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.
The basic reason for forced induction (turbo or supercharger) is not to increase compression or the maximum pressure in an engine cylinder, it is to increase volumetric efficiency (the efficiency of the engine at drawing in air) although forced induction is the most effective method of upping compression.
In computer games we just tick a box, and within seconds our car is fully turbocharged and running much faster. In the real world things are very different.
What is an induction kit and what does it do.
As induction kits are probably one of the most popular modifications for car tuning projects we thought we should add a introductory article to explain what they are, what they do and the theory behind them.
An induction kit is quite simply an air filter. Most cars have air filters mounted in an air box. These filters are generally constructed of paper which filters out the particles from the air and prevents these from getting into the engine. The airboxes are designed to reduce the noise of the engine and have various vanes and angles cut to maximise this noise reduction.
Remaps for diesel engines
Our members frequently talk about their latest mods and power figures. Many of our members have remapped their diesel engines and boast of more power, better economy and unchanged reliability.
But do the claims live up to reality? What sort of power figures can you get from a diesel remap? Diesels have really come so far in a very short time.












