[Longdoggy]

I have been researching the "M3" exhaust mod or whatever we want to call it whereby the mufflers are cut open and straight pipes are welded in place of the perforated pipes yielding more vroom vroom noise .

I was thinking outside the box/muffler of a way to achieve this without actually having to cut open the muffler. So my thoughts go to some way to limit/restrict the perforated pipe airflow.
Surely there must be a way, there is a way to do anything is my usual thought.

I came to the thought of exhaust flex pipe. Now I know this stuff is pretty much useless as a standalone exhaust pipe due to leakage, but leakage is probably going to be minimal because its inside the muffler and perhaps a tiny bit of leakage will help the sounds so that drone is limited and its not sounding so much like an exhaust delete.

I wanted a way to do this without even needing to take off the exhaust tips.
And yes, I do understand that the actuator will be in the way on the drivers side muffler and that there may be some cat-like material in the inner resonator. I've not been able to find out what is inside of this anyway.

So my thought it so try this as a proof of concept on the passenger side muffler and see if I can notice any sound improvement.
If its good then will probably take out the actuator some how and stuff that pipe also.

Basically get a piece about 12-24 inches of 2 1/4 diameter flex pipe like the one at the link below. And snake that fu**er in through the exhaust. Would probably need to drill a flush mounted bolt through the exit side of the muffler in front of the tips to secure the tubing. But maybe it would work?

I dunno, as I said in the title, "off the wall".

Thoughts? Am I crazy? I wanted something reversible and was not sure I was ready to drop a few hundred bucks on something I may not like, cannot reverse, and may compromise warrantee.

http://shop.advanceautoparts.com/p/r...ontent=5600774

[Jsoboti]

This idea is pretty cool but with the OEM pipes being 2.5 inch diameter and the flex pipe being only 2.25 inch diameter I'm wondering if some of the exhaust will go around the flex pipe and still exit into the muffler through the perforated pipe, possibly vibrating the flex pipe and causing a rattle

Cool idea though, please keep us updated!

[Longdoggy]

Originally Posted by Jsoboti

This idea is pretty cool but with the OEM pipes being 2.5 inch diameter and the flex pipe being only 2.25 inch diameter I'm wondering if some of the exhaust will go around the flex pipe and still exit into the muffler through the perforated pipe, possibly vibrating the flex pipe and causing a rattle

Cool idea though, please keep us updated!

Thanks. The more I think about this I have nearly convinced myself that conceptually, this should work. I mean why should it not at least make the sound a little throatier with a little more growl than a 'golf tee mod'.

I figure this mod can be done for less than $50.

Having done some searching on the diameter of the 335 pipes, i've found a number of 60mm (2.36 inches). So maybe 2 1/4 will fit inside of that nicely. Also, at the entry point of the muffler closer to the engine, there is a bend that the flex pipe may lay into somewhat flush to limit/reduce or even possibly eliminate any rattling.

I've put together a quick design image of this for reference.

[Longdoggy]

...and I may have just noticed a flaw in my design. Snaking the inner pipe so far back will block the cross pipe to the other muffler. I guess it would need to stop around that point. If the fit is not super flush I would need some type of high temp rubber seal to make the fit of the inner pipe along the flow of air tight.

I suppose I could also wrap the flex tube in header wrap. This could help fitment all the way through and reduce or eliminate any rattle.

[Jsoboti]

I see the issue, would be cool if it all works out! What about the driver side resonator?

[Longdoggy]

Originally Posted by Jsoboti

I see the issue, would be cool if it all works out! What about the driver side resonator?

I just spent some quality time on my back in the garage under the rear of my e90 with a flashlight and a tape measure.

I don't think I have much to deal with on the drivers side resonator. I can see and catch the perforation with the tape measure so it's hollow as far as I can tell.
My biggest problem there would be the damn actuator flap. I'd prefer to just take that off anyway, but it seems to be pretty well bolted in. Any suggestions?
But before I tackle that side, my proof of concept would be done on the passenger side. If it works and I can notice a little extra sound, then it may make sense to rip out the actuator flap and do the driver side as well.

My rough measurements seem to be somewhere from 12-14 inches of flex pipe needed to block off the perforation but leave room to secure it and not block the cross pipe.
But then again I was thinking, if it's sound I am going for, and the actuator is gone then do I really need the cross pipe connection? Would there be any harm with blocking it? My logic would lead me to believe the result would be more sound.

[JETmn]

So you are going to restrict the airflow in the mufflers and cost yourself HP just to try and get it slightly louder? Not to mention this is probably going to rattle inside the other pipe. Guys on here have got the full PE mod done for $300. Quit being a cheap ass and hacking your car up. It isn't a Honda!

[Longdoggy]

Originally Posted by JETmn

So you are going to restrict the airflow in the mufflers and cost yourself HP just to try and get it slightly louder? Not to mention this is probably going to rattle inside the other pipe. Guys on here have got the full PE mod done for $300. Quit being a cheap ass and hacking your car up. It isn't a Honda!

Lol. I know that.
I guess my inspiration was to have something reversible and simple. Perhaps it's getting more complicated.

I don't think there would be much restriction if any though. Not enough to make a difference.

[Sidewinderpb]

Originally Posted by JETmn

So you are going to restrict the airflow in the mufflers and cost yourself HP just to try and get it slightly louder? Not to mention this is probably going to rattle inside the other pipe. Guys on here have got the full PE mod done for $300. Quit being a cheap ass and hacking your car up. It isn't a Honda!

That's what people said about my PE mod

[Longdoggy]

Originally Posted by Sidewinderpb

That's what people said about my PE mod

Your my inspiration.

[Sidewinderpb]

Originally Posted by Longdoggy

Your my inspiration.

[JETmn]

Originally Posted by Sidewinderpb

That's what people said about my PE mod

I was on board with the PE mod when you were starting it. This one they are stuffing a fairly thick pipe inside the existing exhaust pipe. Now if you could get a thin piece of rolled up stainless sheetmetal inside there, then you wouldn't be clogging up the exhaust pipe. It isn't perfectly straight though, so I don't think that would work. That flex pipe is pretty thick stuff. Reducing the ID of the pipe will also make it quieter, so it won't be the same as the PE mod.

[Longdoggy]

^ bummer. I will still probably see what I can finagle with something from the auto parts store when I get a free day. Just to experiment a little bit.