[BigTuna63]

Here is a catless downpipe that I came across
https://www.maxpeedingrods.com/produ...%20%26%20Parts

Only obvious thing is the construction is 201 stainless vs. the nominal 304. 201 is cheaper than 304, but I have seen it in exhaust applications.

Anyone have any experience with this DP or 201 stainless in a downpipe application? THANKS.

[mike@x-ph.com]

I would not use any exhaust product with 201 construction.

Im not sure where you have seen it being used, but I'm not familiar with any good brand that uses 201 on any BMW exhaust application.

[Info@mad-us.com]

We use 304 stainless on all of our exhausts.

https://mad-us.com/mad-b58-downpipe-...chassis-supra/

[BigTuna63]

Originally Posted by Info@mad-us.com

We use 304 stainless on all of our exhausts.

https://mad-us.com/mad-b58-downpipe-...chassis-supra/

I see other companies including the diameter of their downpipe. For instance CTS states theirs is 4.5". What size is the MAD catless downpipe? Thanks and it appears to be offered at a great price.

[Info@mad-us.com]

Originally Posted by BigTuna63

I see other companies including the diameter of their downpipe. For instance CTS states theirs is 4.5". What size is the MAD catless downpipe? Thanks and it appears to be offered at a great price.

Our current downpipe is 4 inch. Our new version will be a 4.5 and we will also have a 5 inch available.

Don't expect any real gains between the 4 and 4.5 unless you have larger turbos.

[B58]

Originally Posted by Info@mad-us.com

we will also have a 5 inch available.

When will the 5" be available?

[Info@mad-us.com]

Originally Posted by B58

When will the 5" be available?

Mid to late December.

[Glemm1970]

Originally Posted by Info@mad-us.com

Our current downpipe is 4 inch. Our new version will be a 4.5 and we will also have a 5 inch available.

Don't expect any real gains between the 4 and 4.5 unless you have larger turbos.

Pure800 4inch Ok?

[Info@mad-us.com]

Originally Posted by Glemm1970

Pure800 4inch Ok?

Yeah 4 inch pipe is plenty. No matter what size Downpipe you get it tapers down to connect to the smaller exhaust piping. So unless you have a full custom exhaust you won't see any huge differences.

[Wires]

Devil's advocate here: Doesn't going from the header diameter to larger diameter back down to a smaller diameter to the midpipe (if catless) potentially reduce air flow?

Flow speed reduces in larger openings which then can result in becoming turbulent which impedes flow.

It feels that a lot of those options are pure marketing. I could see potential benefits if it went to a cat since it would be less restrictive.

Just asking....

[Info@mad-us.com]

Only thing you really gain would be a quicker turbo spool. Going from a large diameter and then having an aggressive reducer to match the stock exhaust size would not help Hp.

4- 4.5 inches is more than enough.

[WrxToBeamerGuy]

Originally Posted by Glemm1970

Pure800 4inch Ok?

4 inches has always been plenty, i've never had any complaints

[mike@x-ph.com]

Originally Posted by WrxToBeamerGuy

4 inches has always been plenty, i've never had any complaints