One more thing... I discovered that it makes a huge difference to use headphones when you're listening to these exhaust sound clips vs computer speakers.

Hey tirwin, one of the best SRV vids, I had forgotten how excellent, big thanks

When putting dual outlet mufflers on, how do you go about making another hole in the rear valance?

Also +1 Stevie Ray Voodoo Chile cover. One of my favorites

Great info. I'm leaning toward getting the M+K premuffler first, put that in and try it with the stock muffler, see how I like it, then see about replacing the muffler or not. I need to keep my heat (in Minnesota!) and those SSI's, while beautiful, are spendy.

Sounds perfect

I have read that if your exhaust is *too* free flowing it can hurt low end torque. I'm just curious, can anyone explain why that is? It's counter intuitive. Seems like less pressure would be less pressure across the board?

Ehem!! I went 'Hendrix'!!! SSI/M&K 2/2. Never looking back! Lol

2stroke,

I am fortunate to have a great paint and body shop nearby -- John Holt at Hot Wheels. John had a spare valence and the piece that fits under the rear quarter below the bumper. He had a 930 in the shop so he copied the shape of the dual out and then primed and painted it.

I highly recommend the DVD of SRV with all of his appearances on Austin City Limits. I had the opportunity to see him play live just before his untimely death in 1990. It is one of the best memories of my life.

Tin snips? Not nice but there really is no other alternative but you can buy a fiberglass rear valance. You may feel better cutting that one.

I think it was after 78 Porsche went to smaller intake ports on the heads. Point is that if you can only free up the exhaust to the point of maximum benefit to the intake. That is my layman's understanding. There is some physics of fluid dynamics involved that I don't remotely understand. I think the basic idea is that the wrong exhaust creates back pressure/restriction.

Some will find this statement heresy, but Scott Mackie has a thread on here where he did before/after dyno runs on an SSI conversion. The results were underwhelming and far short of the 15hp gains normally cited. I think he moved the torque curve around.

My butt dyno tells me that I got a noticeable difference in the exhaust setup I have now but there were other factors that went into the improvements. My guess is that I got close to the same benefit of SSIs without the cost.

Tin snips will mangle the edge of the sheetmetal and plus the Porsche sheetmetal is pretty thick. So you'd really need to have a GI Joe Kung Fu grip to get the snips to cut cleanly. Better off using a thin cutoff wheel or small air powered body saw.

Exhaust size definitely affects the power of the engine. There's an endless amount of posts here on the forum about it. Pipe size, length, collector type, and more have a significant effect on the engine's ability to pump air in and out.

Porsche has played around with port sizes a lot and that would seem to depend on camshaft profile and the induction. Tim's right that Porsche switched from "large port" heads on the '78-'79 SC to smaller ones on the '80-'83 SC. Then when the 3.2 Carrera came along the head size opened back up. Note the right hand column below

http://forums.pelicanparts.com/uploa...1433515002.jpg

One thing that is somewhat obvious is the valve size increases as the engine size/displacement increases. Port sizes vary depending on injection type, camshaft, induction type (note how the Turbo ports are relatively small) and other stuff way over my head

That's basically discribing a Bursch single in/out. I have the two in/single out of this with early heat exchangers and I'm very pleased with the sound. I'd say it's a bit more ZZ Top (Think La Grange).

http://burschexhaust.com/6cylinder_files/BX-1134.jpg

JoshD--exactly! I found the Bursch muffler to be too quiet for my taste(as heard i clips on a buddie's 911). I opted for a more unique sound going with a chamber style set up.

The Bursch setup is a good template for how to build your own, though.

I'd like to see someone tr to use that on a 2009 911 as in the pic!;)

The Bursch is probably a bit quieter than a homemade Dynomax system. While the primary muffler in the Bursch actually is a Dynomax, there is also a long glasspack muffler in that straight section between the the U-bend and the chrome tip.

A local club member has a 2-in Burch on his '73 T, I really like the sound. They are pretty affordable, too.

I had the Bursch shown above for about a week, their 1 in 1 out is about like the stock sound and didn't fit quite right also, ie not paralell to the road, had an angled look seen from the rear. They do make nice headers though and great customer service.