'93 M40 Cat/O2 removal...

[jmc330i]

Hey guys.

I need to change the exhaust on the touring, but being a '93 its got a cat and O2 sensor. I will be changing to a non-cat exhaust. Now, will the ECU cope and deal with the O2 sensor being unplugged and tucked away like happens on the M20's?

Cheers

[Brianmoooore]

ECU will be happy without an O2 sensor, but you may need to change the air flow meter, if it doesn't have the CO adjuster pot on it, or I suppose you could feasibly wire in a pot elsewhere.
On M40 engines that were designed to use an O2 sensor as an option there is a white/black wire under the bulkhead wiring cover, middle to RH side, that has a plug and socket in it. This plug and socket is left disconnected when used with an O2 sensor, and plugged together when no 02 sensor is used, so connecting the pot. to the ECU.

[jmc330i]

Thanks muchly Brian, and you must be a mind reader.... my next question was about the afm! Lol
I had the afm from my 89 touring out today and noticed the CO adjuster missing from the newer one.
So, I can just use the older afm and connect the white/black wire together and job jobbed?

[Brianmoooore]

Depends if it's there.
An alternative is to weld a lambda boss into the non cat exhaust, and retain the 02 sensor. A cut down M18 nut does the job.

[e301988325i]

Just a heads up, I thought I read the new MOT rules said cats aren't allowed to be removed if original equipment.

See here, no mention of the old pre 91 rule.

http://uk.autoblog.com/2012/01/04/chang ... you-ready/

[jmc330i]

Cheers for the heads up on the new MOT rules. Load of crap they come up with! Not particularly worried by it though, there's ways and means......


A couple years back, I remember pointing out to my MOT tester that my S50 conversion without cats, had lower emissions compared to the much newer euro hatch thing that was tested before it!

[e301988325i]

luck favours the prepared

[78gizmo]

I have got a good M40 cat with lambda sensor stashed in my shed if you need one.....