Early Factory Mufflers

[cegerer]

Somebody educate me. Were there both single-outlet and dual-outlet sport mufflers available from the factory for pre-74 911s?? -- Curt

[silverc4s]

There was a THREE outlet sport muffler, with caps for the 2 sport pipes for the road, and a cap for the (standard) side exhaust for the track. It was available as part of a "sport" kit in the 70's, but I can't tell you much more about it. I think it came with some weber jets and possibly some other stuff as well.

Never heard of a single out "sport" muffler.

[CamB]

Does anyone know what the three outlets look like inside - is it like the single outlet?

I am heavily attracted to the idea of a muffler I can "un-cork" to let rip on unsuspecting country dwellers, then recork for the highway cruise home...

[steveW]

camB!

I have been looking at the idea of making up an exhaust system along the same lines. So far I've started making a jig, but any changes made to the exhausts seems to upset the jetting.

I would like to know how Porsche got around this with the three outlet system.

If it runs in sport configuration, when jetted for the 'road' configuration it would be lean and risk burning pistons.

As far as I know the 3 outlet was essentially the same inside as the single outlet, but with two pipes exiting in almost a straight line from the inlet. The muffler is a sort of double decker set-up where the gasses go in at the bottom and are forced through baffle plates toexit at the end of the top section. The twin out lets exit from the bottom section and are thus almost straight though.

Cheers

[CamB]

Steve - definitely keep us updated --> this is very cool!

Cam

[RSR.guy]

Yeah, the three outlet systems are pretty cool. I have photos of one I cut apart before I repaired it; from a factory SC/RS. I'll try and dig 'em up for you guys.

Basically, the two un-muffled 'sport' sections are straight thru from the headers to the outlet. They utilize a small section of perforated tube, so that when the outlets are capped, the exhaust gasses are forced to go through a series of vertically oriented baffles. The baffles have a series of small holes in them and are welded into the main can.

The caps don't work particuliarly well as far as fully sealing the gas flow, although the noise reduction is decent when they're in place. Also, the caps have a tendency to get rusted on pretty easily. I think this system was Porsche's way of getting past the rule makers when running their race cars through the occasional in-city race stage.

Cheers, Chris

[cegerer]

I don't know if this is a 'factory' 3 outlet muffler or a do-it-yourself, but I took the photo in 1982:



-- Curt

[RSR.guy]

Curt,

Yup, that's a factory piece. The caps are the give away.

Nice photo!

Chris

[Early_S_Man]

The DOWN SIDE of those early rallye kits ... from an esthetic standpoint, were those MUDFLAPS! Came with the twin-outlet sport muffler, too!

[Two Oh]

RSR guy, I too have seen the inside of a 3 exit with caps sport muffler. Doesn't seem efficent to me. All those peforated holes will quite things, but it disrupts the flow. What do you think.

Also, the inside of a early dual in single out muffler look a little odd to me. Some people think the hot dog muffler is acting as a crossover pipe but I don't see it. From looking at the inside of the muffler I see the pulses bumping into each other and fighting to exit. Again I see peforated tubes which slow pulses to an uneven flow.

The hot dog sport muffler may have been the best in its day but is there something more efficent out there?

I remember reading somewhere that a Flowmaster muffler will will produce almost as much HP as megaphones and and will make more HP than a sport muffler.

Any comments, ideas or put downs are appreciated.

Regards -2.0


PS Curt, I do not know exactly what the sport muffler weighs, but I will say it is more than twice as heavy as the stock muffler.