a/f ratio from tailpipe vs a/f ratio before the cat.
Thread Starter
Joined: Apr 2004
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From: USA
a/f ratio from tailpipe vs a/f ratio before the cat.
How accurate or inaccurate are the a/f ratio tester that goes into your tailpipe, compared to welding a bung into the header to test the ratio….will the condition of the cat completely change the results and how does this affect tuning of air/fuel….
FSAE
Joined: Jan 2002
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From: Drinking Beer, UT
Re: a/f ratio from tailpipe vs a/f ratio before the cat. (blk_db2)
A catalyst will affect AFR, it will read leaner than actual.
The closer to the engine you are taking your readings from, the more accurate it will be in terms of RPM-point. The AFR should not have any noticeable change in actual value being in the tailpipe, or in the header, that is unless you are using a catalyst in there.
-MPH-
The closer to the engine you are taking your readings from, the more accurate it will be in terms of RPM-point. The AFR should not have any noticeable change in actual value being in the tailpipe, or in the header, that is unless you are using a catalyst in there.
-MPH-
Joined: Dec 2004
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From: St Paul, MN, USA
No. There should not be any difference in A/F ratio, unless you have any sort of exhaust leak. In which case, your A/F will be lean.
Cats are designed to take the HC (Hydrocarbons), among other emissions, out of your air stream. HCs are commonly referred to as gasoline. So yes, after the cat, if you have one, will have a STRONG effect on your A/F ratio. Damn I love MN. No emissions testing.
Cats are designed to take the HC (Hydrocarbons), among other emissions, out of your air stream. HCs are commonly referred to as gasoline. So yes, after the cat, if you have one, will have a STRONG effect on your A/F ratio. Damn I love MN. No emissions testing.
Honda-Tech Member
Joined: Jul 2004
Posts: 4,640
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From: VA Beach, VA, USA
Re: (JustROLLIN)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JustROLLIN »</TD></TR><TR><TD CLASS="quote">No. There should not be any difference in A/F ratio, unless you have any sort of exhaust leak. In which case, your A/F will be lean.
Cats are designed to take the HC (Hydrocarbons), among other emissions, out of your air stream. HCs are commonly referred to as gasoline. So yes, after the cat, if you have one, will have a STRONG effect on your A/F ratio. Damn I love MN. No emissions testing.</TD></TR></TABLE>
VA doesn't have them either!
Cats are designed to take the HC (Hydrocarbons), among other emissions, out of your air stream. HCs are commonly referred to as gasoline. So yes, after the cat, if you have one, will have a STRONG effect on your A/F ratio. Damn I love MN. No emissions testing.</TD></TR></TABLE>
VA doesn't have them either!
Thread Starter
Joined: Apr 2004
Posts: 221
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From: USA
Re: (hybrid_vtec)
You guys are lucky.... I never had a cat before either, till I moved to Wa. and had to put one back on...
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johnzm »</TD></TR><TR><TD CLASS="quote">i have seen .8 difference in AFR
dont use the tailpipe sniffer </TD></TR></TABLE>
wow .8 is quite a diff. (so i'm sure if the cat was cold, the a/f ratio would be totally different)
I had to use a sniffer cause that's all they had at the place I dyno tuned
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johnzm »</TD></TR><TR><TD CLASS="quote">i have seen .8 difference in AFR
dont use the tailpipe sniffer </TD></TR></TABLE>
wow .8 is quite a diff. (so i'm sure if the cat was cold, the a/f ratio would be totally different)
I had to use a sniffer cause that's all they had at the place I dyno tuned
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