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Old 04-15-2002, 07:09 PM   #1
PeterJ
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2002 impreza RS

Default A/F ratio

I'm somewhat confused on this issue. Does my car (as set from the factory) run rich, or lean. My guess is that it is rich, but that doesn't make sense for emissions... Anyway, it seems like people have varying opinions. How about any changes in A/F throughout the rpm range? Does anyone know?
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Old 04-15-2002, 07:29 PM   #2
Evan J. Kelly
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FlatBlack&BlueRidge Pearl

Default

Rich, although you need a new ecu to really take advantage.
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Old 04-15-2002, 07:29 PM   #3
Kevin Thomas
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1989 1989 XT6

Lightbulb A/F ratios

Your car's air fuel ratio fluctuates (goes up and down, back and forth) to rich-lean-rich-lean over and over again. The only time your car should be running rich is during startup and WOT (wide open throttle). During start-up, once your car warms up and reaches it's operating temperature, it should go back and forth between rich and lean constantly.

If it doesn't go back and forth over and over again (Except for WOT and start-ups), then you have a bad O2 sensor. Hope that helps.
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Old 04-15-2002, 07:40 PM   #4
PeterJ
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Default thanks

Thanks guys...not to misconstrue the issue, but my questioning regarded this initial issue- At what point in the rpm range would a free flowing intake, or even a ram-air intake help the engine produce power? So I guess the answer is, "at WOT" -any more input on A/F ratio's would be helpful. -Thanks
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Old 04-15-2002, 08:40 PM   #5
Evan J. Kelly
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FlatBlack&BlueRidge Pearl

Default Re: A/F ratios

Quote:
Originally posted by Kevin Thomas
Your car's air fuel ratio fluctuates (goes up and down, back and forth) to rich-lean-rich-lean over and over again. The only time your car should be running rich is during startup and WOT (wide open throttle). During start-up, once your car warms up and reaches it's operating temperature, it should go back and forth between rich and lean constantly.
No it doesn't.

Have you looked at a A/F gauge?

The only time it runs lean is at startup.
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Old 04-15-2002, 09:06 PM   #6
Kevin Thomas
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Default Re: Re: A/F ratios

Quote:
Originally posted by Evan J. Kelly


No it doesn't.

Have you looked at a A/F gauge?

The only time it runs lean is at startup.
You are partly correct. The A/F ratio does read lean. Sometimes it doesn't even move during startup. The reason for this is because your oxygen sensor isn't working properly. Your oxygen sensor has to get up to operating temperature (Somewhere north of 600F) before it is operating correctly. During this time, your car runs rich.
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Old 04-16-2002, 12:03 AM   #7
PeterJ
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Default verify

So just to make sure...The two instances my engine runs rich (established so far) are upon start up and at WOT. Correct?
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Old 04-16-2002, 01:32 AM   #8
wistful
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Default

I have an autometer a/f meter with its standalone o2 bung and I get some crazee stuff.

when i turn the car on... it starts in rich.. and slowly makes it way to hyper-ultra super jo-mama off the scale lean. (that's when I know its warmed up).

when I run.. 0-45% throttle its lean. when its at idle.. its off the scale on the lean side. IF i'm just slightly on throttle its really in the lean. 45%-85% its stoich. 85%+ it just gets super rich.

any explanations?

Don
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Old 04-16-2002, 10:41 AM   #9
PeterJ
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Default wistful

I think that sounds normal...from an emissions standpoint anyway. To get lower emissions, en engine must usually run lean. During startup/warmup, however some extra fuel helps get it going and at wot it helps make more power. At any other time, the engine runs lean to reduce polution. That's my understanding...
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