What Is a Dump Valve and Where to Buy

Your suppliers of Blow Off Valves, Dump Valves and Valve Fitting Kits and Components

Forge Motorsport Valves may often be referred to by many names, including Turbocharger Valves, Recirculation Valves, Dump Valves, Blow Off Valves, Atmospheric Valves and Closed Loop Valves. On most turbo-charged engines, valves will allow charge air to be re-circulated around the turbo charger, from the boost side and back to the intake side.

Why and how are Valves used?

The recirculation path is opened and closed by means of either and electrical connection from the engine management to a solenoid that is mounted on the turbocharger housing, or by the vacuum created in the intake manifold. As you accelerate, the turbo charger vanes are spinning and boost pressure is increased; literally blowing air into the engine cylinders. Then, when you change gear, you take your foot off of the accelerator and the throttle valve to the engine closes.

The problem here is that, during this process, the turbo is still spinning and the boost pressure it is producing has nowhere to go. This is a bit like putting your hand over a hairdryer, so that the air cannot get out. What happens at this point is that the turbo begins to stall – the spinning vanes slow down (incurring a lot of stress) and the boost pressure drops. When you open the throttle valve again by pushing down on the accelerator (demanding more power), the turbo has lost its' momentum and boost pressure, therefore causing a pause or a 'Lag' before the engine is producing the required power once again.

What do Valves do?

To combat this loss of power and stress on the turbo, a recirculation or diverter valve is used. On most turbo-charged petrol engines, when the throttle valve closes, the engine management opens the recirculation route around the turbo. This gives the charge air an alternative route and allows the turbocharger to keep spinning, so that when you accelerate again, the is no 'lag' or waiting period.

This system works well and is adopted by nearly all vehicle manufacturers; the only down side to this system is that a turbocharger produces heat. The hot air that leaves the turbo is cooled by passing it through an intercooler before it enters the engine. The cooler the air, the more power is produced.

By recirculating hot air back into the intake side of a turbo, the temperatures increase – this is where a Blow Off Valve or Dump Valve plays its' part. By expelling the charge air to the atmosphere, rather than recirculating it, you do not increase the intake air temperature, but you do allow the turbo to keep spinning. The side effect, which is unacceptable to most vehicle manufacturers, is the noise of the valve expelling the air and the complication where the air entering the engine is monitored or metered.

It should also be noted that the engine management can also use this valve to decrease engine power, when necessary. An example of this is by the Dynamic Stability Control System (DSC). Although you would not normally hear this occurring, when a Blow Off Adapter is fitted, you may well hear the air being expelled; when the DSC operates (going too fast around a bend, for example).

All Forge Motorsport Valves are designed to ensure compability with the engine management, quick response times to maximise their benefites, and quality of design and production for longevity.

For further information on our current range, please click one of the images below. Or, to enquire further about 'What is a Dump Valve?' or 'How are they used?', please contact us on: 01452 380 999, or email: info@forgemotorsport.co.uk