[wantam235i]

Hey guys I wanted to share my exhaust cut out journey with everyone.

Prelude:

Although I was happy with the sound of my high-flow downpipe and and M sport exhaust, I wanted something a little bit more. I initially looked into the resonator delete but found that since it's so small, even regular drivers barely notice a sound increase. I quickly found that "proper" exhaust systems, valvetronic and other wise were very expensive (in the thousands of dollars)

The problem:

I quickly noticed that many electronic exhaust valve cutouts, even ones from reputable brands seem to have high failure rates. I suspect this is due to the motor being directly attached to the exhaust, and being exposed to intense heat, cold, rain, salt, etc. Due to this I started looking at at vacuum/boost activated cutouts. The idea here is the work force is provided away from the exhaust, and a simple butterfly valve near the danger zone would last much longer than an electric motor.

Great now we have a better designed way to operate the exhaust flaps, but there's a problem. The advantage of electric exhaust cutouts is they can be opened/closed on demand with a key fob. Most of the installs I see of vacuum/boost flaps operate directly from the engine, opening at higher engine speed/boost. This means we lose the ability to truly switch between stock/loud modes. We also have to deal with routing a vacuum line all the way from the front to the back of the car.

The solution:

We can combine the best of both worlds by using our vacuum exhaust cutouts with a remote vacuum pump. We can place this in our trunk and route it through a grommet, close to our exhaust.
This is the unit I used, not sure if I am allowed to post directly to the supplier but I searched "vacuum exhaust cut out" on Aliexpress. Cost me about 150 CAD and like 20 or so on import duty.



Finally I needed a y pipe and turndown. Now I noticed that a lot of the y pipes, even from reputable seem to all be the same Chinese product, just with a brand name welded on it. Now I wanted mine quickly so I bought from a known brand of Summit Racing, but I don't think there would be any difference.

Y pipe cost me about 100 CAD


I also feel like you could get away without a turn down, but I bought one anyways. Cost me 43 CAD.


I followed the instructions provided by this guy here:

Now obviously things will be a little different since he is using electric cutout but the general idea is the same. Instead of clamp on I recommend getting weld on for longevity purposes. However if the valve does fail, the clamp on will be easier to service/ replace. You can also pass the vacuum line through the same gromet he passed the power line through.

It cost me 220 CAD to get all three parts welded together. Total cost of labour + parts is ~520 CAD or 390 USD

Results:

Now we get get the sound of a (near) straight pipe when we want it, and go back to stock with the click of the button. The N55 is one of the best sounding BMW engines when given a chance to breath. I was getting bored of my car, looking for something more powerful but this mod has completely transformed the car. Half the experience is the sound and every time the engine sings I have a huge grin on my face. The car feels much more powerful (maybe 2HP gains at redline ).

Some takeaways:

• Although the exhaust is MUCH louder now, I feel like it could be louder. Maybe it's because im young and want to be as obnoxious as possible, but I feel like the use of a y pipe still sends some of the exhaust gases through the normal muffled route. I imagine with higher RPM this problem decreases since the muffler provides more resistance, so I have no clue if this is even true, just a guess and I have no reference to compare it with.
• Band clamps are easier for repairing IF the unit does fail, but tend to leak.
• Always do your research and don't always go for what everyone else does. Had I gone the electric cutout way, I would have paid more for an inferior product. I am very surprised this isn't more popular, one of those situations where the best engineered solution is also the cheapest.

Here are some photos:

[mike@x-ph.com]