Dump Valves

What is a Dump Valve?
Why do manufacturers fit a dump valve?
What can go wrong with a dump valve?
What are the benefits of a GGR Dump Valve?
Why does the GGR Dump Valve have a filter?
What are the advantages of moving the dump valve away from the turbo?
Why do GGR produce alternative diaphragms?

Dump Valve Parts
What is a Dump Valve?
Most production turbocharged engines are fitted with a dump valve. This is to vent away excessive turbocharger boost pressure when the throttle is closed.
All Sierra Cosworth and the original large turbo Escort Cosworth models use the same dump valve. The turbocharger fitted to the latest Escort Cosworth has its own integral unit.
The dump valve is the black plastic saucepan shaped object that you will see connected between the intercooler and the air inlet hose to the turbocharger. You will also see a small hose leading from the top of the valve to the inlet plenim on the engine. Inside the valve is a rubber diaphragm and a steel spring, with a small insert to support the diaphragm where it seats against the dump valve body.
The dump valve has basically two operating conditions; throttle open, and throttle closed. When the throttle is open, the boost pressure coming into the valve from below the diaphragm is equalled by the pressure onto the top of the diaphragm that comes via the small hose from the engine plenim chamber. As the pressures are equal, the spring holds the diaphragm onto its seat, and prevents the pressure venting away. When the throttle is closed, the pressure coming into the top of the valve is significantly reduced, (often to a vacuum), and the pressure below the diaphram lifts it away from its seat, allowing the excess pressure to vent away. As the throttle is reopened, the pressures again equalise, the spring pushes the diaphragm onto its seat, and the boost pressure cannot vent away.

Why do manufacturers fit a dump valve?

It is for a number of reasons. Without a dump valve, when the throttle was closed, the build up of boost pressure would be immense, very similar to closing a quickly flowing water tap. This excess of pressure, (which could be over five times the running boost pressure), would put the components of the system under a great strain. It would try to burst the intercooler and pipework. More significantly, it would put a large strain on the turbocharger itself, firstly stalling the compressor shaft, then trying to force the compressor wheel out of the turbo, against its bearings.
So, the dump valve prevents mechanical damage to the intercooler & turbo pipework, prolongs turbocharger life, and prevents excessive turbo - lag that would be caused by the compressor shaft stalling.

What can go wrong with a dump valve?

The only thing that can go wrong with a dump valve is that the diaphragm can become holed. If this happens, it will not seal, and the boost pressure leaks away all of the time. This will cause the turbocharger to work harder to overcome the leak, (turbochargers will work as hard as they have to, to give the required boost), and this will be noticeable to the driver, as a lack of boost response.
What are the benefits of a GGR Dump Valve?
Our Dump Valve is a direct descendant of the one we developed to use in our Touring Car programme, and has a number of benefits when compared to the standard item. The aluminium body & stainless steel fixings are more robust than the plastic item, and therefore, better suited to the rigours of competition, it is also more pleasing to the eye! The standard valve vents the turbo pressure away through only one small port, and it does this back into the air filter pipework. This means that the air compressed by the turbo, and heated in the process, is then re-compressed, and re-heated. The GGR Dump Valve vents quickly to atmosphere, all around its circumference, allowing the turbo to free wheel, giving quicker response.
Why does the GGR Dump Valve have a filter?
The way the dump valve works means that when the engine is idling, or on the overrun, the vacuum produced by the engine will lift the diaphragm away from its seat, allowing the engine to draw air in via the dump valve (hence, not suitable for cars fitted with air metering units - EscortRS Turbo, new Escort Cos.). In the standard fitting, the dump valve exhaust is connected to the original air filter, so any air drawn in through the valve has already come through the filter. The GGR Dump Valve has its own integral filter fitted to prevent internal engine damage caused by drawing in foreign particles.
What are the advantages of moving the dump valve away from the turbo?
For convenience of plumbing, the manufacturers fit the dump valve as close as possible to the air filter. This also means that it is connected to the hot side of the intercooler. The compressed air from the turbocharger can reach temperatures in excess of 150°C, and this will drastically shorten the life of the rubber diaphragm. Also, for better response, it is preferable to situate the dump valve near to the throttle plate of the engine. If you look at the standard pipework of an RS 500, you will see that Ford Engineers re-sited the dump valve on this homologation model.
To enable the re-positioning of the Dump Valve, GGR produce complete kits consisting of a Dump Valve, a fabricated aluminium pipe to go from the intercooler to throttle body, and all of the relevant silicon hoses and clips to carry out the conversion. The kit also includes two polished aluminium blanking plugs to fit in place of the original dump valve.

