Is it safe to change Open Loop fueling...
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From: Sierra Vista, AZ
Is it safe to change Open Loop fueling... Having issue with the factory OL fueling being soo damn rich at cold start, neighbors hate me 
I want to alter the cold start to something elss cylinder washing, like 12:1 (or leaner if it safe) and gradually lean it out as it gets warmer. Any issues doing this?
Charlie
I want to alter the cold start to something elss cylinder washing, like 12:1 (or leaner if it safe) and gradually lean it out as it gets warmer. Any issues doing this?Charlie
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From: Fredericksburg, VA
Go for it. I have mine leaned out to 14.7:1. Much richer and it hunts for idle on cold startups during the winter. At idle you could run the engine pretty lean because there's pretty much no load on it. Hell, in Australia where they have Lean Cruise enabled in the PCM they lean out the AFR to around 16.5:1 (or something like that) under certain speed, ECT, and MAP parameters, which you typically fall into while cruising on the highway. Just decrease the multiplier until you're comfortable with the AFR you're logging on the WB (and your car still starts and idles properly).
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Cool. Thanks for the info. I was really hoping it wouldnt have any negative effect on something else. Will be getting to this tomorrow. BTW, nice having someone up late to get info from.. of course its only 10:45 Hawaii (3:45am EST).
You cam guys really need to skinny it down some because
you are indexed up in MAP to some really high enrichment.
If you look at the rows about 30-35kPa, which is where
stock A4s idle, that's probably the enrichment you want
at whatever your monster-cam idle MAP turns out to be.
Note that leaner will also idle at lower MAP, and richer
further elevates MAP / depresses vacuum which is part
of the reason for piggy idle richness, some positive
feedback (in a negative sense) there.
you are indexed up in MAP to some really high enrichment.
If you look at the rows about 30-35kPa, which is where
stock A4s idle, that's probably the enrichment you want
at whatever your monster-cam idle MAP turns out to be.
Note that leaner will also idle at lower MAP, and richer
further elevates MAP / depresses vacuum which is part
of the reason for piggy idle richness, some positive
feedback (in a negative sense) there.
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From: Sierra Vista, AZ
Originally Posted by jimmyblue
You cam guys really need to skinny it down some because
you are indexed up in MAP to some really high enrichment.
If you look at the rows about 30-35kPa, which is where
stock A4s idle, that's probably the enrichment you want
at whatever your monster-cam idle MAP turns out to be.
Note that leaner will also idle at lower MAP, and richer
further elevates MAP / depresses vacuum which is part
of the reason for piggy idle richness, some positive
feedback (in a negative sense) there.
you are indexed up in MAP to some really high enrichment.
If you look at the rows about 30-35kPa, which is where
stock A4s idle, that's probably the enrichment you want
at whatever your monster-cam idle MAP turns out to be.
Note that leaner will also idle at lower MAP, and richer
further elevates MAP / depresses vacuum which is part
of the reason for piggy idle richness, some positive
feedback (in a negative sense) there.
I think what your saying is: Yes, guys with larger cams may need to decrease the OL AFR Modifier. How low? Use the 30-35kPa modifier as a base starting point.
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Originally Posted by jimmyblue
If you look at the rows about 30-35kPa, which is where
stock A4s idle, that's probably the enrichment you want
at whatever your monster-cam idle MAP turns out to be.
stock A4s idle, that's probably the enrichment you want
at whatever your monster-cam idle MAP turns out to be.
Good tip!
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So, by scaling down the table to about 95% of the original values, I am able to get my 60 kpa multipliers to be what the 30 kpa multipliers WERE, across the board.
Esentially, this will lean out the idle mixture across the board. Since my MAP readings never fall below 40 kpa, and my 120-192 *F idle MAP is 58-60 kpa, I should be safe right?
What I did notice however, is that at startup, my map readings were 99 kpa for the first 7-8 seconds. It seems to me that it would make more sense to reduce the values in this table more at the 90-100 kpa range. Maybe I'm way off base, maybe Horist or Jimmy can chime in again.
Esentially, this will lean out the idle mixture across the board. Since my MAP readings never fall below 40 kpa, and my 120-192 *F idle MAP is 58-60 kpa, I should be safe right?
What I did notice however, is that at startup, my map readings were 99 kpa for the first 7-8 seconds. It seems to me that it would make more sense to reduce the values in this table more at the 90-100 kpa range. Maybe I'm way off base, maybe Horist or Jimmy can chime in again.
Last edited by kpowr82; Jan 20, 2006 at 04:37 PM.