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Old 02-10-2008, 11:14 PM   #1
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Default Bouncing AFRs

You can see on the graph here the AFRs bouncing from 11 to 13.

Any idea what could be causing this?
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Old 02-10-2008, 11:34 PM   #2
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looks like you have your O2 turned on in boost too
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Old 02-11-2008, 08:29 AM   #3
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O2 turned on in boost?
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Old 02-11-2008, 09:37 AM   #4
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Quote:
Originally Posted by richard_ha View Post
O2 turned on in boost?
running closed loop when in boost.

generally not a great idea as the response time of a WB sensor isn't as quick as a NB.

can be compensated for in the software iirc, but it still won't be perfect.
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Old 02-11-2008, 10:07 AM   #5
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change your open-loop switch point to whatever (60-90kpa) or you have o2 sensor noise.
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Old 02-11-2008, 10:20 AM   #6
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It is set to 90kPa already, isnt it?
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Old 02-11-2008, 10:29 AM   #7
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I'm wondering if I've got a sticky injector or something. Look how rich this went (right to 8.9) after I did a 1/4 mile, even though the PW was 0
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Old 02-11-2008, 12:28 PM   #8
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OK, think I've figured it. The noise on the MAP is causing the acceleration and deceleration flags to get lit so it must be dumping fuel in for the acceleration enrichment. Looks like I'll need a TPS.
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Old 02-11-2008, 12:30 PM   #9
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Where is your MAP line connected?
If you have it on the nipple by the throttle body you should try Ting it off the FPR line instead.
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Old 02-11-2008, 12:36 PM   #10
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Old 02-11-2008, 12:40 PM   #11
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yes
The port near the throttlebody is known to be noisy. It causes issues like you're seeing sometimes. Ting off the FPR port is supposed to cure that.
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Old 02-11-2008, 01:30 PM   #12
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Cool, I also had a "no buzz" t piece so I've used that.
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Old 02-12-2008, 12:52 PM   #13
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What a difference T'ing in there and using a no buzz T piece has made, look how smooth this MAP is now...
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Old 02-12-2008, 01:07 PM   #14
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Quote:
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Cool, I also had a "no buzz" t piece so I've used that.
just wondering what is a no buzz?
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Old 02-12-2008, 01:13 PM   #15
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Its like a normal t piece but the spout that comes off only has a small hole in it to prevent too much fluctuation.
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Old 02-12-2008, 01:58 PM   #16
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You can buy a restrictor for the map line at any advanced autoparts store. AKA No buzz.

Glad that fixed it.
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Old 02-12-2008, 08:59 PM   #17
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Quote:
Originally Posted by bryantaylor View Post
looks like you have your O2 turned on in boost too
Are you sure? Looks like its set to 90kPa to me, unless I'm missing something.
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Old 03-13-2008, 06:12 PM   #18
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Quote:
Originally Posted by cjernigan View Post
You can buy a restrictor for the map line at any advanced autoparts store. AKA No buzz.

Glad that fixed it.
What does this restrictor look like?

Also.. is the vaccuum source next to the throttle body you guys talk about the one on the 1.8 manifold on the top by the fuel rail?
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Old 03-13-2008, 06:30 PM   #19
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The restrictor looks like a little plastic tube with a tiny hole in it.
Do not use the one near the throttle body by the fuel rail.
Tee off of the line going to the fuel pressure regulator, it is a much better signal location.
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Old 03-13-2008, 06:45 PM   #20
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yeah i was gunna make a thread about my jumpy MAP values. It always fluctuates about 5-10 kpa real fast no matter how steady i hold my foot. Ill try it out and hopefully get a better reading
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