Muffler bypass w/valve
 

Installed a muffler bypass for a friend on his '80 Porsche 911 (non turbo unfortunately). Thought you guys might like to check it out. It's got a switch on the dash so you can open/close it whenever you want.

Cut a hole in the pipe just after the cat/before the muffler, welded on short 2.5" tube and 3 bolt flange. Mounted valve then made new tip with another 3 bolt flange and some short bends. Cut off his old muffled tip and welded on matching tips. Now it looks like the old turbo 911's. I think it turned out pretty sweet.

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Re: Muffler bypass w/valve
 

Nice design, it's different.

Re: Muffler bypass w/valve
 

I like it!

Re: Muffler bypass w/valve
 

WHY after the cat?

Re: Muffler bypass w/valve
 

It's a header right up to the cat and would be a pain to plumb from. It's plenty loud like this. Next time I see him I'll take a video with him opening/closing it and I'll post.

Re: Muffler bypass w/valve
 

Yeah, plenty loud. It's likely all that this mod is going to do for your friend since you installed it AFTER the cat. :S

At least you did it yourself.

Re: Muffler bypass w/valve
 

Is that bypass valve aluminum? I doubt it, but it looks real shiny in the pic.

Re: Muffler bypass w/valve
 

a lot of perople use thottlebodies for the same thing. it could be aluminum. it would be fine

Re: Muffler bypass w/valve
 

The body of it is aluminum, the actual flapper valve is steel. I never thought of a throttle body for one of these valves, thanks for the idea.

Performance wasn't the motivation for my friend wanting to do this. He just wanted it to look and sound cooler. He drives like a grandpa (which he is actually...not mine, lol). It was fun to do and was good experience to get under my belt. Always nice when you can use someone else's money and car for learning, ;D

Re: Muffler bypass w/valve
 

i was gonna say, that ain't really doing anything for power, besides maybe letting a little backpressure out that builds before the muffler, but not enough to allow alot more power to be made (unless the muffler is VERY restrictive, since this thing is not really in the 'flow' of the exhaust, more like a BOV, haha

def a "sound" mod

nice job, the tips look good