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Discussion Starter · #1 · (Edited)
Anybody help with an issue I'm having? This is a stock LT1 with a stock tune running no cats. Before anyone suggests it, I am not allowed to add a new tune under the CMC rules.

I had the motor rebuilt over the summer and I took it to the DYNO. Power was 262rwhp 309tq. The problem is that at 4,700rpm the AF ratio drops below 10.



https://www.dropbox.com/sh/vsj7pjhw4uh8cjf/BkT6nV09Js

BTW, I'm completely clueless about this stuff.

All help is appreciated.
 

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look into those codes first

it threw a code 16 at some point, and a code 42

your ignition system is in trouble, in some way. these appear to have been stored from before your dyno run, though

remember even light ignition misses will manifest themselves in extra fuel (the injector pulse happens, but the spark doesn't..)
 

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Noticed you speedometer is not hooked up, so every time you shift (TBS=% and speed = 0) you go into BLM cell 16 (idle fueling) this should not effect you dyno. This sounds backwards, and I can't really figure it out, but I did notice at record 171 your running out of fuel your injector duty cycle went past reliable operation at 86% and increased to 100% at record 179. That's not normal on a stock setup. Have you verified fuel pressure.. If tune is stock you should be starting out at around 11.9 AFR and then droping a bit lower to the 11.7 mark up through 4800 and then drop even lower after that. But nowhere near 10 at 4800. Mine hit 241 HP max when stock at about 5000.
 
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