Project LSX 4.6is

[BigBody]

I always liked the idea of vacuum exhaust cutouts! I dont think id ever go for electric cutouts due to the infamous reliability of the electric motors. Plus you dont need to mount any ugly switches anywhere. I say go for the IS exhaust! With the cutouts you shouldn't really have any back pressure concerns either...

[bcredliner]

Originally Posted by BigBody

I always liked the idea of vacuum exhaust cutouts! I dont think id ever go for electric cutouts due to the infamous reliability of the electric motors. Plus you dont need to mount any ugly switches anywhere. I say go for the IS exhaust! With the cutouts you shouldn't really have any back pressure concerns either...

Vacuum cutouts also have a switch. I have all switches for mods in the console so nothing is visible.

Certainly an individual choice but I wouldn't write off all electric cutouts. Not all cutout motors are created equal. I chose QTP oval cutouts so the opening can be larger than round options. Motors are not a problem and are more than powerful enough to always seal when closed. Some cutouts are either completely closed or completely open. QTP cutouts are on of those that open only as much as you choose.

[BigBody]

Originally Posted by bcredliner

Vacuum cutouts also have a switch. I have all switches for mods in the console so nothing is visible.

Certainly an individual choice but I wouldn't write off all electric cutouts. Not all cutout motors are created equal. I chose QTP oval cutouts so the opening can be larger than round options. Motors are not a problem and are more than powerful enough to always seal when closed. Some cutouts are either completely closed or completely open. QTP cutouts are on of those that open only as much as you choose.

What kind of switch would a vacuum actuated, cutout have? Its solely controlled by boost pressure from your vacuum line. Are you talking about the systems where you mount an electric box with a vacuum pump inside of it?

[crystalworks]

Originally Posted by BigBody

What kind of switch would a vacuum actuated, cutout have? Its solely controlled by boost pressure from your vacuum line. Are you talking about the systems where you mount an electric box with a vacuum pump inside of it?

The switch would activate a vacuum solenoid in the same manner a switch would activate an electric cutout motor.

[bcredliner]

Originally Posted by BigBody

What kind of switch would a vacuum actuated, cutout have? Its solely controlled by boost pressure from your vacuum line. Are you talking about the systems where you mount an electric box with a vacuum pump inside of it?

Crystalworks is correct. Without a switch there would be no control over the opening and closing. The cutouts would be opening and closing based on vacuum present, entirely on their own.

[BigBody]

Originally Posted by bcredliner

Crystalworks is correct. Without a switch there would be no control over the opening and closing. The cutouts would be opening and closing based on vacuum present, entirely on their own.

Yep. Pretty sure thats what OP was referring to. When in boost, the cutout opens. When not in boost the cutout is closed. A popular mod, that involves no switches.

[bmwman528e]

Originally Posted by BigBody

Yep. Pretty sure thats what OP was referring to. When in boost, the cutout opens. When not in boost the cutout is closed. A popular mod, that involves no switches.

Correct. Also keeping it quiet around town and if I'm down on power to 300rwhp out of boost with factory x5 mufflers it will still be plenty fast and once the car starts to build boost the cutouts open thus me having no restriction at all. I still haven't decided that I'm doing this exact exhaust setup but it's definitely one of my top choices.

[bcredliner]

Originally Posted by bmwman528e

Correct. Also keeping it quiet around town and if I'm down on power to 300rwhp out of boost with factory x5 mufflers it will still be plenty fast and once the car starts to build boost the cutouts open thus me having no restriction at all. I still haven't decided that I'm doing this exact exhaust setup but it's definitely one of my top choices.

Vacuum is the greatest when the engine is idling. As RPMs increase vacuum decreases. Vacuum varies somewhat by engine, condition of engine and where the hose is connected so it would be very difficult to offer anything but vehicle specific models. Do you have a link to cutouts that have no switch?

Cutouts reduce restriction but do not eliminate it. The engine is restricted by the stock exhaust manifolds, by the size of the exhaust pipes and by the cats that should be before the cutouts. Headers are always a much better performance option.

[audiophool]

Originally Posted by bmwman528e

Correct. Also keeping it quiet around town and if I'm down on power to 300rwhp out of boost with factory x5 mufflers it will still be plenty fast and once the car starts to build boost the cutouts open thus me having no restriction at all. I still haven't decided that I'm doing this exact exhaust setup but it's definitely one of my top choices.

You know what would be really good if available: exhaust cutout that uses a pressure actuator rather than vacuum, and would open the cutouts anytime you have higher boost pressure. Or am I nuts?


BTW, this build look sooooo tempting.

[crystalworks]

Originally Posted by BigBody

Yep. Pretty sure thats what OP was referring to. When in boost, the cutout opens. When not in boost the cutout is closed. A popular mod, that involves no switches.

Ah, yes. Similar to the exhaust flaps on e46's, and I'm sure other BMW mufflers. I assumed OP would want control over the flaps... though I guess he still does, with his right foot.