For those of us who like to sometimes be loud and fast, and sometimes be slower and quieter, electric exhaust cut outs sound pretty appealing. I know that the Volkswagen .:R32 uses these from the factory, but I don't know how they are setup.



Product on SummitRacing.com...

It takes them about 2-3 seconds to open the butterfly 90 degrees. It uses a 3 position momentary rocker switch kind of like a window switch. These could be installed on a dump pipe, or on a muffler, etc.

I was thinking that this would be awesome for my NA S4. I have an electronic switch for my 5th and 6th ports so I could setup a relay to open up the electric cut outs too at the same time.

How would these be properly installed? If you just hooked it up as a dump pipe on the side of the midpipe (before Y pipe on dual exhaust) it would just be a secondary route for exhaust to flow. It doesn't seem like you would get the full benefit because the exhaust would still go to the mufflers and out your side dump instead of just out the side dump. In order to make it truly flow all out the side dump you would need two of these. One to block off the main exhaust, and one to open up the side dump. That would cost well over $400 to install though because these are $190 each!

The other problem is that they don't just "flick" open. They slowly rotate.

Here is a video of the cut out in action:
http://www.buickgn.com/cutoutclip.MPG

As you can see it took 2.5-3 seconds for it to fully open. That's an eternity.
Somehow Volkswagen overcame these obstacles and made it work on the .:R32. If they can do it, we can do it. Now any ideas?

 

I don't think you need to worry about closing off the rest of the exhaust system. In general, the exhaust will flow out the least restrictive path available.

I always thought it would be interesting to have a twin midpipe with a valve (not a dump, but just a valve) in one of the pipes. The idea is that you would get better velocity and flow with one pipe at low RPM and then open the other pipe when you need it at high RPM. However, it sounds like those valves open too slowly to work for this kind of thing.

The Ferrari 360 (or 355?) had a valve in the exhaust system for tuning (or noise control? both? I'm not sure). The new Z-06 has two valves (though they don't look electric) near the exhasut tips, clearly visible in recent ads.

-Max

 

Your idea sounds good. Although this thing doesn't open fast enough for that to work %100. I understand what your saying though. At low RPMs that would generate extra back pressure, and at high rpms it could allow extra flow. Assuming you could get it to move faster than what it does.

I could rig up a dump pipe off the midpipe and either just dump it straight to the ground, or weld an entire section of mandrel bent tubing to a side exit right by a rear tire like this car has:



I'm not familiar with the underside of my RX7 though and I don't know if it has enough room for three different exhaust pipes lol. I doubt it does. I'll check it out the next time I lift my car up. Anyone have pics of the underbelly of an FC?

 

Check out this vid. This is the DMH unit. It seems to work pretty good!

http://www.dmhperformance.com/DMH.mpeg

 

Couple picks of a similar concept:




This is pretty much what I had in mind, although I think I would extend the outlet all the way to the side of the car. I wouldn't want any back-pops or flames under the car and that would resonate terribly.

So far from researching around it seems to work excellent on piston engines. I don't know about a rotary though.

 

Keep in mind that exhaust pressure could possibly "help" the thing open up.

 

The 20B Cosmo's had a system where two of the four exhaust tips open up under load. Basically, it was just a butterfly valve with a lever attached to a diaphragm canister with boost pressure fed to it. Very simple. Would've worked well if mine wasn't rusted shut. lol

 

i've got a cutout that's controlled by a wastegate actuator...opens up automatically under boost.

i think it was atpturbo.com where i got it, but can't remember for sure

 

I have one on my RX3. Pretty cool. I run two mufflers on my 12abp. The header collector is 3 inch, to a 3 inch muffler. Then I run the electric cutout. Past the cutout, the exhaust narrows to 2.5 inch, though a 2.5 inch muffler. I drive on the street through both mufflers, and open the cutout to only run on the 3 inch muffler at the track. The car has to be off to be able to hear the cutout fully open when hitting the switch. If you arent careful, you may not hold the button long enough, and the cutout doesnt fully open.

 

Well I think I am going to try and pull this off. My car is in storage for winter so it's the perfect time for little projects like this.

 

I am planning on doing something similair I want to run a 3" dp on my 87 TII and then about 3 quarters of the way down the dp i am going to install this. I am going to have the dp taper down to match up to the stock cat after the cutout so I can run pretty much a stock sound for normal driving and hit the switch to open up to 3" when I really need it ie the track. I have been looking into this and will prob do something like this after winter.

 

Oh wow so your going to modify it to run right off the downpipe? Holy loudness.
Is the oxygen sensor going to be located before your dump, or after the dump?
I don't even know if it matters. I'm not very familiar with the RX7 yet. If I had some underbelly pics (ehh hem) I could plan this better!

 

It will dump after the 02 and yes the ****** is going to be loud that is why its for track and racing purposes only i dont need the power at all times and i want my car fairly quiet for normal driving...

 

Well, I had the manual cutout on my stockport 12a, its a big cast iron Ypipe with flapper valve in it, and a cable running inside. Pull the cable, and I had an open header. Push it, and had full exhaust. Now, I dont know if it was because I had it right after the header or what, but I melted the valve right outta that thing. It would get red hot all the time, and finally just gave out. And the valve in question looks a helluva lot weaker than mine was.

 

My exhaust never gets that hot. I plan to run this after the cat anyway so I don't think it should be quite as severe as what your describing.

The construction of the valve is:

"The cutouts have a maintenance-free, CNC-machined, billet 6061-T6, aircraft-grade aluminum body with a 300 series stainless steel shaft. They also have INA needle bearings "

That sounds pretty good. The only thing I would worry about is the needle bearings.

 

This is just a nit, but I don't want backpressure, I want the better exhaust velocity that a smaller pipe would give at low flow levels. They aren't the same thing.

-Max

 

This past spring had one installed on my 85 13b which has the Racing Beat header presilencer and main rear muffler...had a y pipe inserted just before rear axle with straight thru pipe over the axle and a pipe coming out the back next to the rear muffler..added a tip plus two tips on rear muffler looked like a triple exhaust.
At the track and on closed road sections opened it up...very loud... worked most of the summer...but eventually got stuck open for the last two days of Targa Newfoundland.

After the event took it apart and found the rotary firery breath had warped the butterfly..
Great fun in traffic when it worked ...pull alongside a Harley and guess who caused the most noise.......