Lizard928

Keep in mind that dumping the exhaust could actually result in less overall HP.

rawky

How does that work exactly? Does it open over a certain rpm?

Do you have any photos or any places that I can get some from?

PorKen

Weird. What about OEM systems with variable muffler inlets, or variable length exhaust pipes?



I have a vacuum valve in the HeX-pipe™ on my '86.5. (It forces the exhaust down the longer passenger side pipe at high vacuum, but opens pretty quickly when you snap open the throttle.) I thought it might make for more torque at smaller throttle openings, but it's tough to say yay or nay with the automatic. (Someday I'll put it on the manual, for a better test.) It does make it quieter however. This setup is actually more quiet than with the factory cats...which I put on for special occasions.

svp928

Ken, where did you get that? It looks like the old cold-start flapper they put on American cars pre-'75 or so, that closed one side of the exhaust manifold and forced exhaust thru the port under the intake...
Lol, brought back some memories....

PorKen

It is a heat riser valve, but made for headers (for California). 2.5" ID. I bought them from Summit. (BTW: it took over a month to arrive.)

http://www.summitracing.com/parts/DTE-HR212-3V/

svp928

Heat riser! I couldn't remember that phrase for life of me....getting old sucks..
The old cast iron ones cracked, stuck shut, rattled--- pain in the azz. I was trying to think of a way to quiet things down at will- that looks like it would work fine. Thanks Ken!

PorKen

You'll need two 2.5" header flanges to sandwich the valve, too.

svp928

Actually, what I plan on doing is making my own chamber, maybe even square- with a big butterfly drilled full of holes. That way, I can pretty much shut it completely and still have flow, but not so noisy. Then, optimally, it should be controlled by the ecu to move from closed to open by best torque- just like you had planned. Probly be easier to just tie it to rpm and have full open by 4000 or so.
At the speed I get around to things, I will be too old to drive by the time its done......
Several new cars have something like this already- a friend dropped by with a ZR-1 to see if we could get the exhaust bypass to work on a switch, so he could pass sound tech at Laguna- 92db. That car has 4 exits, and 2 of them are on a butterfly so they only open by command from the ecu- some percentage of throttle, rpm and man. pressure. When they do open, you definitely know it! In the end, he just put some 90deg turnouts to point away from the mic, and that got him by..

slate blue

By PorKen

If they are OEM they are allowed, so the Ferraris etc can keep theirs, even if your car complies with noise levels with the valve closed it is illegal.

Greg

Daniel5691

Hi,

Is anyone currently experimenting with these types of diverter systems?

I do wonder if there were any actual performance gains, or.... if it just makes the exhaust sound louder and angrier...... ? ?

James Bailey

Makes the noise sound like a rusted out muffler on an old chevy truck..... or Saturday night at the local dirt track...