Exhausts interchangeable?

[Cloggy Saint]

As above, will a pre-facelift fit a facelift car? Cheers.

[Grrrmachine]

Which engine? M10 was in pre and post and that should swap. M20 seems to have had half a dozen different systems, and you need the whole lot from engine to tail for it to work.

[Cloggy Saint]

M20 engine. I just ordered a rear box for a 2 piece but since noticed it's specified for models from '85 - '87 and mine's from '89.

[Grrrmachine]

I think you'll be sending that back. Pretty sure all pre-facelift systems have the rear box and about a foot of pipe that just gets past the rear beam. In contrast, the facelift rear end has well over a metre of pipework from the backbox, mating up at the back of the catalyst with six inches to spare.

I fitted my rear exhaust this morning

[capri_rob]

My bronzit pre-facelift '87 had a 3 piece system, the touring ( early '88 ) has a 2 piece - I understand that they are not interchangeable - the 3 piece front section wont bolt up to the manifold designed for a 2 piece as the flanges are different.

I believe you can chop the pipes after the front box and fit a 3 piece rear box but it requires some bodgery to get right.

I do believe also that some facelift cars ( despite my touring being an early one with a 2 piece system ) were fitted with 3 piece systems

If you don't mind swapping the manifold there are many more 3 piece options available than 2 piece if you want to go aftermarket.

[Cloggy Saint]

The plan is to change my touring from 2 piece to 3 in order to lose the cat' and to accomodate a 6 branch without the need to cut/weld. Sooo, is a pre-facelift 3 piece back box the same as a facelift 3 piece back box?

[capri_rob]

You need to change the manifold

Plus you need a back box with either angled or S-Shaped tailpipes - pre facelift 3 piece rear boxes where the pipes exit from the centre of the box will NOT clear your rear valance


The lower box is the 3 piece from my pre-facelift 325i - wouldnt fit as the pipes would foul the valance - not the best pic but you get the idea

The Scorpion rear boxes that have straight-outlets are offset to the left to clear the valance

prefacelifts dont have this issue as there is no cutout in the valance

[Cloggy Saint]

I plan on changing the manifold. I ordered the backbox from ECP, anyone know if they'll be angled or straight? Cheers for the help Rob.

[gooner1]

No worries, Ed.

Ooops, wrong Rob.

[capri_rob]

No probs mate - just had a quick look on ebay most of the aftermarket standard looking exhausts seem to have angled pipes which should be fine - this shows what it needs to look like if they come out straight :

http://www.ebay.co.uk/itm/BMW-325-EXHAU ... 4cf6cd16a7

[Cloggy Saint]

No worries, Ed.

Ooops, wrong Rob.

Thanks to both Robs! Next question, why can't i find a 3 piece centre section anywhere? Ecp, GSF and CP4L are all out of stock and i can't find one on ebay

[Grrrmachine]

Cloggy, when I had my Hartge manifold I got my hands on a cheapo 323i centre section - that's designed to work with the "short" rear box, but I still had to fab up some pipes from the centre to the manifold because I didn't have the original Hartge ones.

What 6-branch are you using?

[Cloggy Saint]

Hottuning

[Grrrmachine]

In that case, by the looks of it it's supposed to mate up to the pre-facelift centre, which is part number 18121177935.

Here's a 20 quid cheapie:

http://allegro.pl/tlumik-srodkowy-bmw-e ... 80835.html

You'll also need to find the special exhaust clamps and gaskets, and the pre-facelifts use a different kind of mount at the gearbox; it wraps itself around the two pipes, instead of bolting to a pre-welded mount.

I've got a brand new unused BMW original one here...

[Cloggy Saint]

I've got a brand new unused BMW original one here...

A brand new unused centre section?

[Grrrmachine]

No, the clamp to hold the pipes to the gearbox - it's different to the catalyser system.

Non-cat (parts 12 and 16):



Cat (part4):

[gooner1]

Hottuning

See, didn't hurt too much did it?

[Cloggy Saint]

I'm sure it would be diferent if a certain member wasn't banged up!

[Cloggy Saint]

No, the clamp to hold the pipes to the gearbox - it's different to the catalyser system.

Non-cat (parts 12 and 16):



Cat (part4):

Wouldn't I need #22 as well? Are you selling?

[Grrrmachine]

Got my numbers mixed up You should have 12 already on your gearbox, it's 17 and 22 you'll need, once you get all your other parts. I've got it in my spares stash if you want to Paypal me some beer tokens (they're not that much from BMW anyway - about 12 quid for the pair).

[gooner1]

Ed, you do have the X pipe section, don't you

[Cloggy Saint]

Ed, you do have the X pipe section, don't you

Yes.

[gooner1]

Ed, you do have the X pipe section, don't you

Yes.

..... and you know that you don't need the downpipes from
a 3 piece system?

Lifted from an old thread.

In effect,the BTB/hottuning and similar manifolds directly replace the stock manifold AND downpipe,ending at the forward end of the centre section of the three piece system.

Therefore, no flanges to cut.

[Grrrmachine]

Ed, have you got the rings that slide over the downpipes that allow you to bolt it to the centre section? If not I'll chuck them in the envelope with the clamp.

[Cloggy Saint]

This is getting confusing now! The downpipe from the hottuning manifold has a sleeve type fitting so how can I use these to mate up with the flange on the centre section?

[Grrrmachine]

Downpipe will have sleeves to X-pipe, and X-pipe will have flanges to the centre section.

[Cloggy Saint]

X-pipe has sleeves at both ends

[Grrrmachine]

I suppose it's because they don't know what centre section you'll be using. You may need to take your X-pipe to an exhaust place and have them expand the lip on one end if you plan to mate it to a standard BMW centre section, so I'll chuck in a pair of these old flanges for you. Otherwise you'll need to cut the corresponding lips off your centre section and use a sleeve to join them, but considering the angles involved it can get very tight there.

[Cloggy Saint]

Cheers Grrr, if you can include a pair of rings that would be great. This whole thing is turning into a complete ball-ache, I was under the impression it would be a plug and play job.

[Grrrmachine]

It's not that much of a ballache; look:



Follow the pipes right to left. You have your twin-port downpipe which drops at a 45-degree angle to a pair of straights. That's your new hottuning manifold and X-pipe. Then it kinks 45 degrees to the right, and you can see the flanged joints on the centre section. The idea is that one of the X-pipes slides into one of the centre section pipes, so no flange needed (just the clamp). The other pair of pipes come together as flanges, and use a special crush gasket between them.



Here's the clamps in action (this is the rear box, but it's the same principle):



And here's how the pipes on my Hartge lined up with my cheapo 323i centre section:



Finally, if you don't want to take it to a specialist, you can get "repair sleeves" which slot over one of your X-pipes and provide a flange. A standard exhaust clamp will hold it in place:



I really need to dump all this in the Wiki...

[gooner1]

Grrr, where's the X pipe section in the first pic?

[Grrrmachine]

Gooner, that pic is just a standard 3-piece system. No six-branch, no x-pipe.

[gooner1]

Aaah, got you mate. Was still on my first Java intake.

[Cloggy Saint]

Cheers for the pics Grrr, I'll just have to get all the bits together and see what i can work out.

[Grrrmachine]

No worries. I've dropped the clamps in the box with the mount, and I've lopped off some flanges from a cheap exhaust so you can see what's needed. Should be with you shortly.