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Old 04-26-2005, 05:28 AM   #1
overdose
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Default On UTEC does STFT/LTFT affect WOT fuelling?

lately i've been trying to find out why my car varies in performance on utec 4.2c w/ stg4 basemap and it hasnt been tuned yet (ur785cc/utec/vf30/fmic/txs shorty), however with the performance varying so much day to day i've been trying to make sure there's no other problems before i drive far away for a tune... i have the injectors scaled @ 420/785 and it seems to run fine yet it's slow some days fast others (15-16psi, logs look the same on good and bad days... same maf voltages etc)

My fuel trims ARE NOT tuned but it idles ok cold and great warm, do they affect my WOT fuelling at all since i'm sure they're way off?
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Old 04-26-2005, 07:24 AM   #2
ride5000
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not if you're running open loop fueling.

have you recently sent your butt-dyno out for calibration?

ken
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Old 04-26-2005, 09:53 AM   #3
MMBOOST
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I was under some of the same incorrect assumptions. Its more that you tune your fuel to achieve certain fuel trims - they're not something you directly adjust. Fuel trims are just an indicator that you really can get a handle on by just looking at the AFRs in your 0% column. I would _really_ recomend using OLF, as with what Ken pointed out, it makes life much easier. Your ST and LT trims are calculated based upon your 0% column performance. LT affects high load fueling, unless you're using OLF where the UTECignores the ECU, uses its own background map and the modification to MAF voltage that you have in your map. This way, what the ECU is trying to accomplish as it manhandles the 0% isn't affecting all the precious work you've done in the 10%-100% column. WIth that said, now you go back and look at your 0% column AFRs. If they're rich, your trims are probabaly deep in the negative. If they're lean, your trims are probabaly deep in the positive. If you're hitting around 14.7 when at low throttle, you're probabaly happily close to 0% trims.

jason
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Old 04-26-2005, 10:11 AM   #4
overdose
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yeah i'm using OLF
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Old 04-26-2005, 11:16 AM   #5
hippy
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While you use a base stage four map along with your larger front mount, huge injectors, and intake, changes in performance dependent on load should be expected. I would bet the difference has to do with boost(but I could be wrong). If you run 15psi, you're in the 80% load column and the fueling and timing will be run through that column. If you're at 16-18psi, you will be in the 90% load column and the fueling and timing will be run through that column. At least that's my guess.

peace
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Old 04-26-2005, 11:34 AM   #6
overdose
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don't see why load column matters at all though since the logs coinside between the good days and now the bad, yet the performance is drastically reduced
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Old 04-26-2005, 11:49 AM   #7
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let's see some logs
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