Why do GGR produce alternative diaphragms?
We have found that in extreme conditions, even when the Dump Valve is relocated on the cold side of the intercooler, failure of the standard diaphragm can eventually occur. To address this we have put into production two replacement diaphragms. The Fluorocarbon diaphragm is made from a stronger material, and has an increased overall thickness. The ultimate is the Silicon Polyester Reinforced diaphragm. This has the additional strength of fabric reinforcement, bonded within the diaphragm.
Dump Valve Parts · Back to FAQs & Features · GGR Home
Correspondence/Requests
Sales Enquiries: sales@grahamgoode.com
Technical Enquiries: tech@grahamgoode.com
Tel: (+44) 0116 244 0080
Fax: (+44) 0116 244 0140

	What is a Dump Valve? Why do manufacturers fit a dump valve? What can go wrong with a dump valve? What are the benefits of a GGR Dump Valve? Why does the GGR Dump Valve have a filter? What are the advantages of moving the dump valve away from the turbo? Why do GGR produce alternative diaphragms? Dump Valve Parts

What is a Dump Valve?
	Most production turbocharged engines are fitted with a dump valve. This is to vent away excessive turbocharger boost pressure when the throttle is closed. All Sierra Cosworth and the original large turbo Escort Cosworth models use the same dump valve. The turbocharger fitted to the latest Escort Cosworth has its own integral unit. The dump valve is the black plastic saucepan shaped object that you will see connected between the intercooler and the air inlet hose to the turbocharger. You will also see a small hose leading from the top of the valve to the inlet plenim on the engine. Inside the valve is a rubber diaphragm and a steel spring, with a small insert to support the diaphragm where it seats against the dump valve body. The dump valve has basically two operating conditions; throttle open, and throttle closed. When the throttle is open, the boost pressure coming into the valve from below the diaphragm is equalled by the pressure onto the top of the diaphragm that comes via the small hose from the engine plenim chamber. As the pressures are equal, the spring holds the diaphragm onto its seat, and prevents the pressure venting away. When the throttle is closed, the pressure coming into the top of the valve is significantly reduced, (often to a vacuum), and the pressure below the diaphram lifts it away from its seat, allowing the excess pressure to vent away. As the throttle is reopened, the pressures again equalise, the spring pushes the diaphragm onto its seat, and the boost pressure cannot vent away.

Why do manufacturers fit a dump valve?
	It is for a number of reasons. Without a dump valve, when the throttle was closed, the build up of boost pressure would be immense, very similar to closing a quickly flowing water tap. This excess of pressure, (which could be over five times the running boost pressure), would put the components of the system under a great strain. It would try to burst the intercooler and pipework. More significantly, it would put a large strain on the turbocharger itself, firstly stalling the compressor shaft, then trying to force the compressor wheel out of the turbo, against its bearings. So, the dump valve prevents mechanical damage to the intercooler & turbo pipework, prolongs turbocharger life, and prevents excessive turbo - lag that would be caused by the compressor shaft stalling.

What can go wrong with a dump valve?
	The only thing that can go wrong with a dump valve is that the diaphragm can become holed. If this happens, it will not seal, and the boost pressure leaks away all of the time. This will cause the turbocharger to work harder to overcome the leak, (turbochargers will work as hard as they have to, to give the required boost), and this will be noticeable to the driver, as a lack of boost response.

What are the benefits of a GGR Dump Valve?
	Our Dump Valve is a direct descendant of the one we developed to use in our Touring Car programme, and has a number of benefits when compared to the standard item. The aluminium body & stainless steel fixings are more robust than the plastic item, and therefore, better suited to the rigours of competition, it is also more pleasing to the eye! The standard valve vents the turbo pressure away through only one small port, and it does this back into the air filter pipework. This means that the air compressed by the turbo, and heated in the process, is then re-compressed, and re-heated. The GGR Dump Valve vents quickly to atmosphere, all around its circumference, allowing the turbo to free wheel, giving quicker response.

Why does the GGR Dump Valve have a filter?
	The way the dump valve works means that when the engine is idling, or on the overrun, the vacuum produced by the engine will lift the diaphragm away from its seat, allowing the engine to draw air in via the dump valve (hence, not suitable for cars fitted with air metering units - EscortRS Turbo, new Escort Cos.). In the standard fitting, the dump valve exhaust is connected to the original air filter, so any air drawn in through the valve has already come through the filter. The GGR Dump Valve has its own integral filter fitted to prevent internal engine damage caused by drawing in foreign particles.

What are the advantages of moving the dump valve away from the turbo?
	For convenience of plumbing, the manufacturers fit the dump valve as close as possible to the air filter. This also means that it is connected to the hot side of the intercooler. The compressed air from the turbocharger can reach temperatures in excess of 150°C, and this will drastically shorten the life of the rubber diaphragm. Also, for better response, it is preferable to situate the dump valve near to the throttle plate of the engine. If you look at the standard pipework of an RS 500, you will see that Ford Engineers re-sited the dump valve on this homologation model. To enable the re-positioning of the Dump Valve, GGR produce complete kits consisting of a Dump Valve, a fabricated aluminium pipe to go from the intercooler to throttle body, and all of the relevant silicon hoses and clips to carry out the conversion. The kit also includes two polished aluminium blanking plugs to fit in place of the original dump valve.

Why do GGR produce alternative diaphragms?
	We have found that in extreme conditions, even when the Dump Valve is relocated on the cold side of the intercooler, failure of the standard diaphragm can eventually occur. To address this we have put into production two replacement diaphragms. The Fluorocarbon diaphragm is made from a stronger material, and has an increased overall thickness. The ultimate is the Silicon Polyester Reinforced diaphragm. This has the additional strength of fabric reinforcement, bonded within the diaphragm.

Dump Valve Parts · Back to FAQs & Features · GGR Home
Correspondence/Requests Sales Enquiries: sales@grahamgoode.com Technical Enquiries: tech@grahamgoode.com Tel: (+44) 0116 244 0080 Fax: (+44) 0116 244 0140