Exhaust Question

[MissileMech]

I have a '95 540i/6 and the cats installed on the car are P/N Boysen 1741431 & 1741432 and I can't find a reference that they are the right cats for my car. Another number on them is 411247 but neither seems to be identifiable as far as what model they are associated with. The closest I have found is P/N 18301437546 as far as physical appearance and application (E39 540i). Does anyone have an idea what car my cats are made for?

[Blak540i]

I know that magnaflow makes universals that fit the 540. You could start here http://www.turnermotorsport.com/BMW-...onverters.aspx

[mrgraybeard]

Those numbers are correct for an E34. I just checked them against some cats I have for a 1995 540i. 1741432 is for the right side, 1741431 is for the left. The other numbers I found were 411246 (r) and 411247 (l)

Looks like there's also a date of manufacture stamped on the housing, btw. It says 10 94 on the cat that came off my car, which was assembled in Oct. 1994.

[gixxerboy63]

I have a pair of universal cats to fit your car that I would sell cheap... Only used about 1500 miles! Worked great on my car, but I went to a completely new stainless steel exhaust setup when I decided to go FI....
I'll even throw in the X-pipe that was installed at the same time!

$300 for everything! PM me if interested.

[MissileMech]

Those numbers are correct for an E34. I just checked them against some cats I have for a 1995 540i. 1741432 is for the right side, 1741431 is for the left. The other numbers I found were 411246 (r) and 411247 (l)

Looks like there's also a date of manufacture stamped on the housing, btw. It says 10 94 on the cat that came off my car, which was assembled in Oct. 1994.

Thanks for the info. There appears to be a wrong cross brace between the pipes as well so I will have to get the right one since these are the correct cats.

I assume you shake them to check for loose material but what else can you do to check if they are still good?

[mrgraybeard]

I assume you shake them to check for loose material but what else can you do to check if they are still good?

Check to see how much exhaust back pressure you have. Hook up an exhaust back pressure gauge at the oxygen sensor bung on each converter and rev the engine to about 2500 rpm. If the gauge registers any significant increase in pressure from idle, the converter is restricted and needs replacing.

[MissileMech]

Check to see how much exhaust back pressure you have. Hook up an exhaust back pressure gauge at the oxygen sensor bung on each converter and rev the engine to about 2500 rpm. If the gauge registers any significant increase in pressure from idle, the converter is restricted and needs replacing.

Excellent...thanks!

Does anyone have a cross-brace forward of the cats that attaches to the transmission? I don't see one in realoem and the cross-brace I have doesn't attach to the trans properly. Is it possibly for a 4 or 5 speed trans?

Excellent...thanks!

Does anyone have a cross-brace forward of the cats that attaches to the transmission? I don't see one in realoem and the cross-brace I have doesn't attach to the trans properly. Is it possibly for a 4 or 5 speed trans?

Again, according to realoem the '95 530i has a bracket but it looks like it is not required on the 540. So, I think the PO installed (improperly) a 530 exhaust. Are there any brackets I need to install to support the exhaust forward of the cats?