325i 320i exhausts

[Andros]

Are the 325i and the 320i exhaust systems the same or will I need to change the back box to a 325i for better performance?

[magpie]

if the 320i one has twin pipes all the way through it's the same.

[Andros]

Ok thanks

[pacerpete]

325 system actually SHOULD have a bigger bore all the way through and it has a bigger downp[pe flange, so no, a 325 system is not the same. Obviously most of these turds have been got at over the years and you may well come across a 320 with a 325 manifold and system and vice versa.

[Andros]

Well all it is I,ve had 325i fitted in my 320i and kept my 320 exhaust system as its fits so would I be better to get a 325 system in the future and would I gain more power with the 325 system on there?

[pacerpete]

Well all it is I,ve had 325i fitted in my 320i and kept my 320 exhaust system as its fits so would I be better to get a 325 system in the future and would I gain more power with the 325 system on there?

I would not bother , the difference between a quality 320 system and a crap 325 one will be negligible. Obviously if/when your system is fooked, it might be worth seeking out a 325 one but beware of the previously mentioned downppipe flange issue.

[Kedge]

I've also found that there is a difference between pre and post facelift downpipe flanges.

[B7]

I've also found that there is a difference between pre and post facelift downpipe flanges.

Corrct. There are 4 bolt flanges and 3 bolt flanges. 325 down pipes wont fit a 320 manifold as Pete says and there were also twin gasket manifolds as well where each down pipe had it's own triagular gasket.

http://www.realoem.com/bmw/partgrp.do?m ... g=18&fg=10

http://www.realoem.com/bmw/partgrp.do?m ... g=18&fg=05

[Gavla]

Are all 325i twin exhausts?

[pacerpete]

All 325i's had a twin pipe system. Pre facelift 320s had a single system as did early facelift 320s.

LHD cars had two manifolds with two separate triangular gaskets as mentioned by B7 above.

[HairyScreech]

The pipe diameter of the pre and post facelift pipes are the same except for about the first 8" of the down pipe, the pre facelift is smaller.
However this can be sorted by welding the first 8" of the post pipes to the pre down pipes.
(just something i had to do to mine and worth a note here).

[Simon13]

325i systems use 44mm bore pipework right the way through. 320 stuff is 40/38mm iirc

[Duke137]

Can I use a bit of scaffold pipe if I need to?

[Andros]

Does that mean the 325 manifold won't meet straight up to my 320 exhaust

[Andros]

My car is a pre face lift I think

[pony]

Anyone on here know for 325i preface lift without catalytic converter and post facelift with catalytic converter what is the difference in loudness ?