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Old 01-22-2010, 06:37 AM   #1
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Default Strange AFR behaviour

I'm having the below issue....

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(original thread on msextra.com http://http://www.msextra.com/forums...=34600&start=0)

At 1894-ish (2nd manual mark) I go to WOT, AE, (which needs tuning!) kicks in and the AFR's drop as expected, where they shoot up to a solid 14:1 - which is way too lean for my liking and I was the point of the datalog - to tune out , suddenly they drop to 10:1 for no obvious reason. Then pop back up to 14:1.

From what I can gather it seems it's possibly an injection timing issue. It's only happened with sequential injection.

it's definately NOT a wideband issue, nor is it noise on the injectors causing them to spike at that RPM. I've scoped the injectors and they're fine.

It happened on my old and busted 96 engine and my new 2001 engine.

I've cribbed the sequential injection settings from DIYAutotune's DIYPnP basemap, this uses a fixed injection timing of -350deg. I'm hoping (nay praying) that I can resolve this by enabling the injection timing table and in the 2-3k zone change the timing from -350 to something which stops the above.

I've not a clue on where to start though, should I start at -300 or is that too big a jump? or should I roll over in the other direction and start at -360 -> 50deg?

Help!
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Old 01-26-2010, 08:03 PM   #2
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I'm going to add my afr issue here as well. Maybe we can both get some answers. I have an isue right at ~4k rpm. I get larges oscillations in afr. Before and after the rpm range of 3.8k to 4.3k I don't run into this issue. PW and duty cycle look good. Is it possible that one of my COPs can fizzle in a certain rpm range and not the whole range. At this point it is the only thing I can think of that would affect afr, and cause the car to jerk without disrupting the PW or duty cycle.

What's everyone's' opinion

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Old 01-26-2010, 08:47 PM   #3
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Quote:
Originally Posted by djp0623 View Post
I have an isue right at ~4k rpm. I get larges oscillations in afr.
Post your VE table.
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Old 01-26-2010, 09:03 PM   #4
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This is after a week of autotuning

Last edited by miatauser884; 01-26-2010 at 09:17 PM.
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Old 01-26-2010, 10:07 PM   #5
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I'd bet it has to do with that really funky valley in your fuel maps. Fuel maps shouldn't look like that. Hand-smooth that and see if the oscillation goes away.
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Old 01-26-2010, 10:36 PM   #6
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Shoot me the datalog & msq to [email protected] dot com. Hard to get into detail typing on phone, but it looks like a funky lean spot to me.
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Old 01-27-2010, 12:33 AM   #7
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Originally Posted by Savington View Post
I'd bet it has to do with that really funky valley in your fuel maps. Fuel maps shouldn't look like that. Hand-smooth that and see if the oscillation goes away.
The autotune eventually creates this ve table no matter what table i start with. The trough looks crazy as hell, but it seems to work except for this issue.

Smoothing the troughs do not work. My car runs like ****, then the autotune puts these troughs in there and my car runs a lot smoother.

I agree though, it seems like the transition area would create a problem if it gets stuck in the middle interpolating.

Maybe I need to smooth it and then autotune with the hard setting??
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Old 01-27-2010, 12:41 AM   #8
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Quote:
Originally Posted by djp0623 View Post
The autotune eventually creates this ve table no matter what table i start with. The trough looks crazy as hell, but it seems to work except for this issue.

Smoothing the troughs do not work. My car runs like ****, then the autotune puts these troughs in there and my car runs a lot smoother.

I agree though, it seems like the transition area would create a problem if it gets stuck in the middle interpolating.

Maybe I need to smooth it and then autotune with the hard setting??

This is the portion of the evening where you manually tune since the computer is not doing it properly. I also suggest you make the idle cell area the same VE number in roughly 6 cells. they must be linear in almost all areas unless you're fine tuning to the point that you don't need our help. You're almost there but its time to think with your brain, not the computer.
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Old 01-27-2010, 11:45 AM   #9
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I did a little smoothing. I will see how it drives today.

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Old 01-27-2010, 12:13 PM   #10
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That looks better. The 41 that you replaced with a 59 was likely your big problem (3900 / 60).
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