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SVTPerformance's Chain of Restaurants
Tuning À la carte
Help! SCT tuner mistake
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<blockquote data-quote="BruceH" data-source="post: 11294900" data-attributes="member: 106410"><p>I say no way because they constantly change to maintain stoich. It's quite normal for them to fluctuate from - to + in correction.</p><p></p><p>I monitor mine constantly via interceptor gauges and like you I have my maf xfer tweaked as good as it gets. The trims still move around especially during varying throttle positions and loads. At idle with a fully warmed up motor my trims don't move more than .01 (1%) but during normal driving they will change. In order to have 1% your trims would read .995 to 1.005 and the long term trims would be at 1.00 using an sct device. On my interceptor gauges it would be - .5 to +.5 as it reads no change as a 0 vs 1.00 during an sct datalog.</p><p></p><p>Fuel injectors have an allowed tolerance of 6% from most manufacturers so even with a perfect maf xfer there will still need to be a fueling correction made. That 6% isn't going to be linear either, it will show up at different points throughout the rpm range. Gasoline will also vary. Think of the difference between pure gasoline with a stoich of 14.64 vs. E10 at 14.1. Then add in "up to 10% ethanol" and you could have anything inbetween. The ecu is still going to maintian the stoich commanded in the tune no matter what the fuel. This will cause trims to vary too.</p><p></p><p>With all that said keep in mind I'm just a hobbyist and tune my own car to keep my mind occupied, I really like the learning aspect of it and enjoy discussing all the parameters involved.</p></blockquote><p></p>
[QUOTE="BruceH, post: 11294900, member: 106410"] I say no way because they constantly change to maintain stoich. It's quite normal for them to fluctuate from - to + in correction. I monitor mine constantly via interceptor gauges and like you I have my maf xfer tweaked as good as it gets. The trims still move around especially during varying throttle positions and loads. At idle with a fully warmed up motor my trims don't move more than .01 (1%) but during normal driving they will change. In order to have 1% your trims would read .995 to 1.005 and the long term trims would be at 1.00 using an sct device. On my interceptor gauges it would be - .5 to +.5 as it reads no change as a 0 vs 1.00 during an sct datalog. Fuel injectors have an allowed tolerance of 6% from most manufacturers so even with a perfect maf xfer there will still need to be a fueling correction made. That 6% isn't going to be linear either, it will show up at different points throughout the rpm range. Gasoline will also vary. Think of the difference between pure gasoline with a stoich of 14.64 vs. E10 at 14.1. Then add in "up to 10% ethanol" and you could have anything inbetween. The ecu is still going to maintian the stoich commanded in the tune no matter what the fuel. This will cause trims to vary too. With all that said keep in mind I'm just a hobbyist and tune my own car to keep my mind occupied, I really like the learning aspect of it and enjoy discussing all the parameters involved. [/QUOTE]
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SVTPerformance's Chain of Restaurants
Tuning À la carte
Help! SCT tuner mistake
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