Unofficialbmw.com

[haber]

It happens that we have a full good e and a full i exhaust system for the two cars we are working on. Can anyone say for sure if there are interchangable between an e and i engine? In other words if you put the full system on from the manifold back will it matter which you use?

I also notice from the parts listing that an e and i exhaust manifold is slightly different but a super eta uses the same as an i. Anybody know if there is any substantial difference again and if swapping parts is acceptable?

We might put the e system on the tired old i car and the i system on the e which may turn into a hybrid e to i conversion or turbo or ??.

Thanks,
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[robert1700]

Two big issues, the exhaust cover plates near the gas tank are different and the O2 sensor location. They will bolt at the exhaust manifolds fine.

You can easily move the O2 sensor by adding or subtracting the wires. You will need to change the exhaust covers to which exhaust system you are using. This will make sense once you are under the car.
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1987 325i Convertible
51,000+ miles
Sold to a friend car is now destroyed, such a same.

[m78]

If they are interchangable and nearly identical, what is the advantage in swapping them? what is to be gained?
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Lachssilber Metallic 203 1988 325i sedan with 200,xxx miles

Top Speed 220 km/h

(OO=00=OO)

[haber]

Well the i exhaust is dual all the way back and will probably support more flow if we increase the power on the 2.7 as planned. And it sounds better.

The 2.7 liter is the car my son intends to keep while the i car is tired and will probably not hang around once fixed. It's getting all the less desirable parts we have just to get it running OK again.
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[idanity]

the single pipe is much lighter...
but i am running the oem dual pipes for now, this will be changing dramatically soon, and what i do know is that the oem pipes will last forever, while everyone i know who had theirs replaced, has rusted out in 5 years ...*or less

oem ftw, and if he will be going turbo, then single pipe.
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[haber]

just a follow up...

First, they are both pretty heavy but I did not think to weight the two systems. BMWFans should list the component weights if curious.

So I moved the e exhaust to the i car since the i system had broken welds all around the muffler inlet and really droned inside at cruising speed. Sounded good outside but terrible inside. My daughter appreciates the quiet car while my son would like a little more noise for his. Since the dual pipe cat section is in good shape it will go on his car and it will get a new muffler minimum at the rear since the rest of the pipes are good or a SS cat back system maybe.

Any suggestions on just a muffler with dual inlet and outlet?

I see the difference in the rear tunnel heat shield but not sure why they changed it since the eta shield is big enough for the dual and runs basically the same route. It looks like they just added weight as the i shield is monstrous and basically looks like it could have the pipes run left or right out the back. No reason for that I can see?

Why they put the eta O2 sensor where they did is a mystery. Tucked between the trans support brace and tunnel brace I think. They must have had way to many beers for lunch that day since the i location is much easier to work with. I did lengthen the i 4 wire sensor and this was more trouble than swapping the whole exhaust system. You can't solder connections on O2 wire so I had to crimp and seal splices at the sensor end then pull the connector apart to solder the wires to the terminals at the firewall end. I used a 4 cond Belden wire rated for 105C for the extension with an overall braid shield and ran it sorta up along the top of the transmission rather than around the drives side.

Another difference is the later cars went to two hangers for the muffler and have an extra hanging point for the rubber donut. but the mufflers are almost identical in circumference so the dual brackets work on the old muffler and vice versa just fine.

As I posted in the "325i running away" the mixed up components passed emissions testing with flying colors. Thankfully, one less thing I can stop worrying about on a car now 600 miles away.
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