320/325 exhaust question

[Chaos]

ive been told on the phase 2 cars the exhaust is basically the same on 2.0 and 2.5 anyone know how true this is ?

[TOURINGDADDY]

im pretty sure they are the same and im sure some 1 will correct me if wrong the only diff i know of is 2 piece and 3 piece

[Richy325iTouring]

thought you asked this before nick

[Chaos]

thought you asked this before nick

no rich.
i asked if there was a difference between scorpion for 320 and 325 not standard ehxausts - and besides no one replied.

[rowemeister]

I'm pretty sure the bore of the 325 exhaust is larger than the 320 bore. Also is the later 320 exhaust a twin pipe from the manifold back like the 325?

[Simon13]

a 325i system will fit on a 320 provided it has a 2.5 manifold i tink!

320's are quite a restricted engine

[Wilson]

I'm sure some 320 pipes are single pipe from centre back

[Brianmoooore]

A couple of months ago I tried to put the rear box from a 320 touring on a 325 touring.
The two boxes had been side by side on the floor and appeared to be identical (apart from the rot in the 325 one).
When I tried to fit it, I found, after much cursing, that the pipe that slides over the stub pipe on the front box of the 325 system, was very slightly too small.

[TOURINGDADDY]

well guess that means i was wrong

[rowemeister]

So the moral of this story is don't believe TouringDaddy . lol

[Simon13]

320 is smaller bore pipe is what i'm thinking

[Brianmoooore]

I had always thought they were the same, untill I tried as above.
The difference in diameter is very small, and I don't think there would be a problem fitting a 325 back box to a 320.
I was pretty pissed off when I found it wouldn't fit, after I thought I'd struck lucky when I found a new rear box on a 320 breaker I'd bought, and had gone to the trouble of taking both boxes off.

[Simon]

I've just gone through the ETK, and compared all part numbers between a 1990 320i and a 1990 325i. Manifolds are identical part numbers, centre boxes are identical part numbers, and rear boxes are different.

Surely if the centre boxes are the same, then the pipe diameters for the rear boxes are going to be the same? I have a suspicion that the different part numbers may be the way the tailpipe exits?

I've managed to fit a 325i back box, to a 320i centre box no problem, and vice versa, a 320i back box to a 325i centre box.

[Martinaston]

I've got (what i was told is) a 325 system on a 320 and had no problems fitting it.

If as some of the posts say the rear pipe is smaller can you not just flare the pipe to make it fit and use a U-bolt.
(yes i too have seen the muppets at kwik-fit)

[Brianmoooore]

I've got another 325 touring that needs a new rear box in the next week or so. I'll try the 320 box on that, giving myself a bit more time, this time.
Yea, I could probably make it fit by sawing two cuts along the pipe with a hacksaw and opening it up a bit

[koos]

my 320 has twin pipes from the manifold all the way back, original middle box from new 1991, quality exhaust, rear one only replaced recently.

[Brianmoooore]

Tried the 320 rear box on another 325 touring today, and the reults were the same as before.
The stub of pipe on one side of the 325 front box, that slides inside the pipe to the rear box, is about 1mm 1.5mm too big to fit in.
The socket on a 325 rear box is about 2mm bigger than that on the 320 box.
Strange thing is, it only appears to be the stub and socket that are a different size. The rest of the pipe, and the other parallel pipe appear to be the same on the 320 and 325.
Ended up making four cuts with a hacksaw in the belled section at the end of the 320 box, forcing the box onto the stub pipe of a spare 325 front box, and MIG welding over the opened up saw cuts. The clamp on the 320 box had a big enough internal diameter to allow the pipe to be expanded.

[e30-320i]

my 320(f plate) geos into single pipe from centre back.

[Brianmoooore]

All mine are tourings. I think they always had full twin pipe systems.

[telski789]

the 320 manifold definetly has smaller holes in the flange which meets the exhaust manifold,other than that it will fit. if your going to put a 325 system on a 320i you'd be silly not to fit a 325i exhaust manifold. dont put a 320i exhaust on a 325i,you'll restrict the flow bucketloads.

Tel

[Simon]

the 320 manifold definetly has smaller holes in the flange which meets the exhaust manifold,other than that it will fit. if your going to put a 325 system on a 320i you'd be silly not to fit a 325i exhaust manifold. dont put a 320i exhaust on a 325i,you'll restrict the flow bucketloads.

Tel

ETK says different.

[dazleeds]

i did have a full 325i system on my 320i but middle box went so put original system back on but left the 325 manifold as i sheared a stud fitting it and didnt wanna risk anymore studs and all fitted straight on and goes well
but i have heard the ports are slightly bigger for the 25 Daz

[Simon]

The ports are different, but the manifolds are the same...even the exhaust manifold gaskets are the same size between 320i/325i.

[telski789]

well i have 2 manifolds,one off my 320i lump and the other off my last 325i lump and the sizes are different,probably about 10mm

[Wilson]

well i have 2 manifolds,one off my 320i lump and the other off my last 325i lump and the sizes are different,probably about 10mm

10mm is a lot.. are you sure?

[Simon]

well i have 2 manifolds,one off my 320i lump and the other off my last 325i lump and the sizes are different,probably about 10mm

Can you do some pics?

I've checked every number on the etk, only very early 320i has different manifold. Every other number between 320i/325i is identical, even ecp and gsf list identical part numbers for their exhaust manifold gaskets, these wouldn't be the same if they had different bores.