Replacement exhausts - anyone have a review of BM Catalysts.

[VPCAPTAIN]

Hi all a bit off topic but my 2011 E92 318i coupe has a blowing exhaust flexi.

Surprisingly all of the Indy garages I’ve visited have said no to cutting the flexi out and fitting a new flexi that’ bolts straight onto the CAT outlet flange.  Suitable parts are available at AUTODOC.  but they all say no.

looking at Realoem I now have the option of replacing the front - mid section of exhaust with both a NOX catalyst and Silencer included.

inputting the part number from Realoem gives 18307568057 ( RP CATALYTIC CONVERTER + Front Muffler)

BM CATALYSTS say there part is OEM compatible and it’s listed as BM92053H with fitting kit FK92053B plus a 60mm dia joining clamp to attach the the rear pipe.

retails around £350 from Autoparts or Parts in Motion.

 

just after an opinion if anyone has on their durability etc 

 

thanks Rob 

Edited March 18, 2023 by VPCAPTAIN

[Ray112]

In all fairness, these garages sound  like simply don't have a welder. I can't imagine even one reason why just flexi pipe can't be replaced unless your exhaust pipe is quite rusted and brittle already, which usually isn't common with BMW exhausts. Replacing just flexi pipe is well known practice, which been used for decades. It just doesn't make sense to replace original catalytic converter with aftermarket one when all it needs is new flexi pipe. 

There's usually even clamp on options available, where you cut off old flexi pipe and new one is little wider, so you just push it over your exhaust pipe. Then tighten with U clamps. No need for welding then. 

So I wouldn't replace whole catalyst, just have talk with couple more garages.

[VPCAPTAIN]

Thanks @Ray112 appreciate your input and totally agree garages just being lazy or wanting easy money swapping out exhaust rather than fitting a relatively simple  unbolt the flange and cut out the flexi (which is the weakest link) and most likely needing replacing before the rest of the exhaust pipe.  
 

will do some more knocking on garage doors 

[Keliuss]

My BM Cats experience:

Original Cat was stolen off my 95' E34. Bought a BM Cat, fitted it a week before test and it passed emissions. Cat section pretty long, it's from manifold down to mid section. Exhaust developed a rattle about 500 miles later. Substrate in the cat broke loose inside the canister. I'm in Ireland so wasn't worth trying to claim warranty as I'd have to ship it back to UK. Ordered another BM Cat and cut open the first to inspect and keep as a "straight pipe". Canister is about 10" long but the substrate only occupies approx. 2.5". Reminiscent of a packet of crisps these days - 20% crisps, 80% air. 

Used my empty "straight pipe" until test time again. Fitted second new BM cat, drove it about 300 miles and then tested. Failed emissions. Booked it in again a week later, even worse results. Tried one more time but emissions defo getting worse. Then I noticed that familiar sounding rattle again. Yep, same thing.

Took the car to an exhaust specialist, really nice guy who knows his stuff. Told me the BM Cats are "complete shite". Said he would only ever use one in some sort of theoretical emergency, if he had no other choice and had to put something onto a car to get it through the test. 

The Walker branded cat he put on had much more substrate material. Perhaps 8" or so.

You know the old saying, "Go cheap, go twice", or in the case of idiots like me three times lol.

Keliuss

Edited April 6, 2023 by Keliuss