Exhaust valves

[RPSN]

It's 100% certain to be a vacuum. Given the conversion is to take a feed from the inlet manifold which has a vacuum in it, not a positive pressure

I would think so.

However, the earlier set-up was also operated by a vacuum as shown in the diagram I posted, which seems to show the air flow going into the exhaust valves?

To be 100% certain, the vacuum pipe that connects directly to the exhaust valves would need to be removed and checked.

My read of that diagram is clear
The vacuum pump creates a partial vacuum and that is stored in the reservoir. The suction applied to the exhaust valves goes through a damper, which will be there to smooth the process so the valves open progressively and not in a jerk motion as the pump works. To close the valves air enters the pipework through a filter and valve which is undamped and thus allows the valves to close rapidly. If not then when closing you'd have to wait ages for the vacuum to decay by leakage. Air flow is bi directional in the pipe depending upon the desire to open or close.

Later cars simply eliminated the vacuum pump and reservoir [noisy and unreliable] with a straight vacuum from the inlet manifold

Your reading of the diagram is not as clear as the manufacturer’s information that came with it, i.e.....

“In the pipes between the solenoid valve and the exhaust valves, a restrictor is installed in parallel with a check valve. The restrictor slows the flow of air through the pipes, to damp the opening of the exhaust valves. The check valve ensures that air flows only through the restrictor when the exhaust valves are opened, but allows the restrictor to be by-passed when the exhaust valves are closed, to give an undamped closing movement.”

Also the diagram seems to show the air flow going into the exhaust valves?

100% certainty of the air flow would be achieved by removing the vacuum pipe that connects directly to the exhaust valves (which are operating correctly) and checking for suction or blowing. As I’ve said, I would think that suction would be felt but I’m not 100% sure of this?

Yes, later cars had the vacuum conversion due to the active exhaust vacuum pump being noisy (as shown in the JTB00365NAS2 document I posted earlier).

 

[Jaguandy]

Yes, my mistake, rapid closing, slower opening. I forgot the vacuum closes the silencer valves.

 

[RPSN]

Air flow is bi directional in the pipe depending upon the desire to open or close.

The following additional information refers to the early F-Type TOPIx ‘Active Exhaust Vacuum Control Diagram’ I posted earlier......

“The solenoid valve is connected to ground through the ECM (engine control module). When the ECM determines the exhaust valves require closing it connects the solenoid valve to ground.”

“When the solenoid valve energizes it opens the pipe connection from the reservoir and vacuum pump to the exhaust valves and closes the atmospheric vent. The depression at the reservoir and vacuum pump is then sensed at the exhaust valves, via the check valve, and the exhaust valves close.”

“When the ECM determines that the exhaust valves require opening, it disconnects the solenoid valve from ground. The solenoid valve de-energizes, closes the pipe connection to the exhaust valves, and opens the atmospheric vent. Atmospheric pressure is then sensed at the exhaust valves, via the restrictor, and the exhaust valves open.”

It seems that in effect, the system sucks air to close the exhaust valves and blows air to open them (due to the operation of the atmospheric vent).

 

[cj10jeeper]

Ok you’ve edited your post, but were interpreting it wrongly. To close the valve vacuum is created. There is no ‘blowing’. There is no compressor, no positive pressure, etc. to open them
It’s entirely a vacuum system which when released atmospheric pressure brings the valve back to open state

 

[RPSN]

As you can see from my previous post which includes information from TOPIx, the operation of the atmospheric vent (sensed by the exhaust valves) determines the opening and closing of the valves. In effect, the system sucks air to close the exhaust valves and blows air to open them.

By the way, there is an air flow in this Active Exhaust Vacuum Control system which is why it has an ‘Air flow check valve’ and ‘Air flow restrictor’ (shown in the diagram).

As stated in the TOPIx information that I provided along with the diagram....

“In the pipes between the solenoid valve and the exhaust valves, a restrictor is installed in parallel with a check valve. The restrictor slows the flow of air through the pipes, to damp the opening of the exhaust valves. The check valve ensures that air flows only through the restrictor when the exhaust valves are opened, but allows the restrictor to be by-passed when the exhaust valves are closed, to give an undamped closing movement.”

Also, here are some of your earlier comments regarding suction and air flow in the system.....

“I would take the pipe off one side and see if it is creating a suction”

”The suction applied to the exhaust valves”

“To close the valves, air enters the pipework”

“Air flow is bi directional in the pipe depending upon the desire to open or close”

Off out in the car now....weather’s too nice to be indoors

 

[Philskill]

It doesn't blow air as such, it opens the valve to Atmosphere, which returns it to it's natural state of open (likely using a spring or diaphragm internally)

Thus it sucks air to close them, but releases the attained suction to atmosphere to open (via a restrictor to open them slowly), e.g. the spring in the valve opens it as it no longer has opposing pressure on each side of the valve diaphragm to counteract the spring.

 

[cj10jeeper]

It doesn't blow air as such, it opens the valve to Atmosphere, which returns it to it's natural state of open (likely using a spring or diaphragm internally)

Thus it sucks air to close them, but releases the attained suction to atmosphere to open (via a restrictor to open them slowly), e.g. the spring in the valve opens it as it no longer has opposing pressure on each side of the valve diaphragm to counteract the spring.

Thanks Phil - spot on and as I have been saying for a couple of days

My analogy in reverse of this but maybe easier for folks to follow is you blow into a balloon to inflate it. Keep it pinched closed and when you want to deflate it you don't 'suck' it out, just let the spring of the balloon and atmosphere deflate it to resting state

 

[RPSN]

It doesn't blow air as such, it opens the valve to Atmosphere, which returns it to it's natural state of open (likely using a spring or diaphragm internally)

Thus it sucks air to close them, but releases the attained suction to atmosphere to open (via a restrictor to open them slowly), e.g. the spring in the valve opens it as it no longer has opposing pressure on each side of the valve diaphragm to counteract the spring.

Thanks Phil - spot on and as I have been saying for a couple of days

My analogy in reverse of this but maybe easier for folks to follow is you blow into a balloon to inflate it. Keep it pinched closed and when you want to deflate it you don't 'suck' it out, just let the spring of the balloon and atmosphere deflate it to resting state

Thanks for your efforts guys but the TOPIx information and diagram in my previous posts explain exactly how this system operates.

As Philskill mentions....”it sucks air to close” the valves. However, to open them, the air travels back and through the air flow restrictor which slows the flow of air through the pipes to the exhaust valves. This is clearly shown in the TOPIx diagram and information I posted i.e.....“The restrictor slows the flow of air through the pipes, to damp the opening of the exhaust valves. The check valve ensures that air flows only through the restrictor when the exhaust valves are opened”

I have incorporated.....”In effect, the system sucks air to close the exhaust valves and blows air to open them” because this is effectively what it does.

With regards to cj10jeeper’s ‘balloon example’, of course you wouldn’t suck the air out of it.....it blows out on its own, which produces air flow. A similar principle is used to open the exhaust valves.

Back to the OP whose valves don’t appear to be working (ouch!). You mentioned that you were going to have another look at the vacuum lines to make sure they’re all connected. Did you find anything untoward, especially in the vacuum pipe connections in the rear left wheel arch behind the NVH (Noise/Vibration/Harshness) pad?

You previously asked if the exhaust valves are open (loud) upon startup until the vacuum closes them. I can confirm this is correct.

 

[S1jor]

I am yet to check the vacuum lines properly, I will report back when I have done