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Exhaust reducer sleeves 135i > 125i diameter

3K views 3 replies 2 participants last post by  Mike_RS 
#1 ·
I've got a Performance exhaust from my e82 125i and I was hoping to install this on my 135i. The 125i has a 2.5" diameter pipe and the 135 a 2.75" pipe, I was considering using an adapter to mate the two.

I know this inducing a very slight restriction just before the back box but it's only a 7mm step down and the fact the performance back box is a freer flowing box in comparison to the stock 135i back box would surely counteract any added back pressure by the adapter?

I know in an ideal world i should just get the 135i version which is 2.75 straight through. I'm not really looking to add performance by doing this, just a little more sound and get rid of the stock looking pipes until I eventually buy the 135i version later in the year.

Am I going to do any damage running a 7mm step down?
 
#2 ·
Turns out the 125i performance exhaust is exactly the same for the 135i! There is reducer pipe welded into the muffler to reduce the pipework to 2.5" to marry up to the 125i mid section. I'm going to cut out the 2.5" (63mm) pipe and weld in a 2.75" (70mm) which will then marry up perfectly to the 135i mid section with no restriction.

I'm going to start a separate thread on the project if anybody is interested :headbanger:
 
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