To Cat or not to Cat

[john <j.s.smith@xxxxxxxxxxxx>]

I recently replaced the rear section exhaust on my '89 325i - with no
problems. But I can see that sometime in the next year the front section
will need replacing too - and this section has the Cat in it.  I've done
some asking around and the easy fix is (of course) to buy a new front
section with Cat and O2 sensor. However this is hugely expensive here in
the UK as my car is lhd as was imported when I returned from working in
Germany.  

A few "facts":

- - I should think the Cat is shot now anyway as it is the original one
that was fitted to the car in '89

- - The car recently past the UK emission test. Don't know how tough that
is - they stick an instrument up the tailpipe and measure the gases.
Anyway, it past without problem. (The engine runs beautifully - I
replaced the cyl head 3 years ago inc valves and injectors etc etc)

- - The workshops (inc BMW) that have done emission tests have always
produced printouts that show NO CAT - even though IT HAS A CAT - I can
see it - it's there.

- - A supplier here in the UK sells a front section exhuast without Cat
(The '89 325i was supplied with or without Cat anyway I believe). I
would have to weld the O2 sensor in place myself.

My questions are:-

- - If I get the front section without Cat and weld an O2 sensor in
myself, is there a real danger the car will fail the emission test
(given point 1 above)?

- - If there is no Cat, could I just wire a resistor in place of the O2
sensor because - well, there is no Cat. to "protect" - or, is the O2
sensor doing a more complicated job in the emission control loop? 

I don't like dishing out pollution anyway - so I'll probably end-up
getting the green option - but I'd be interested in digest opinions on
the above.

- -Thanks

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