Dump Valves are usually found on engines with turbo's added to them. They are usually located between the Turbo outlet and the throttle body. When changing from a turbo boosted state to an off throttle state (for example in between gear changes) the turbo continues to attempt to pressurise the inflow of air, however as the throttle is closed, this prevents the compressed air from entering the engine. When this happens the build up of pressure exceeds the default spring pressure setting inside the dump valve and the excess pressure is dumped by the valve, hence the name dump valve.

So what would happen if a dump valve wasn’t fitted?

Most modern cars that have a turbo fitted have a dump valve of some kind fitted to the. Just because the engine doesn’t make a hissing noise every time they change gear, doesn’t mean they don’t have one. They will but it won’t be connected to a device that produces the noise and it will be smaller, so it doesn’t need to dump as much gas from the system.

However if someone as running a high powered car with a turbo and it didn’t have a dump valve then you could expect certain problems to arise. All of the problems would arise because of a massive build up in pressure; symptoms of this would be;

·         Components being placed under a large amount of pressure

·         Intercooler and other pipe work would eventually burst

·         The turbo charger would also suffer by stalling the compressor shaft then trying to force the compressor wheel to rotate in the opposite direction.

So dump valves aren’t just there to sound nice or badly depending on your point of view. They also have a performance benefit and mechanical benefit. This is why you have to inform your insurance that you have had one fitted.

Can Dump Valves Fail?

The main fault and realistically the only thing that can fail on the dump valve is the diaphragm can be punctured. If this happens tiny leaks will appear and there will not be a pressurised seal in the unit. This will usually force the turbo charger to overwork and is tries to over pressurise to compensate for the lost gas.

Are all dump valves the same?

No certainly not, in fact there are some cowboy parts that have started to appear from China and other countries where quality on automotive parts compared to the price to send them back mean they are not cost effective to send back to the factory.

However even if they do work as they should, some are still much better and give better results than others. Usually you get what you pay for and dump valves are no different. Companies such as Baileys have built a massive reputation in this field, and built it over many years. There are many others and we go into this in other sections of this site.

Some manufacturers have filters built in; this is sometimes used to prevent the engine from lifting the diaphragm when on idle, thus drawing air into engine through the dump valve. However some other manufacturers use a connection to the engine’s own air filter to solve this problem and keep out dust and other contaminants from getting into the engine.

Where should I place the Dump Valve?

Dump valves should be placed pretty near the air filter and away from the turbo unit is the model of vehicle allows.

Some suppliers such as Samco will provider kits and high pressured hoses to extend the distance the dump valve is from the turbo. The benefits of moving the dump valve away from the turbo is that the turbo can run in excess of 150 degrees Celsius and will shorten the life of your hoses, causing them to crack and puncture much quicker.

There are full kits or partial kits specifically made for certain types of cars, so you don’t have to buy standard high pressure silicon hoses and cut them as needed, some come pre-measured and with instructions on where to best for them for each car.

How much do dump valves cost?

Dump valves usually costs anything from £29 upwards towards £2000 on some highly modified cards. Essentially they all do the same thing but the more expensive ones tend to have better designed diaphragms (quicker reacting). The other main difference is the type of materials they are made out of.  With some being mixed with material such as cheap steel, plastic and other imperfect raw ingredients. It all makes the dump valve susceptible to damage from not just hot gases and hot pressurised gasses.

So if you buy from a reputable manufacturer then you shouldn’t have much problem, otherwise after time you may suffer from leaks and punctures in the valve.

Where is the best place to buy one?

The best place to buy dump valves is from the internet in our experience, most of the manufactures have resellers online and there is no difference in quality or after service. None of the big manufactures will only sell through retailers, they don’t sell to the general public direct.

Are there any guarantees with dump valves?

Yes as long as you don’t try to modify the device or damage it in anyway, all dump valves sold in the UK should come with 12 months warranty.

Diesel dump valves what are they?

Diesel dump valves work in exactly the same way as their petrol turbo counterparts although the pressure they work under are much reduced and often any sound whooshing sound is fake.

What are fake dump valves?

Fake dump valves are for cars that have no turbo attached yet their drivers wish to have the whooshing noise. They are usually looked down upon as a bit of a joke from most car enthusiasts. The upside to having one is that they are easy to fit and you don’t need to tell the insurance company about having it added to your car.

The downside to having a fake dump valve is that they tend to go off at strange times, such as when  you aren’t changing gear or even when braking. So they aren’t realistic to others who are watching from a far.

Some other drivers rate them as low as “Go faster Stripes”, so be careful if you are adding these to impress people because they simple won’t.