Sport Muffler v2.0

[blee]

My version of the "sport muffler" mod - - - - - - an alternative to the standard "straight-through" approach.



Cutting open a stock 2 in 1 out muffler revealed not one, but two layers of skin.
Drilling out/around the large spot welds takes patience.








Rather than just cutting two holes and adding tips, I tried to route the exhaust gases through a path that somewhat mimics the standard path while letting it ~breathe~ a little easier. The idea was to create a muffler that wasn't too loud, while less restrictive.



Once you cut out the two pipe sections in the middle, you can flatten them out and cut them to a half-moon shape and weld them into the lower chamber to isolate the flow path. There should also be enough old material left over for the two round pieces that plug the two holes - (1) exhaust tip & (1) internal plug. Ergo, no new material needed.

Then a butt-load of welding!





Viola!
A little louder than the single-out DANSK Sport muffler I had with a dramatic increase in throttle response (Unexpected surprise!) and zero droning!
I'm digging it.

https://youtu.be/iZbZ1aEvxCo

Vrmmm Vrmmm!

[Trackrash]

Nice work. Great documentation.

[kenikh]

Sweet! Was this before or after the campout?

Sent from my Nexus 6P using Tapatalk

[blee]

Before.

[kenikh]

I will pay more attention next time!

Sent from my Nexus 6P using Tapatalk

[al lkosmal]

Nice work Brian.

regards,
al

[MIK911]

Nice job!
Post up a sound clip/youtube vid.

[MARISOL78sc]

Originally Posted by MIK911

Nice job!
Post up a sound clip/youtube vid.

From his post................https://youtu.be/iZbZ1aEvxCo

[75 911s]

Well done! I did the "1.0" mod if you will. This looks like a much more logical design.

Have you noticed pop and gurgle? Did you have any issue lining up the dual out? What size are the pipes? ZERO drone? :-)

[Geronimo '74]

Sounds great, look great!
(Luckily, none of your welds are visible...)

[blee]

G-man, I thought I did pretty well with the welds I know, not the prettiest beads. The original thought was to just tack the tips in place and take it over to the welder since my research revealed that MIGs don't do well with Stainless Steel? But, to my surprise, the tack went on so well that I just finished it off with my MIG. Yah, you can't really see it. Plus, it's not that bad! Now I'm fixated on the welds. Thanks G!

Duane - there is "gurgle" when you lift-off the gas, but no popping. Come to think of it, I did have popping with the single-out DANSK Sport. I kind of like the gurgle.
The tips are 2.5" U.S. made 304 stainless tubing purchased online from Race Mufflers - Stainless Mufflers - Oval Race Exhaust. Ordered two-feet for $13/ft. - very nice quality.

[Elombard]

Looks great - I noticed the double layer of steel on these mufflers as well. I wonder if that is one of the major contributors to the stock mufflers being so quiet compared to any aftermarket set ups?

Wish I could buy one of these from you!

[Trackrash]

Originally Posted by blee

G-man, I thought I did pretty well with the welds I know, not the prettiest beads. The original thought was to just tack the tips in place and take it over to the welder since my research revealed that MIGs don't do well with Stainless Steel? But, to my surprise, the tack went on so well that I just finished it off with my MIG. Yah, you can't really see it. Plus, it's not that bad! Now I'm fixated on the welds. Thanks G!

Duane - there is "gurgle" when you lift-off the gas, but no popping. Come to think of it, I did have popping with the single-out DANSK Sport. I kind of like the gurgle.
The tips are 2.5" U.S. made 304 stainless tubing purchased online from Race Mufflers - Stainless Mufflers - Oval Race Exhaust. Ordered two-feet for $13/ft. - very nice quality.

What welder and wire are you using?

Originally Posted by Elombard

Looks great - I noticed the double layer of steel on these mufflers as well. I wonder if that is one of the major contributors to the stock mufflers being so quiet compared to any aftermarket set ups?

Wish I could buy one of these from you!

I don't believe all of the old banana mufflers, like a Dansk, are double skinned.

There used to be a couple of guys, many years ago, that would do the sport mod to stock mufflers. Might be easier to find a good used one.

[Elombard]

I don't believe all of the old banana mufflers, like a Dansk, are double skinned.

I agree I think the weight thing and cost of manufacturing probably convinced them not to manufacture this way.

Not a lot of people shopping for an aftermarket "Quiet" muffler.

Yeah If I had a converted muffler at one time but it was load and droned. I want one that is re-routed like yours is.

Probably have to build one myself.

Thanks again for sharing this awesomeness!

[Inkblot]

Very cool mod! Thx for posting. I'm about to cut open my stock banana muffler to see what needs repair, and tempted to perform the same modification while I'm in there.

Couple of questions:

Did you stuff the old wadding back in? Or replace it? Same locations?

Why the little strips under the new SS tubes? Structural, or to help w alignment, etc?

Any pics of the internals, after you were done, but before you buttoned the lid back on?

Thanks- and nice work.

Jake

[blee]

Jake -

Discarded the wadding - it turns into dust when handled.
The strips are for structural support - ala M&K.
Sorry, no pictures of the innerts before closing her up. I was on a mission by then to finish and forgot to take pictures. It did look just like my drawing, maybe just not as pretty.
The trickiest part was fabbing & welding in the two half-moon pieces to isolate the center chamber. You want to make sure you have a pretty good seal in order for the whole back-pressure path-thing to work, plus there's lots of heat where the exhaust manifold attaches so you want to be sure they will hold.

Have driven the car about 3K miles this summer with this muffler - I wouldn't trade it for anything else! The sound is just right and the rev-response is intoxicating.

Enjoy the journey!

[rbogh901]

Originally Posted by blee

Jake -



Have driven the car about 3K miles this summer with this muffler - I wouldn't trade it for anything else! The sound is just right and the rev-response is intoxicating.

Enjoy the journey!

I plan to.

And I like this approach.
How did you make the cuts for the twin pipes?

[larrym]

looks like you successfully duplicated the euro sport muffler that was installed on my 914-6 in Germany circa 1972 (and which i am still running)

.

and - or - the old school town-and-country version

[blee]

Originally Posted by rbogh901

I plan to.

And I like this approach.
How did you make the cuts for the twin pipes?

Your standard hole saw.

[rbogh901]

I was thinking that might be it but can't imagine how much it would jump around as you bore from the side. Just go perpendicular to the surface best you can and then oval it out to fit the angle of the pipes I suppose.