Z3 1.9 exhaust and cat

TriumphZ3

TriumphZ3

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Me again; I'm in the middle of a prolonged service including coolant and brakes so plenty to ask about BUT: this morning's dilemma is the exhaust. There's a loud rattle on startup and when accelerating, which I've traced to the catalytic converter. This one appears to have been welded into the exhaust system, no idea why, but the welds and the remains of welding wire point to a bodge. I've already replaced the rear half of the exhaust, thinking it was the silencer but it's still there.
I need a new exhaust, 1998 1.9 petrol.
The Net is full of them and they all mention that as its' pre 2001 I don't need type-approved; however I'm wary of a £100 exhaust including cat. Any recommendations for a (moderately-priced!) replacement that will pass emissions at the next MOT?
This is the sort of cheapie out there:

www.ebay.co.uk

CATALYTIC CONVERTER FITS BMW Z3 1.9L 16V 1997-1999 | eBay

Find many great new & used options and get the best deals for CATALYTIC CONVERTER FITS BMW Z3 1.9L 16V 1997-1999 at the best online prices at eBay! Free delivery for many products.
www.ebay.co.uk
 
My experience unfortunately is that only OEM cats work to emissions MOT standard on the M44 engine. Had two "mid priced" systems fitted that wouldn't pass; had to resort to a BMW OEM cat to pass. Had no issues since (3/4 years ago now). Only down side is that they are costly, especially if you don't have a OEM cat to part exchange; incidentally, the trade in allowance/surcharge for the old OEM cat from BMW is almost the same as a new aftermarket cat, which tells something!
 
I've read just this morning that the 'cat rattle' was a recall back in the day in the US but NOT Europe; it's due to a 'monolith' falling down inside.
I've got a mate works for BMW and have asked him to talk to the mechanics and see what their preferred option is.
Interestingly enough, mine was welded into the exhaust pipe which seems to be an option with an aftermarket (but good) CAT if I can find one.
 
A few times you've said your cat is "welded in". Maybe I've misunderstood something but, in my mind at least, the front exhaust section downpipes below the manifold to the cat is all one piece. The cat is welded to that front section. Isn't that what you've got?

When you buy a cat this is what you get.

Screenshot_20230926-194507_Gallery.webp


If yours has welding wire hanging off it then maybe it's been repaired. Or somebody has cut one from a different car and transplanted it in.
 
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Duncodin said:
A few times you've said your cat is "welded in".
If yours has welding wire hanging off it then maybe it's been repaired. Or somebody has cut one from a different car and transplanted it in.
Click to expand...

Yes, it's been welded in to the exhaust. The contour of the exhaust looks original, as does the shape of the CAT, so it may be a correct type, welded in to replace an earlier version that gave up. It was apparent to me even as a newbie to Z3s. I could do the same again if I can find a suitable replacement as the rattling is driving me up the walls.

IMG_6463.webp


IMG_6465.webp
 
Oh Mon Joo!!
Just been quoted £1190 EXCHANGE for a replacement cat / front exhaust from BMW. I think I'll put up with the rattling for another while, if turning the music up saves me that much.
 
zroadster.org

Emissions M44

Hi Guys time for a story that will get to a point 🤔 ( I promise) When I bought Lynne's zed got it cheap as it had a number of serious issues but let's not diverse to much . One of the issues was it had a bit of a major starting and running fault after a bit of diagnosis ended up with the...
zroadster.org zroadster.org

This thread may be of some help to you as an alternative .

Stephen.
 
It was, and it seems that's my only option - get a CAT off another car and weld it in. The link used in that post is gone now, sadly.
I have a mate runs a scrapyard so will see what he can find that will suit the engine and exhaust bore of the Z3 and work on that.
Although: if, as other posters have said, I'll get two years out of an eBay cat, then two years for £100 is £50 per year, or 22 years before I hit the price of the BMW version.
 
