Catalytic converter on m42

[Alex]

Quick question how do i convert a standard m42 engine to run with a Cat, as my car is 1994 and will need a cat for Mot regs.

can i use my m40 exhaust and run that cat with an m42 setup ?

ps: i dont want to know the mot man

[MrWhite]

The MOT test goes by the age of the engine, so long as you can prove that it came from an older car. I have a K reg touring (subject to newer emissions regulations I think) with an M42 from a G reg iS in it. No Cat and no issues at MOT time.

[jmc330i]

As above, although its the age of which ever is oldest. My K reg touring passed MOT with no cat - between 1992 and 2001 its generally a visual check I believe, if the car will pass the emissions test without the cat fitted, it won't fail because it doesn't have one. Cars registered after 2001 must have a cat fitted regardless.

[Alex]

The engine is out of a 1998 bmw z3

[jmc330i]

Is the engine already fitted to the E30 and being driven, or a conversion just been done?

[Alex]

In the process

[jmc330i]

Are you using the Z3 loom etc to include the lambda sensor?

[78gizmo]

The question is a bit confusing, (how to convert M42 to run with a cat?), as you later say it out of a 1998 Z3, which would already run a cat as standard (and probably be M44).

Anyway, to answer the second question, none of the M40 exhaust at all will fit, i tried when i did my M40 to M42 conversion (i also have an L reg touring). The front section is the wrong shape and the bore size is much to small to weld or join it to any of the M42 exhaust.

To get around the mot situation, as said by others, you can test emmisions to the age of the engine if its older. Its up to you to prove this. So if you arrive for the mot armed with a "recipt" from a scrapyard/ebay seller/vehicle recyclers, or a letter from a garage saying you have been supplied or had fitted an engine from a 1990 318is, i doubt they wouyld query it (I wouldn't!).

[Alex]

I'am basically using an m44 bare engine with all m42 bits strapped to it so would be in theory a 1.9 M42

[78gizmo]

Ideal, just fabricate a recipt or something to say its a 1990 M42 318is engine in there, cant think why any mot tester would bother to prove its not.

I think from memory there is a problem to get round with temp sensors, the M44 uses 1 to do both functions, the M42 has 2 and they dont fit the M44. Try a search on here maybe.

[jmc330i]

I'd say put it all in with the M42 exhaust, it should pass the emission test without a cat fitted. Only a very picky MOT tester will bother about the lack of cat - but as I said above, it shouldn't matter as long as it passes the gas test.

[Alex]

Thanks

i'am still yet to buy a shagged m42 engine for all the ancilliries so if i get a recipt for that i guess i could use that ?