[flinchy]

Originally Posted by ucsbwsr

I highly doubt this flows worse than "stock." Stock has cats, a resonator, and a muffler (on my 535xi). Also the oem piping isn't 2.5" like some may think, rather it is metric and ends up being ~2.3". Furthermore my piping (maybe E9X too) is compromised/squished at the beginning of the cat-back portion which would be a bottleneck if the rest of the system had c-converters etc. removed.

Out of curiosity what measurements did you use for "stock exhaust".

Evan

oh yeah, i'm sure because it's got no cats and the muffler is free-er flowing, it's not necessarily a downgrade

but.. N55 mids (cat delete) and a free-er flowing muffler on the stock dimension twin pipes...

or heck, the aftermarket options for direct bolt on that come in 2.5"

measurements used were the inner diameter of the pipes. Yeah there's a crush or two that MIGHT be smaller, but marginally. I actually think it's something like 2.36" from memory even, not 2.25".

I mean.. people have done 600+hp on the stock setup, so it's not bad.

Not saying this exhaust is a bad idea either, it clearly sounds AWESOME.

Originally Posted by Yournamehere90

Not that I agree with Flinchy's opinion, but he did say 2.25", not 2.5"

It's not so much opinion as math. Yeah i worded it badly as i'd assume 100% stock vs this = this wins out in flow.. but a couple of tweaks to stock will outflow this

It explains why this exhaust sounds really nice on cold start. because it's smaller. the larger you go, the worse they sound on cold start from what i've heard haha.

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When it comes to exhausts (to me personally), sound > flow, all day! (Within reason)

[ucsbwsr]

flinchy, do you have any links/resources regarding flow rates for different diameter piping? I am interested to see some info as it pertains to exhaust and intake piping. Thanks in advance!

Evan

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All parts ordered, but the install will take a while as my workshop is installing my Dodson DCT clutch packs and upgraded DCT pan.

I've decided to go with a dual 3" inlet to single 3.5" outlet. I hope this plays out well, as this thread was the reason I did it! Haha

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Thanks to all the inspiration on this thread, I finally got mine done today!

I added a hi-flow cat in the middle, and my rear mufflers are valvetronic, so pretty much straight through when open.

[ucsbwsr]

Originally Posted by _ink

Thanks to all the inspiration on this thread, I finally got mine done today!

I added a hi-flow cat in the middle, and my rear mufflers are valvetronic, so pretty much straight through when open.

Exhaust looks great, what will it do in the rear section? Split to the traditional 335is dual outlet? It will be interesting to hear what it sounds like with that little C-converter and no resonator. What is the cell count on the converter?

Also, remind me of what turbos you are running?

It looks like the merge collector starts with 2.5" flanges and enlarges to 3" dia shortly after, is this correct?

Evan

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Originally Posted by ucsbwsr

Exhaust looks great, what will it do in the rear section? Split to the traditional 335is dual outlet? It will be interesting to hear what it sounds like with that little C-converter and no resonator. What is the cell count on the converter?

Also, remind me of what turbos you are running?

It looks like the merge collector starts with 2.5" flanges and enlarges to 3" dia shortly after, is this correct?

Evan

I stuffed up on my order of the merge collector, as I thought the AR's were 3" true all the way, they actually reduce to 2.5" so I had to purchase some 3" - 2.5" reducers.

Details of the Cat are 100 CPSI with a 5" body, so it's a race cat with the largest possible internal holes.

I was running an ipe exhaust, so I've retained the rear mufflers which are valvetronic, pic below as well as the centre section comparison.

I'm running RB's.

[big_ed]

Originally Posted by _ink

All parts ordered, but the install will take a while as my workshop is installing my Dodson DCT clutch packs and upgraded DCT pan.

I've decided to go with a dual 3" inlet to single 3.5" outlet. I hope this plays out well, as this thread was the reason I did it! Haha

Hey man, keep us posted. I want to know how your setup turned out as well...and how it sounds also! Maybe you end up motivating someone else!

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Originally Posted by big_ed

Hey man, keep us posted. I want to know how your setup turned out as well...and how it sounds also! Maybe you end up motivating someone else!

It's still early days...

But for me the new system is actually a lot quieter than previous, and you know that awkward moment when you're in a high gear, low rpm and you mash the pedal, there's a 'drone fart' moment under 3000rpms? That has completely disappeared.

I'm putting both of this down to the introduction of the 3.5" pipe allowing the exhaust gases to flow much much better and easier. I could probably remove the cat, however I don't really want to deal with the smoke and smell that comes with it.

The other 2 things I have observed with this are:

1. Torque curve has shifted.. I've lost the perky nature of the RB's under the 3k rev range, will speak to my tuner about this.

2. Gear shifts are a lot smoother (yes, even noticeable on the DCT)