Had a look and yes your right link doesn't work and they no longer list an m44 cat still do the m43
You could always message them see if maybe still have one .
Atp spares ( Germany)
They were selling a m44 front section but as i said in above link the actual cat was not your usual cheap euro 2 cat that lasts 5 minutes.
But a type approved 103r certified euro 3 cat hopefully a bit closer to original than the usual ones so again hopefully better performing and longer lasting.
Stephen.
 
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Thanks all three of you, given me food for thought. That last post with the link from Trevor, he doesn't post to Northern Ireland... :( They all hate us!
Might try spursfan... it'll cost me a packet of choccy biccies for the mate with the scrapyard just to see if he has anything suitable that could be welded in. Lots of options there, many thanks.
 
After 25 years both my original cats are fine, and produce barely measurable quantities of CO at MoT time - you get what you pay for.
 
And how does that help anyone who needs a replacement? My 2000 Z3 2.0 passed the emission test with almost zero readings, but so what? Yours isn't a 4 cyl. either so you can't compare.

Tony.
 
Has the OP contacted spurs fan? I don't think he likes shipping/wrapping big stuff but the OP sounds happy to weld in a cat so if spurs fan has one in his shed I'm sure he'd chop out the cat and ship that (I've been in that shed, it's like the tardis)

Even a 20 year old OEM cat will probably work fine. Mine's pushing 25years and it's never given any problems come MOT time.
 
Duncodin said:
Has the OP contacted spurs fan? I don't think he likes shipping/wrapping big stuff but the OP sounds happy to weld in a cat so if spurs fan has one in his shed I'm sure he'd chop out the cat and ship that
Click to expand...

I will! No problems welding one in, the rattling from my current one is embarrassing given the lovely throb of the exhaust at idle, then this dustbin lid rattle as I accelerate. It spoils the image.
Just need to find a free day to get my head organised, but that sounds like a plan.
 
Perhaps I should have spelt out my meaning - that if you intend to keep the car for ages a comparatively expensive cat may be the best answer, and that a good one can last a long time. However, I do not think that I deserved the brusque comments from T-Tony, but it does not take much to work him up! Sometimes I wonder why I bother . . .
 
The aftermarket ones are absolute rubbish and rarely pass a straight MOT. The problem with the 1.9 is that the catalytic converter is too far away from the engine to really heat up and even the genuine ones can struggle a bit. I always give the car a good 10+ mile run using 5000 rpm bursts and the MOT man does the emissions first. The green 1998 car I sold last September had a new cheap s*** Euro cat (BM Catalysts crap) and only just scraped through. This year after 2000 miles or less it failed the MOT on emissions. A clean up of the lambda sensor scraped it through again. Same with my 318ti - I refit the theft prone BMW cat for the MOT.
If you garage the car and the theft risk is minimal, I’d be very tempted to fit a genuine cat. I find that the car drives and sounds better anyway.

I should add that the BM thing I fitted to mine 2 years ago collapsed and blocked the exhaust. I took it off, gutted it and ordered another new one. That cracked after 1000 miles and had to be rewelded. Both give an unpleasant drone on the overrun on the motorway - the factory cat also doubles as a primary silencer and the cheap crap ones don’t.
 
Ianmc said:
My experience unfortunately is that only OEM cats work to emissions MOT standard on the M44 engine. Had two "mid priced" systems fitted that wouldn't pass; had to resort to a BMW OEM cat to pass. Had no issues since (3/4 years ago now). Only down side is that they are costly, especially if you don't have a OEM cat to part exchange; incidentally, the trade in allowance/surcharge for the old OEM cat from BMW is almost the same as a new aftermarket cat, which tells something!
Click to expand...
Fully agree with @Andyboy (above). Only OEM cats are likely to pass a "straight" MOT on the M44. Can't say much more than repeat above. :)
 
The type 3 approved are fine. And will pass, well mine did after numerous fails with non approved ones. Not legally required but have enough active ingredients to meet emmisions. And can be found new for under 200
 
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