Modding the Magnaflow 16533 cat-back

[rkneeshaw]

I have catless headers and the Magnaflow 16533. I love the sound, great exhaust, but its just a touch on the loud side, and there's a slight bit of rasp in the 3500-4500 RPM range. I've been thinking of ways to address these problems but without hacking up this exhaust too much or going with a full custom cat-back. Plus, the tone of this setup is just damn sexy, if I could just drop the decibels a few notches I'd have a permanent smile on my face....

Rob43 on e46fanatics posted an interesting possibility: replace the x-pipe with a resonated x-pipe, such as a Magnaflow 11386 (or 14386 if you like polished). The 11386 is a muffler with an internal x-pipe:

https://image.ibb.co/e7HaOQ/11386.jpg (https://imgbb.com/)

https://image.ibb.co/hvitA5/1386_Internal.jpg (https://imgbb.com/)

Rob43 suggested placing the 11386 here in place of the existing xpipe:

https://preview.ibb.co/mymDA5/16533.jpg (https://ibb.co/jYudck)

The thought is you maintain the benefits of the xpipe, and probably even keep the tone exactly the same but the resonated xpipe would simply lower some decibels and just maybe eliminate that last bit of rasp in the mid RPMs.

I like this idea, so I slid under the car to take a few measurements and I think this is doable, with about 1/2" of clearance all around. Basically the 11386 is a 4" tall by 9" wide oval muffler with internal x-pipe. The length of the muffler body measures 14" and is 20" long overall. The catch is you won't be able to simply rip out the xpipe and swap in the muffler; the muffler will have to be moved downstream about 3 inches or so in order to fit into a heatshielded "pocket" under the car, and I won't lie, I think it will be tight. 1/2" on all sides is not a lot of room, but its enough!

Here are a few more pics from under the car to give you an idea of what we've got to work with:

https://preview.ibb.co/eiZuHk/IMG_20120616_00074.jpg (https://ibb.co/gvjGV5)

https://preview.ibb.co/k5JX3Q/IMG_20120616_00073.jpg (https://ibb.co/iQ01xk)

https://preview.ibb.co/fAn3A5/IMG_20120616_00072.jpg (https://ibb.co/dUTX3Q)

https://preview.ibb.co/fbq1xk/IMG_20120616_00071.jpg (https://ibb.co/c1WkOQ)

https://preview.ibb.co/cTfC3Q/IMG_20120616_00070.jpg (https://ibb.co/fAhQOQ)

So I think you can tell there is room for the body of the 11386 if it starts halfway down the current x-pipe position.

Also, there will be minimal bending required on just one of the 2.5" pipes that runs from the current x-pipe to the rear muffler. In my estimate it only needs to move laterally about 1/2".

My biggest challenge right now is finding a qualified exhaust shop that I would trust to do a good job...

[rkneeshaw]

UPS man came today:

https://preview.ibb.co/bNNgxk/IMG_20120709_00097.jpg (https://ibb.co/ctDX3Q)

https://preview.ibb.co/memwV5/IMG_20120709_00098.jpg (https://ibb.co/cmMVq5)

https://preview.ibb.co/kmJock/IMG_20120709_00099.jpg (https://ibb.co/mwjTck)

https://preview.ibb.co/gVJX3Q/IMG_20120709_00100.jpg (https://ibb.co/ewzGV5)

Booked at an exhaust shop for Sat July 28. :applause2

[johnrando]

Good info in both posts, thanks. GL w/ the mods.

[328ioc]

I am about to order this exhaust probably around the time you have the resonator installed.

I am keeping the stock headers for now though. But I am glad you like the sound and I would love a before and after sound clip if you have the time.

Sent from my DROID RAZR using Tapatalk 2

[Johal E32]

I have Dinan muffler on my car but I still think it's too quiet :shifty

Could I just replace my "mid" muffler with a Magnaflow X-pip to get more noise?

Thanks in advance!

And good luck w/ the exhaust!

[328ioc]

I have Dinan muffler on my car but I still think it's too quiet :shifty

Could I just replace my "mid" muffler with a Magnaflow X-pip to get more noise?

Thanks in advance!

And good luck w/ the exhaust!

It should make it louder. In theory its basically a resonator delete.

[imola red zhp]

Has anyone gone straight pipe with resonator only?

sent from dennis' personal electronic device

[rkneeshaw]

I am about to order this exhaust probably around the time you have the resonator installed.

