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Old 05-01-2008, 11:26 AM   #11 (permalink)
Daox
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Stock intake systems create virtually no restriction at ecodriving rpms. No gains to be had there, sorry.

Pumping losses occur when an engine is not able to take in as much air as it wants to thus creating a vacuum in the intake manifold. For example, lets use a 2 liter engine. Every two times the engine spins around (4 cycle engine) it wants to suck in 2 liters of air. Restrictions occur upstream of the combustion chamber that limit the amount of air that enters the engine. The first item is the intake valve(s). These are controlled by the camshaft and really can't be easily altered. The next item upstread is the throttle. The throttle is used to decrease engine output so you don't accelerate like crazy. However, as you close the throttle, the engine has to work harder as it is still trying to suck in 2 liters of air. This decreases engine efficiency and is why accelerating at high loads is more efficient.

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