[joshua12334]

Here's my idea to modify the OEM M2 Exhaust to M2 MPE. The goal is to keep the exhaust nice and quiet but also have the ability to loud. The yellow circles are the OEM exhaust valve.


M2 Hybrid exhaust, HOW IT WORKS?:
when it's in comfort/eco modem, the valves remained closed, exhaust soundwaves and gases go through the muffler.
When it's switched to Sport / Sport+ mode, the valves open up, exhaust soundwaves and gases go through the muffler and outer tips, a straight piped design just like the MPE.

Do you think this is a good design to accomplish the goal that's mentioned above? Are the valves located at the right location (Closer to the Y pipe? Closer to the tips?)

THE LAST GRAPH IS A M2 OEM MUFFLER THAT'S BEEN MODIFIED WITH TWO EXTRA PIPES AND A VALVE

[CalAcacian]

There's a number of issues with this solution. Unless you have the MPE already, it's a huge waste of money.

Even if you do have the MPE, the routing of the hybrid doesn't make much sense. 1. The valves should be much closer to the split to prevent pressurizing the closed branches and causing back pressure with the valves closed.

Second, you can't just plumb a line into a random spot on the muffler. the current entrances are on the sides, you might get really unfavorable effect by welding a pipe into a different spot.

[AndrewC1989]

Originally Posted by cfanb8

The goal is to keep the exhaust nice and quiet but also have the ability to loud.

This seems like a pretty complicated way of achieving that. Why make a custom exhaust when there are already so many good established options on the market that are designed the exact same way? If price is an issue just go to the classifieds section or ebay and buy one second-hand. Or if that's too expensive buy a used sport cat and a valve controller. Way less work and really not that expensive all things considered.

[joshua12334]

Originally Posted by CalAcacian

1. The valves should be much closer to the split to prevent pressurizing the closed branches and causing back pressure with the valves closed.

That was my plan, the exhaust shop said it should be in the middle.

Originally Posted by CalAcacian

Second, you can't just plumb a line into a random spot on the muffler. the current entrances are on the sides, you might get really unfavorable effect by welding a pipe into a different spot.

There isnt any new pipe getting installed on the muffler. That's the OEM pie going into the muffler on the OEM Muffler. Two new pipe goes to the outer tips. Just like the MPE

[joshua12334]

Originally Posted by AndrewC1989

This seems like a pretty complicated way of achieving that. Why make a custom exhaust when there are already so many good established options on the market that are designed the exact same way? If price is an issue just go to the classifieds section or ebay and buy one second-hand. Or if that's too expensive buy a used sport cat and a valve controller. Way less work and really not that expensive all things considered.

The whole design only requires two new pipes and one valve. I have not found any exhaust that reminds as QUIET as the oem and as LOUD as the MPE which is why i came up with this design.

[CalAcacian]

Sell the MPE (if you already have it, or just don't buy it) and you will be able to build custom exhaust that does what you want for a fraction of the cost.

If you actually want to do this here is my suggestion (I have designed and run multiple fully custom exhausts built with off the shelf parts, and designed them for friends):

Go for 3.5 in piping back from the stock down pipe. Run an 18inch 3.5 in and out cherry bomb glasspack in the center of the car. These are straight through "mufflers" that really are fantastic resonators. Split your 3.5 in piping at a Y just behind the rear axle. Both exits to the Y should also be 3.5 in pipes. On one end of the Y, put your stock exhaust valve. That should run directly to dual tips at the rear left of the bumper.

The other end of the Y should run to a Magnaflow 5"x8" 3.5 inlet straight through muffler (or OEM muffler if you want it quieter, but this is a bad idea because you would have to reroute the exit and ruin the flow) that ends at dual tips to the rear right. That will cost you about $500 bucks to build, $750 max. You'll end up with exactly what you want.

[CalAcacian]

Originally Posted by cfanb8

That was my plan, the exhaust shop said it should be in the middle.


There isnt any new pipe getting installed on the muffler. That's the OEM pie going into the muffler on the OEM Muffler. Two new pipe goes to the outer tips. Just like the MPE

Ah, you didn't label that as the OEM muffler on the pic. You're going to spend about $2000 bucks too much with this design.

[AndrewC1989]

Originally Posted by cfanb8

I have not found any exhaust that reminds as QUIET as the oem and as LOUD as the MPE which is why i came up with this design.

https://f87.bimmerpost.com/forums/sh....php?t=1432744

Super quiet with valves shut in comfort and loud as all hell when they're open in sport+.

$4000 for everything brand new. I'm sure you could get it all used for ~$2000.

[BMWF87Melb]

Originally Posted by cfanb8

The whole design only requires two new pipes and one valve. I have not found any exhaust that reminds as QUIET as the oem and as LOUD as the MPE which is why i came up with this design.

Appreciate your effort and thought here but have you heard the N55 MPE in person?

I find the N55 MPE in comfort with ASD delete with valves closed is quieter than stock in comfort - but there is obviously 3k rpm drone with the MPE.