7 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHCatalytic Converter
Leading reported evidence
Install engine
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
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1
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Read evidence and context
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Performed · outcome unconfirmed
The pre-cat O2 sensor is used for engine control and must be installed for the engine to run properly.
Leading evidence: 'Install engine' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Adjust fuel/air mixture' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed
The pre-cat O2 sensor is used for engine control and must be installed for the engine to run properly.
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Suggestion
The engine controller will attempt to adjust the fuel/air mixture to see if this brings the output of the converters into acceptable readings.
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Suggestion
Cat bypass pipes (just straight pipes that replace the cats) are available with a bung for each O2 sensor.
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Suggestion
This could lead the engine to run closer to detonation than it would otherwise, or produce less HP than it would otherwise.
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7 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Generation: 20261027T075545Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Have any of you guys out there removed just the Cats off alone without changing anything else the 996 Carrera, if so how was your performance and did it make a noticable difference?
The next question I need to know did it throw off any codes or check engine lights in the ECU system. By the way I have 2001 Tiptronic not stickshift.
I appreciate any input regarding this matter.
you have 2 O2 sensors on each cat. they compare O2 in against O2 out of the cat. the difference is processed by the computer. And generates fault code if necessary. You can buy a set of hi flow cats and that will allow you to use the car normally w/out screwing it up
They (you THEY) say that 02 extenders will negate the check engine light. If you screw in the 02 extender (into the "bung") and then screw in the sensor, supposedly you don't get a CEL. The "in" sensor should be okay, the "out" on the far side of the cat is the one you want to defeat. Of course you know this is illegal for anything but "off road" use.
But, if you're going for noise and weight reduction, give it a try. I think the extenders are like $6 ea. and the "L" shaped ones are recommended.
Let us know if you try it.
The pre-cat O2 sensor is used for engine control and must be installed for the engine to run properly. The post-cat sensor is used to measure the scrubbing efficiency of the cat. You must have the pre-cat sensor.
Cat bypass pipes (just straight pipes that replace the cats) are available with a bung for each O2 sensor. When the ECU detects that the second sensor's response is consistent with poor cat efficiency, it will "throw a code" (check engine light will come on), but it shouldn't damage your engine. There are also ways to mimic an efficient cat, one of which was pointed out in post #4.
The engine controller will attempt to adjust the fuel/air mixture to see if this brings the output of the converters into acceptable readings.
Running one of these engines with non-factory and hacked up O2 sensor connections is not a good idea. While doing so may not damage the engine the engine's air/fuel mixture may not be as ideal as it would be otherwise. This could lead the engine to run closer to detonation than it would otherwise, or produce less HP than it would otherwise.
Sincerely,
Macster.
This is a source reference. Confirm exact model applicability in the original material.
