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09-19-2020, 03:07 AM | #1 |
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E85 LTFT Above 10% at Idle
Hello, another fuel trim thread here.
I read all that I could understand about expected fuel trims for running on e85, but it seems like my LTFT hovers anywhere from +7% to +15%, averaged at 12%, never any lower than 7 at idle. Stock intake, just header and catback. Checked for exhaust leaks and none that I saw. It drops upon load and gets to ~5% @ 3k rpm so I assume that part is good. This happens across multiple fill ups, and fluctuates within the same tank/different days. I've read that temperature can skew readings a bit and idle isn't crucial, but also that it should be within +/- 10% throughout. So why would this be and is it something to look into? Does this indicate a leak or would that be more severe values? Any suggestions? Thanks. https://datazap.me/u/pizzachicken/9-...og=0&data=1-11 https://datazap.me/u/pizzachicken/9-...og=0&data=1-11 |
09-19-2020, 08:42 PM | #2 |
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If this is a flex fuel tune and your running a flex fuel sensor then your fuel trim can be up to around 10% ltft on one fuel and zeroed on another fuel. This is usually normal.
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09-19-2020, 08:54 PM | #3 |
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09-20-2020, 06:43 AM | #4 |
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09-20-2020, 02:53 PM | #5 | |
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Quote:
Perhaps I'm interpreting your instructions wrong, but shouldn't "normal" ltft values stay within +/- 10%? Suppose it's possible I'm getting true 85% but these higher trims seem to be consistent throughout multiple fill ups and different stations rated for e70% - e85% (Los Angeles). So you're saying seeing up to 15% ltft at idle should not be alarming? If so i'll take your word. Would there be a max ltft % to allow before being concerned, and if so what else should I look into then? |
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The Following User Says Thank You to Pizzachicken For This Useful Post: | steve99 (09-20-2020) |
09-20-2020, 06:13 PM | #6 | |
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if you have stock intake and no leaks intake or exhaust +15 is a little unusual. The leaks wont be huge and often hard to detect. From the logs it does look like a leak as trims are only high at idle then ok once rpm rises and you on throttle |
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09-20-2020, 06:27 PM | #7 |
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Would high positive trims most likely be exhaust leak then or can it be intake as well? Believe I've seen you say intake leaks result in negative trims. I couldn't find any leaks at the flanges, unless it's a crack within the wrapped header piping or the shielding of the overpipe.. thought that was unlikely. Any other reason if I absolutely can't find a leak? And anyhow, is it safe to drive for the time being if it's just at idle? Thanks.
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09-22-2020, 06:26 AM | #8 | |
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yes it would be safe to drive if its only big trim at idle exhaist and ibtake leaks can send ltft high positive at idle it only takes a small leak |
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09-28-2020, 02:09 AM | #9 | |
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Also, if I happen to figure out a fix, can I expect to see it reflected in the trims immediately or would I have to get some miles in? |
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09-28-2020, 07:16 AM | #10 |
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I also just switched to E85 with the 4.0x tune and am experiencing the same thing. No exhaust leaks. I haven't been able to monitor the WOT LTFT but next time I am at the track I will try to remember. Seems to be performing great. Solid boost over 93. Only other thing I have noticed since making the switch is that it takes the car a little longer to start. Otherwise I am pretty happy.
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