Variable Valve Timing VVT

 Variable Valve Timing VVT

We know Internal Combustion (IC) Four-stroke Engine has two engine valves one is called Intake (inlet) and another one is called exhaust (outlet) per engine cylinder. How does the Engine Valve work? The engine valves are doors like devices for opening and closing, for the inhale, air-fuel mixture or air intake the engine cylinder through the intake valve and exhale burned gases exit through exhaust valves. Cam on the rotating camshaft operates the valve train or valve mechanism. Other words intake and exhaust for proper breathing in the smooth engine operation purposes. 

Before we should know to understand the Valve Timing of the four-stroke engine. The purpose of valve timing is the timing of the opening and closing to the valve about the engine piston position. It depends on the arrangement of valves and valve train or mechanism.

There are several different arrangements of valves and valvetrain / mechanism

• Location of the camshaft. (the location of camshaft either cylinder block or cylinder head.)

• How the camshaft is driven. (Camshaft are driven by timing gears, timing chain, sprocket toothed timing with a belt.)

• Type of valvetrain  / valve mechanism. (type of valve train or mechanism either it Over Head Cam Engine or Overhead valve engine, either camshaft cylinder block or cylinder head.)

• Numbers of valves per cylinder. ( the engine have more than two valves per cylinder or some have three-four valves in each cylinder. This is known as the Multivalves engine.)

The purpose of these add-on valves is to allow the engine to breathe more easily and freely. The added valves allow or intake more air-fuel mixture to enter and the burned exhaust gases to escape more freely.

Variable Valve Timing VVT

Most multi-valve engine designs especially the Double Overhead Camshaft (DOHC) engine has Variable Valve Timing is set up for most modern IC engine. The main purpose of the VVT technology developed was to enhance engine performance, less fuel economy and reduce emission levels (hydrocarbon HC and Nitrogen oxide Nox).

This Variable Valve Timing operation is done by valvetrain or valve mechanism through engine valve timing. Before conventional engines, there is fixed valve opening and closing timing, fixed valve lift and fixed valve duration. According to engine valve timing open and close the intake and exhaust valves are operated by camshaft in a four-stroke engine. After Multivalve engine design, the variable valve timing introduced by many automakers set up their modern engines for better engine performance efficiency, and average mileage as well as reducing emissions gases. Engine performance depends on intake quality and quantity of air and fuel ratio, that is it should vary engine speed and engine load condition.

Variable valve timing technology is the adjustment of existing valve timing which the valve opening and closing intake and exhaust with different speeds and engine loads. Variable valve Timing system control and monitor by electronic control unit ECU/ECM. VVT System operates engine oil through hydraulics with the timing chain or timing belt. In other words, say that changing valve opening and closing time varies the timing of intake and exhaust valve opening and closed on according to engine speed or rpm and load.

• Closing intake valves late. 

• Opening intake valves early.

• Closing intake valves early. 

• Closing exhaust valves early.

When does the intake valve open? It opens earlier or later. The valve lift, How much does it valve open? It little bit or lots more time. Valve duration, How long does it valve open? It short time or lt longer time. 

The necessity of VVT Technology

In the conventional engine air-fuel mixture enters the engine cylinder specific amount of charge or mixture which fixed amounts of charge, but VVT technology design engine air-fuel mixture or charged enters as required amount into the cylinder with the help adjustment regular schedule of valve timing which open and close intake and exhaust valve time for them according to engine speed or rpm. When high rpm the duration of intake and exhaust decreases resulting in opening the intake valve earlier and the exhaust valve later. Sometimes both valves are open for a while it is called valve overlap. This mechanism is done engine management system or Electronic Control System ECU/ECM. So that the engine performs more efficiently and powers it also reduces emissions as well as less fuel consumption.

Variable Valve Timing VVT design engine A similar technology has been given a different name by the manufacturer, Honda- called Intelligent Variable Timing aLift Electronic Controlrol I-VTEC. Hyundai -Variable Timing Valve Train VTVT. Toyota -Variable Valve Timing-intelligent VVT-i, Ford Variable Cam Timing VCT. Renault / Volvo Continuous Variable Valve Timing CVVT. Volkswagen / Suzuki Variable Valve Timing VVT.