Vacuum exhaust valves
Discussion
I am working on a project to have a vacuum valve in my exhaust for some extra noise
however I am struggling to find out how to wire and connect the vacuum pipe from the engine to the exhaust valve
my understanding there is a solenoid, so how would this work? on for loud or off for loud?
as the throttle opens I assume that the vacuum will reduce? if so how do I get round this as the valve will shut again?
so anyone with knowledge of how the sports exhaust on cars like Porsche work please
however I am struggling to find out how to wire and connect the vacuum pipe from the engine to the exhaust valve
my understanding there is a solenoid, so how would this work? on for loud or off for loud?
as the throttle opens I assume that the vacuum will reduce? if so how do I get round this as the valve will shut again?
so anyone with knowledge of how the sports exhaust on cars like Porsche work please
Do you mean an exhaust silencer cut-out?
Not illegal at all, oh, no, officer!
Have you seen: https://www.youtube.com/watch?v=cKgTuIFKAvo&ab... ?
Not illegal at all, oh, no, officer!
Have you seen: https://www.youtube.com/watch?v=cKgTuIFKAvo&ab... ?
Ie a porsche with the sports exhaust.
I am aware there are two different types, pressure and vacuum. the Porsche valves work using vacuum
so is it a case solenoid on/open, the exhaust vales open, but how do they remain open because as you open the throttle more won't the vacuum drop?
I am aware there are two different types, pressure and vacuum. the Porsche valves work using vacuum
so is it a case solenoid on/open, the exhaust vales open, but how do they remain open because as you open the throttle more won't the vacuum drop?
Edited by Petrolhead on Saturday 13th March 11:49
Some BMW E46 & E90's 3 series had a vacuum system. Twin tailpipe exhaust box with a butterfly in one of the outlets. Have a look on https://www.realoem.com/bmw/enUS/select at 330i models, they tended to have them, it will list all the parts & the diagram will show where all plum in.
A mate had a E90 with it on, he just pulled the vacuum pipe off the rear box to have it open all the time.
A mate had a E90 with it on, he just pulled the vacuum pipe off the rear box to have it open all the time.
Broadly speaking:
The valve is a butterfly style metal valve that sits in a position to bypass some of the silencing.
Most usually for an OE application, they block the "straight through" path through the back box in quiet mode, which forces the exhaust gas to pass into and through the silencer box, and hence more noise is absorbed. When actuated, the butterfly flap opens, and the gas can continue straight through the silence in the pipe in which it entered. This is obviously much less restrictive (so the engine can make more power) but also, it means much less noise is absorbed.
The valves use a rubber diaphram style actuator, and are sprung open usually, ie if disconnected they are straight through. This is done because a valve that failed to closed, the higher restriction mode, could cause engine to operate incorrectly at high rpm/load, where it would be normally expected to run with low backpressure. Applying a vacuum to the valves actuator causes the diaphram to be sucked to the end of it's travel, which pulls the valve closed, shutting of the straight through path, and putting the system into queiter mode
The valve is controlled by a standard 3 port pneumatic solenoid, driven by the engine control unit. That valve can either connect the actuator to the source of vacuum, or connect it to open air, ie no vacuum, depending on if it is powered or not (google "3 port pneumatic solenoid" for more info on how that works)
Because the system does not need a constant "flow" of vacuum, it only needs a small amount of air to be pulled out of the actuator diaphram each time it is operated, usually a small diameter vacuum line is taken from the inlet manifold, through a one way valve and into a small plastic vacuum resevoir, usually of about 300 to 500cc, and from there to the inlet port of the control solenoid. That vacuum resevoir gets pulled down to the lowest inlet manifold pressure as the engine runs at low loads (throttle closed) a pressure of typically about 30 kPa (abs). The resevoir is used because you want the valve to actuator even at full throttle when there is no inlet manifold vacuum or of course on a turbo engine, where inlet manifold pressure will be positive.
(a lot of modern OE systems have moved to electric actuation to avoid this issue and simplify the plumbing etc, but making an electric motor and gears etc work in a hot, vibrating, underfloor environment is not easy)
Most aftermarket "screamer" valves are intended to be fitted effectively as a "Hole" in the exhaust, ie upstream of the silencing, and are therefore sprung shut, and opened with the vacuum source rather than the OE opposite approach.
The valve is a butterfly style metal valve that sits in a position to bypass some of the silencing.
Most usually for an OE application, they block the "straight through" path through the back box in quiet mode, which forces the exhaust gas to pass into and through the silencer box, and hence more noise is absorbed. When actuated, the butterfly flap opens, and the gas can continue straight through the silence in the pipe in which it entered. This is obviously much less restrictive (so the engine can make more power) but also, it means much less noise is absorbed.
