Hulled out Catylic convertor
09-01-2005, 07:00 PM
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Hulled out Catylic convertor
I hull out my cat, and know my ECL light wil not go off. I reset the ECU, and that made it go away for a little while, but now it is on all the time. Any suggestions from those that have put on a midpipe with no cat. How did you handle the oxygen sensor, and ECL coming on? 
09-02-2005, 04:56 AM
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Why would you gut your catalytic converter?
Power gains are almost nil, and you make the PCM freak out about fuel mixtures, making the engine run too rich/lean.
But there was ways to "fool" the PCM into thinking the o2 sensor is reading correctly, but you will need to put the cat back on, get a digital voltimeter, and measure the readings from a working exhaust setup, and make a series of resisters inline with the o2 sensor that will create those desired readings after you remove the cat again.
Either way, its a dumb idea. Just get a hi-flow cat from Magnaflow if you absolutely must.
Power gains are almost nil, and you make the PCM freak out about fuel mixtures, making the engine run too rich/lean.
But there was ways to "fool" the PCM into thinking the o2 sensor is reading correctly, but you will need to put the cat back on, get a digital voltimeter, and measure the readings from a working exhaust setup, and make a series of resisters inline with the o2 sensor that will create those desired readings after you remove the cat again.
Either way, its a dumb idea. Just get a hi-flow cat from Magnaflow if you absolutely must.
09-02-2005, 08:37 AM
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A cat-less midpipe would likely present less resistance to exhaust flow than a gutted cat. The catalytic converter body is larger in diameter than the exhaust piping, presenting an expansion zone (as flow enters) and then a contraction (as flow exits). Both of these will introduce slight (or not-so-slight, depending on the shape of the transition) flow restrictions.
A cat-less midpipe would be just more pipe at the same diameter as the rest of the exhaust piping, eliminating the 'minor losses' associated with flow transitions, and presenting only friction resistance.
That's how it works out on paper. In reality, the difference may be so small that you would never notice it. To be honest, the difference between either and a high-flow "honeycomb-style" cat is probably also not noticeable from a flow standpoint (though it definitely makes a difference environmentally).
A cat-less midpipe would be just more pipe at the same diameter as the rest of the exhaust piping, eliminating the 'minor losses' associated with flow transitions, and presenting only friction resistance.
That's how it works out on paper. In reality, the difference may be so small that you would never notice it. To be honest, the difference between either and a high-flow "honeycomb-style" cat is probably also not noticeable from a flow standpoint (though it definitely makes a difference environmentally).
09-02-2005, 12:12 PM
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Tube Weld
I wonder if I could weld a pipe through the cat to cut down the buffer of air that now exists in the cat? What do you think?
Last edited by urby1970; 09-02-2005 at 12:14 PM.
09-06-2005, 12:57 AM
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I don't get why you would gut your cat. Get a pipe made and save the cat for inspection reasons. You won't be abled to get rid of the MIL. The PCM is looking at the downstream O2 sensor voltage to monitor the cat. If you gut the cat, the downstream O2 will 'switch' too much causing the MIL to light up because the PCM thinks your CAT is gone. (Which in your case, it is).
09-09-2005, 09:26 PM
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fixed the CEL problem
Used plug anti foulers, that I found at Advanced auto. Used two foulers, gutted the first one, and left the second alone. No more CEL, and good pickup from gutting the CAT. I plan on buying a B&B midpipe here shortly. 
09-10-2005, 11:49 PM
#14
He's as bad as Can
09-12-2005, 10:22 AM
#15
Oil Injection
you just destroyed a $1200 mazda part!
Its always a good idea to just replace the car with a bolt in midpipe, or a highflow cat, that way you could change back and fourth when you want.
Also this talk of welding a pipe inside your hollowed out cat to reduce the flow restriction??? thats just making a midpipe....but its heavyer cause of the extra cat sheild on the outside.
As far as the PCM sensor goes, some cars seem to be more or less sensitive to it. there are no quick fixes for it, so for now you can try some of the methodes that work for others..but its not quite the same as a civic that you can just bolt in a MIL elinator.
Its always a good idea to just replace the car with a bolt in midpipe, or a highflow cat, that way you could change back and fourth when you want.
Also this talk of welding a pipe inside your hollowed out cat to reduce the flow restriction??? thats just making a midpipe....but its heavyer cause of the extra cat sheild on the outside.
As far as the PCM sensor goes, some cars seem to be more or less sensitive to it. there are no quick fixes for it, so for now you can try some of the methodes that work for others..but its not quite the same as a civic that you can just bolt in a MIL elinator.
09-12-2005, 02:20 PM
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Originally Posted by GTAW
It's been quite awhile since I installed it and forgot about it. I guess with no check engine light, it was out of sight out of mind type of thing. It's funny to see so many wanting to get rid of the P0420 code yet, not many believe that anything works. 
God, I have well over 1400 miles on it. I have to say when I modified the OEM exhaust (from before the muffler on back) with a Borla XR-1 (3" back) one light came up which was from the heater circuit on the 02 not warming up as quickly as the ecu thought it should. I installed a 2.5" resonator and that some how was,I guess, enough to slow down the exhaust flow.
I am happy with the results.
God, I have well over 1400 miles on it. I have to say when I modified the OEM exhaust (from before the muffler on back) with a Borla XR-1 (3" back) one light came up which was from the heater circuit on the 02 not warming up as quickly as the ecu thought it should. I installed a 2.5" resonator and that some how was,I guess, enough to slow down the exhaust flow.
I am happy with the results.
09-13-2005, 10:40 PM
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Originally Posted by KYLiquid
you just destroyed a $1200 mazda part!
Its always a good idea to just replace the car with a bolt in midpipe, or a highflow cat, that way you could change back and fourth when you want.
Also this talk of welding a pipe inside your hollowed out cat to reduce the flow restriction??? thats just making a midpipe....but its heavyer cause of the extra cat sheild on the outside.
As far as the PCM sensor goes, some cars seem to be more or less sensitive to it. there are no quick fixes for it, so for now you can try some of the methodes that work for others..but its not quite the same as a civic that you can just bolt in a MIL elinator.
Its always a good idea to just replace the car with a bolt in midpipe, or a highflow cat, that way you could change back and fourth when you want.
Also this talk of welding a pipe inside your hollowed out cat to reduce the flow restriction??? thats just making a midpipe....but its heavyer cause of the extra cat sheild on the outside.
As far as the PCM sensor goes, some cars seem to be more or less sensitive to it. there are no quick fixes for it, so for now you can try some of the methodes that work for others..but its not quite the same as a civic that you can just bolt in a MIL elinator.
09-23-2005, 10:10 PM
#18
Originally Posted by TeamRX8
what happened to the guy that made a special length O2 fitting that he claimed cured the CEL problem?
here it is
https://www.rx8club.com/series-i-tech-garage-22/midepipe-cel-problem-fixed-72790/
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