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dave 328 View Drop Down
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Joined: 21-October-2003
Location: United Kingdom
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Points: 835 		Direct Link To This Post Posted: 02-December-2004 at 06:58

Yours is too new kbannon. Has to be made/registered before August 92. So unfortunately you need to get a new cat.

Whats wrong with your cat?

I have seen some stuff called Cat Back (I think) which is added to the fuel and supossed to recoat the cat with the 'special' metals so it works again - not sure how affective it is, but they offer a guarantee!!

328 Coupe Sport, Digital climate, full leather, OBD computer, De-restricted with M50 manifold, big bore throttle, chippeduk remap, custom cold cone intake and X-brace
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kbannon View Drop Down
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E39 525i Sport Individual

Joined: 09-October-2002
Location: 64 Zoo Lane
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Points: 15508 		Direct Link To This Post Posted: 02-December-2004 at 05:36
does this apply to the E39? Any adverse effects? My cat is dead and with road tax due (€850), christmas (€loads) & an inspection II (€loads & loads!) on the horizon I would prefer to save some money!
Current: 2009 E60 520d "Sport" tractor
Previous: 1989 E30 320i SE
1997 E39 523i
2003 E39 525i Sport Individual
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dave 328 View Drop Down
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Points: 835 		Direct Link To This Post Posted: 02-December-2004 at 05:09

Or you could just knock out the cat's insides, then you'll be cat free and won't need to replace the pipe. Quite a few modern turbo diesel owners do this for better turbo spool up and the cat sin't required ona diesel for an MOT.

And as said you won't need to adjust ECU settings as the lambda corrects fuelling whether cat is fitted or not.



Edited by dave 328

328 Coupe Sport, Digital climate, full leather, OBD computer, De-restricted with M50 manifold, big bore throttle, chippeduk remap, custom cold cone intake and X-brace
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Savo View Drop Down
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Joined: 26-July-2004
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Points: 128 		Direct Link To This Post Posted: 01-December-2004 at 18:16

Thanks for the advice Andrew & Gordon, I think I'll leave the car as it is though its good to know that if the Cat ever gives me any bother I can just remove it. 

The Viper 2 chip has made a noticeable improvement to the car.  When I first installed the chip I went out for a blast, first impressions where that there was not really any change but later I took the car for a longer drive and was really surprised with the difference.  The car feels a lot more responsive and pulls a bit harder from low revs.  I managed to drive the car for four miles on the motorway keeping the mpg thingy on the dashboard above 30 varying my speed between 50 & 70 (up and down hills).  This would never happen normally.  I have just done 140 miles on £20 of petrol @ 84.9p per litre which I think is pretty good for my car considering in the past I have had it well down below the 100 mile mark!

I don't know anything about the Stone Brother Racing header pipes.



Edited by Savo



1992 525I Sport, Bilstein Sport Suspension. Viper 2 Chip
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Big Red View Drop Down
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Joined: 09-May-2004
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Points: 57 		Direct Link To This Post Posted: 01-December-2004 at 17:31

Removing the cat will make a slight difference in performance, as the exhaust gases will flow through the system easily.

You will not need to make any other modifications if you remove the cat.

Do not remove the 02 sensor, as you will put the engine management system into open loop all the time and will be overfuelling it.

The o2 sensor has no bearing on whether you have a cat fitted or not.

The o2 sensor senses oxygen in the exhaust gases, and adjusts the mixture accordingly.

The cats job is to burn of any excess gases as they are passed through it.

Once a cat reaches operating temp, the monolithe lights, and as the exhaust gases pass through it, the dangerous ones are burnt of.

Whether it has a cat or not, the o2 sensor still has to manage the engine fuelling.

cat just finishes the process of.

 

Hope this helps.

 

Regards,

 

Gordon
If it isn't broken, Don't try to fix it.
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Andrew Rolland View Drop Down
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Go away rain

Joined: 19-August-2004
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Points: 6579 		Direct Link To This Post Posted: 01-December-2004 at 03:13

The all important cut off date is 01.08.1992. Ref source www.buypartsby.co.uk/catalytic_mot.php

Cars registered before 01.08.1992 do not need to have a cat fitted to pass the emissions tests. 

Cars registered after 01.08.1992 need to have a cat fitted to pass the emissions tests.

Removing a cat is bit of a pointless exercise in cars registered before 01.08.1992 because you will need to faff around with the engine management settings to cope with the different exhaust back pressure, for example you don't need a lambda sensor anymore.  You will need a straight thru replacement pipe that bolts in the gap left from the cat or a complete new exhaust.

I had a 3.0i 24v Vauxhall Senator before which had twin cats (£700 worth if they went belly up!) but as mine was registered on 04.09.1990 it didn't need them for the emissions test.  Other Senator owners talked about removing them and fitting them with two straight pipes of the same length, they reckoned the power gain was about 10% or 20 bhp but if you didn't remap or re programme the ECU to run without the cats it would cause bother later. And sorting the ECU on such an old car isn't worth doing.

It's a lot of work to do it properly for not much gain so it's up to you.

Andrew
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Phantom_Mark View Drop Down
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Joined: 21-September-2004
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Points: 194 		Direct Link To This Post Posted: 30-November-2004 at 20:08

Im looking at doing mine aswel, also wanting that Viper2 chip when I can find time to go down and have it done, hows your car with that chip then mate ? mines a '91 model so same engine I do believe.

Also looking at those Stone Brother Racing header pipes, they claim between 15bhp and 30bhp extra power - 200 quid on ebay atm

<<<<< The only way is up >>>>

( unless your in a 5 series, then sideways is cool too )


91' 525 24v Sport, Stainless Race Manifolds, PowerFlo Stainless + Decat, Big Bore Throttle Body, Viper 2 Chip + 17's, std BMW Air Filter :D
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Savo View Drop Down
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Points: 128 		Direct Link To This Post Posted: 30-November-2004 at 16:56

Hi, my 525 is registered 01.01.92.  Am I right in thinking I can get away with removing the Cat?  If I do is there any improvement in power or mpg and is it easy enough to do?  I probably won't do it anyway, I'm just interested if anyone else has tried. 

Thanks

Andrew



1992 525I Sport, Bilstein Sport Suspension. Viper 2 Chip
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