M3 exhaust modification

[Blade929]

I like the idea of the clamps but it might be rather difficult to get a good fit because of clearance and that the pipes do snake a bit. You can tell realative to this picture that the length is about 8 inches or so with the bends. The lower and upper vary due to the snaking.

[adc]

Originally Posted by DirtyJersey

Anyone have a good idea of how long the perforated pipe part is? Guessing each side would be the same. Another member and I are thinking about getting the clams to use for this rather than the tape or welding new pipes. At 2.5 inches long we're trying to figure out how many clamps we'd need if this was the route we're going.

I've used pictures posted by the OP to estimate how many "pipe diameters" we need to cover. I cannot be sure without holding the clamp in my hand, but it looks like it's fairly squarish in size (diameter = length).

Looks like 1 clamp can cover the small perforations and another 2 would cover the long straight section of the big perforated pipe. Unfortunately, the pics clearly show the big-perforations-pipe being slightly curved - so we wouldn't be able to completely cover it with straight clamps. Another narrow - band style clamp might be needed to cover the last semi-straight section, and since not all the perforations are covered in the clamp scenario, we'd need to pack all the fluffy material back in so that we don't get nasty resonances.

So about 6 of the wide clamps and 2 narrow bands would be my best guess at this point. The biggest attraction of the clamps is, of course, the ability to go back to stock without a pipe re-weld. I think it's a bigger attraction to sedan owners, as it seems hard to find a stock OEM E90 muffler on the used scene. I think if I had a coupe, I'd buy a used muffler and simply weld the pipes in.


One final thought for anybody thinking about the clamp method - use red loctite (I think that's the high temp one) on the clamp bolts - you wouldn't want them to start rattling inside the muffler can after 3000 miles...

[Otacon132]

Do NOT use clamps and stupid exhaust wrapping with clamps.....just weld a straight pipe into place, PLEASE. You guys drive a 50k bmw - not a 15k honda, so do things correctly. Explain the difference between a straight pipe and clamps and exhaust wrap. The sound will be the same, and it wont come undone after X amount of miles.

Here are pics of the mod in progress:













As for the sound results and my impressions:

As far as a cold start, it starts off by sounding like a v8 muscle might sound like, and in my opinion the perfect sound in regards to how a stock m3 should cold start and idle. Once it warms up, it idles like stock and it cant be heard. To compare, it sounds almost like my slk 55 amg on start up but minus the engine whine - or any amg for that matter, raw v8 sound but only difference is that it shuts up and idles like stock once it warms up.

With the engine still cold and warming up you can notice that something is not completely right, there is a reason bmw does make their muffler the way they do - it just sounds odd at times when its cold (manual tranny...idk if that has something to do with it, but from stop to moving the exhaust sometimes backfires oddly while engaging gear)

Once the car is warmed up and at running temp, its basically a stock sounding car - just louder. It sounds fine, and you can tell its louder - a lot louder from the outside, and there is a very very nice tone as the rpm's climb from 3k-4k, both with the windows open and closed. Under WOT the car sounds stock from the cabin, i cant really tell its "loud" but you can tell it is louder and different. From the outside its definitely at least 70-80% louder over stock, and people turn heads to see.

Im very very happy with the mod overall, definitely something i don't regret doing. This will hold me off until i go with straight pipes and some sort of muffler in the rear. There are no power gains on this - and if there are, its something that you would not feel what so ever. Its hard to see power gains (and now that i think about it, nearly impossible) with just replacing 6 inches of a perforated pipe in a stock muffler that has 4 different 90 degree bends and all the cats in the muffler in place.

In closing, that pipe is there for a reason - to quite down the exhaust and make it sound like it should for the normal consumer. Covering it with exhaust wrap is no different than just a straight pipe in its place, only that the wrap is honestly in my opinion idiotic and just the wrong way to do it (and more expensive most likely). Weld a straight pipe in there, leave the other small perforated pipe alone and just put the stuffing back into the muffler. Replacing the small perforated pipe is hardly going to do anything,there is such a small amount of perforation that it is not worth covering - leave it as it probably helps muffle SOME sound. I don't think making this stock muffler louder would sound good but we will see once i add my straight pipes with resonators in the future.

If i had to do this again, i would most likely spend an extra 200 bucks and put in two magnaflow generic mufflers with some tips. Im sure the outcome would be the same as what this mod is trying to achieve. The exhaust note would be louder and sound right at a cold start. In the future im going to go with a straight pipe midsection and see what that sounds like, if im not happy with the sound on the stock muffler i will add resonators. And even more into the future ill be going with test pipes and a flash/tune on top of the mid pipe, and will see what happens with the stock muffler when i hear what that sounds like.

[adc]

Originally Posted by Otacon132

Do NOT use clamps and stupid exhaust wrapping with clamps.....just weld a straight pipe into place, PLEASE. You guys drive a 50k bmw - not a 15k honda, so do things correctly. Explain the difference between a straight pipe and clamps and exhaust wrap. The sound will be the same, and it wont come undone after X amount of miles.

