What are the advantages of DVVT engine?

——————————————— The following content is taken from Geely's website.

Geely G-POWER 1.8L CVVT all-aluminum engine with completely independent intellectual property rights is the first CVVT engine independently developed in China, which comprehensively improves the technical level of engine design and manufacturing in China. 1. 1.8L CVVT all-aluminum engine: CVVT (intelligent continuous variable intake timing system), which adjusts the intake angle of the valve according to the different working conditions of the engine, provides sufficient combustible gas, effectively improves the fuel utilization rate, and reduces the exhaust emission (reaching the Euro III emission standard) while ensuring efficient power output. The fuel consumption is equivalent to that of 1.5L engine, and the power output is comparable to that of 2.4L engine, with excellent performance in power, economy and environmental protection. Four advantages: (1) Power surge adopts in-line four cylinders, water cooling, DOHC, 16V and CVVT multi-point injection (the EFI system adopts Bosch M7.9.7 version). Maximum power 102 kw and maximum torque 172 N? M, the top speed can reach 185km/h, and it has the international leading high lift (57 KW/L). (2) Economical and fuel-efficient: The internationally leading plastic intake manifold design is adopted to effectively reduce intake resistance, increase intake volume and reduce power loss. The fuel consumption of 90km/h is only 6.5L/ 100km. (3) The lightweight and low-noise all-aluminum engine can reduce the weight by 30% compared with the traditional cast iron cylinder block, which can prolong the service life of the engine; Adopting die-casting aluminum alloy crankcase structure can obviously reduce engine noise and improve the rigidity of cylinder block structure. Hydraulic mounting is adopted on the engine bracket, which reduces the vibration and noise of the engine and improves the driving comfort. (4) The semi-return oil supply system is scientific and environmentally friendly, which can reduce the fuel tank temperature 10℃ and fuel vapor 1/3. Through the reasonable matching of transmission system and the streamlined body modeling design with low wind resistance, the fuel consumption of the whole vehicle is reduced by about 5%-7% compared with similar models. After the expert evaluation of FEV, an internationally renowned engine design company, the minimum fuel consumption rate is 238 g/kW h, and the vehicle emission reaches the Euro III standard. Two. Five innovative technologies 1, CVVT (intelligent continuous variable intake timing system) 2, high pressure casting aluminum alloy cylinder block and processing technology 3, split crankcase, integral main bearing cover and processing technology 4. The first plastic intake manifold manufactured by friction welding process in China. Five innovative technologies of electronic control system, including CVVT control module, are described in detail: 1, CVVT (Intelligent Continuous Variable Intake Timing System) technology: ensure that the engine can change the valve opening and closing time and intake air volume under different road conditions, and improve fuel utilization while ensuring sufficient traction output. Geely 1.8LCVVT all-aluminum engine's CVVT internal sealing device and CVVT system oil filter device obtained two patents. CVVT (intelligent continuous variable intake timing system) is a technology that changes the time of camshaft opening intake valve in the morning and evening through electro-hydraulic control system, so as to control the required valve overlap angle. The working principle is that when the engine is running at low speed and small load (idle state), the opening time of intake valve is delayed and the valve overlap angle is reduced to stabilize the combustion state; When the engine is running at low speed and heavy load (starting, accelerating and climbing), the opening time of intake valve is advanced and the valve overlap angle is increased to obtain greater torque; When the engine is running at high speed and heavy load (high speed), the opening time of intake valve is delayed and the valve overlap angle is reduced, thus improving the working efficiency of the engine; When the engine is in a medium working condition (driving at a medium speed and uniform speed), CVVT will also delay the opening time of the intake valve and reduce the valve overlap angle, thus reducing fuel consumption and pollution emissions. The application of CVVT system improves various technical indexes of the engine: (1) the torque at the middle and low speed ends is increased10%; (2) The power at the high-speed end is increased by 8%; (3) Fuel economy is improved by 5%; (4) On the basis of limiting the emission of nitrogen oxides, HC emission can be reduced by up to 25%; 2. High pressure casting aluminum alloy cylinder and processing technology: the cylinder is cast with water pump vortex. The cylinder liner of aluminum alloy inlaid with alloy cast iron adopts high pressure casting process, which reduces the weight by 30% compared with the traditional cast iron cylinder block. 3. Split crankcase, integral main bearing cover and processing technology: The die-casting aluminum alloy crankcase structure is adopted, and the pre-cast cast cast iron main bearing cover adopts the internationally advanced fine boring and honing technology, which can obviously reduce the engine noise and improve the structural rigidity of the engine block. 4. Plastic intake manifold: the first case in China is made by friction welding process, and the intake port is added with a steady flow cavity to improve the intake efficiency at high speed; Optimize the diameter and length of the manifold channel, taking into account high speed, high power and medium and low speed torque. The adoption of high-temperature resistant plastic intake manifold not only has light weight and good heat insulation effect, but also has smooth inner wall, which improves gas flow, engine performance and fuel utilization, and ensures economic and efficient power output. 5. Electronic control system including CVVT control module: The intelligent continuous variable intake timing system, namely CVVT, is adopted to realize intelligent control of engine power output through the electronic control system, which greatly improves engine power and economy and reduces emissions. Third, superior handling and driving freely combined with the special road conditions in China, according to a large number of road test data, the optimized suspension system has been carefully adjusted, and with the high rigid body, the superior handling and driving stability are guaranteed, while the ride comfort and quietness are improved. Front suspension system (McPherson independent suspension): By optimizing the wheel alignment, the vehicle's mobility can be fully exerted, with strong road adaptability and compact structure, which not only saves space, but also is lighter, which is beneficial to the lightweight of the whole vehicle. Rear suspension system (longitudinal swing arm+torsion beam composite suspension+anti-roll bar design): a popular form of rear suspension in Europe and America. In the torsion beam suspension, the camber and toe-in of the wheel can change with the vertical vibration and yaw vibration of the car body to ensure the stability of straight driving and good steering driving. VVT is the abbreviation of English, and its full name is "VariableValveTiming", which means "Variable Valve Timing" in Chinese, but it should be called "Intelligent Variable Valve Timing System" according to Toyota's translation. The system mainly controls the camshaft of the intake valve, and has a small tail "I", which is the English code for "intake". These are the literal meanings of "VVT-i". This technology has been applied since the end of 1990s, and has been widely adopted by Toyota. It doesn't look like the latest technology now. It's just that Toyota didn't introduce VTEC as readily as Honda did. Recently, seeing the vitality of China market, it introduced VVT-i engine in a low-key way and assembled it on domestic small-displacement cars such as Weizi 1.0 and Tianjin Teyue. Only corolla has a share of medium-displacement cars. After all, VVT-i engine is the mainstream configuration of Toyota. From this perspective, the technology of domestic Corolla and Toyota is synchronous.

