found out something interesting about the 1M exhaust...

[flzrider]

Originally Posted by 011100001

Does any know of anybody completely changing the mid-pipes on the N54? I had a wild thought and was wondering if someone might have done this already... Being that I already have the Berk Muffler Delete Pipe installed, converting the mid-pipe into one 3.5" exhaust. To accomplish this I would have a "Y" pipe installed immediately after the down pipes collecting into a 3.5" exhaust. it seems like this would be a bit more manageable underneath the vehicle and remove all of the exhaust restrictions after the DP's.

That seems logical, but I would worry that there may be a good reason for having 2 separate pipes and that merging into 1 pipe so close to the turbos may be detrimental.

[Dackelone]

Originally Posted by Derek8819

Does the 1M mid pipe have a different part number than the regular N54s?

Yes. At least according to RealOEM.com While the parts diagrams look the same the part numbers ARE different.


1M mid pipes...


135i N54 mid pipes...



1M mid pipes (w/secondary cats) bmw #18307845669
135i N54 mid pipe (w/secondary cats) bmw #18307559994


And lets not forget that the 1M also has different main cats than a 135i N54. The 1M's main cats are higher flowing cats than what the 135i came with from the factory.

Dackel

[Dackelone]

Originally Posted by HERR FSTIR

I have MadDads installed and my OEM mid pipe is sitting on the shelf. So I went out into the garage and took a picture of inside the stock mid pipe resonator. I don't see any perforations. Am I missing something?

THAT is what my friend said. That the pipe that runs inside of the resonator where the mid pipes form a Y... that THAT pipe is a straight thru pipe. So the resonator is a dummy.


I really don't know why BMW built the exhaust with that resonator box around the straight (& non perforated) Y pipe.

[MrBimmer]

Since the cats are higher flowing, is it safe to go for stage 2 tuning with it?

[Dackelone]

Originally Posted by MrBimmer

Since the cats are higher flowing, is it safe to go for stage 2 tuning with it?

I believe it was Harold at HP Autowerks who first mentioned the higher flowing cats of the 1M(I believe). I would start by asking him.

[flzrider]

Originally Posted by katsooba

did he take any pictures of this?
sound intriguing
im about to modify my N55 midpipes to a Y pipe magnaflow,
if you say the mid-muffler is a dummy, than why would i do what i planed?
and why does the BMW PE has a Y pipe in their kit, if the mid-muffler is a dummy?

or is it a different story for the n55 midpipes?

Keep us updated on this. I'm curious what a 1M would sound like with straight mid-pipes.

[Rich@GTBPerformance]

Very interesting Dackelone!

[-Z-]

n/m

[Mahlzeit]

What would it cost to have a muffler shop cut out the stock 1M mid-pipe's cats and replace w/ short sections of tubing?

And - does the fake resonator box have any effect? If not on flow, then sound? hmmm

[ozinaldo]

Originally Posted by Mahlzeit

What would it cost to have a muffler shop cut out the stock 1M mid-pipe's cats and replace w/ short sections of tubing?

And - does the fake resonator box have any effect? If not on flow, then sound? hmmm

I think that was BMW's rather "economical" way of designing a sporty exhaust for 1M in a hurry, while trying to match the environmental norms too! Result is a confused mess, managing not being green or sporty enough. Among the trio most useless section of the stock exhaust is by far the mid pipe, well maybe after the China special muffler

[Papethova]

so we have 3 variations of mid pipes??

n54 cats and resonator
n55 no cats with resonator
1M cats with no resonator

[Dackelone]

Originally Posted by Papethova

so we have 3 variations of mid pipes??

n54 cats and resonator
n55 no cats with resonator
1M cats with no resonator

Yup! Totally correct.

[MDORPHN]

Originally Posted by Dackelone

Yup! Totally correct.

Interesting stuff. Also explains why the N55 mids dampen the drone.

Neil

[0110001]

Originally Posted by flzrider

That seems logical, but I would worry that there may be a good reason for having 2 separate pipes and that merging into 1 pipe so close to the turbos may be detrimental.

