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A Honda K24A Engine with i-VTEC. VTEC (described as Variable Valve Timing & Lift Electronic Control, but stands for Valve Timing Electronically Controlled) is a system developed by Honda to improve the volumetric efficiency of a four-stroke internal combustion engine, resulting in higher performance at high RPM, and lower fuel consumption at low RPM.
The timing, duration and lift of these valve events has a significant impact on engine performance. Without variable valve timing or variable valve lift, the valve timing is the same for all engine speeds and conditions, therefore compromises are necessary to achieve the desired result in intake and exhaust efficiency . This has been described ...
The Alfa Romeo Twin Spark engine, introduced in the 1987 Alfa Romeo 75, also uses variable valve timing. [3] [4] The Alfa system varies the phase (not the duration) of the cam timing and operates on the inlet camshaft. [5] Alfa Romeo's variator is a cylindrical chamber that contains a pressure chamber and piston along with helical splines.
In Honda's 2006 Civic Hybrid, the 1.3-liter i-VTEC engine uses a 3-stage valve design, an advancement from the 2005 i-VTEC technology. Aside from weight and friction reduction, the engine operates on either low-speed timing, high-output timing or 4-cylinder idling when the VCM system is engaged, each yielding better engine output upon varying ...
Three-stage VTEC is a multi-stage implementation of Honda's VTEC and VTEC-E (colloquially known as dual VTEC) technology, implemented in some of the company's D series engines from 1995 to the present day, allowing the engine to achieve both fuel efficiency and power. VTEC-E (for "Efficiency") is a form of VTEC that closes off one intake valve ...
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In order to improve the optimisation of the valve timing for differing engine speeds and loads, the system is able to vary the timing and duration of the inlet valve opening. It achieves this by using a complex and finely machined mechanism to drive the inlet camshafts.
In an external combustion engine, such as a steam engine, the control of the valve timing is by the valve gear. In a typical piston valve arrangement, the timing of the intake and exhaust events for each cylinder are inextricably related as they are governed by the movement of a single piston uncovering two ports. However, the duration of the ...