Exhaust Talk: Episode 04 | Valves Explained

Back with more answers to your common questions, exhaust talk episode 4 explores the functionality of exhaust valves, how they work and the difference this makes to the sound of the exhaust.

What does an exhaust valve do?

In its simplest form an exhaust valve, or flap exists to modulate the level of sound emitted from your vehicles tailpipes. When closed your exhaust will produce a quiet comfortable tone and when open will allow your engine to sing a little louder, a pretty straight forward concept.

How does an exhaust valve work?

Dependant on your application exhaust valves can work in different forms. Most OEM vehicles will come with an electronic exhaust valve which will be operated by the drive mode functionality of the vehicle. For example in comfort mode your valve is going to remain closed keeping the car peaceful and quiet, when you switch over into sport the exhaust valve opens to allow for more noise to be produced from the exhaust system.

Other applications (generally higher performance cars) will work on a vacuum system that requires pressure to be applied to the valve for it to open, this occurs when exhaust gasses create enough pressure for the valve to open so will generally produce more of a tone and open the valve further dependant on how heavy your right foot is.

Most valved systems will send exhaust gasses through silencers when the valves are closed, opening the valves allows for some of the exhaust gasses to bypass the silencer resulting in a sportier tone produced from the exhaust.

Can I have a valve installed?

If your car isn't equipped with a valved system from factory, it is possible to install one at a later date, however this can be tricky, expensive and may not always give the greatest results dependant on where the valve is installed on the exhaust system. It will also require some tinkering with electrics to make the system operational.

What is the difference between a stock valve and a Cobra Sport valve?

When you upgrade to a Cobra Sport system if you opt for the valved version and your car already has a valve installed nine times out of ten will utilise your factory motor to operate the valve. The main difference is likely to be the size of the valve, due to the bore of the exhaust pipework, the chances are the Cobra Sport system will house a larger diameter pipework which will mean installing a larger valve to fit the pipework.

Will Valves effect the performance of my car?

In short no, although a closed valve will technically provide a slight increase in back pressure most modern cars have their turbo's controlled by the ECU meaning you will not feel any loss or gain in performance dependant on the positioning of your valve unless your car is running an extremely aggressive tune that maximises the turbo's output.