07-30-2023, 12:48 PM | #45 |
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Take advice as you please. Been a tech for 16 years now. Google it. My answer is 100% facts. Talk to any tuner or racer. Good luck.
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07-30-2023, 02:46 PM | #46 |
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I could be wrong w the G8x DME, but traditionally only the pre cat sensor is used for AFRs. Post cat is narrowband and just says or rich/lean. It's used to make sure the pre sensor is tuned right. Unless someone knows if the post sensor on this platform differs.
At any rate, changing most things in the intake and exhaust stream (as long as diameter stays the same to keeps flow characteristics fairly even) without a tune is.. "fine", but I would not label it as "safe". Mods push the ECU further outside of its base calibration and closer to its limits. In most cases this will be fine, but enough of them and/or in the right circumstance, and you'll hit the limitations of the fuel trims and the car won't be able to correct back to optimal. Imagine a seesaw where one kid keeps getting fatter. It's generally fine and you can still use it w the small kid working harder. Once one kid gets fat enough, it no longer works. Where that limit is on the G8x would be the question. On other platforms I've worked on, fuel trims are limited to 20% outside of the base calibration (EDIT: looks like at 30% our DME will go into limp mode) Last edited by evidence; 08-06-2023 at 01:19 PM.. |
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07-30-2023, 03:14 PM | #47 |
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You are correct, pre-cat is bosch LSU 5.2 (wideband), post-cat is bosch LSF Xfour (switching).
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07-30-2023, 03:27 PM | #48 | |
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Not sure what you mean be trims being way off, you think LTFT is way off? Also, why does the additive target jump from nothing to the map2 level in the middle of the pull, that's weird no? |
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07-30-2023, 03:40 PM | #49 |
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It would take a few minutes of STFTs being non zero before LTFTs changes, and it would slowly step towards STFTs being 0 by modifying LTFT in small increments. The stepping of trims also means STFTs can be slower to respond in realtime if LTFTS are not calibrated.
So if you reset the learned calibrations (which bm3 etc can do) and then rip on the car right away with mods, you can definitely have a bad time. Say 20% off of base trims is the limit. if LTFT is 0%, STFT has +20% room. If LTFT is learned at +12%, STFT still has 20%, making your max higher at 32%. This is the reason why running mods without a tune can get you into trouble. You're left with less of the FT window for the car to work w because you didn't retune the base calibration to near 0. |
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07-30-2023, 04:08 PM | #50 | |
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The big question in this thread seems to be whether running catless downpipes creates an insurmountable challenge for the stock tuning that will "destroy the engine", as one poster suggested. If the short blips of high AFR post-shift as shown in that log above are really thought to be cause for concern, I'd like to see someone's log running catless downpipes with a flash tune to see the difference. |
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07-30-2023, 04:21 PM | #51 | |
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Short blips of lean AFRs, extra heat, small amounts of knock all start to add up. These engines can take a beating, but if you're serious about power and longevity, get a tune. Of course more power lessens the longevity of a motor also, but at least it's more fun for all the trouble |
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07-30-2023, 05:43 PM | #52 | |
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08-02-2023, 12:12 PM | #53 |
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08-02-2023, 05:00 PM | #54 |
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08-02-2023, 05:53 PM | #55 |
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Good question, I sent my logs to Terry Burger and he said they were fine as well. Not sure what would cause different cars to react differently.
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05-11-2024, 12:04 AM | #56 | |
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Was it also superknock code? |
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05-14-2024, 09:54 PM | #57 |
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The superknocking cylc 2 code came back. I checked plugs and coil and they are all good. Again, car never go into limp mode or cut power. Still shadow codes. Also, I remembered that these downpipes have built in minicats inside. IDK if that is the possible cause for this code.
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