Wednesday, July 30, 2008

Apa itu BOOST ?

Boost refers to the increase in manifold pressure that is generated by the turbocharger in the intake path or specifically intake manifold that exceeds normal atmospheric pressure. This is also the level of boost as shown on a pressure gauge, usually in bar, psi or possibly kPa This is representative of the extra air pressure that is achieved over what would be achieved without the forced induction. Manifold pressure should not be confused with the amount, or "weight" of air that a turbo can flow.
Boost pressure is limited to keep the entire engine system including the turbo inside its design operating range by controlling the wastegate which shunts the exhaust gases away from the exhaust side turbine. In some cars the maximum boost depends on the fuel's octane rating and is electronically regulated using a knock sensor, see Automatic Performance Control (APC).
Many diesel engines do not have any wastegate because the amount of exhaust energy is controlled directly by the amount of fuel injected into the engine and slight variations in boost pressure do not make a difference for the engine.

Turbo System

How Turbochargers Work
Principle of operation
A turbocharger is a dynamic gas compressor or liquid pump, in which a fluid from one stream is pumped, and in he case of a gas compressed, by the mechanical action of an impeller which is powered by a turbine that recovers energy from another fluid stream.
In almost all cases the impeller and turbine are mounted on ends of a single shaft passing through a center hub rotating assembly (CHRA) between the impeller and turbine. The CHRA contains bearings for the shaft and may also contain systems for lubrication and cooling.