how to mount magnaflow on Eta with 2 pipes

[z6ne]

Reposting this from exhaust subforum:

So I have an 86 Eta, and it has dual pipes coming from headers into the stock muffler. I don't know if this is stock or not because I also think the cat has been deleted.

I'm looking into a used magnaflow for a fair price, and have a few questions on mounting it. This muffler has only a single inlet pipe, waiting on more info for it (part number and diameter of inlet pipe).

My questions are these:

Are the dual pipes on an Eta stock? The PO did a bunch of wierd shit to the car so I wouldn't be surprised if they are not stock.

Is it advisable to use a Y pipe to divert the 2 pipes into 1 pipe, then to muffler inlet? Is there a desirable place to do this to minimize any loss in airflow? (right in front of muffler VS back further towards headers?)

My county does not require emissions testing on a car of this age, so are there any positives/negatives of leaving the Cat. off? Should I get a resonator? Does this only affect sound or does it have other effects?

sorry for all the noob questions, I searched a lot on multiple forums and could only come up with so much. thanks for any advice

[Vivek]

Nope, it looks like he switched a full I exhaust from the manifolds back. On an eta it merges into 1 and goes 2 manifolds->down pipe (single outlet)->cat->resonator (I think)->muffler. it's basically the same on a stock 325i except it's dual pipes the whole way through.

[z6ne]

so how far back should I put the Y pipe on there? Or is that not a good option?

[Vivek]

It depends on the diameter of the inlet to the muffler (if it's too small you should consider a different muffler since it could cause a bit too much back pressure). I'm no exhaust designer and I don't know the physics of how the gases flow, so I can't comment on the ideal place for where it should go, but I'd assume as close to the muffler as possible would be logical.

[z6ne]

thanks for the input. Are there any people on here that are skilled in exhaust setups?

Dude's only asking $35 for a magnaflow used a couple times and taken off. I'm yet to get a part # from him but I'm poor and building my car bit by bit, so every deal helps.

[F34R]

thanks for the input. Are there any people on here that are skilled in exhaust setups?

Dude's only asking $35 for a magnaflow used a couple times and taken off. I'm yet to get a part # from him but I'm poor and building my car bit by bit, so every deal helps.

If it is a magnaflow I would snag it for 35.

[z6ne]

If it is a magnaflow I would snag it for 35.

Yeah I figured I would. Even if it doesnt end up working on my car (without expensive mods) I can at least sell it and make a bit of profit. He said it was only 65 new though, so I really just wanna figure out the model number to see what's up with it, maybe he just got a good discount.

[CabbE30]

The magnaflow is only going to give you sound over your current set up. The performance of the "i" exhaust is about maxed out already for the M20.

[F34R]

The magnaflow is only going to give you sound over your current set up. The performance of the "i" exhaust is about maxed out already for the M20.

i exhaust adds 19hp, known fact ;)

[z6ne]

i exhaust adds 19hp, known fact ;)

yeah I hear ebay chips add 35 :mrgreen:

[z6ne]

any tips on mounting it?

[z6ne]

ttt

[F34R]

any tips on mounting it?

Weld it on.

[z6ne]

Weld it on.

:zzz:

specifically the placement of the Y pipe