The valves use a rubber diaphram style actuator, and are sprung open usually, ie if disconnected they are straight through. This is done because a valve that failed to closed, the higher restriction mode, could cause engine to operate incorrectly at high rpm/load, where it would be normally expected to run with low backpressure. Applying a vacuum to the valves actuator causes the diaphram to be sucked to the end of it's travel, which pulls the valve closed, shutting of the straight through path, and putting the system into queiter mode
The valve is controlled by a standard 3 port pneumatic solenoid, driven by the engine control unit. That valve can either connect the actuator to the source of vacuum, or connect it to open air, ie no vacuum, depending on if it is powered or not (google "3 port pneumatic solenoid" for more info on how that works)
Because the system does not need a constant "flow" of vacuum, it only needs a small amount of air to be pulled out of the actuator diaphram each time it is operated, usually a small diameter vacuum line is taken from the inlet manifold, through a one way valve and into a small plastic vacuum resevoir, usually of about 300 to 500cc, and from there to the inlet port of the control solenoid. That vacuum resevoir gets pulled down to the lowest inlet manifold pressure as the engine runs at low loads (throttle closed) a pressure of typically about 30 kPa (abs). The resevoir is used because you want the valve to actuator even at full throttle when there is no inlet manifold vacuum or of course on a turbo engine, where inlet manifold pressure will be positive.
(a lot of modern OE systems have moved to electric actuation to avoid this issue and simplify the plumbing etc, but making an electric motor and gears etc work in a hot, vibrating, underfloor environment is not easy)
Most aftermarket "screamer" valves are intended to be fitted effectively as a "Hole" in the exhaust, ie upstream of the silencing, and are therefore sprung shut, and opened with the vacuum source rather than the OE opposite approach.
Max_Torque said:
Broadly speaking:
The valve is a butterfly style metal valve that sits in a position to bypass some of the silencing.
Most usually for an OE application, they block the "straight through" path through the back box in quiet mode, which forces the exhaust gas to pass into and through the silencer box, and hence more noise is absorbed. When actuated, the butterfly flap opens, and the gas can continue straight through the silence in the pipe in which it entered. This is obviously much less restrictive (so the engine can make more power) but also, it means much less noise is absorbed.
The valves use a rubber diaphram style actuator, and are sprung open usually, ie if disconnected they are straight through. This is done because a valve that failed to closed, the higher restriction mode, could cause engine to operate incorrectly at high rpm/load, where it would be normally expected to run with low backpressure. Applying a vacuum to the valves actuator causes the diaphram to be sucked to the end of it's travel, which pulls the valve closed, shutting of the straight through path, and putting the system into queiter mode
The valve is controlled by a standard 3 port pneumatic solenoid, driven by the engine control unit. That valve can either connect the actuator to the source of vacuum, or connect it to open air, ie no vacuum, depending on if it is powered or not (google "3 port pneumatic solenoid" for more info on how that works)
Because the system does not need a constant "flow" of vacuum, it only needs a small amount of air to be pulled out of the actuator diaphram each time it is operated, usually a small diameter vacuum line is taken from the inlet manifold, through a one way valve and into a small plastic vacuum resevoir, usually of about 300 to 500cc, and from there to the inlet port of the control solenoid. That vacuum resevoir gets pulled down to the lowest inlet manifold pressure as the engine runs at low loads (throttle closed) a pressure of typically about 30 kPa (abs). The resevoir is used because you want the valve to actuator even at full throttle when there is no inlet manifold vacuum or of course on a turbo engine, where inlet manifold pressure will be positive.
(a lot of modern OE systems have moved to electric actuation to avoid this issue and simplify the plumbing etc, but making an electric motor and gears etc work in a hot, vibrating, underfloor environment is not easy)
Most aftermarket "screamer" valves are intended to be fitted effectively as a "Hole" in the exhaust, ie upstream of the silencing, and are therefore sprung shut, and opened with the vacuum source rather than the OE opposite approach.
thank you so much, just the answer I was looking forThe valve is a butterfly style metal valve that sits in a position to bypass some of the silencing.
Most usually for an OE application, they block the "straight through" path through the back box in quiet mode, which forces the exhaust gas to pass into and through the silencer box, and hence more noise is absorbed. When actuated, the butterfly flap opens, and the gas can continue straight through the silence in the pipe in which it entered. This is obviously much less restrictive (so the engine can make more power) but also, it means much less noise is absorbed.
