Multi-valve technology as early as 1912 has appeared, the first multi-valve engine was the Peugeot GP racing engine. Later, this kind of engine was also used in Bentley and Bugatti concept cars, but none of the above models were production vehicles. For the next 50 years, ordinary civilian vehicles still use the traditional 2-valve design. This situation continued until the 60s, Honda in its 600 models using a multi-valve technology engine, which is the earliest use of multi-valve technology, ordinary civilian vehicles. By the 1970s, more cars began designing with 4-valve technology, such as the 1976 Lotus, the 1975 Chevrolet Cosworth Vega, the 1979 BMW M1 and many more. At this time of the 4 valve engine or a single camshaft, driven by the rocker valve. In the early 1980s, Honda adopted a 3-valve engine design and matched it to its mainstream models. By the mid-1980s, both Toyota and Honda began to make common use of 4-valve engines and became the leader in this field of technology, using the engine technology in their mainstream models. European carmakers are nearly 10 years behind Toyota and Honda in this area. Multi-valve technology increases engine output by improving intake air. Due to the limited inlet air intake area of ​​the 2-valve engine, it is easy to cause the air intake to be not smooth at high speed, and the multi-valve technology can effectively change the situation. Here are a variety of multi-valve engine classification 3 valve engine multi-valve engine early widespread use of 3 valve, which is due to the technical structure of the 3 valve is simple - the three valves can be arranged in a straight line, so Only one camshaft is needed to drive the inlet and exhaust valves of a row of cylinders simultaneously. Until now, low-cost designs such as the older Mercedes-Benz V6 and V8 engines, the Chrysler 1.3-liter engine from Kia Motors and many others have still been adopted. Of course, this low-cost design is very limited to improve the working efficiency of the engine. 4 valve engine The traditional 2 valve engine can only occupy the top 1/3 of the combustion chamber area as the inlet area, intake efficiency is limited. 4-valve engine product relative to the 2-valve engine, the intake cross-section can increase more than 50%, more suitable for high-speed smooth operation. At the same time, because the design of 4-valve can be arranged in the center of the combustion chamber spark plug, the flame can be more evenly distributed to the combustion chamber corners, the combustion of the mixture can burn more fully, the heat loss is small, so 4 Valve engines are also more conducive to improve combustion efficiency and reduce emissions. 4-valve engine can design two camshafts to actuate the valves, one to actuate the intake valve, one to actuate the exhaust valve, control can be more accurate, and more new technologies can be used. Most mainstream 4-valve engines now feature a double overhead camshaft design. Honda and Mitsubishi still prefer single-overhead camshafts on their common civilian vehicles to reduce costs. It needs to be placed on the camshaft rocker arm, and ultimately through the rocker to drive the valve. Although this design can reduce costs, but adds more frictional resistance and inertia, affecting the engine output power at high speed. Therefore, the Honda and Mitsubishi sports cars, for performance reasons, are equipped with dual overhead camshaft design engine. 5 Valve Engine This is a controversial multi-valve engine technology. The biggest controversy is whether designing five valves per cylinder can really and effectively increase the work efficiency of the engine. Currently, Volkswagen and Audi use this technology on many models of engines, but it does not significantly improve the engine's power output. Many of the 5-valve engines with the same displacement technology have no clear advantage in terms of power and torque compared to mainstream 4-valve engines. In fact, the VW itself is also gradually replacing the previous 5-valve engine with a conventional 4-valve engine. Compared with the 4-valve, the early 5-valve can not provide higher intake efficiency. However, if the combustion chamber can be designed as a plum shape as shown, the valve may cover a larger area. Faraday's F355 is the use of this design to improve breathing efficiency at high speeds. However, its drawback is also obvious. Without the size limitation, faster intake will hurt torque output at low speeds. Therefore, this design is not suitable for the use of ordinary civilian vehicles, but more suitable for use in sports cars. Now 5 valve engine, each cylinder has three intake valves and two exhaust valves, they plum-shaped distribution. Although the single exhaust valve is relatively large, but the total area is larger intake valve. On the F355, the outer intake valve opens 10 degrees ahead of the inner intake valve, making it easier to create eddy currents that allow the air and gasoline to mix well, resulting in higher combustion efficiency and better emissions. The advantages of a 5-valve are not yet obvious overall, with only a few automakers using this technology (Volkswagen, Ferrari and early Bugatti). However, due to its high speed range advantages, there are still a few manufacturers have always been more interested in 5 valve technology, and even Ferrari F1 car. Only, this technology is not a long time to use, a few years, Farah F1 engine has changed back to 4 valve design. Drawbacks and Solutions - Variable Valve Technology Earlier 4-valve engines also had disadvantages over 2-valve engines - with no good torque output at low speeds. The reason is simple - a large intake cross-sectional area will slow down the air flow, which is very unfavorable for low engine speed operation. Low-velocity air flows into the intake manifold, mixing air with fuel, resulting in knocking and reduced torque output. Therefore, the conventional 4-valve engine can only effectively improve engine performance at high speed, and this situation is only changed as variable valve technology is popularized in more and more vehicles. Here's an example of variable valve technology Toyota introduced in the mid-80s T-VIS (Toyota Variable Intake System) concept. T-VIS improves fuel mixing efficiency at low speeds. The principle is simple, with one throttle valve installed in one of the intake manifolds. Below 4650rpm, the throttle valve is closed, this time equivalent to 2-valve engine, when the speed exceeds 4650rpm, the throttle valve is open, this time equivalent to 4 valve engine. Since this technology effectively improves the combustion efficiency and torque output of the 4-valve engine at low rotational speeds, many manufacturers have adopted the technology after Toyota.
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