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Old 12-08-2008, 10:54 AM   #1
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Angry Ugh Injector Duty Cycle Woes

When I did my dyno pulls recently I saw that I was hitting 80% duty cycle on my injectors and my AFRs were leaning out at the top very rapidly.

Yesterday, I installed a Walboro 255HP (enough to flow for future goals) and changed the fuel filter. It was a messy job and I got high from the gas but everything was buttoned up AOK.

Afterwards, I did some datalogs on the Hydra and saw that my AFRs were no longer leaning out but my injectors were still running at 80% duty cycle about 6000-6500 RPM. My AFRs were around 9.5.

Am I saturating the O2 sensor with fuel now? Is my fuel map just way too top-end heavy because of past autotune attempts with a clogged fuel filter and do I just need to back down those cells?

I'm running 750cc injectors at boost levels of 11psi.
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Old 12-08-2008, 11:01 AM   #2
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9.5 is VERY rich... I'd target low 11-ish.
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Old 12-08-2008, 11:37 AM   #3
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I'd target high 11s. I'd expect your DC% to drop once you lean it up.


maybe you're just making 410BHP.
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Old 12-08-2008, 12:04 PM   #4
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lean it out and your duty cycles willdrop a lot
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Old 12-09-2008, 01:49 AM   #5
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Yeah, I did the same thing when I upgraded to the 255. My duty cycles were sitting at 95% before and now they are under 80% and I am still tuning. Yes, it is still a little rich, but not nearly as much as it was. Just do some more tuning.
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Old 12-16-2008, 06:53 PM   #6
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80% IDC isnt bad at all, you just dont wanna go too much higher. Also not having an adequate fuel pump can cause a lean condtion
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Old 12-16-2008, 07:40 PM   #7
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It's fixed. I just needed to retune. I redid my street autotune with the Hydra and duty cycle adjusted itself down to 50% max. All is well, thank you all!
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