I am keeping the stock headers for now though. But I am glad you like the sound and I would love a before and after sound clip if you have the time.

For sure, I'll have to use my phone but want to document this change for everyone.

I think you'll love the magnaflow catback, it should sound really awesome on your car

[328ioc]

For sure, I'll have to use my phone but want to document this change for everyone.

I think you'll love the magnaflow catback, it should sound really awesome on your car

No biggie now. I saw your other thread with the video. It sounds great.

Sent from my DROID RAZR using Tapatalk 2

[Jesse M]

Has anyone gone straight pipe with resonator only?

sent from dennis' personal electronic device

I am straight pipe with headers, and a single magnaflow 1-2 muffler in the rear.

[imola red zhp]

I am straight pipe with headers, and a single magnaflow 1-2 muffler in the rear.

How is sound? Loud. Raspy???

sent from dennis' personal electronic device

[rkneeshaw]

Thats got to be LOUD

[JupiterBMW]

I have Dinan muffler on my car but I still think it's too quiet :shifty


Can you post a sound/video of the exhaust? Any chance you could take a sound clip under load (while driving) too..?? I would MUCH appreciate!

[rkneeshaw]

SUCCESS

I just left the exhaust shop a few hours ago. Greg at Great Lakes Customs (http://www.greatlakescustoms.com) did a fantastic job in my opinion, I couldn't be happier!

So first of all, it fits! I'm not going to lie, its tight, but I have about a 1/2" clearance around the tightest spots.

Now in terms of sound I am very happy to confirm that this modification both reduces the sound levels slightly AND kills the last remaining rasp I had in this system. The tone of this exhaust is awesome, and with this modification it is consistent and smooth all the way through the power band. Now if you like the exhaust to sound a little raw, then this isn't for you because it smooths it out. But in my opinion it is perfect. Finally my BMW once again sounds as smooth and refined as it is, something I haven't heard since I first installed my headers.

I did take some videos before and after, but the problem is the mic on my camera did not pick up the rasp. In fact, if you watch and listen to this video you can't tell that the last segment was recorded AFTER the modification. The "after" clip actually sounds louder in the video, which is the opposite of reality. So I'm sorry guys, you'll have to take my word for it. It sounds MUCH better; down to a moderate volume level with zero rasp and the sound of pure sexy time.

http://www.youtube.com/watch?v=wFS402aRfDk

And here's a few pictures of the install:

https://preview.ibb.co/hEbkOQ/IMG_20120727_00011.jpg (https://ibb.co/gg0C3Q)

Cut this section out and reused everything except the x-pipe and about 6" of pipe after that
https://preview.ibb.co/g14uHk/IMG_20120727_00010.jpg (https://ibb.co/nBR8ck)

https://preview.ibb.co/bUmwV5/IMG_20120727_00017.jpg (https://ibb.co/dudX3Q)

https://preview.ibb.co/bB18ck/IMG_20120727_00016.jpg (https://ibb.co/e1mKiQ)

https://preview.ibb.co/ihDMxk/IMG_20120727_00015.jpg (https://ibb.co/cJ9uHk)

https://preview.ibb.co/gd0eiQ/IMG_20120727_00014.jpg (https://ibb.co/e5P5OQ)

https://preview.ibb.co/iDAJck/IMG_20120727_00019.jpg (https://ibb.co/mfnaOQ)

https://preview.ibb.co/gGtFOQ/IMG_20120727_00018.jpg (https://ibb.co/fiJh3Q)

https://preview.ibb.co/gLkjHk/IMG_20120727_00020.jpg (https://ibb.co/fn9Bxk)

I can't keep my windows up now, it just sounds so good!

A huge thank you to rob43 for the great idea!

[Johal E32]

sounds perfect! I'm looking for a sound like that. I'm assuming no drone when you are cruising on the freeway?

[jreyes19]

Wow sounds and looks good

Sent from my SAMSUNG-SGH-I997 using Tapatalk

[johnrando]

Nice work!

[rkneeshaw]

I'm assuming no drone when you are cruising on the freeway?

None. In fact probably the second biggest thing I noticed right away apart from the removal of the rasp was below 2k RPM's is significantly less boomy. I'm really very happy with how this has turned out, even 5 days later I'm still noticing how much more "refined" or "polished" this sound is, and how it is not nearly as obnoxious as it was before.