Text/Qin Ming
We all know that the role of the closed cylinder is to save fuel in the case of low power stop, but in theory, turning off half of the cylinder is equivalent to half the workload of the engine, so the energy consumption should also be reduced by half? According to the understanding, these models equipped with closed-cylinder technology engines have not greatly improved fuel consumption. So let's take a look at this closed cylinder technology, what are the technical characteristics and advantages and disadvantages?
Closed cylinder technology was popular in the United States a long time ago, because the oil price in the United States was low at that time, resulting in the production of V8, V12 these large-displacement models too much, and then the high price of oil, found that it could not be stopped, so there was the emergence of closed cylinder technology, to this day many American brands are still fond of this technology, such as GM and Ford and other brands.
However, the closed cylinder technology is not able to be carried at will, mainly for V6, V8, V10 and other large displacement engines, the three- and four-cylinder machine is not unusable, mainly the effect is not too obvious, the closed cylinder technology can make the engine part of the cylinder stop working, reduce energy consumption. At present, the major car companies to achieve engine closure technology mainly through the oil stop and oil stop gas two ways, the first way to stop oil is to stop the engine injection, the valve is still working normally, so the air as usual through the intake valve, will also be damped leading to pump gas losses, it is conceivable that the cylinder has stopped working, intake and exhaust is doing useless work, no doubt will increase the loss of energy and components, that is a bit of a near and far away.
The way to stop the gas and stop the oil should be more thorough, not only stop the injection of oil but also stop the exhaust movement, which is undoubtedly a lot better than the energy-saving effect, so the major factories have set their sights on how to stop the valve work. For example, GM, Ford and Honda all have their own closed-cylinder technologies.
General-purpose closed cylinder technology was first installed on the Cadillac model L62 V8-6-4 engine, when the technical name was DoD (Displacement on Demand) intelligent fuel management system, when the power is excessive, DOD will control the closure of the excess cylinders, can be converted from 8 cylinders to 6 cylinders and 4 cylinders in the working mode, the fuel saving effect is obvious, due to technical limitations at the time, the operation is unreliable, and later shelved.
Later, the 2.0T engine mounted on the Cadillac XT4 was equipped with Tripower three-stage intelligent cylinder change technology, which mainly through the three-stage pulley cam with special chute and slider to achieve lateral displacement of the camshaft, and there is a solenoid valve for adjusting the valve lift above the chute, controlling the slider to reach down into the chute, because the slider is fixed, there is a key between the camshaft and the cam, then with the trajectory on the cam surface, the camshaft also begins to displace laterally, so as to achieve different sizes of cams and valve top rods connected, to achieve the effect of closing the cylinder.
Unlike the general closed cylinder technology, Ford uses a rocker arm structure to achieve the effect of closing the cylinder, the rocker arm is mainly composed of two parts, one end is connected to the hydraulic oil, and the other end is connected to the cam. When the controller receives the instruction to close the cylinder, it will reduce the amount of oil in the rocker arm, and the cylindrical pin of the rocker arm will be recycled, resulting in the inability to connect with the cam, and the cam is completely in independent motion, which is how the valve is disconnected from the camshaft to achieve the effect of closing the cylinder.
The main purpose of closed cylinder technology is to reduce emissions and reduce fuel consumption, but there is a common misunderstanding here, after the 4-cylinder engine closes two of the cylinders, its fuel consumption cannot be reduced by 50%, but only about 20%. Why can't half-closed cylinders reduce fuel consumption by 50%? This is because the two cylinders that do not do work still have to continue to reciprocate with the crankshaft, and the friction during the movement, etc., consumes part of the energy, and although the intake and exhaust valves stop moving, the cam that was originally connected to it is still rotating, and it will also lose part of the energy, so it cannot be reduced by half.
In addition, although shutting down the two cylinders can help the engine improve fuel efficiency, it will also bring a new problem, that is, the uneven distribution of heat in the cylinder block. Since two of the cylinders stop working, the heat generated will be significantly lower than that of the cylinders that continue to operate, which will lead to uneven heat distribution in the engine block. The uneven heat distribution of the engine for a long time may lead to deformation of the engine block and affect its stability, so an additional dynamic thermal management system is required to accurately balance the heat of different positions of the engine through an independent coolant circulation circuit, increasing the complexity and cost of the engine.
Due to the increasingly serious emission problems in recent years, closed cylinder technology has gradually returned to everyone's sight, it is interesting that under the emission problem of new energy, battery intelligent technology continues to innovate and continue to move forward, while traditional fuel models are "turning back to eat the old", which also means that the arrival of the new energy era has been unstoppable.