Exhaust!

UK forum for general and technical discussion about the Z3 roadster

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Zedbedee
Joined: Sun 15 Mar, 2009 20:04
Posts: 154

  Z3 roadster 2.0
Location: Yeovil

Exhaust!

Post by Zedbedee » Sat 27 Apr, 2019 21:29

I will need to do some work on my exhaust before the next MOT and I'm finding some slightly strange things. I've owned my V reg 2.0 litre for about 10 years and I'm fairly sure it has the original exhaust. Looking at RealOEM the exhaust part numbers for the 2.0 litre are the same as for the 2.8 litre which I found a bit strange. But then my actual arrangement is different to the diagrams in RealOEM. I have the two 3 branch manifolds/headers and each one has an oxygen sensor it after the branches have combined. The manifolds connect to two pipes by flange mounts which looks normal. From the flanges the exhaust is all one piece, the pipes entering two cats and from the cats they go into one pipe with a small resonator and from there to the back box which has the vacuum valve in the tailpipes. All the replacement systems I have seen online have the oxygen sensors after the cats and are in two parts with a centre joint. I really don't want to spend £600 or more on a complete stainless system but would like to know what other people have done and why my oxygen sensors seem to be in a different place to RealOEM. I would expect that putting them before the cats rather than after would give very different readings. Also slightly concerned that aftermarket cats may give emissions problems at MOT time. Any thoughts??

Mike Fishwick
Joined: Fri 19 Jun, 2009 11:27
Posts: 2017

  Z3 roadster 2.8
Location: Daglan, France

Re: Exhaust!

Post by Mike Fishwick » Sun 28 Apr, 2019 19:22

Yes - the 2 litre used the same exhaust system as the September 1998-on 2.8. The system is in one welded piece from the three-bolt flanges near the engine, without a central joint, so perhaps your system is not the original. The earlier 2.8 used a single cat with a joint after it, but this was not used on the M52TU engine.

You should have a lambda probe before each cat to monitor oxygen levels, and also one after each catalytic converter to monitor their performance - see if there are a pair of unused connectors tucked away above the heat shield in front of the cats.

I had a stainless system made from the Y-piece pipe after the cats, with a larger front silencer and a rear silencer which is not painful to my ears - it cost about £400 at MJI Exhausts of Walsall.
A Z3 is not just for Christmas - it's for life!

Zedbedee
Joined: Sun 15 Mar, 2009 20:04
Posts: 154

  Z3 roadster 2.0
Location: Yeovil

Re: Exhaust!

Post by Zedbedee » Mon 29 Apr, 2019 13:16

Thanks for the info. My system is one piece from the manifold joints but there are no oxygen sensors after the cats and so sign of wiring that I can see. I've never had a problem with emissions at MOT time though. The fact that the vacuum diverter valve is in the back box makes me believe it is the original system, does anyone re-instate that feature? Now thinking of just getting a decent rear silencer and putting a joint in but I do like originality!

bowei001
Joined: Mon 13 Apr, 2009 17:38
Posts: 202

  Z3 roadster 2.0
Location: Sudbury

Re: Exhaust!

Post by bowei001 » Mon 29 Apr, 2019 13:23

On our 2.0 (1999), the 2 rear sensors are difficult to see as they are nearly horizontal between the pipes and all the wiring and connectors are clipped up behind the heat shield between the pipes and the body. They should be there if the system is original (and as you have the vacuum valve in the back box it appears to be.)

Mike Fishwick
Joined: Fri 19 Jun, 2009 11:27
Posts: 2017

  Z3 roadster 2.8
Location: Daglan, France

Re: Exhaust!

Post by Mike Fishwick » Mon 29 Apr, 2019 14:59

If you have an originality fetish, and wish to replace the rear silencer, BMW sell a seperate silencer and an suitable sleeve with suitable clamps to attach it. It would probably be cheaper to have a stainless cat-back system made up, unless you think that the droning exhaust note is worth listening to!

I always used to try hard to admire the 'wonderful' sound of a straight six exhaust, but never found it! The only Z3 models which do sound nice are the 2.2 and 3 litre models, where the exhaust system is seperated all the way into the rear silencer.
A Z3 is not just for Christmas - it's for life!

Juvvajuvva
Joined: Sun 06 Nov, 2016 16:52
Posts: 75

  Z3 roadster 2.8

Re: Exhaust!

Post by Juvvajuvva » Tue 30 Apr, 2019 21:32

One of my zd’s is a 2.8 97/98 pre TU crossover and it had one single lambda at the middle/front. Check if your ECU is single or dual Lambda.
Mine had the genuine exhaust on it.
I then stripped out the entire loom and fitted a remapped twin lambda ECU with s50b32 manifolds, cats and Sebring back boxes.
If you look on real OEM be sure to put in your VIN.

Gareth 161
Joined: Thu 08 Mar, 2012 23:41
Posts: 116

  Z3 roadster 3.0i
Location: Cornwall

Re: Exhaust!

Post by Gareth 161 » Thu 13 Jun, 2019 14:13

Your exhaust pipe set up is the same as I had on my 2000 3.0 z3 which was original and had reached a point where it needed replacing throughout.
Looking at the oem pictures there did seem to be various different exhaust systems fitted which didn’t help as could not afford a complete system from bmw!
Luckily I found a complete system on eBay which came off a 2.2 I believe and as a 6 cylinder it looked very similar to mine. After looking at the various oem pictures and part numbers it proved to be the same exhaust and as in much better condition than mine, I got it fitted..
However I wanted to replace the rear box for a lighter stainless box with a slightly better sound but as no join before the rear box I cut the pipe about 6 inches behind the rear hanger where it is a straight section of pipe and bought a stainless box fitted with a clamp. I sealed up the pipe which originally went to the exhaust flap and all works well with a slightly deeper tone but no droning.
Hopefully you can find something but the above proves that the oem pictures can be a bit misleading although are correct once you look deeper into them!
2001 3.0 Z3, 2008 Subaru Forester Xten

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