Q about modifying muffler

T77911S · 12-02-2008, 06:44 AM

i have been considering moding my 2 in 1 out muffler. i was looking at the picture and to me, it looks like when you add the 2 pipes, the exhaust goes straight out. so why cut the other 2 holes?
i was thinking of leaving mine 1 out and cutting a hole where the red is. i dont want it too loud.

John Brandt · 12-02-2008, 06:46 AM

wouldn't be cricket

911st · 12-02-2008, 07:55 AM

You just do not know unless you try. Your idea seems good. Also could consider cutting a hole in the bulk head in the right side so gasses can skip the diffuser and first nosel. Your mod only takes out the defuser.

I suspect most the sound control comes from the internal muffler volume and the long internal tail pipe.

One proven mod is to just add a second bull horn or tail pipe on the passengers side. You can see this skips the long run of the stock tail pipe. Some say is is loud some not. It has proven to equal the factory sport muffler in power potential. Could keep it hidden up under the car and cap it when needed.

If you car is CIS it should be mostly self compensating for less back pressure with a sport muffler but it is worth checking your A/F's.

T77911S · 12-02-2008, 09:21 AM

i thought about the right bulkhead. also thought about a hole in the center bulkhead to the left of the red circle, also with and without the hole at the red circle. another option is cut a section out of the long pipe above the circle. i want somehting that will also make the tone a bit deeper.

am i looking at the diagram wrong, or does the exhaust bypass all the baffles in the sport version?

i have heard the dansk dual out on the sides, did not like it much. sounded like a truck.
i had a modified sport muffler on my 914-6, wasnt bad, raspy sounding. better than the dual side output dansk.

Mycar · 12-02-2008, 09:42 AM

Very interesting thread, I`ve been considering this myself.If it helps,here are a set of cutaway photos. Sorry they`re not bigger.

http://www.pbase.com/9146gt/rally_muffler_of_a_gt_911_muffler_exposed

Mike.

T77911S · 12-02-2008, 09:58 AM

the pics are very helpfull! the holes in the first baffle are much bigger than i thought. for alll the work to get in there, i dont think my orginal hole is worth it. maybe cut where the red is and another in the cnter bulkhead?
or maybe just drill holes on the left like the ones on the right?

im sooooo confused!

what did you decide about your mods?

Mycar · 12-02-2008, 11:34 AM

Quote:

Originally Posted by T77911S

what did you decide about your mods?

Until I read this thread, I`d decided against it.

Firstly,I love the idea of a rorty, snorting muffler but what with it being a bit antisocial, how often would I uncap the twin pipes? Probably a lot to start with but then prehaps it would become just a gimmick.

Secondly, the change in back pressure will require carb adjustment and I can`t go retuning my car everytime I whip the caps off, I`ll wear the Webers out.

Thirdly, originality, my car never did have this type of muffler, but this one doesn`t count.... you can always swop back.

In a perfect world I`d have the guys at MK ship me one of these beauties. This one was sent on to a fellow DDKer and he was sooo happy

cool bling for the UK

Then I`d have a muffler for every occasion and I wouldn`t have to carve up my lovely stainless Dansk. Unfortunately your Dollar is strong now, three months ago every thing was half price

Decisions, decisions.... I think I`ll think about it.

Mike.

911st · 12-02-2008, 03:29 PM

Again, the proven is to add a second tail pipe on the other end.

I totally gutted a two in and just left a little tail pipe on it. It was nasty loud.

One other though is to cut out everything to the right of the second to last bulk head. That would take out most of the short pipe and shorten the long tail pipe some. Again an experiment.

Would be nice to do a before and after dyno run w A/F's.

Basically, getting the baffle out of the way is one step, getting the small tube out of the way is a second step.

Adding two tail pipes like the stock sport muffler gives you a straight pipe sport muffler that can be caped to let the it act like a stock muffler.

One other change I have seen is to cut out the stock exit pipe like on you diagram and put two tail pipes on sport muffler style but at the outter ends of the two end bulk heads. My favorite.

T77911S · 12-03-2008, 03:30 AM

911st, the 2 pipe on the outer ends may be a good option, but a lot of work.

the dansk i heard that had the 2 out on the ends made me think a redneck owned it, yes i am in the south and can say that, after all, the directions to my house include turn off the paved road.

berettafan · 12-03-2008, 05:31 AM

just did this mod, including the internal cuts, and it is most definitely not a quiet car.

it is, in a few words, FARKING AWESOME!

odd thing is inside the car the sound is not much louder at all.

you can certainly do the two new outlets first and save the cutting for later of you don't mind making a large opening at the top.

i left the original side outlet on mine and capped it.

http://www.youtube.com/user/longhoodfan

911st · 12-03-2008, 06:16 AM

Quote:

Originally Posted by T77911S

911st, the 2 pipe on the outer ends may be a good option, but a lot of work.

the dansk i heard that had the 2 out on the ends made me think a redneck owned it, yes i am in the south and can say that, after all, the directions to my house include turn off the paved road.

Ya, I am not a big fan of the bull horn style conversion. Though I saw one where the second pipe was just hid up under the skirt on a 3.2 Carrera.

I do very much like the conversion with the two sport style pipes that exit from the ends of the can instead of in the center like on a factory style sport muffler. This keep most the standard muffling on the driver side and some on the pasanger side. It is potentialy a very good conversion. In theory if one was at a track that had noise restrictions, the pasanger side could be caped for near stock muffling.

This should be a little more mellow, looks right and makes as much HP as the sport.

RWebb · RWebb's Garage

Quote:

Originally Posted by T77911S

911st, the 2 pipe on the outer ends may be a good option, but a lot of work.

the dansk i heard that had the 2 out on the ends made me think a redneck owned it, yes i am in the south and can say that, after all, the directions to my house include turn off the paved road.

y'all got PAVED roads???

The sport muffler (twin straight outlets) can add a few hp if the motor is tuned for it.

The twin cow horn styles do not add hp, but do make more noise than stock muffler. It is intermediate in noise rel. to the sport muffler. I have this type (a Monty).

berettafan · 12-03-2008, 10:31 AM

Jon Sycip does a rally muffler like what i did (but MUCH nicer) and you can find video of such a muffler on his 2.7. The sound is quintessential Porsche.

911Etarga · 01-20-2009, 10:34 AM

How would these ideas work? They should make the muffler flow more freely(more HP), and increase the sound. All you would need to do is make a round cut above the area you are working on, then weld or JB weld the cut back on....? I am going to do this, or something like it today, I will take picks.

T77911S · 01-20-2009, 12:40 PM

i would be curious as to how it sounds with the pipe in the top pic removed. other than that i would just cut out a big hole where you have the circle. i cut out the baffle on the right. only a very slight change, not worth the work just for that.

Zeke · 01-20-2009, 12:48 PM

JB weld softens with heat.

911Etarga · 01-20-2009, 01:36 PM

here is what I just did.