![](https://www.carref.com/cms_admin/images/dump-valves-266x114.jpg)
Blow off valves and dump valves.
When the throttle is closed (when you lift off the accelerator) in a turbo driven engine there is a build up of pressure as forced air is still coming from the turbo. Lifting off the throttle is a lot like putting a plug in the sink – the flow through is stopped and water would just build up and overflow the sink.
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How to avoid engine knock and pinging![](https://www.carref.com/cms_admin/images/air-intake-injector-266x114.jpg)
So what exactly is engine knock and how dangerous is it? What causes engine knock and how can it be avoided?
You may notice a knocking or rattling noise from your engine or a sudden loss of power under full throttle.
Immediately back off the throttle and only use low rpm engine speeds until you can get the engine investigated.
The chances are that you are suffering from a condition known as “engine knock”.
Benefits & advantages of Winter tyres & snow tyres![](https://www.carref.com/cms_admin/images/snow-tyres-266x114.jpg)
With the poor winter driving conditions hitting the UK in 2010 many drivers are looking at winter tyres. Other countries are prepared for the snow and poor weather and are used to the concept of winter tyres.
So what are winter tyres, what do they do and are they a good idea?