I'm not advocating exhaust tape - I'm the clamp guy =). I think if properly applied, a clamp should stay there as long as needed - with the added benefit that it can be easily brought back to stock. I'm just not sure that after initially welding in straight pipes you can then re-weld the original perforated ones back in, if you wanted to sell the car.

Speaking of welding, those pipes in your muffler look like mild steel not stainless steel - you may want to ask them about this. Regular steel will rust inside...

If i had to do this again, i would most likely spend an extra 200 bucks and put in two magnaflow generic mufflers with some tips. Im sure the outcome would be the same as what this mod is trying to achieve.

It's possible the outcome will be different, simply because the Magnaflows won't have those Helmholz (anti-resonating) chambers built-in, so they will probably drone. The idea behind tinkering with the OEM muffler is to keep the drone out.

Personally I've listened to Magnaflow mufflers on the M3 and didn't like it. If I ever go for an aftermarket unit, it'll probably be along the lines of Gintani Sport.

[Blade929]

Originally Posted by Otacon132

Do NOT use clamps and stupid exhaust wrapping with clamps.....just weld a straight pipe into place, PLEASE. You guys drive a 50k bmw - not a 15k honda, so do things correctly.

Why not relax and not get so inflamatory? To each their own. If the wrapping fails, I will just get it welded like you did. It's not about the $200 it's about determing if you are goiing to like the result or not and there is no way to tell until you do the mod. I'm going to get together with ADC but until I did the mod I don't think others in this area had tried it. As others mod the exhaust it continues to evolve and improve. I have sealed everything and no sound deadening and the volume is perfect for me but it's subjective.

[Otacon132]

Originally Posted by Blade929

Why not relax and not get so inflamatory? To each their own. If the wrapping fails, I will just get it welded like you did. It's not about the $200 it's about determing if you are goiing to like the result or not and there is no way to tell until you do the mod. I'm going to get together with ADC but until I did the mod I don't think others in this area had tried it. As others mod the exhaust it continues to evolve and improve. I have sealed everything and no sound deadening and the volume is perfect for me but it's subjective.

Sorry if i came across as aggressive. Im simply making a point that kinda makes logical sense in terms of what your trying to achieve - and achieving it in the most effective way, not being aggressive or attacking anyone.

in regards to the piping that was used on my muffler, it is stainless steel - just not polished...

And i guess that is probably the only reason which would justify using clamps and wrap, to return it to stock....but again, i think common sense would justify just buying another oem muffler for 50-100 bucks, you will spend that welding the modified exhaust back shut anyway.

On another note, i just took the car out for the second time, really happy so far with the new sound.

[DirtyJersey]

Do u guys think leaving an inch or two of the perforated pipe in place will subdue the sound a bit or will it have a different affect and make it sound completely stock again? Im fearing it might be too loud which is why im asking.

Where do u guys think i can find the stainless steel piping? Place im doing it at is not a muffler shop. Also, Im guessing itll need to fit into the existing pipe and not be the same size as well?

Btw great pic Otacon123!

[Otacon132]

Originally Posted by DirtyJersey

Do u guys think leaving an inch or two of the perforated pipe in place will subdue the sound a bit or will it have a different affect and make it sound completely stock again? Im fearing it might be too loud which is why im asking.

Where do u guys think i can find the stainless steel piping? Place im doing it at is not a muffler shop. Also, Im guessing itll need to fit into the existing pipe and not be the same size as well?

Btw great pic Otacon123!

just replace the pipe, leaving just a little wont do much at all - and its not super loud to begin with. as for SS piping, im sure any muffler shop will carry it, but your gonna need to go to them to weld anyway...

[Blade929]

No worries Otacon it just sounded like bashing and especially bashing Periokid's setup without whom we would not have this mod at all. I agree with you in principal that welding>clamps>tape.

[adc]

No success today...

I took off the exhaust after talking on the phone with a local exhaust shop (Kelley's Kustom Performance) and went to see them. I wanted them to weld in the straight pipes. After taking one look at the thread pictures and the exhaust, the owner gave me a quote for $500 and 3 business days to do it right - so I left, went back home and put the exhaust back on the car.

If someone here knows a performance shop in the MD/DC/VA area that can do it for a reasonable amount, do it right, and within one day, I'll try again.

In the meantime, I guess I'm back hunting for a stock OEM exhaust to purchase and butcher at a leisurely pace.


