll elaborate...
When the MAF and VE are tuned correctly (by correctly, I mean with an accurate wideband on the lambda scale with new O2 sensors) there should be no LTFT corrections to begin with.
What can cause LTFT's? Shitty fuel, dirty air filter, plugged fuel filter, weak FPR, etc...the list is endless. The STFT's drive high enough long enough to become a long term correction, and then STFT's work within the LTFT's. There are no LTFT adjustments in PE...however, if there is an LTFT correction in use exactly when PE/BE is called for, that correction factor will carry over into PE if it's positive (b/c the PCM will always default to the richest AFR for safety) even though it is open loop and O2 sensor data is disregarded. These values are not retained in memory for future PE applications.
So here's the scenario...your fuel pressure regulator is going bad. The car had been tuned within 0-3 LTFT's using a wideband/lambda, now during normal cruise there is a LTFT correction of +12 that is carried over to into PE, which otherwise would be very lean at the exact point where the most damage can occur. I don't see a downside here.
The inverse of this, a fuel injector is going bad and dumping more fuel than intended causing a LTFT value of -8. The PCM will disregard this subtraction of fueling (again defaulting to the richest values).
If STFT's alone do a sufficient job, disable the LTFT's fudge the injector data and see how well things go. Enable LTFT's with the wrong injector data and things will get much better @ 131* ECT as soon as they become active.
Again, if this is an all out effort for max power where an overly rich condition will hurt performance, it's a good idea. On a 95%+ street driven vehicle where the potential to run lean over a long period of time will do more damage than possibly running a little rich only when in PE, I'd take it. There are many people that complain about headers causing crazy fuel trims, I've never had a problem with this. If the headers/cam cause lazy O2 sensors, this can also be adjusted for in the tune.
When the MAF and VE are tuned correctly (by correctly, I mean with an accurate wideband on the lambda scale with new O2 sensors) there should be no LTFT corrections to begin with.
What can cause LTFT's? Shitty fuel, dirty air filter, plugged fuel filter, weak FPR, etc...the list is endless. The STFT's drive high enough long enough to become a long term correction, and then STFT's work within the LTFT's. There are no LTFT adjustments in PE...however, if there is an LTFT correction in use exactly when PE/BE is called for, that correction factor will carry over into PE if it's positive (b/c the PCM will always default to the richest AFR for safety) even though it is open loop and O2 sensor data is disregarded. These values are not retained in memory for future PE applications.
So here's the scenario...your fuel pressure regulator is going bad. The car had been tuned within 0-3 LTFT's using a wideband/lambda, now during normal cruise there is a LTFT correction of +12 that is carried over to into PE, which otherwise would be very lean at the exact point where the most damage can occur. I don't see a downside here.
The inverse of this, a fuel injector is going bad and dumping more fuel than intended causing a LTFT value of -8. The PCM will disregard this subtraction of fueling (again defaulting to the richest values).
If STFT's alone do a sufficient job, disable the LTFT's fudge the injector data and see how well things go. Enable LTFT's with the wrong injector data and things will get much better @ 131* ECT as soon as they become active.
Again, if this is an all out effort for max power where an overly rich condition will hurt performance, it's a good idea. On a 95%+ street driven vehicle where the potential to run lean over a long period of time will do more damage than possibly running a little rich only when in PE, I'd take it. There are many people that complain about headers causing crazy fuel trims, I've never had a problem with this. If the headers/cam cause lazy O2 sensors, this can also be adjusted for in the tune.
Last edited by DMM; 09-02-2013 at 11:05 PM.
09-04-2013, 08:45 AM
#15
DMM - Not at all, never thought anything of it! (Im hoping my previous post didn't come across that made it seem like so)
You bring up the validity of a malfunction or part failure being protected. I could see that. I usually have the 'performance cap' on, rather than daily light modified.
Always a good discussion. I could continue by asking "Why do you have bad injector data int he first place"... but I see where you are coming from. No need to discuss.
I thought I would post my notes on some terms and definitions so that others could read.
Short Term Fuel Trim (STFT): A rapid, non-stored fuel adjustment described by percent fuel error.
Long Term Fuel Trim (LTFT): A slow, averaged, stored fuel adjustment described by percent fuel error. Can be modified or reset to zero by firmware or reset to zero by user action (VCM Controls, removing battery power).
Fuel Trim Cell (FTC): A pointer to the FTC matrix (array) described by the LTFT boundaries of MAP & RPM and stored in RAM. Also includes cells for Idle, canister purge, WOT, transmission selection (P/N, gear) and AC on/off. See the help file for more definitions of FTC per vehicle type.
