[parksjm7]

The flange where the midpipes meet the downpipes appear rough, but mating surface is smooth and do not rattle. Wanted to get opinions on whether I should put these on or not - Will clamp them on an otherwise stock exhaust system - keeping primary cats and stock e92 N54 muffler (no Perf. Exhaust)

My concerns:

1 - Rattling by the lower V-brace at the end of where secondary cats used to be - these are slightly wider than the stock midpipes

2 - Slight loss of low end torque? I've seen this from 135i N54 folks who change their midpipes to N55 version that dont' have secondary cats. I believe stock mids are 2.35" diameter vs these are ~2.5" dia, slightly wider, as far as I know that reduces backpressure by a miniscule amount, but I don't think it's enough to make a difference.

Thanks in advance for your inputs!

[Bimmer_Bro]

Originally Posted by parksjm7

The flange where the midpipes meet the downpipes appear rough, but mating surface is smooth and do not rattle. Wanted to get opinions on whether I should put these on or not - Will clamp them on an otherwise stock exhaust system - keeping primary cats and stock e92 N54 muffler (no Perf. Exhaust)

My concerns:

1 - Rattling by the lower V-brace at the end of where secondary cats used to be - these are slightly wider than the stock midpipes

2 - Slight loss of low end torque? I've seen this from 135i N54 folks who change their midpipes to N55 version that dont' have secondary cats. I believe stock mids are 2.35" diameter vs these are ~2.5" dia, slightly wider, as far as I know that reduces backpressure by a miniscule amount, but I don't think it's enough to make a difference.

Thanks in advance for your inputs!

You should be fine. My exhaust is 3.5 inch and I didn't lose any low end. The less back pressure on the turbos the better.
It might sound very raspy tho. I know a lot of guys put In a vibrant resonator on the mid pipe to combat this.

[parksjm7]

Originally Posted by Bimmer_Bro

You should be fine. My exhaust is 3.5 inch and I didn't lose any low end. The less back pressure on the turbos the better.
It might sound very raspy tho. I know a lot of guys put In a vibrant resonator on the mid pipe to combat this.

Yes, I heard without both primary and secondary cats there will be rasp, however I have the stock downpipes with primary cats and stock mufflers installed, do you think it will still be too much rasp?

[Bimmer_Bro]

Originally Posted by parksjm7

Yes, I heard without both primary and secondary cats there will be rasp, however I have the stock downpipes with primary cats installed, do you think it will still be too much rasp?

That's a good question, I am not sure. Most have the primary's gone as well. I will let someone else chime in on this or you may just have to wing it! It's easy for an exhaust shop to add a resonator if needed.

[haaken675]

Not to get too far off topic, but do you have any info or a link for the midpipe? I did a quick search and came up empty. Would love an aftermarket midpipe if the bends were not crushed like OEM and the cats were already out. Would make putting in my resonators easier.

[parksjm7]

Originally Posted by haaken675

Not to get too far off topic, but do you have any info or a link for the midpipe? I did a quick search and came up empty. Would love an aftermarket midpipe if the bends were not crushed like OEM and the cats were already out. Would make putting in my resonators easier.

Riss Racing went out of business a long time ago - around 2010 I believe.

It appears there is one available from cp-e for the 1series:

https://www.bimmerworld.com/Exhaust/...i-N54-N55.html

[haaken675]

Originally Posted by parksjm7

Riss Racing went out of business a long time ago - around 2010 I believe.

It appears there is one available from cp-e for the 1series:

https://www.bimmerworld.com/Exhaust/...i-N54-N55.html

That would explain why searching didn't bring anything up!