decatting a BX
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tomsheppard
- Posts: 1801
- Joined: 19 Dec 2002, 14:46
- Location: United Kingdom
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decatting a BX
Have TZI with cat, 1991. Can I decat it without falling foul of the law or the fuel injection?
Tom -
It's only a question of regulations.
Technically the Cat lives a life on it's own - hoping the Lambda sensor & engine management controls the combustion to safe levels for the Cat.
Removing the Cat thus simply means the Lambda sensor & engine management continues to control the combustion - as they hav'nt got the faintest idea whether the cat is there - is working - or not.
That's also why the Lambda sensor is located BEFORE the Cat - in the exhaust manifold.
In fact "upgrading" an older car/engine to an injection system with Lambda sonde would reduce the emissions - even with no Cat fitted.
But of course not to those low emission levels the Cat provides.
The Cat should be considered as an "after-burner" device - reducing the contents of half/un -burned remnants from the combustion.
Removing the Cat COULD give slight problems due to the fact the exhaust then has less resistance in flow. A small (& cheap) damper box (expansion chamber) fitted instead of a Cat would likely solve such problems.
It's only a question of regulations.
Technically the Cat lives a life on it's own - hoping the Lambda sensor & engine management controls the combustion to safe levels for the Cat.
Removing the Cat thus simply means the Lambda sensor & engine management continues to control the combustion - as they hav'nt got the faintest idea whether the cat is there - is working - or not.
That's also why the Lambda sensor is located BEFORE the Cat - in the exhaust manifold.
In fact "upgrading" an older car/engine to an injection system with Lambda sonde would reduce the emissions - even with no Cat fitted.
But of course not to those low emission levels the Cat provides.
The Cat should be considered as an "after-burner" device - reducing the contents of half/un -burned remnants from the combustion.
Removing the Cat COULD give slight problems due to the fact the exhaust then has less resistance in flow. A small (& cheap) damper box (expansion chamber) fitted instead of a Cat would likely solve such problems.
I looked at doing this once on a TZI. I decided the best way was to fit the down pipe for an 8v GTI having first welded in a nut or threaded socket to enable the lambda sensor to be refitted to the non cat setup to enable the ECU to still regulate the mixture.
But in the end I decided it was not worth the trouble....As even if the cat failed and the co in the exhaust gas went up it would still pass the MOT here and the performance/economy increase while welcome would be hardly noticable.
But in the end I decided it was not worth the trouble....As even if the cat failed and the co in the exhaust gas went up it would still pass the MOT here and the performance/economy increase while welcome would be hardly noticable.