The valves use a rubber diaphram style actuator, and are sprung open usually, ie if disconnected they are straight through. This is done because a valve that failed to closed, the higher restriction mode, could cause engine to operate incorrectly at high rpm/load, where it would be normally expected to run with low backpressure. Applying a vacuum to the valves actuator causes the diaphram to be sucked to the end of it's travel, which pulls the valve closed, shutting of the straight through path, and putting the system into queiter mode
The valve is controlled by a standard 3 port pneumatic solenoid, driven by the engine control unit. That valve can either connect the actuator to the source of vacuum, or connect it to open air, ie no vacuum, depending on if it is powered or not (google "3 port pneumatic solenoid" for more info on how that works)
Because the system does not need a constant "flow" of vacuum, it only needs a small amount of air to be pulled out of the actuator diaphram each time it is operated, usually a small diameter vacuum line is taken from the inlet manifold, through a one way valve and into a small plastic vacuum resevoir, usually of about 300 to 500cc, and from there to the inlet port of the control solenoid. That vacuum resevoir gets pulled down to the lowest inlet manifold pressure as the engine runs at low loads (throttle closed) a pressure of typically about 30 kPa (abs). The resevoir is used because you want the valve to actuator even at full throttle when there is no inlet manifold vacuum or of course on a turbo engine, where inlet manifold pressure will be positive.
(a lot of modern OE systems have moved to electric actuation to avoid this issue and simplify the plumbing etc, but making an electric motor and gears etc work in a hot, vibrating, underfloor environment is not easy)
Most aftermarket "screamer" valves are intended to be fitted effectively as a "Hole" in the exhaust, ie upstream of the silencing, and are therefore sprung shut, and opened with the vacuum source rather than the OE opposite approach.
Max_Torque said:
The valve is controlled by a standard 3 port pneumatic solenoid, driven by the engine control unit. That valve can either connect the actuator to the source of vacuum, or connect it to open air, ie no vacuum, depending on if it is powered or not (google "3 port pneumatic solenoid" for more info on how that works)
Because the system does not need a constant "flow" of vacuum, it only needs a small amount of air to be pulled out of the actuator diaphram each time it is operated, usually a small diameter vacuum line is taken from the inlet manifold, through a one way valve and into a small plastic vacuum resevoir, usually of about 300 to 500cc, and from there to the inlet port of the control solenoid. That vacuum resevoir gets pulled down to the lowest inlet manifold pressure as the engine runs at low loads (throttle closed) a pressure of typically about 30 kPa (abs). The resevoir is used because you want the valve to actuator even at full throttle when there is no inlet manifold vacuum or of course on a turbo engine, where inlet manifold pressure will be positive.
(a lot of modern OE systems have moved to electric actuation to avoid this issue and simplify the plumbing etc, but making an electric motor and gears etc work in a hot, vibrating, underfloor environment is not easy)
Most aftermarket "screamer" valves are intended to be fitted effectively as a "Hole" in the exhaust, ie upstream of the silencing, and are therefore sprung shut, and opened with the vacuum source rather than the OE opposite approach.
these are the parts Porsche Sell for their sports exhaust retro fit https://www.design911.co.uk/uploads/pdfs/Instructi... Cant see any resevoir
Edited by Petrolhead on Saturday 13th March 17:16
Edited by Petrolhead on Saturday 13th March 17:19
Petrolhead said:
I am working on a project to have a vacuum valve in my exhaust for some extra noise
however I am struggling to find out how to wire and connect the vacuum pipe from the engine to the exhaust valve
Are you planning to design and build it yourself, or fit a kit? however I am struggling to find out how to wire and connect the vacuum pipe from the engine to the exhaust valve
If you're designing it, it's up to you to decide what you want it to do and then design it to do that.
If you're buying a kit, you'll need to fit the kit however it was designed to be fitted.
https://www.amazon.co.uk/Xpork-Exhaust-Downpipe-Cu...
forget the vaccum ones too much pfaff.... get an electrical one and run it from a switch... wiring so much simpler than running vaccum pipes everywhere and trying to hook into the engine etc.
forget the vaccum ones too much pfaff.... get an electrical one and run it from a switch... wiring so much simpler than running vaccum pipes everywhere and trying to hook into the engine etc.
ruggedscotty said:
https://www.amazon.co.uk/Xpork-Exhaust-Downpipe-Cu...
forget the vaccum ones too much pfaff.... get an electrical one and run it from a switch... wiring so much simpler than running vaccum pipes everywhere and trying to hook into the engine etc.
Having got some more info I am starting to think that electric will be much easierforget the vaccum ones too much pfaff.... get an electrical one and run it from a switch... wiring so much simpler than running vaccum pipes everywhere and trying to hook into the engine etc.
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