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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > Modifed n55 exhaust



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      09-20-2010, 09:04 PM   #1
Calvin@Vishnu
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Modifed n55 exhaust

A few days ago, we whipped up a quick 'n dirty exhaust for our n55 135. Nothing earth-shattering and completely conventional. In fact, it's conceptually identical to what we made years ago and still have on our n54 335.

We replaced the factory midpipe and installed a fully divorced dual 2.5" pipes. This removed the stock resonator and 2-to-1 merge:


And we also removed the factory single entry muffler and replaced it with dual 2.5" staight-thru Magnaflow exhausts. The piping was made of mild steel. And crush bent. Mandrel bending would be preferable but, for now, this will work just fine. It should be noted that crush bent exhausts are really quite fine in systems that don't require sharp bends. In the case of our car, the pipes are reasonably straight (no acute angles):



The factory downpipe:

It splits off into 2 outlets so that BMW could still use the same exhaust components they used for the twin turbo n54. We retained this component since it houses the single catalytic converter. We were tempted to go fully catless for testing purposes. But that will have to wait for the time being.

The factory 135 muffler:

Single Entry, dual outlet. The left outlet is open/closed by the vacuum operated actuator. The internal layout of the muffler housing is pretty convoluted. No doubt designed for sound muffling and not for minimum restriction.

Replaced by this:

We decided to go with dual/parallel mufflers since we would essentially be cutting exhaust flow velocity/volume in half. Which basically makes the mufflers more effective both in terms of sound reduction and exhaust flow.

View from the back:

We added some simple 2.75" SS tips and oriented that with a nice gangsta lean. Enough to look a little different while not screaming LOOK AT ME.

Sound:
Very quiet! Using two mufflers instead of one makes HUGE difference. The exhaust growl is a bit deeper in note. Not much louder though. Which is unfortuante since we were hoping for a more inspiring sound!

Power:
It helps! Haven't re-dyno'd the car yet. With the factory muffler, we were seeing 275whp with the factory tune and 335whp with the Procede. I certainly hope we've picked up another 10whp. Should know soon enough
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      09-20-2010, 09:14 PM   #2
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So thats the hookup that Shiv has from the East Coast!! Now we know where to bring our modified cars!! lol
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      09-20-2010, 09:14 PM   #3
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Not feelin the postion of the tips :/
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      09-20-2010, 09:41 PM   #4
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Quote:
Originally Posted by ak335 View Post
Not feelin the postion of the tips :/
+1

crush bends
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      09-20-2010, 09:57 PM   #5
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Quote:
Originally Posted by cn555ic View Post
So thats the hookup that Shiv has from the East Coast!! Now we know where to bring our modified cars!! lol
lol.. not quite. The car is front the East Coast. All the exhaust work was done here in CA. Only took a couple of hours. And should give us a definitive idea of how much power we can expect out of a catback in an n55.

Also, by no means am I suggesting that you guys should install crush bent piping in your BMW. We just did it for quick and dirty testing purposes. Cutting mandrel bends and piecing together a production quality exhaust wasn't possible (or needed) given our time constraints
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      09-20-2010, 10:13 PM   #6
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I hope the two mufflers were welded together... or else I think they would bang against each other...
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      09-20-2010, 10:16 PM   #7
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Quote:
Originally Posted by SfValley335i View Post
I hope the two mufflers were welded together... or else I think they would bang against each other...
Yep. They are welded together. And all original hanger points were used. The whole exhaust barely moves 1/4" when pushed/pulled. It's not going to vibrate or rub against anything.
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      09-20-2010, 11:00 PM   #8
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dude...looks pretty damn good! i like how its angled

but most important VIDEOS!!!!!!!!! :0)
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      09-20-2010, 11:13 PM   #9
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Calvin, you guys gonna order up AR's new downpipe? Would be a great addition to that setup.
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      09-20-2010, 11:47 PM   #10
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love the tips.....
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      09-21-2010, 12:29 AM   #11
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Nice work Calvin!!

That car ripped without the exhaust... Will be interesting to see how it goes now. I was really impressed how well the N55 can go with just a Procede. I have a N54 135I 6MT with Procede, DCI and decat pipes, but the 135I N55 just with Procede seems to have the measure of my N54 with more mods. I think we will see some really nice results from the N55 platform, and we already have it in a few months at the same level the N54 took years to get to.

Adrian
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      09-21-2010, 10:43 AM   #12
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Quote:
Originally Posted by Calvin@Vishnu View Post

The factory 135 muffler:

Single Entry, dual outlet. The left outlet is open/closed by the vacuum operated actuator. The internal layout of the muffler housing is pretty convoluted. No doubt designed for sound muffling and not for minimum restriction.
Did you cut open the muffler to view the layout? I think we would all enjoy seeing that...
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      09-21-2010, 04:53 PM   #13
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i have a muffler delete on my car and it sounds like sex!!!
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      09-21-2010, 08:19 PM   #14
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+ 1 on not really feeling the "gangsta lean"
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      09-21-2010, 08:25 PM   #15
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All the money you guys make and you go with a hack job? WHy?
Arnt the n54 midpipes identical to the n55?
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      09-21-2010, 08:41 PM   #16
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Quote:
Originally Posted by Clap135 View Post
All the money you guys make and you go with a hack job? WHy?
Arnt the n54 midpipes identical to the n55?
I didn't want to use the typical off-the-shelf 135 54 midpipes that merged both pipes into 1 outlet. I wanted to try something new and stay fully divorced all the to the tips. The other option was to do a single 3.5" exhaust all the way from the turbo outlet to a single tip (with single muffler). But that would have required cat removal and the installation of an aftermarket cat which I don't have too much faith in.

Regarding this design, if the results are good, we will go into production with it. But with SS (not aluminized steel) and mandrel bends (not crush). But first things first. The angled tip was mainly done so that we could use a more gradual pipe bend exiting the muffler body. I think it looks nice but will probably go with something more traditional looking for production.

-shiv
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      09-21-2010, 08:55 PM   #17
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Holy shit shiv tore the crap out of those rfts. Pic #5
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