Agreed; I'm far from a mechanical engineer but I think it would be for closer regulation of back pressure. Not enough and you loose your low-end Tq; too much and you have spooling issues... Though the logical side of me says, two 3' inch pipes = 6" for two small turbos. My personal opinion, formulated from years of tuning, it's over kill. 4" total would be ample to move the exhaust... It's only a 3.0L motor... You might not get the exhaust note that one would dream of but I'm a functionality person... Plus one pipe seems a bit more manageable then two. Just my .02

[flzrider]

Originally Posted by 011100001

Agreed; I'm far from a mechanical engineer but I think it would be for closer regulation of back pressure. Not enough and you loose your low-end Tq; too much and you have spooling issues... Though the logical side of me says, two 3' inch pipes = 6" for two small turbos. My personal opinion, formulated from years of tuning, it's over kill. 4" total would be ample to move the exhaust... It's only a 3.0L motor... You might not get the exhaust note that one would dream of but I'm a functionality person... Plus one pipe seems a bit more manageable then two. Just my .02

I actually am a mechanical engineer and even then i'm not so certain, haha.

In terms of cross sectional area, 2 3" pipes is nearly equivalent to 1 4.25" pipe. But a 4.25" pipe should theoretically be able to flow a bit better since it has a smaller wetted perimeter (surface area in contact with flowing fluid) thus less friction.

[katsooba]

i thought that the two pipes on the midpipe are 2.35 - 60mm diameter each
its about 3.35 cross section area

[0110001]

^ I have no idea... It just seems a bit easier to modify that way vise trying to understand what BMW Eng did. Custom make the exhaust so if you don't like the exhaust note you can add to or take from rather easy.

[jhonson3141]

guys, i have no drone at all from my 1m. is that normal with you guys? it was a chinese spec so we might have some minor difference.

[ozinaldo]

Originally Posted by jhonson3141

guys, i have no drone at all from my 1m. is that normal with you guys? it was a chinese spec so we might have some minor difference.

People have different perceptions of drone plus as you say Chinese market received modified exhaust muffler for 1M from factory. There were also different diagnosis in relation to source of drone in 1M: muffler, mids or an area under the trunk carpet, or a combination of some/all of these. My suggestion is since you don't have drone or you have but doesn't even bother you, just accept it as it is and don't worry about that, there were other people who claimed they never had any drone outside China.

[jhonson3141]

Originally Posted by ozinaldo

People have different perceptions of drone plus as you say Chinese market received modified exhaust muffler for 1M from factory. There were also different diagnosis in relation to source of drone in 1M: muffler, mids or an area under the trunk carpet, or a combination of some/all of these. My suggestion is since you don't have drone or you have but doesn't even bother you, just accept it as it is and don't worry about that, there were other people who claimed they never had any drone outside China.

wow, you have a serious understanding of variation of 1m!

the reason i am pointing of the is that some chinese 1m owner is not happy with the muffler. It's has a piece of metal that block 2 exhaust exit makes sounded more quite, unbalance burn on exit, and perhaps less power.

I am one of those unhappy costumer. So i swap to meistershaft resonator mid and back. guess what??

very annoying drone from 2000rpm to 2900rpm. i cant hear radio, not Bluetooth telephone. even more not happy??

btw, i really like your N55+evolve post, what is one of the reason i have moved to this forum.

[ozinaldo]

Originally Posted by jhonson3141

wow, you have a serious understanding of variation of 1m!

the reason i am pointing of the is that some chinese 1m owner is not happy with the muffler. It's has a piece of metal that block 2 exhaust exit makes sounded more quite, unbalance burn on exit, and perhaps less power.

I am one of those unhappy costumer. So i swap to meistershaft resonator mid and back. guess what??

very annoying drone from 2000rpm to 2900rpm. i cant hear radio, not Bluetooth telephone. even more not happy??

btw, i really like your N55+evolve post, what is one of the reason i have moved to this forum.

I still have some drone with my set up as well but compared to stock drone it is nothing really, totally negligable. I had drone between 2000 to 2900 with stock and it was quite annoying, now I have around 2200 to 2400 maybe and also less present even if you stick at that particular rpm. Doesn't bother me anymore, not in the city not on the highway.

I heard Meisterschaft with mids generate drone so maybe you try putting back your stock mids to experiment?

One thing is almost for sure the N55 midpipe minimizes and in some cars eliminates the drone.

[0110001]

^ Well I think I'm going to just modify my N54 Mids and see how they sound... The cost of that would be far less then buying new mids and/or buying N55 mids.