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Old 07-29-2009, 12:47 PM   #1
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Default Decel Enrichments?

Is there anything to cut fuel faster when I lift? I go pretty rich when I lift the throttle before over run kicks in, and by pretty rich I mean fatter than 11:1 in most cases. I've tried reducing the decel % under acceleration wizard but it would cut fuel too violently if i was just lifting the pedal a little while cruising. It's not a big deal, but if I could solve it, it'd be cool.
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Old 07-29-2009, 01:06 PM   #2
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have you considered tuning your <30kPa rows above 2000 rpm?
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Old 07-29-2009, 01:09 PM   #3
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when I run it through MLV, it's always wants to pull fuel at my entire <100kPa 3000rpm column cause I always shift there. Otherwise I could probably pull a bunch from the lower cells themselves...
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Old 07-29-2009, 01:36 PM   #4
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so what if it pulls from the <100kpa/3000 rpm region? make a note of what the map has in it before hand and let it do its thing.
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Old 07-29-2009, 01:43 PM   #5
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I used to let it do it's thing, i had a few cells that were lower than where I idle at. Then I had to cruise on the highway at 3000RPM, didn't work out so well. So I usually shift when I'm in boost, the entire column was way too lean out of boost. But get what your getting at.
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Old 07-30-2009, 11:58 AM   #6
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I was wondering the same thing. You can lean it enough with decel set to like 60% but the problem is when cruising or in boost, if it senses decel because your foot moved on the pedal, it cuts fuel as well and that's not good. I don't know what can be used to detect real decel and just noise or slight falling change in tps signal.

The thing is you can be at 120 kpa and lift of the throttle to slow down or shift or it could be just noise or slight movement of your foot but MS can't make a difference and does the same in both cases.
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Old 07-30-2009, 12:00 PM   #7
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I dropped my bottom row of my fuel table down to 15% from 40% and my spark table 17 across. Made no real difference. I moved the over run to trigger after .1s but it's still a touch too slow, IIRC I'm already at 80% decel enrichment, any more and it would trigger during normal driving.
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Old 07-30-2009, 12:07 PM   #8
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I apparently was shooting GIANT flames on track this last weekend. I wonder if I should adjust stuff
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Old 07-30-2009, 12:07 PM   #9
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at around 60%, you will get good results when decelerating but it will kill the engine as soon as you go in boost. I personally left it at 100% to avoid any fuel cut, rather go rich than lean in boost.
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Old 07-30-2009, 12:14 PM   #10
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I got the same problem of going really rich when I let off the gas. I guess I should start to fix this.
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Old 07-30-2009, 12:38 PM   #11
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i'll post my msq later because my car doesn't do this. However, now that I'm switching to no-cat, get ready for the fire!!!
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Old 07-30-2009, 12:38 PM   #12
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I have none of these problems surprisingly.
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Old 07-30-2009, 01:28 PM   #13
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Are you guys running TPS overrun or MAP overrun?
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Old 07-30-2009, 01:29 PM   #14
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Tps.
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Old 07-30-2009, 01:56 PM   #15
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I'm pretty sure this is why my stock cat has **** rattling around inside it. Happened at my last autox. I'm pretty sure i was dumping lots of fuel in there and melted it down on the inside. I bet i'd shoot flames like split does if I had a straight through exhaust.

In for solution.
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Old 07-30-2009, 02:01 PM   #16
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I have no cat, dont shoot flames. it doesn't happen for that long, but i don't like seeing it hover at 12:1-11:1 for no reason before overrun. I watch the fuel cells and I completely removed fuel from that area but it didn't do anything.
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Old 07-30-2009, 03:05 PM   #17
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Same here, no flames, just a rich condition for a split second when lifting off the throttle, around 10:1-12:1 depending on the initial map and rpm.
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Old 07-31-2009, 12:33 AM   #18
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Same for me, was just wondering lately how I could change this...
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Old 07-31-2009, 07:00 AM   #19
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Nice explanation from msextra.com:

Quote:
If you are running WOT, then the injectors are dumping a heap of fuel into the engine.Just because you take your foot off the pedal doesn't mean that fuel disappears, even if the injectors stop right then.As the amount of air is also greatly reduced it has to go rich till the feul cloud is spent.The dip will exist but you may be able to reduce its duration. This is why as revs increase there is no advantage to sequential injection over batch.The injectors are firing when the valves are shut due to engine demand.
Greets
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