This whole "backpressure required" ONLY has validity IF the computer is not adjusted for it. The neccesity for computer adjustment while running with open exhaust is completely dependant on how well the particular exhaust system flows to begin with.
For example if you took a car that had a very restrictive exhaust to start with and changed to open exhaust the car could certainly run worse because running open exhuast would require an air/fuel ratio that is beyond the adjutability range of the computer.
Don_w has no problems running open exhuast because his "regular" exhaust is already very unrestricted. Someone else may not have this situation.
So there is some validity to Sharky's comment but Don is right also, each for their respective vehicles.
It just depends on the individual setup.
Just keep in mind that IF the engine has a correct air / fuel ratio there absolutely will NOT be any problem running with open exhaust.
However if changing to open exhaust causes the A/F ratio to lean out really bad not only would you loose power you could even end up with burned valves, but again this is only of the correct A/F ratios are not maintained.
This is why a good wideband A/F gauge is worth every penny.
Particularly if you are using exhaust cutouts and you are unsure of how it will effect your A/F ratio.
On an additional note, when I was running a vehicle with a carb I used to take a different set of secondary metering rods when I uncapped my headers at the track to make SURE I wasn't running too lean.
ok I'm done now. Sorry for the wordy explanation but it seems like people were over simplifying the question.

 

The wingnuts do sound iffy; the first thing I'll probably do is go to a hardware store and get some nuts&bolts so I can apply enough torque to keep them shut.

Also, these would probably do the trick: http://store.summitracing.com/partde...5&autoview=sku

 

Don, just saw your video w/the open cutouts.. MAN THAT SOUND SICK!!! dude.. that's what I am wanting on my car.

 

nuts and bolts sounds like a good idea man... I never really got around to it... I got so fed up with them so quick I just hacked them off and took of the cat.

 

LMAO! However, he has seen the light! Now if it was the other way 'round...

 

I had Adam weld up custom stub out on the X-pipe as close to the headers as possible. The frame rails and other stuff presented a lot of interference, so this was the only place they would fit well. Pics are below.



The typical "Y-pipe" wouldn't fit anywhere I wanted it, so as noted above, the stub outs were customized. The electronic valve (p/n 815-EC250D) I bought from Jegs: http://www.jegs.com/webapp/wcs/store...0002_757985_-1



All of my drag racing vids are with the cutouts open too... here is a link: http://www.cardomain.com/ride/2450734/2




Pics of cutouts being installed











And this is where I put the switch. Two seconds and they are wide open.

 

I have the summitt cutouts on my son's GT and no problems. Personally we both like the way they sound. No problems with the wing nuts either just tighten them down good.

 

man that looks sweet!! I'm gonna have to talk to my buddy who does all my exhaust wrok about this. Now this may be a silly question but those that make any power or do you lose any power with that set up?

 

Don, that's a great looking (and sounding) setup, thanks for the pics.


rwag, Where did you mount yours? I'm thinking right after the H, pointing away from the driveshaft

 

Honestly, I can't feel any difference one way or the other. I did it purely for the sound.

 

I want some after my prochamber!

 

I had two quicktime electric cutouts (QTECs) on my '98 WS6 ... LOVED THEM! - sounded sweeeeeeeet .. I may do it to the stang as well ..

oh .. they dyno'd my car with them closed and open .. I no longer have the dyno sheet but it was something like 7 hp gain with them open compared to closed

 

don.. yeah I figured there wasnt much of a "gain" per say but just for the sound it would be totally worth it. I'm thinking this maybe som ething i need to get done soon.

 

I just recieived the cutouts; I'll be installing them tomorrow, probably right after the H. The edge of the pipe sticks out about 1mm from the flange, so the gasket doesn't fit flush against the flange. This isn't possibly part of the design, is it? I'm going to sand down the edge so it fits flat.

 

Did the install today... These things ROAR!


http://forums.bradbarnett.net/showthread.php?p=915264