VVT-i is a device to control the valve timing of the intake camshaft. By adjusting the valve timing of camshaft angle, the power and fuel economy of the engine in all speed ranges are improved and the exhaust emission is reduced. VVT-i system consists of sensor, ECU, camshaft hydraulic control valve and controller. The ECU stores the optimal valve timing parameter values, and feedback information such as crankshaft position sensor, intake manifold pressure sensor, throttle position sensor, water temperature sensor and camshaft position sensor is collected in the ECU and compared with the predetermined parameter values to calculate the correction parameters and send instructions to the hydraulic control valve to control the camshaft timing. The control valve controls the position of the oil pan valve according to the instruction of ECU, that is, changes the hydraulic flow, and selectively sends signal instructions such as advance, delay and invariability to different oil circuits of VVT-i controller.

VVT-i system can be divided into two types according to the installation position of the controller. One is installed on the exhaust camshaft, which is called vane VVT-i, and this is what Toyota Previa installed. The other is installed on the intake camshaft, which is called spiral groove VVT-i and installed on Toyota Lexus 400, 430 and other advanced cars. Their structures are somewhat different, but their functions are the same. The vane VVT-i controller consists of a housing driving the intake camshaft and an impeller connected to the exhaust camshaft. The oil pressure from the leading or lagging oil passage is transmitted to the exhaust camshaft, which makes the shell of VVT-i controller rotate, drives the intake camshaft and continuously changes the intake timing. When the oil pressure is applied to the advance side oil chamber rotating housing, the intake camshaft rotates in the advance direction; When the oil pressure acts on the rotating housing of the oil cavity on the lagging side, the intake camshaft rotates in the lagging direction; When the engine is stopped, the camshaft hydraulic control valve is in the maximum lag state.

