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Old 03-27-2009, 01:12 PM   #21
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Joe, thanks for the reply, but like you said, i'm too rich AND too lean simultaneously

Would regapping the spark plugs help at all? Maybe the gap's too small resulting in incomplete combustion? but wouldn't that lead to a very rich mixture which my wideband would let me see??

If anyone can, please take a look at my datalog.. The 'test' starts after the 2nd shutoff event, around record 4752 thru 6077.

-Tomaj
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Old 03-27-2009, 01:31 PM   #22
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Wikipedia... yea...

Three way catalysts:

These three reactions occur most efficiently when the catalytic converter receives exhaust from an engine running slightly above the stoichiometric point. This is between 14.6 and 14.8 parts air to 1 part fuel, by weight, for gasoline. The ratio for LPG, natural gas and ethanol fuels is slightly different, requiring modified fuel system settings when using those fuels. Generally, engines fitted with 3-way catalytic converters are equipped with a computerised closed-loop feedback fuel injection system employing one or more oxygen sensors, though early in the deployment of 3-way converters, carburetors equipped for feedback mixture control were used. When a 3-way catalyst can be used in an open-loop system, NOx reduction efficiency is low. Within a narrow fuel/air ratio band surrounding stoichiometry, conversion of all three pollutants is very complete, sometimes approaching 100%. However, outside of that band, conversion efficiency falls off very rapidly. When there is more oxygen than required, then the system is said to be running lean, and the system is in oxidizing condition. In that case, the converter's two oxidizing reactions (oxidation of CO and hydrocarbons) are favoured, at the expense of the reducing reaction. When there is excessive fuel, then the engine is running rich. The reduction of NOx is favoured, at the expense of CO and HC oxidation.
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Old 03-27-2009, 01:33 PM   #23
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Quote:
Originally Posted by ctxspy View Post
Joe, thanks for the reply, but like you said, i'm too rich AND too lean simultaneously
No, like I said- so far you're only tuning one variable, and you seem to have found the threshold point. It's time to move the fuel slightly back in the direction it was (put it where you found the low NOx point, for starters) and then try advancing the timing a few degrees to see if that does anything positive for CO.
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Old 03-27-2009, 08:15 PM   #24
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Joe, thanks. I must've misunderstood, I'll give that a shot and see what happens.

I wonder how many times i can go back before they get tired of seeing me
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Old 03-27-2009, 11:01 PM   #25
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Originally Posted by Joe Perez View Post
No, do you?

Even if you do go open-loop in boost, there's value in having valid data up there so that VEA has something to chew on.
I don't boost full stop. But I see where you're coming from with the VEA, hadn't thought of it like that.
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Old 06-28-2009, 11:41 PM   #26
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This is kinda old news by now, but i wanted to post in case anyone comes by this thread searching about emissions inspection.

I was able to pass with pretty good margin by dialing in the tune with MLV, and in the process discovering what i think is a bug (maybe). My AFR targets in the MS were always coming up 0.883 richer than what was in the table.. somewhere something was screwy. My solution -- just add 0.883 while NOT tuning in MLV, then make the changes while tuning, then go back, etc. So in the end, enabling EGO correction did the trick and i sailed through.
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Old 06-29-2009, 01:28 PM   #27
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Do you have MLV set correctly for your wideband?? I had the same problem until I realized that I had it set wrong...
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Old 06-29-2009, 07:07 PM   #28
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Yeah that's all fine. I followed Joe's instructons to get AFR instead of volts in megatune, and then proceeded to enter all my values in megatune. When i open MLV i see the same values so that's A-OK.

The issue comes into play when you go ahead and try to use gEGO. It was always trying to correct way too rich. I noticed there's a target AFR gauge, so i loaded that and noticed that it was always off by .883. It seems that some formula somewhere isn't carried through to everything, hence gEGO's target is off.

I hope that explains a little more.
-Toma
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