Introduction:
BMW's 6-cylinder power unit is not only lighter than all competitors' products, but also offers outstanding power output and performance. This is largely due to BMW's unique fully variable Valvetronic electronic valve control. This system can continuously adjust the valve opening and control the time according to the accelerator pedal position.
On traditional engines, the control of output power is almost entirely achieved by throttling the intake air with a throttle valve. In this process, a part of the power will inevitably be lost. In contrast, Valvetronic electronic valve control technology can minimize engine load changes and cycle management requirements, ensuring extremely high fuel utilization and better engine response speed. Other benefits include improved engine running smoothness and minimized exhaust emissions.
The BMW in-line 6-cylinder power unit, which uses a magnesium-aluminum alloy crankcase and is equipped with the second-generation BMW Valvetronic electronic valve, achieves higher engine speeds through a more compact structure of the overall system. As a result, faster acceleration is ensured through valve operation, allowing the driver to get a faster response when stepping on the accelerator pedal, and forming a larger speed reserve in each gear.
On gasoline engines, BMW's Valvetronic technology can be said to be the best variable valve technology today.
Technical principle:
BMW's engine using Valvetronic technology is the world's first engine without a throttle valve (also called a throttle valve, or throttlebutterfly in English). The throttle valve is a valve in the engine intake manifold that looks like a butterfly (the throttle valve is called a throttlebutterfly in English, and butterfly means butterfly).
So what are the advantages of eliminating the throttle? This advantage is fuel saving. Various test results show that Valvetronic engines can save more than 7% in fuel consumption than traditional engines. To understand why an engine without a throttle saves fuel, we must first understand how a traditional engine's throttle works. When you step on the accelerator to refuel, you may feel that the engine is refueling, but in fact, when you step on the accelerator pedal, you do not directly increase the amount of oil injected into the engine cylinder, but change the size of the intake pipe throttle switch, thereby changing the amount of oil entering the cylinder. The amount of air. The car's injection fuel supply system monitors the amount of air passing through the throttle before deciding how much fuel to inject. This is how the throttle controls the engine. The main purpose of this design is to prevent the fuel and air mixture ratio from changing at different throttle openings to avoid flameout.
So why does an engine without a throttle save fuel? When you lightly step on the accelerator, the throttle valve is only slightly opened. However, at the same time, the piston moves downward, trying to suck in air from the nearly closed intake pipe. At this time, a vacuum will be formed between the throttle valve and the piston, and the external atmospheric pressure will affect the piston movement. Great resistance consumes a lot of energy. The lower the engine speed, the tighter the throttle is closed, and the greater the energy loss is caused. Therefore, the Valvetronic engine can save fuel consumption by subtracting the throttle, especially at low speeds. In a traditional engine, the air in the intake pipe passes through the throttle valve, and then passes through the intake valve on the top of the cylinder before entering the engine cylinder. The intake valve's opening and closing time is controlled by the timing belt and camshaft. The opening depth of the intake valve remains fixed regardless of the speed.
As for the Valvetronic engine, as the name suggests, Valve means valve tronic means electronic control. After eliminating the need for a throttle valve, the engine directly controls the intake air volume by electronically controlling the opening depth of the intake valve. The overall mechanism is actually quite complicated and professional to explain. Generally speaking, the signal from a traditional engine when stepping on the accelerator is transmitted mechanically to control the throttle valve of the intake pipe. The signal from the Valvetronic engine when the accelerator is stepped on is electronically transmitted to the stepper motor on top of the engine's intake and exhaust valves. After receiving the signal, the stepper motor will rotate appropriately and change the opening depth of the intake valve through the transmission shaft, piston top rocker arm, and tappet. The shallower the accelerator is stepped on, the shallower the intake valve will be opened, and the deeper the accelerator is stepped on. The deeper the intake valve is opened.
The Valvetronic engine eliminates the need for a throttle valve and directly controls the intake valve electronically to adjust the intake air. In addition to saving fuel, another important advantage of this design is that the throttle response time is accelerated. Traditional engines use an accelerator to control the throttle. When you step on the accelerator and open the throttle, you have to wait for air to flow in and fill the intake manifold before a large amount of air enters the cylinder. In the Valvetronic engine, stepping on the accelerator directly controls the opening depth of the intake valve, and a large amount of air immediately enters the cylinder.
The opening depth of the intake valve of Valvetronic engine is the shallowest 0.25mm and the maximum is 9.7mm, a difference of 38.8 times. The reaction time required to change from the shallowest to the deepest is only 0.3 seconds. BMW's Valvetronic engine is manufactured in a brand-new engine factory in the UK. The entire Valvetronic system is a pre-assembled module that can be directly installed on the top of the engine cylinder. BMW claims that engines using Valvetronic technology are 14% more efficient than traditional engines, but this is not entirely due to Valvetronic technology. BMW said that 7% of this comes from Valvetronic technology, 3% comes from reducing friction losses, and 4% is due to the 6-speed automatic transmission. However, because the Valvetronic engine adds many more intake valve control mechanisms, as well as more mechanical contact and friction, the efficiency and smoothness of the engine are not good when it exceeds 6,000 rpm.
The Valvetronic engine uses a combination of software and hardware to replace the traditional throttle structure. The word Valvetronic means electronic control to replace the traditional mechanical control valve mechanism.
Valvetronic modifies the timing and lift of the intake valve. The Valvetronic system has a camshaft like a traditional engine, and also has an eccentric shaft, roller and ejector mechanism, and is composed of Driven by a stepper motor, by receiving signals from the throttle position, the stepper motor changes the offset of the eccentric cam, indirectly changing the action of the intake valve through some mechanical transmission.
Comparison of traditional valve mechanism and Valvetronic mechanism The fuel injection system monitors the air flow flowing through the throttle valve to determine the amount of fuel required for engine combustion. That is to say, when the throttle valve is opened The wider it is, the more air will flow into the combustion chamber. At lighter throttle the throttle section is even close to closing. When the piston is still running, part of the air enters the intake manifold. At this time, there is a partial vacuum in the intake manifold between the combustion chamber and the throttle. The suction and pump resistance of the piston waste energy. The engineer will The phenomenon is called "pumping loss". When idling, the throttle valve is only partially opened, so there is more energy loss.
The helical gear of the improved motor changes the rotation amount of the eccentric shaft, driving the middle rocker arm and the traditional camshaft to move with each other, and then transmits the pressure to the rocker arm and finally depresses the valve.
Valvetronic can minimize pump loss by reducing valve lift and the amount of air entering the combustion chamber.
Compared with the traditional twin-convex engine, Valvetronic uses an additional eccentric shaft, stepper motor and some central rocker arms to control the opening or closing of the valve. If the rocker arm is pressed A deeper intake valve will have a higher lift. Valvetronic has a way to freely control the valve lift. Long intake means a large valve lift, and short intake means a small valve lift.
Advantages:
In the Valvetronic engine, the cooling water flows through the cylinder head, which can reduce the temperature by about 60%.
The water pump only needs half the original size, reducing power loss by about 60%.
The power direction oil is heated quickly, reducing the power usage of the hydraulic pump.
Installing the water pump and the power pump on the same shaft, and a heat exchanger between cooling and oil, reducing the temperature by 30%.
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