Recirculation hose = lean a/f - The Saab Link Forums

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Performance Modifications for the NG900 / Old 9-3 This forum contains PERFORMANCE related Q&A's for the NG900 and 9-3. This may also include suspension.

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Old 02-26-2008, 06:04 PM   #1
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Recirculation hose = lean a/f

I have a 99 9-3 and do not have the recirc hose on so it makes the blow-off noise. I have been told by several saabers that taking the hose off is fine for the car and will not hurt it. HOWEVER... in class at school (UTI) we were playing with the 5-gas analyzers. I decided to experiment and discovered that with the hose on the vehicle, the a/f was a perfect stoitiometric 14.7:1. But with the hose off, it ran a lean 17.8:1. I have no A/F gauge, this is all from a 5-gas analyzer (a piece of equipment costing thousands). How have I not heard of this before especially when several saabers I know have an A/F gauge. Have u never seen it? I dont know what to think. In fact, it seems backwards. Seems like with the hose off it should run rich but I don't know.
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Old 02-26-2008, 06:19 PM   #2
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The 1" hose back to the intake will not affect the a/f metering. the little hose will however give the engine extra air and make idle fast. All the fuel metering is happening by the manifold pressure "MAP" (Along with rpm, throttle angle and air temp but not relevant to this) Maybe you need to control the experiment a little better. Could be another. Car will not idle well with 17.8 lambda 1.2 it is not possible.

On a t7 car they are fueled primarily by MAF or airflow measured at the air filter so you could.. But by the pic it is a 9-3 base/se not a vig..
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Old 02-26-2008, 10:21 PM   #3
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The 1" hose back to the intake will not affect the a/f metering. the little hose will however give the engine extra air and make idle fast. All the fuel metering is happening by the manifold pressure "MAP" (Along with rpm, throttle angle and air temp but not relevant to this) Maybe you need to control the experiment a little better. Could be another. Car will not idle well with 17.8 lambda 1.2 it is not possible.

On a t7 car they are fueled primarily by MAF or airflow measured at the air filter so you could.. But by the pic it is a 9-3 base/se not a vig..
Hi Nick. Would it be adviseable to pull off the hose on my currently stock 2000 Vig?
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Old 02-26-2008, 10:34 PM   #4
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Hi Nick. Would it be adviseable to pull off the hose on my currently stock 2000 Vig?
I have a t5, but from what I know about t7s, that will throw a code. The MAF will be expecting the recirculated air, and it will be missing, thus a CEL.
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Old 02-26-2008, 10:36 PM   #5
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Hi Nick. Would it be adviseable to pull off the hose on my currently stock 2000 Vig?
you will throw codes
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Old 02-26-2008, 10:43 PM   #6
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you will throw codes
Ok then i will rather no try. Thanks guys.
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Old 02-27-2008, 07:55 AM   #7
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Anyway, back to the topic at hand. All i know is that at idle; 14.7:1 with hose; 17.8:1 without hose.
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Old 02-27-2008, 08:06 AM   #8
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You are missing something, I run a catch can and don't recirculate that air or the air from the bpv and my car idles right at 14.7/1. It did effect the vacuum at idle, but not the a/f...

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Old 02-27-2008, 08:33 AM   #9
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you will throw codes
Will it go into limp mode?
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Old 02-27-2008, 09:25 AM   #10
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Will it go into limp mode?
no
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Old 02-27-2008, 03:15 PM   #11
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Is your BPV functioning properly? It would seem like its sucking un-metered air in through that.

edit: nm T5 system, no air metering. My de-de-dee for the day.
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