Z1 Exhaust

richard.wales · Post by **richard.wales** » Sun 11 Jul, 2010 14:21

The exhaust on my 1989 Z1 is a one piece system that bolts to the manifold. BMW confirm that this is correct for my chassis number and a replacement is available for roughly £2,000. The problem is that the down pipes have become detached from the flanges which are bolted to the manifold flanges. £2,000 seems an awful lot of money to solve this particular problem, although I admit that the rear silencer is showing considerable signs of rusting.
I have a copy of the BMW Repair Manual + Specifications which shows 4/91 on the cover - presumably published in April 1991. This shows a multipart system consisting of 2 down pipes, primary muffler (catalytic converter) and final muffler. Presumably, the Z1 exhaust system was changed between 1989 and 1991; can anyone confirm that this was so? The answer to my problem would seem to be to purchase the two later model down pipes and get an exhaust specialist to cut off the old pipes and fit flanges in front of the cat. converter. Does anyone know whether the manifold remained unchanged when the exhaust system was modified. Has anyone else encountered a similar problem (flanges becoming detached from down pipes?

Racing Tortoise · Post by **Racing Tortoise** » Mon 12 Jul, 2010 09:18

May sound odd, but your best bet may be to have a custom system made up in stainless steel using your old system as a template - a good exhaust supplier can do this. I had this done by Powerflow on my previous Z1 and it was the cheapest option by a long way.

You could also de-cat. A 1989 car is not required to have a catalyst to pass an MoT so far as I'm aware.

felix · Post by **felix** » Mon 12 Jul, 2010 14:49

Here's the diagram from the online parts catalog - http://bmwfans.info/parts/catalog/Z1/Ro ... _catalyst/ No signs that the design changed for later cars.

BBZ149 · Post by **BBZ149** » Mon 12 Jul, 2010 18:49

There is only one place I’ll ever use again for exhausts:

http://www.nouvalari.com/bespoke_exhausts.php

My basic back box:
http://www.zroadster.net/forum/viewtopi ... =nouvalari
Jet's master piece no longer has any images in the post, the Dutch and Germans love his design and Nouvalari will make anything you want for the best price you’ll find anywhere!

Jet's design made by Nouvalari

TJS · Post by **TJS** » Tue 13 Jul, 2010 12:57

For what its worth I do have an original rear silencer box sitting in the workshop should someone need a replacement. It came off the car at 20k kms (BTB unit went on) and is in reasonable condition. slight rust mark on the underside of the outer skin but its not perforated.

A tip ... if you are thinking of removing the rear box from the car on your own get some help .. it's bloody heavy !

Racing Tortoise · Post by **Racing Tortoise** » Tue 13 Jul, 2010 14:59

Quite quiet these BTB boxes aren't they!? My soon-to-arrive replacement Z1 has one fitted and it's quite the shrinking violet next to my 1-series, let alone the last Z1!

I see that's probably due to the silly little peashooter exhausts hidden inside the wide oval exits. Do you reckon there's a safe way of doctoring it to make the actual exhaust exits bigger (and therefore sound a bit fruitier)?

TJS · Post by **TJS** » Wed 14 Jul, 2010 20:27

The BTB box has a more "seriousl" sound than the standard system without being a pain in the butt on a long journey. Personally, I quite like it.

Aesthetically, the twin exit set up really suits the car. I am sure BTB could modify the box if you asked and paid them.

I have always taken the view that the Z1 isn't an out an out sports car in terms of performance on the basis most modern warmed over hatchbacks and nearly all turbo diesels will spank it. A loud sports exhaust without the corresponding power to match expectation is slightly embarrassing.

Racing Tortoise · Post by **Racing Tortoise** » Thu 15 Jul, 2010 09:39

I agree that aesthetically the BTB system suits the car though I hate exhausts where you can see little pipes hiding inside showy large openings (step forward many modern cars). I think I'm just used to my last car, which was really quite a noisy little beggar. Mind you it has an LSD and went like a scalded cat by Z1 standards (would be interesting to rolling-road it as and when possible), so it was a little more appropriate.

This new one feels and sounds rather more sedate!

And besides, some of us don't have a Trevor to play with and therefore need to get our aural kicks somewhere else!

Bluebaur · Post by **Bluebaur** » Thu 15 Jul, 2010 09:53

If you are wanting a little more noise without going to extreme lengths, then a Nouvalari is the answer. I believe it may be cheaper to purchase a Nouvalari than for BTB to alter existing. Nouvalari use a slightly larger diameter perforated tube within their sports exhausts and the design allows two empty chambers on either side of the main silencer where the tail pipes emerge. There is an added benefit to this as my recent MOT has proved. A 20 year old car with nearly zero emissions!! The probe was placed in the tail pipe but effectively it was in fresh air. Fortunately MOT testers have not started to use decibel meters yet.

richard.wales · Post by **richard.wales** » Mon 19 Jul, 2010 10:47

Thanks to all who responded to my original query and particularly to Felix whose diagram matches the set up of my exhaust system (2 piece, not one piece as I said originally). Last week I took the Z1 to Infinity Exhausts at Yate (moving to Codrington in the new year) who lightly welded the flanges to the downpipes, in situ, both to check that the weld would take and to ensure that everything was positioned correctly for the proper fix. I then went off for a spot of lunch whilst they let things cool down, removed the front section of the exhaust assembly, welded the flanges and replaced. All was ready for my return, at a cost of £100. Note that I supplied BMW replacement nuts and gaskets. The nuts are copper and self tapping - they are not suitable for re-use. At this stage, there is no point in replacing the rear silencer box but I was interested in the various comments. To me a replacement box must match the original's aerodynamics as otherwise one of the features of the Z1 design is lost and the gap between boot and bumper becomes pointless. Noise is not an issue as the Z1 looks like a real sports car so why shouldn't it sound like one?