Cats Gone

try ENGL
http://www.engl-production.de/UK/startpage-UK.htm

Stainless would be great but apart from Engl or a Pro exhaust place that can make one you could .....

http://shop.ebay.co.uk/i.html?…_sacat=See-All-Categories

Hope this helps..

Alex

Zitat von m888jmk;90363

Help please. Both cats on my 96 840ci are breaking up. BMW have one set at Bracknell. Cost including brackets and new Lambda sensors a staggering £2244 !

That price can't be just for the cats can it? You will still have to replace the cats even with a stainless system which I agree will be half the price. Powerflow fitted a complete system for me 10 years ago for £960 inc Vat but excluding the cats, as having a '91 I didn't need them anymore.

Bob Beebe, I think, recently had a new stainless system as is over the moon with it.

My advice would be to fix the fault that is causing the cats to prematurely fail as soon as you have a new system fitted. The usual suspects are a failing MAF or fuel-rail pressure regulator. There are many companies that will fit after-market cats - or complete systems for a lot less than a quarter of the price of one OEM cat. I have used http://www.exhaustsuk.co.uk of Sheffield (excellent) and Longlife at Basingstoke.

Zitat von Nifty50;90366

That price can't be just for the cats can it? ....

Well, the EPC list them at Euro-900 each, which approximately transalates in to GBP 900 + VAT each side. It includes the cat and the down-pipes.

The original ones are actually Stainless Steel, but some parts of the pipework are covered with a galvanised steel heat-shield, which creates a secondary wall.

I think they contain a ceramic matrix monolith, but if you go for aftermarket ones, you can choose a metal-matrix type (a la CSi), which will give lower back-pressure and be more resilient to harsh treament.

These were GBP 60k - 80k cars 12-20 years ago (with inflation, 90k - 120k today) and many parts still have prices to match, added to which there's been a steady and rapid increase in prices over the last 3 years.

These exhaust parts on the EPC are labelled as "remanufactured", which I guess means BMW is having to get suppliers to remake them in small quantities, which must partly account for higher prices.

For some parts there's no choice, but I think with the exhaust system there are good aftermarket alternatives.

.

As an e39 V8 (same M62 engine) owner for many years. I've seen on many of the US forums that magnaflow cats have always been the aftermarket cat of choice.

http://cgi.ebay.co.uk/BMW-840C…ories&hash=item2304cd86e2

Thats just about right for the cats - with my 850 the cats needed replacing and I was quoted £900.00 each excluding fitting - the year of manfacture (1991) enabled me to drop them of and re map the car, but the BMW Exhaust was still in exess of £3.500

Hi Steve,

So you dropped the cats but still went for the original exhaust then at that cost? What told you it needed remapping because mine was never remapped and I haven't had any problems?

Cheers
Graham

careful with eliminating the cats altogether.
My suspision is that the O2 Sensors aren't externally heated and need the heat from the cats to work properly. So, if you drop the cats, your engine will not run optimally. We would need to heat the O2 Sensors apropriately...

Zitat von fuzzifikation;90701

careful with eliminating the cats altogether.
My suspision is that the O2 Sensors aren't externally heated and need the heat from the cats to work properly. So, if you drop the cats, your engine will not run optimally. We would need to heat the O2 Sensors apropriately...

Interesting! Are you able to expand at all on this suspicion? What would be the symptoms and effects on the engine's performance?

Hi Graham, I belive that for optimised running the car needs to know if it has cats or not I will check that with my mechanic.

with regards to the sensors they will always be hot from the exhaust gasses anyway.

I have ben running the car this way for nearly two years now and BMW exhaust keeps the car origional - also they provided the infills which removing the cats exposed. my MPH on a good journey is arround 22-23

not 100% sure that my memory serves me right on this, but I remember that the early M70's have the O2 sensors infront of the Cat's, but on leter models, or the M73 there are additional sensors after the cats.

Like I said I'm not sure, but with the o2 sensors infront of the cat's it should not have an effect.

Horsepower gains are up for debate, but I doubt you will see an increase, you may get some ponys back that have been lost over the years, and the engine responce may improve due to a better flow when the clogged up old cat's are gone.
Removing them will also change the backpressure which again effects the torque curve, you may loose some low end torque, but I doubt you will notice it.

Zitat von Nifty50;90702

Interesting! Are you able to expand at all on this suspicion? What would be the symptoms and effects on the engine's performance?

An O2 Sensor needs at least 650°C to start operating. somewhere between 700-850°C is a good operating range. Only when it's hot enough, it delivers reliable values.

One can argue that the exhaust gas will provide that heat. Unfortunately, that may not be the case in all engine operating ranges. Especially at low load (constant low speed driving or idling) the heat in the exhaust drops significantly along the pipes. Modern engines have the O2 Sensors fitted almost immediately after the engine (where temperatures will - in average - are well below 900°C (except for high speed high load driving). Additionally, O2 Sensors are heated internally.

On our 8er, such a heating is - to my knowledge - not implemented. It has been proposed in the original design, but (again, afaik) wasn't realised.
The cats are quite hot and - I assume - their heat is used for the O2 sensors to operate well.

I don't know whether the sensor transmits lean or rich values when not at operating temperature. I assume lean.

Cats are about £200 each inc vat here:-

No affeliation etc..

http://www.onlineautomotive.co…ts.aspx?CategoryID=114063

The V8's all have heated Oxygen sensors, and from the circuit-diagrams, the V12's are heated as well.

Zitat von E31Gill;90736

Cats are about £200 each inc vat here:-

No affeliation etc..

http://www.onlineautomotive.co…ts.aspx?CategoryID=114063

At that price, there's probably little or no platinum in them. They look like the ones enclosed in 'aluminised' steel, as sold on eBay. I doubt they'd last much more than one year. But, it depends in what you want with the car.

Nogie I think you are correct and if my memory serves me right the o2 sensors are in front of the cats - I cannot test this as iam away from the car right now but will try to remember to look when I get back.

I have not noticed any change in the cars performance torque or otherwise - but the reasons why sound mechanically feasable

They are indeed in front of the CATs

Sometimes I amaze myself

Item #23 is the O2 sensor. item #29 exhaust temperature probe appears to have been removed from the M70 9/91, and at the same time added to the S70.
(I suspect it is a ETK error for the M70 and that this sensor was added, not removed, I dont think I have it on my 6/90 M70)

Note: M70 and S70 V12 configuration.




This is the M73 configuration, with a O2 sensor both before and after the cat's items #7 and #8





This is the M60 4.0 V8 config.
One single front mounted O2 sensor.



This is the M62 4.4 V8 configuration, again two o2 sensors, one front and one behind the cat.