sstrickstein

So
I've been watching Bitchin Rides on discovery. They did two cars adding cut outs with a push button on the dash. Has anyone ever put a cut out system on a 928? I started my car once with the exhaust off and it made the hair on my neck stand up! I'm thinking this might be a project I wanna do!

https://www.quicktimeperformance.com/OVAL/

hacker-pschorr

My 79 had a two stage muffler I can open / close on the fly.

Open is un-muffled off the headers. I almost never close the valve.

Todds Turbo also has a secondary exhaust he uses when pulling into the shop at night so he doesn't disturd the neighbors.

Chris Lockhart

I planned to put them on my '89 GT but never got the chance.

Ed Scherer

Otherwise it would be so loud that they'd crap when he drives by?

sstrickstein

Would it be OK to put them in the Y pipe before the catalytic converter or because my O2 sensor is in the CAT I have to do it afterwards?

Fsharp9

Needs to be after the O2 sensor just ahead of the resonator, Sensor needs to see all of the exhaust flow to determine A/F ratio

sstrickstein

I thought so

sstrickstein

Boy is love to put a set on my wife's 996 and not tell her!

sstrickstein

So I had the car on the rack today. The big pipe between the cat and the resonator is the place. But it's right in front of the transmission. Angle the cut out down and to one side?

Fsharp9

I have the Borla system on my car and I was just going to delete the resonator and put it there

Imo000

You can put a muffler bypass on it. They are louder than any straight through 928 exhaust. Had one on mine. I love loud engines but this too much even for me.

hacker-pschorr

Here is mine, it's packed full of fiberglass muffler material.












Sounds like this:

sstrickstein

Cool work. But if I do it it will be a welded in valve in the large exhaust pipe after the catylist.

ptuomov

An opinion:

I like the muffler bypass system such as that in Hacker's photo.

These sort of valves should be operated automatically based on something like throttle position and rpm in N/A motor or something like exhaust manifold pressure or intake manifold pressure in a turbo system. With the turbo system its especially easy to just have pneumatic actuation at the cutout valve. I guess that for N/A car you could set the diaphragm such that a spring tries to open the cutout and the intake manifold vacuum closes it. At WOT, there's no intake manifold vacuum and the spring opens the valve. At idle there's significant vacuum and the valve is closed.

That way, you don't have to remember to push any buttons, the car is automatically reasonably quiet if you're not driving it hard. And since the muffled exhaust tract flow plenty for the low boost and/or low rpm operation, you literally lose nothing in terms of performance.

davek9

I was thinking of something like the newer Mustangs use, and be able to open and close the dumps.