Edit: To help someone who may want to take off the OEM exhaust on their own, a few quick pointers:
- Remove the clamps towards the front of the car - easy as pie
- Slip off the orange rubber hangers in the middle - easy if you soak them liberally in WD40 (use a flathead screwdriver)
- Slip off the orange rubber hangers at the bumper end - a little tougher, WD40 helps, and so does removing the 2 black screws that hold the bumper edge in place.
- Finally unscrew the black side hangers from the car and drop the muffler.
- To reassemble, it was very easy using a piece of 2x6 placed horizontally under the exhaust, then lifting it in place with a floor jack.
- Guide it in place as you lift, then screw in 1 nut on each side (on the black side hangers), just enough to catch.
- Wiggle in the pipes then screw in the other nuts on the side hangers.
- Tighten the clamps.
- Re-hang the 4 orange rubber thingies (2 in the middle pipes, 2 at the bumper). Soak liberally in WD40 and it goes in real easy.

Good luck!

[kitw]

I had a rough time with the hangers. They are really hard to get off and tear easily if you just pull on them.

I bought one of these:



And it made the job MUCH easier.

[JCtx]

No need to mess with the hangers people; just remove them along with their brackets . By the way, I installed black hangers, which are a bit shorter than stock, and now the exhaust is tucked up perfectly, plus no orange visible from the back . Noticed the orange hangers have metal surrounds too, which is complete overkill IMO when the main black hangers already have. Plus their safety straps. That's enough. Good day.

[adc]

Originally Posted by kitw

I had a rough time with the hangers. They are really hard to get off and tear easily if you just pull on them.

I bought one of these:



And it made the job MUCH easier.

Mmm nice - what is it called on Amazon?

[Blade929]

Originally Posted by adc

No success today...


If someone here knows a performance shop in the MD/DC/VA area that can do it for a reasonable amount, do it right, and within one day, I'll try again.

I would try Robert at Extreme. They did some work on my E46 and we very reasonable. It's kinda an old school shop so if you are going to try to shop him the thread to get an estimate I would bring a laptop.

http://baltimore.citysearch.com/prof...flers_inc.html

[adc]

Originally Posted by Blade929

I would try Robert at Extreme. They did some work on my E46 and we very reasonable. It's kinda an old school shop so if you are going to try to shop him the thread to get an estimate I would bring a laptop.

http://baltimore.citysearch.com/prof...flers_inc.html

Thanks!

I think perhaps I'll talk to him on the phone, then snail-mail him the pics from this thread and then talk to him again after he's looked at them. He's a little too far for me to drop by in my lunch break...

[kcdude24]

I tried to read most of these OEM mod threads and still can't clearly see how there is room to weld the replacement pipes all the way around. I was wondering if you could just weld a few metal patches over the perforations without cutting the original ones out....so the more you cover, the louder it gets right?

[Grail05]

^ there is no way on getting the entire pipe welded so mine was welded 70% then used a exhaust paste to cover the rest

Oh and yes the more u cover the lauder it gets but it will drone like a mofo

[kcdude24]

Originally Posted by Sean05

^ there is no way on getting the entire pipe welded so mine was welded 70% then used a exhaust paste to cover the rest

Oh and yes the more u cover the lauder it gets but it will drone like a mofo

Why would covering part of the perfs make it drone more? It appears some are just replacing two of the pipes and leaving the ones with smaller amount of perfs. I was thinking about having a metal piece cut that wrapped all the way around the pipe and then welded in to place. That way the original perforated pipes stay in place.

[adc]

Originally Posted by kcdude24

I tried to read most of these OEM mod threads and still can't clearly see how there is room to weld the replacement pipes all the way around. I was wondering if you could just weld a few metal patches over the perforations without cutting the original ones out....so the more you cover, the louder it gets right?

I've asked myself this very question. I came up with a hybrid clamp-weld solution. Cover as much of the perforations with wide stainless steel exhaust clamps (the one which are 2.5" wide), then spot-weld them in place. Weld the clamp's screws as well to avoid any possible rattles.

By virtue of the clamp being round & smooth & designed to seal exhaust joints, I think it would work better than just any metal patch.


But the more I think about this, the more it makes sense to try to acquire a second-hand OEM exhaust and experiment on it.

[M3Rolly]

Won't there be rough transitions of the pipe inner diameters when welding in pipes? Will the transitions (whether small or big, or rough or smooth) affect the exhaust flow?

[paul walker]

So I'm going to be doing this mod, it's similar to what I did with my Cayenne Turbo stock exhaust mod I did and recently purchasing the M3 I had this in mind already just glad to see others have taken the stride in doing this.

I'm going a different route though, I'm completely removing all the bends and opening the entire exhaust up and going to block off the center completely so that my design will be just like dinan's muffler design. I'm just debating on putting in the resonated pipe into the outside parts and restuffing the muffler or not, I may just go straight pipe from the muffler inlet to the outlet / tips.

[paul walker]

Here's my plan on what I'm going to do, it's a lot more work than what you guys have all been doing but like I said it's similar to what I did on my Cayenne Turbo and this made me a lot of power on that car. I may just weld straight pipes through instead of reusing the perforated pipes, I may even try both just to see the difference in sounds.