Valve Timing

Also found in: Wikipedia.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Valve Timing


the periodic movement of inlet and outlet members of an internal combustion engine, by which the cylinders are filled with a new charge of fuel (intake, inlet) and exhaust gases are removed (exhaust, outlet). Depending on the type and construction of the engine, valve timing may be categorized as valve, rotary, slide (nonvalve), sleeve, and combined types.

In valve-type engines there are two main arrangements of valves: in the head of the cylinders, as the upper or overhead system, and the so-called lower or side system. In the former the valves are actuated by a rocker arm from a camshaft, which is in turn driven by the crankshaft through a pinion or chain drive.

In diesel marine and locomotive internal combustion engines there are additional cams and reversing devices in the valve timing system. These make it possible to change the direction of rotation of the crankshaft.

Rotary valve timing employs plane rotating gears and disks that have ports cut into them. When the disk rotates, its ports match up with the ports at the bottom and head of the cylinder and the exchange of gases takes place.

The so-called slide-valve system uses slide valves driven by the crankshaft of the engine.

The sleeve valve system is used in two-cycle engines. The cylinder walls have slots that are opened and closed by the piston moving within the cylinder.

The most widespread combined type of valve timing is a modified sleeve-valve system in which exhaust takes place through an outlet valve and intake, through a slotted device.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Summary: Automotive camshaft phase variator is also known as a variable valve timing or variator.
The model is equipped with a new in-line four-cylinder engine that is four kilogram lighter and offers the automaker's new ShiftCam variable valve timing tech on the intake port.
At its heart is a 2.4-L 4 In-line 16 Valve DOHC Clean Diesel with Variable Geometry Turbo and MIVEC (Mitsubishi Innovative Valve timing Electronic Control System) 4N15, which gives a maximum output of 178.5 hp at 3,500 rpm and a maximum torque of 430 N-m at 2,500 rpm.
Mitsubishi Innovative Valve timing Electronic Control (MIVEC) technology provides optimal valve timing at both low and high rev ranges, delivering ample performance to make the most of every straight and curve in the road, without impacting fuel economy.
The in-cylinder charge temperature during compression has remained almost constant in the investigated load range using the same valve timing. However, experiments not presented in this paper revealed that density is a major influencing factor on the ignition behavior.
Pennsylvania, US-based powder metal component solutions provider Alpha Precision Group (APG) has acquired Michigan, US-based Mercury Manufacturing Company (MMC) to enhance Alpha's presence in emission control, variable valve timing and variable cam timing and gain access to new markets, the company said
The refined aluminium-alloy DOHC 24-valve engine is equipped with Variable Valve Event & Lift (VVEL) that combines hydraulic-controlled variable valve timing and electronically controlled variable valve lift on the intake side to help improve performance and response.
Embellished with a custom "Centennial Edition" paint and decal package--included standard throughout 2017--the C20/C35 line of lift trucks features a new Ford 2.5-liter LPG four-cylinder engine with smooth-running variable valve timing, sequential multiport LP fuel injection and extended maintenance intervals (up to 500 hours).
Variable valve timing can help to mitigate against this, and many engines today employ a form of mechanism that can vary the time the valve opens.
In internal ignition engines, variable valve timing is the process of changing the timing of a valve lift event inside the cylinder, and it is used to improve performance, fuel consumption or emissions.