cat to non cat exhaust? (1991 318i)

[A1BMW325iSport]

Evening all,
I am in need of a new centre section, car is a 1991 318i Touring, but there is a cat and lambda sensor fitted.

I wonder if I just fitted the standard type 318i exhaust on, is there then no provision for the lambda sensor? do I just unplug it? and would the emissions be ok for mot? Cat not needed for MOT on pre 92 cars right?

Thanks in advance

edit: pics from realoem...

cat system with lambda sensor


standard system without lambda sensor? looks like i would need different bracket to gearbox also

[felix27]

pre 95 cars do not need a cat i belive but keep the lamda sensor because the m42 actualy produces more power with one(just improves ur air fuel)

[A1BMW325iSport]

where would the lambda sensor fit mate? from the diagrams it doesn't look to have provision on the standard system

[djk]

Suggest you ask in tech help, or ask mods to move this thread - There's bound to be someone on here who knows for sure.

A cat is required to pass emissions testing on cars registered after 01/08/1992 iirc - K reg onward.

[hennabm]

A cat is required to pass emissions testing on cars registered after 01/08/1992 iirc - K reg onward.

Not quite true - so long as the emissions are met, a missing cat in itself is not a failure.
You don't need a cat to pass a cat test, depending on the car. My old 525e would pass a cat test and had never seen a cat.

[Martinaston]

The gearbox mount is the same regardless, If you get a non cat just unplug the sensor loom from under the battery tray.

[A1BMW325iSport]

The gearbox mount is the same regardless, If you get a non cat just unplug the sensor loom from under the battery tray.

thanks are you sure about the bracket though as the bracket on my system is the welded on as in top picture

[djk]

A cat is required to pass emissions testing on cars registered after 01/08/1992 iirc - K reg onward.

Not quite true - so long as the emissions are met, a missing cat in itself is not a failure.
You don't need a cat to pass a cat test, depending on the car. My old 525e would pass a cat test and had never seen a cat.

Yeah, I knew this was the theory, I just assumed that there were no cars in practice that would pass the 'cat test' without a cat - learn something new every day!

[Martinaston]

The gearbox mount is the same regardless, If you get a non cat just unplug the sensor loom from under the battery tray.

thanks are you sure about the bracket though as the bracket on my system is the welded on as in top picture

Oh well, ignore that then. mines a 91 with the other type

[Brianmoooore]

Yeah, I knew this was the theory, I just assumed that there were no cars in practice that would pass the 'cat test' without a cat - learn something new every day!

Any car running on LPG with an engine in half decent condition will pass easily.

[Brianmoooore]

If the lambda sensor is removed, there is a single pole plug and socket (in a black/grey (?) wire) under the wiring cover on the bulkhead, near the middle, which has to be plugged together.
This connects the CO potentiometer on the air meter to the ECU, so that CO can be adjusted manually. It will then need adjusting while the car is attached to a CO meter, of course.

[Brianmoooore]

........to pass emissions testing on cars registered after 01/08/1992 iirc - K reg onward.

Or fitted with an engine built after this date.
If fitted with an earlier engine, a post 1/8/92 car will be tested to the earlier emissions standards. I have an '88 car and a '93 car that have had their engines swapped. Both are tested to the earlier standard.
There's also a grey area in the regs, which applies if the engine number is unreadable!

[hennabm]

If the exact match cannot be made for the engine then it goes to default limits.

[A1BMW325iSport]

If the lambda sensor is removed, there is a single pole plug and socket (in a black/grey (?) wire) under the wiring cover on the bulkhead, near the middle, which has to be plugged together.
This connects the CO potentiometer on the air meter to the ECU, so that CO can be adjusted manually. It will then need adjusting while the car is attached to a CO meter, of course.

ah i see thanks, thats just what i needed to know.