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Old 06-16-2012, 04:38 PM
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Default tuning ignition timing

Here's a question on ignition timing. Long story short, I've been working for a while on working out the kinks on an engine overhaul, and I just about have it all sorted. It's a built-up 350 with a Crane 227 cam, completely reworked heads, headers, intake, etc. The most fundamental issue has been fuel efficiency - running at about 12-15MPG under all circumstances. The breakthrough came with replacement of the opti vent harness, which was mucking up the opti (among other things). Obviously I replaced the opti at the same time. Since then, it now reads consistently 15-24 MPG (streets vs highway).

The one remaining "issue" is ignition timing. My scanner reports it consistently negative, by about -30 to -50. The question is, is that even a real issue, or is it just a programming thing? I'm not an expert on tuning, so I just installed a mail-order tuned computer from Bryan Herter. But, as I understand it, the computer programming has some sort of baseline setting for ignition timing, and is pulling the timing back because the baseline setting is too high. Is that right? Would it not be possible to just reprogram it with a lower setting for ignition timing? Everything else on the car seems to be running great.
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Old 06-16-2012, 04:53 PM
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theres no way the engine would even run at 30+ degrees retarded timing so I doubt thats an accurate reading of actual timing.

in fact, when at cruise and all the relevant parameters are met, egr is commanded on and ignition timing is advanced from what I remember.

other variables are the knock sensors and what octane did you get a tune for?
did you make sure you didnt overtighten the knock sensors?
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Old 06-16-2012, 05:04 PM
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and thinking some more, if mileage is good and it is running fine with no issues I'd say leave it alone.
just make sure it aint pinging/knocking when you floor it with yor brown shoes
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Old 06-16-2012, 09:11 PM
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I suspected knock retard at first too, so I scanned specifically for that. Knock sensors check out fine, and no knock was ever detected. Certainly no audible knock either. I guess I should just leave well enough alone.
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Old 06-19-2012, 12:35 PM
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The spark advance timing numbers come up with a negative sign for positive spark advance. I guess you can think for it as moving the spark BACK in the timing of events, so its negative. Either way, if it ain't broke.....
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