Are these LTFT's too rich?
Re: Are these LTFT's too rich? That is perfect. You want a slightly negative Ltrim to ensure the computer doesn't add more fuel at WOT. The cars stock run very rich (typically) at WOT.
Ryan K.
Ryan K.
Thread Starter
TECH Fanatic
Joined: Feb 2002
Posts: 1,640
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From: Austin, Tx.
Re: Are these LTFT's too rich? oops... I thought I had listed my mods.
-Mac mid's
-ORY pipe
-descreened stock MAF
-lid
I assume that is still good? <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
-Mac mid's
-ORY pipe
-descreened stock MAF
-lid
I assume that is still good? <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Staging Lane
Joined: Dec 2001
Posts: 93
Likes: 0
From: Houston, Texas USA
Re: Are these LTFT's too rich? Other than possibly forcing the LTrims too negative and throwing a "Bank X too rich" code, is there any drawbacks to running say, -10% LTrims?
On the surface, I can't see how, since the -10% is simply the amount of correction the PCM has made to the AFR, so the motor is not really running that rich. The -10% simply indicates that a very rich condition would exist if the PCM did not correct the AFR.
So if the PCM is correcting the AFR, is all the effort to get the LTrims "just slightly negative" really necessary? Wouldn't it be just fine if they were just plain "negative", so long as they are not too negative to force a "too rich" code?
On the surface, I can't see how, since the -10% is simply the amount of correction the PCM has made to the AFR, so the motor is not really running that rich. The -10% simply indicates that a very rich condition would exist if the PCM did not correct the AFR.
So if the PCM is correcting the AFR, is all the effort to get the LTrims "just slightly negative" really necessary? Wouldn't it be just fine if they were just plain "negative", so long as they are not too negative to force a "too rich" code?
On The Tree
Joined: Jan 2003
Posts: 172
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From: Central MD
Re: Are these LTFT's too rich? You're on the right track Dean98TA. The computer is making a ten percent correction and the fuel trim is going to be close. But over time, this number should decrease back towards zero, as long as you aren't adding more mods. The computer should not make a ten percent correction all the time forever. If you have -10.0 LTFT's, you should also have very big STFT's. Like -14.5. It will take the computer a while to move back toward zero. I had my car at -11.0 after headers, off road pipe, K&N intake and took about 2K miles to get back to my current -2 to 0.00 LTFT's.
Basically, the computer makes these corrections over a long period of time. Not a few hours or a few miles.
Basically, the computer makes these corrections over a long period of time. Not a few hours or a few miles.
On The Tree
Joined: Dec 2002
Posts: 176
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From: Orlando, FL
Re: Are these LTFT's too rich? The relationship between LTrims and STrims is not accurately described above. For a give cell the LTrims will change until the STrims are hovering around 0. If the LTrims are -10% that does not necessarily mean the STrims are going to be big also. If the STrims are infact big you will see the LTrims continue to move in the same direction until the STrims are hovering around 0%. The LTrims will change striving to keep the STrims around 0. The PCM does not try to keep the LTrims around 0.
Tim
Tim
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From: Austin, Tx.
Re: Are these LTFT's too rich? I tapped a run today and got false KR from my banging Y-pipe. It retarded my timing by about 10-15 deg. in 3rd gear. <img border="0" title="" alt="[Frown]" src="gr_sad.gif" /> I wonder how much HP that retarded timing is taking away from me. <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
Note to self: FIX BANGING Y-PIPE!! <img border="0" alt="[bang head]" title="" src="graemlins/gr_banghead.gif" />
Note to self: FIX BANGING Y-PIPE!! <img border="0" alt="[bang head]" title="" src="graemlins/gr_banghead.gif" />
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Re: Are these LTFT's too rich? Tim S. has it just about right, but I'm going to expand on what he said a little. Now let's think about it like that game on The Price is Right where that man tries to climb up the mountain while yodeling all the way up. You have to get the price inside a certain range to win the prize. As the guy climbs up the mountain the range slides up the mountain with him. When he STOPS you must have the price in the RANGEFINDER to win the prize. Now let's relate that to OBDII. The range is your LTFTs and the man is your STFTs. The range can move up or down, but the man can ONLY move up or down INSIDE of the range. He can't get out of the range OR the range will move to keep him inside of the range. The range can go from -23% to +23(that's your LTFTs). The man moves inside of the range(-5% to +5% your STFTs). If BOTH the LTFTs and the STFTs go past the pos or neg limits at the SAME TIME your DTC goes set. The STFTs can NOT go to 14% or anything close to it because the RANGE(LTFTs) move to keep within the range before it ever got close to 14%. The STFTs might TRY to go that far, but the range(LTFTs) make a correction to keep the STFTs in check. Before your STFTs ever got to 14% you SES would have been "ON" a long time ago.
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Re: Are these LTFT's too rich? The value you have is good.
I hope you didn't average cell 22 in your calculations to come up with your Lterm values.
I got mine as close to -1 as possible so that I could a. dial in WOT well; and b. get the best gas mileage . . . well . . . as good as I can get with numerous 175+ mph runs <img border="0" alt="[evil]" title="" src="graemlins/gr_devil.gif" />
I hope you didn't average cell 22 in your calculations to come up with your Lterm values.
I got mine as close to -1 as possible so that I could a. dial in WOT well; and b. get the best gas mileage . . . well . . . as good as I can get with numerous 175+ mph runs <img border="0" alt="[evil]" title="" src="graemlins/gr_devil.gif" />
