![]() Please verify any information in question with a sales representative. These are electro-mechanical or electro-hydraulic valve-lifters and cam-less valves systems etc.While every reasonable effort is made to ensure the accuracy of this data, we are not responsible for any errors or omissions contained on these pages. Additionally, to conform to stricter emissions norms, manufacturers have developed many other supportive systems. Also, it provides precise control of the valves while opening/closing. Thus, it facilitates ‘ low-lift‘ of inlet valves during idling or slow speeds and ‘ high-lift‘ at high speeds. Nowadays, the ‘VVL’ system is being increasingly used in combination with ‘Variable Valve Timing’ (VVT) systems to improve the performance.Īdditionally, this design also alters the lift (or travel) of the inlet valves along with valve timing depending upon the engine’s speed. The term VVTL stands for ‘ Variable Valve Timing and Lift’ which is an advanced supporting system to alter the ‘lift’ of the valves. The term VVL stands for ‘ Variable Valve Lift’ while VVEL stands for ‘ Variable Valve Event and Lift’. Dual VVTi Engine (image courtesy, Toyota) What is VVL / VVEL / VVTL? Some more advanced design use ‘Dual’ systems which is ‘Dual VVTi’ – one each for varying the inlet & exhaust valve timings independently. Furthermore, it moves the camshaft ahead and advances the timing of the opening of the Inlet valves. It is operated by engine oil pressure and a solenoid-operated oil control valve which is controlled by the engine’s ECU. Although there are different mechanisms to achieve the variation, this is mainly accomplished by using a ‘variable-timing camshaft’ and solenoid valves.Īpart from this, the CVVT uses the flexible hydraulic connection between the camshaft and its sprocket. ![]() Additionally, it optimizes the valve timing for all engine speeds and conditions. Besides, the CVVT varies the valve timing continuously (or infinitely) which is digitally controlled by the engine ECU. Variable Valve Timing diagramįurthermore, the newer generation VVT design implements ‘Continuous Variable Valve Timing’ or CVVT system. Thus, it provides smooth idling at low rpm and maximum power at high rpm. Besides, VVT also provides best of both worlds. In addition, VVT more often improves performance and reduces emissions. upto 3500 rpm and other for the ‘full-load’ condition, i.e. This design enables two different set of timings which includes one for the ‘part-load’ condition i.e. The first-generation VVT design uses two-step variation which optimises the engine for two different engine speeds. The Variable Valve Timing system further optimizes the timing of opening and closing the valves for multiple engine speeds. This helps to increase engine’s breathing which also improves its ‘ volumetric efficiency’ to a large extent. At high speed, the Inlet valves open quite earlier so that more air-fuel mixture or ‘charge’ enters the cylinders. The VVT varies the timing of opening and closing of valves for multiple engine speeds. To overcome this deficiency, the engineers developed VVT or ‘Variable Valve Timing’ mechanism. However, as the engine speed increases, it considerably reduces the time required to fill the cylinders fully.As a result, the engine would receive less amount of charge (air-fuel mixture) which causes power-loss especially when the engine runs at high speed. In older conventional engines, the time for which the valves remained open was optimised only for single engine speed. This is because to produce more power, it needs to suck more air-fuel mixture (charge) for burning. Similarly, when the engine runs at high speed it needs to open its inlet valves earlier, faster & for a longer period. Thus, it causes faster breathing and/or wider opening of the mouth to receive more air. This is because when the human body is subjected to heavy work, it increases the need for air-intake. Besides, while carrying out activities like swimming or lifting a weight the persons also need to open the mouth to get more air. For e.g., if the person/s are sitting or sleeping, they will breath slowly as compared to when they are walking or running. ![]() The rate at which humans breathe mainly depends upon the work carried out by humans. Let’s try to understand in the begining, why to vary the Valve Timing/VVT?įirstly, read here first what is ‘ Engine valve-timing’? An automotive engine actually ‘breaths’ (inhales/exhales) thru’ its valves just like the humans do.
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