Controlling LTFTs
Thread Starter
Teching In
Joined: Jun 2005
Posts: 14
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Controlling LTFTs Finished my VE Tuning. Got everything sweet.
Running with LTFT disabled, STFT is between -3 and +3 sweet as.
When I turn on my LTFT again, I get values up to 5 and 6, but my STFTs are still in the same range.
What is going on? How do I stop my LTFTs going crazy?
Running with LTFT disabled, STFT is between -3 and +3 sweet as.
When I turn on my LTFT again, I get values up to 5 and 6, but my STFTs are still in the same range.
What is going on? How do I stop my LTFTs going crazy?
now tune using the lt's and the st's its gonna take alot longer as you have to wait for em to get learned Ive had good luck with this method I do it over a week or too in the end its worth it better mileage and you can run more timing.
did you reset trims after tuning with stft and enabling lt's?
or Ive heard of people just leaving the long terms disabled
did you reset trims after tuning with stft and enabling lt's?
or Ive heard of people just leaving the long terms disabled
Thread Starter
Teching In
Joined: Jun 2005
Posts: 14
Likes: 0
I did the standard thing.
Got LTFT and STFTs close (less than 10 total). Then disabled LTFTs and tuned using STFTs only.
Driving around now (after the car has reached operating temp), with LTFT Learn disabled, STFTs are -3 to +3.
When I enable LTFT Learning, all of a sudden it starts adding 4 to 6 (richening) to areas that were previously 0. I'm just curious why it does this.
I want to run lean, 12.8:1 in PE mode. A 5% addition takes me from 12.8:1 to 11.9:1. Not where I want to be at all.
Got LTFT and STFTs close (less than 10 total). Then disabled LTFTs and tuned using STFTs only.
Driving around now (after the car has reached operating temp), with LTFT Learn disabled, STFTs are -3 to +3.
When I enable LTFT Learning, all of a sudden it starts adding 4 to 6 (richening) to areas that were previously 0. I'm just curious why it does this.
I want to run lean, 12.8:1 in PE mode. A 5% addition takes me from 12.8:1 to 11.9:1. Not where I want to be at all.
Originally Posted by VYSSWagon
I did the standard thing.
Got LTFT and STFTs close (less than 10 total). Then disabled LTFTs and tuned using STFTs only.
Driving around now (after the car has reached operating temp), with LTFT Learn disabled, STFTs are -3 to +3.
When I enable LTFT Learning, all of a sudden it starts adding 4 to 6 (richening) to areas that were previously 0. I'm just curious why it does this.
I want to run lean, 12.8:1 in PE mode. A 5% addition takes me from 12.8:1 to 11.9:1. Not where I want to be at all.
Got LTFT and STFTs close (less than 10 total). Then disabled LTFTs and tuned using STFTs only.
Driving around now (after the car has reached operating temp), with LTFT Learn disabled, STFTs are -3 to +3.
When I enable LTFT Learning, all of a sudden it starts adding 4 to 6 (richening) to areas that were previously 0. I'm just curious why it does this.
I want to run lean, 12.8:1 in PE mode. A 5% addition takes me from 12.8:1 to 11.9:1. Not where I want to be at all.
When you reenable lt's the actual trim is then the lt's combined with the st's cut and paste both as a percentage on the ve. The st's are hyper active kids the lt's are ridalin. So I tend to use the lt's as a percentage and the st's as 1/2 percentage under the special paste functions.
In a perfect world the ve table will command 14.7 everywhere and the pe table will be able to set the afr by the actuall number. So the closer the ve table is to perfect (14.7) the closer your pe divisor will be to 1.148 and 12.8:1 afr. Im still using narrowbands and thats my take on them.
Are you commanding 12.8 all the time or just when entering pe?
I saw the same behavior, just turned LTFT's back on last night. I figure I'll give it a week then start logging again. My STFT's were all within -5 to zero, none in the positive. I figure why reset the fule trims before turning LTFT back on; you just got the trims where you wanted them and the LTFT's were not being counted. So I just turned LTFT back on.
TECH Resident
Joined: Aug 2003
Posts: 970
Likes: 4
From: England UK
Originally Posted by indygoat
Is there anything wrong with permanently leaving LTFTs off?
I cant see any problem leaving the LTFT's off, if your pump looses pressure the fuel trims help compensate, but how often does that happen...
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The only thing I don't like about running open loop all of the time is the motor can really lean out if temps go up. I've seen a car go from 14.0 at idle to 17.0 at idle when sitting in traffic on a warm summer day. Fuel trims and closed loop help control this. Unless there's some magic table to compensate for this, I'll be sticking to my fuel trims.
On a side note, your STFT's have to be spiking somewhere if you're getting positive LTFT's. If STFT's hit +3 consistently, LTFT's will increase until the STFT's stay within a +/- 2% range. Low airflow situations like light throttle and idle can be hard to dial in due to lower exhaust temps and flow. What I tend to do for these spots is filter out all data points where -0.1%<STFT's<0.1%. That way, you're getting the swings and not so much of the lazy 0's. If that doesn't help, add 1% to the areas you're seeing the STFT spike up (giving you +LTFT's) until they don't do it anymore. Keep in mind, smoothing can also cause more trouble than good sometimes. So, don't go too crazy with that either.
On a side note, your STFT's have to be spiking somewhere if you're getting positive LTFT's. If STFT's hit +3 consistently, LTFT's will increase until the STFT's stay within a +/- 2% range. Low airflow situations like light throttle and idle can be hard to dial in due to lower exhaust temps and flow. What I tend to do for these spots is filter out all data points where -0.1%<STFT's<0.1%. That way, you're getting the swings and not so much of the lazy 0's. If that doesn't help, add 1% to the areas you're seeing the STFT spike up (giving you +LTFT's) until they don't do it anymore. Keep in mind, smoothing can also cause more trouble than good sometimes. So, don't go too crazy with that either.
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