How it works (Closed Loop only!):
------------------------------------------------------------
The PCM reads the o2 sensor value and compares it with the last reading to see if it switched from rich to lean or lean to rich. If it hasn't switched, it averages that value with the last and uses the proportional o2 error tables to determine how much the pulsewidth needs to be changed to make the o2 switch.
This averaged value (filtered) is then turned into the STFT value. If the o2 has been rich for a while (filtered, averaged) the STFT goes negative, pulsewidth drops, and vice versus.
Now, if the STFT goes above/below a preset limit over a period of time (~450msec), the LTFT will be Incremented (if STFT+) or Decremented (if STFT-) accordingly. If STFT is *way out of whack*, LTFT will Increment or Decrement more rapidly based on filter values in the closed loop control.
When the engine operating conditions cause the FTC to change, the last LTFT value from the current FTC is stored in RAM to be retrieved the next time the engine returns to that particular FTC. The LTFT value for the current FTC is then loaded from RAM and the process repeats.
You bring up the validity of a malfunction or part failure being protected. I could see that. I usually have the 'performance cap' on, rather than daily light modified.
Always a good discussion. I could continue by asking "Why do you have bad injector data int he first place"... but I see where you are coming from. No need to discuss.
I thought I would post my notes on some terms and definitions so that others could read.
Short Term Fuel Trim (STFT): A rapid, non-stored fuel adjustment described by percent fuel error.
Long Term Fuel Trim (LTFT): A slow, averaged, stored fuel adjustment described by percent fuel error. Can be modified or reset to zero by firmware or reset to zero by user action (VCM Controls, removing battery power).
Fuel Trim Cell (FTC): A pointer to the FTC matrix (array) described by the LTFT boundaries of MAP & RPM and stored in RAM. Also includes cells for Idle, canister purge, WOT, transmission selection (P/N, gear) and AC on/off. See the help file for more definitions of FTC per vehicle type.
How it works (Closed Loop only!):
------------------------------------------------------------
The PCM reads the o2 sensor value and compares it with the last reading to see if it switched from rich to lean or lean to rich. If it hasn't switched, it averages that value with the last and uses the proportional o2 error tables to determine how much the pulsewidth needs to be changed to make the o2 switch.
This averaged value (filtered) is then turned into the STFT value. If the o2 has been rich for a while (filtered, averaged) the STFT goes negative, pulsewidth drops, and vice versus.
Now, if the STFT goes above/below a preset limit over a period of time (~450msec), the LTFT will be Incremented (if STFT+) or Decremented (if STFT-) accordingly. If STFT is *way out of whack*, LTFT will Increment or Decrement more rapidly based on filter values in the closed loop control.
When the engine operating conditions cause the FTC to change, the last LTFT value from the current FTC is stored in RAM to be retrieved the next time the engine returns to that particular FTC. The LTFT value for the current FTC is then loaded from RAM and the process repeats.
07-26-2015, 12:03 PM
#18
HP Tuners guru's needed! Using the ltft is only good for all rpm under 3500-4000 rpm. Anything above that should have wb.
I go through the gears in 2-5 and hold the rpm for 10-20sec at 500rpm increments. Then ingive it a 40% throttle accel till 4000rpm. after i log the stft and ltft i use my exel table add them all together getting an average then take 75% of that and adjust my maf hz accordingly.
I zero the trim and try it again seein the new log.
This way i keep the trim at +/- 4 which is acceptable
Then i hit the dyno for 3-5 gear pulls and i average the afr and adjust the maf hz accordingly. You have to use the gears you will most likely be in and then do a real world test, if you can. Thankfully i use wb for my main sensors so i just use the ben on my tuner and adjust the last bits taking into account drag and wind resistance...
I go through the gears in 2-5 and hold the rpm for 10-20sec at 500rpm increments. Then ingive it a 40% throttle accel till 4000rpm. after i log the stft and ltft i use my exel table add them all together getting an average then take 75% of that and adjust my maf hz accordingly.
I zero the trim and try it again seein the new log.
This way i keep the trim at +/- 4 which is acceptable
Then i hit the dyno for 3-5 gear pulls and i average the afr and adjust the maf hz accordingly. You have to use the gears you will most likely be in and then do a real world test, if you can. Thankfully i use wb for my main sensors so i just use the ben on my tuner and adjust the last bits taking into account drag and wind resistance...