The spiral groove VVT-i controller includes a gear driven by a timing belt, an internal gear rigidly connected with the intake camshaft, and a movable piston located between the internal gear and the external gear. There are spiral splines on the surface of the piston, and the piston moves along the axial direction, which will change the phase of the internal gear and the external gear, thus causing the continuous change of the valve distribution phase. When the oil pressure is applied to the left side of the piston, forcing the piston to move to the right, the intake camshaft will advance by a certain angle relative to the camshaft timing pulley due to the helical spline on the piston. When the oil pressure is applied to the stone side of the piston, forcing the piston to move to the left, it will delay the intake camshaft by a certain angle. When the ideal valve timing is obtained, the camshaft timing hydraulic control valve will close the oil passage to balance the pressure on both sides of the piston and the piston will stop moving. Now all advanced engines have "Engine Control Module" (ECM), which is responsible for ignition, fuel injection, emission control, fault detection and so on. The ECM of Toyota VVT-i engine automatically searches for the optimal valve timing corresponding to the engine speed, air intake, throttle position and cooling water temperature under various driving conditions, and controls the camshaft timing hydraulic control valve, perceives the actual valve timing through the signals of various sensors, and then carries out feedback control to compensate the system error and reach the position of the optimal valve timing, thus effectively improving the power and performance of the automobile and minimizing the fuel consumption and exhaust emissions. Recently, I heard that there are dual VVT-i engines on the market. I don't know if it's true or not. I don't know what that is.

CVVT engine mainly draws lessons from the technical mode of VVT-i, so there is no essential difference between the working principle of CVVT and VVT-I, except that controlling valve timing has no function of controlling valve lift. Therefore, the engine will only change the time difference between intake and exhaust, but not the air intake. Simply put, its working principle is that when the engine changes from low speed to high speed, the electronic computer will automatically apply oil pressure to the small turbine in the driving gear of the intake camshaft, so that the small turbine rotates at a certain angle relative to the gear housing under the pressure, so that the camshaft rotates forward or backward within 60 degrees, thus changing the opening time of the intake valve and achieving the purpose of continuously adjusting the valve timing. Therefore, under the action of the above structure, it can ensure that the engine can change the valve opening and closing time according to different road conditions, and improve the fuel economy while ensuring sufficient traction output.

CVVT system includes the following parts: oil pressure control valve, intake cam gear, crankshaft sensor, cam position sensor, oil pump and engine electronic control unit (ECU). The toothed disc of the air intake cam comprises an external gear driven by a timing belt, an internal gear connected with the air intake cam and a control piston which can move between the internal gear and the external gear. When the piston moves, the spiral gear on the piston will change the position of the external gear, thus changing the timing effect. The displacement of the piston is determined by the oil pressure control valve, which is an electronic control valve, and its oil pressure is controlled by the oil pump. When the computer (ECU) receives input signals such as engine speed, air intake, throttle position and engine temperature, it will determine the operation of the oil pressure control valve. The computer will also use the cam position sensor and crankshaft position sensor to determine the actual valve timing of the intake cam. When the engine is started or shut down, the position of the oil pressure control valve changes, so that the intake cam timing is in a delayed state. When the engine is idling or loading at low speed, the timing is also in the delayed position, which improves the stable working state of the engine. The intake cam is in the advanced position when it is in the middle position, and it is in the advanced angle position to increase the torque output when it is in the middle, low speed and high load. When at high speed, it is in a delayed position to facilitate high-speed operation. When the engine temperature is low, the cam position is in the delayed position, which stabilizes the idle speed and reduces the fuel consumption.

α-CVVT engine is the world's leading engine technology. CVVT engine refers to "continuously variable valve timing system". The application of this system enables the valve of CVVT engine to control the opening and closing of the valve at any time according to the engine state, which makes the fuel burn more fully, thus improving the power and reducing the fuel consumption. Its working principle is to change the valve closing time according to the inertia principle, so as to increase the amount of air entering the cylinder: everything with mass has inertia, and the air sucked into the engine cylinder also has inertia, and will keep the trend of entering the cylinder after the intake process is over. At this time, if the valve closing time is delayed, the cylinder can suck in more air, which can improve the efficiency. Therefore, the longer the valve closing time delay, the higher the performance at high speed; Conversely, the earlier the valve closes, the more stable the low-speed operation and the greater the torque. From this point of view, Cerato's CVVT engine seems to be the worst of several engines. Therefore, I think that neither manufacturers nor 4S stores should recommend CVVT engines as the biggest selling point to customers. I also hope that friends who plan to buy a car will not be confused by CVVT engines. Although the engine is the most critical component in a car, the more advanced the better. It is important to match the whole vehicle.