AFR's with CAT
Apr 27, 2009, 01:27 PM
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AFR's with CAT
Hi all, a friend of mine wants me to check the fueling on his subaru, the car is stock but has just been rebuilt.
my wideband is used with a tailpipe sniffer, so am wondering how the stock catalytic convertor affect afr readings?
my wideband is used with a tailpipe sniffer, so am wondering how the stock catalytic convertor affect afr readings?
Apr 27, 2009, 01:44 PM
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I dont know what the readings are going to be like.....hence the question.
have heard a tuner here in the uk say it was about 0.6 (afr) different.........don't know if that was a constant though through the rev range.
.....pain in the arris to put a decat (test pipe) on the scooby downpipe....specially with rusted turbo bolts.
(but surely this also wouldn't give a correct reading as it is being run with the restrictive cat)
have heard a tuner here in the uk say it was about 0.6 (afr) different.........don't know if that was a constant though through the rev range.
.....pain in the arris to put a decat (test pipe) on the scooby downpipe....specially with rusted turbo bolts.
(but surely this also wouldn't give a correct reading as it is being run with the restrictive cat)
Apr 27, 2009, 01:50 PM
#4
I dont know what the readings are going to be like.....hence the question.
have heard a tuner here in the uk say it was about 0.6 (afr) different.........don't know if that was a constant though through the rev range.
.....pain in the arris to put a decat (test pipe) on the scooby downpipe....specially with rusted turbo bolts.
(but surely this also wouldn't give a correct reading as it is being run with the restrictive cat)
have heard a tuner here in the uk say it was about 0.6 (afr) different.........don't know if that was a constant though through the rev range.
.....pain in the arris to put a decat (test pipe) on the scooby downpipe....specially with rusted turbo bolts.
(but surely this also wouldn't give a correct reading as it is being run with the restrictive cat)
If its a major problem maybe goto an exhaust shop and have them weld in a bung?
Sorry to hear its a scooby i know those exhausts can be a bugger! What kind of scooby is it?
Apr 27, 2009, 01:59 PM
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the scoob is a stock '98 uk wagon (bar a fuel reg), car is running fine at the moment after the rebuild but was wondering if I could check the fuelling at the tailpipe without too many issues.
I was wondering if anyone has done any logs with a wideband pre and post cat, is there a constant calculation I could use to get a semi-accurate reading.
don't really know how a cat works, will readings vary from one cat to another?
I was wondering if anyone has done any logs with a wideband pre and post cat, is there a constant calculation I could use to get a semi-accurate reading.
don't really know how a cat works, will readings vary from one cat to another?
Apr 27, 2009, 02:01 PM
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Apr 27, 2009, 02:02 PM
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A cats efficiency can change over time and I believe that would mess up your readings as well.
Have a bung welded in pre cat, take it to the dyno and when done, use a bolt to block it up.
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Apr 27, 2009, 02:08 PM
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precat would be right next to the turbo, isn't too much heat bad for the o2 sensor.
....will be checking car on the road (not a fan of rolling roads/dynos)
....will be checking car on the road (not a fan of rolling roads/dynos)
