Do I need LTFT trims
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TECH Resident
Joined: Aug 2004
Posts: 875
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From: Portland Oregon
Do I need LTFT trims I have been running without MAF, SD tuned for over a year and have tuned my VE table many times. The car runs good now so to test my tune, I disabled the LTFT. To my surprise, it ran perfect. I have a wideband readout on the dash, it was stuck on 14.3 for cruising, that's where it always runs, WOT was right on 12.7, it idles good, everything is good, and it is more consistant than with the trims on. Should I just leave them off. They always seemed a little over active. Do I need long term fuel trim??
Thread Starter
TECH Resident
Joined: Aug 2004
Posts: 875
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From: Portland Oregon
Turn them off permanently.. I am tempted, It sure runs good without. My VE must be right on because I drove for about an hour, and my A/F was stuck 14.3 most of the time. Have you ever heard of anyone adjusting the sensitivity of the fuel trims. I'm not even sure that is possible. When I look at my scans, I see the STFT a little rich, then bam, the LT shifts to -12, it seems to over react. I would expect -2 or -4 but the LT are pretty radical.
10 Second Club
Joined: Jul 2008
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From: Columbus Ohio
I have mine off without issues. Just remember that now you have made your tune so close to perfect that the switching that goes on with your narrowband O2s is actually throwing it off. This always seems to be an even bigger deal on cammed cars. I'm sure there is a more technical answer, but fuel trims can cause more trouble the their worth.
Thread Starter
TECH Resident
Joined: Aug 2004
Posts: 875
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From: Portland Oregon
Excellent, I am going to leave them off. It seems like I have been chasing them around for quite a while. My A/F is good on the wideband, but the LTFT go +/-12 so I add or subtract some fuel to those cells. I have done that so many times, I think I really have the VE worked out. With the trims off, it will be easier to see if the VE is right on. Why didn't I do this a long time ago.??
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Thread Starter
TECH Resident
Joined: Aug 2004
Posts: 875
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From: Portland Oregon
My O2 are still on and the STFT are active, so there is still some adjusting going on there. For a track car, open loop would be fine. I like the closed loop for street driving. With this much cam, it's not a real street cruiser, but I go for a run in the country when ever the weather is good in Oregon.
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I have one car I tuned in open loop, NO oxygen sensors at all...
I always turn off LTFT though, and usually leave STFT... but if its tuned right, it should work well no matter what... as you go up in elevation the map sensor will show that the air isnt as dense and adjust the tune accordingly..
I always turn off LTFT though, and usually leave STFT... but if its tuned right, it should work well no matter what... as you go up in elevation the map sensor will show that the air isnt as dense and adjust the tune accordingly..
If your O2 are not working, you are running in open loop all of the time?
My O2 are still on and the STFT are active, so there is still some adjusting going on there. For a track car, open loop would be fine. I like the closed loop for street driving. With this much cam, it's not a real street cruiser, but I go for a run in the country when ever the weather is good in Oregon.
My O2 are still on and the STFT are active, so there is still some adjusting going on there. For a track car, open loop would be fine. I like the closed loop for street driving. With this much cam, it's not a real street cruiser, but I go for a run in the country when ever the weather is good in Oregon.
