The Day Has Come!

I finally found an exhaust shop that was local to my office/home, so I decided it was time to pull the trigger on making this old man’s car sound like it actually has a 4.4L twin-turbo V8. There aren’t a lot of aftermarket parts for this specific model, so I had to get creative with what I wanted to do. After thorough research, I figured a custom setup would produce better power and sound than the only performance kit I could find, the $2.4k Dinan exhaust system (which only replaces the rear muffler and honestly, doesn’t make much of a difference in sound).

Being a luxury car, BMW really shined with how well they insulated the cabin and reduced the sound of the powerful V8, but this can also cause issues with highway drone and such with custom exhausts, leading me to think I would need some kind of backpressure (to accommodate the turbos), and an X-pipe to equalize the exhaust chambers a bit. In the end, I went with removing both the front and rear middle resonators and replaced them with an X-pipe section and some straight pipe. Then, I removed the large rear muffler, and replaced it with 2 MagnaFlow ‘straight-through’ performance mufflers, painted black, and then had it routed through the factory exhaust outlets. I also decided to just open up the active exhaust valves and modify them so they stay that way, so I have the sound I want in all driving modes (comfort, eco, sport).

As you can see, the rear muffler is massive, reducing practically all engine noise while probably weighing 60+ pounds.

One of these middle resonators actually had some form of an X-pipe feature, so I am glad I decided to install one in the new system.

I can’t imagine how restrictive that muffler is. While just a cat-back doesn’t increase a ton of power, I feel that it will still be worth it for efficiency purposes.

The X-pipe really steals the show in my opinion. I have seen countless 550i’s and such with the same engine as mine with custom exhaust setups that sound raspy, typically in true-dual fashion, thus producing a similar noise as a 4-cylinder car (since each pipe has 4 cylinders pumping through it).

Results

Overall, I couldn’t be more pleased with the sound. I didn’t get a chance to record any audio of it yet since I had to pick it up after work, but I will upload some shortly. The exhaust note is quiet while driving through neighborhoods, but really screams with a deep roar when you hit the gas. I have noticed no interior exhaust drone, and my butt dyno tells me that the car likes the change, at least.

Now that the exhaust is done (until ARM Motorsports downpipes once the extended warranty expires), I am now looking at either purchasing the ARM Motorsports cold air intakes or making my own (doesn’t look that difficult). I want to route the air filters to behind the grill, allowing for colder air to be collected. At the moment, I threw in some K&N drop-in air filters, but I really would love to hear the turbos a bit more. But, before I spend any more money on this car, I need to figure out the wheel situation as mine have a decent amount of road rash; I think I will just sand and paint them since I like the design, but we will see!