Friends who pay attention to the car should all discovered that from the 1990s, the direct 6 engine replaced by V6, has gradually recovered in recent years, and there is a major momentum of the finals of the fuel machine life. In addition to loyal to the baby, Mercedes-Benz also abandon V6 in 2017, and it turned around to 6 camps. At the same time, Hiroshima Small Factory Mazda is also developing a straight 6 engine for the next generation. This is not forbidden, how can the six cylinders return to the mainstream? Is it strong than the V-shaped six-cylinder engine?
While V6 and straight 6 belong to a six-cylinder engine, but in fact Straight 6 is far below V6 in research and development and manufacturing cost, and the specific advantages are reflected in the following aspects. 
Since each sleeve cover of the top camshaft engine is now required, this means every V6 The engine will definitely pay two sets of intake exhaust, a total of four camshafts, in order to complete normal gas supply. Not only that, but the relationship is far from the distance between the two side cylinders of the V-type engine, two high-pressure oil rails and ignition systems including high-pressure packages and ignition coils are also available. 
When the exhaust gas generated after the work is treated, the V6 engine is also required to separately, and it is considered three-yuan catalysis. Only the characteristics of the exhaust gas treatment can only be completed under high temperature conditions, so the three-way catalysts of most V6 engines are arranged adjacent the position of the engine (as shown above). This means that every three cylinders of the engine must be equipped with an oxygen sensor + threeThe metallogenic, a V6 engine requires two sets of oxygen sensors + ternary catalyst to achieve connection with subsequent exhaust systems.
At this time, it is revealed that the manufacturer is turning the straight six-cylinder engine, because the six cylinders are in a straight line relationship, so it only You can do your job using a set of gas supply and oil supply systems. In terms of exhaust, the straight six-cylinder engine can directly connect the six exhaust manifolds to a three-yuan catalytic to complete the task.
After the manufacturing cost, let’s take a look at V6 and How much is the cost of research and development in 6. At present, most of the automotive manufacturers have begun to use modular concepts to create an engine, in which BMW is a faithfulness of the straight six-cylinder engine, and it is god into the engine modularization. First create a single cylinder of 0.5L, and spell three is 1.5T three-cylinder machine. Add a cylinder to create a four-cylinder machine for 2.0T. If the head of the two three-cylinder engine is coiled together, and change the crankshaft and ignition order, you can directly make a straight six-cylinder engine.
At this time, the V6 engine is revealed, although the engine difficulty of spelling a V6 with two three-cylinder engines, even a straight 6 It is easier, after all, even if there is no need to adjust, but because the V6 engine has two timing systems, and two crankshaft links that need to work together, the difficulty is also straight in the engine’s adjustment. The engine is much higher, thereby causing the rising boat in the R & D cost. 
BMW straight 6 engine
This is not difficult for straight six engines, because 6 cylinders of straight six are in a straight line, So just put, the exhaust system is arranged on both sides of the engine. At this time, the middle cylinder plays the role of the natural barrier, which can effectively avoid the high temperature of the exhaustion affects the cool intake air intake. In addition, the current six-cylinder engine is usually equipped with a turbocharger on the inquiry six-cylinder, which is also installed on the exhaust gas, effectively eliminating the impact of ultra-high temperature turbine on intake temperature.
V6 intake schematic
It is foreseeable that the V6 engine such that the ambient temperature will inevitably increase the annular temperature of the turbocharged. That is to ensure that the gas temperature entering the engine is cool, thereby increasing the oxygen content of the intake, so it is necessary to reduce the intake air temperature for the engine to reduce the intake air temperature. However, the large intercooler will inevitably trigger the rise in manufacturing costs, and bring additional weight and ultimately drag the power of the engine. Therefore, compared to the straight six-cylinder engine, the V6 engine also needs flowers in heat dissipation.Take more costs.
In fact, the manufacturing cost is only the introduction of the straight six-cylinder engine The level advantage is because the absolute advantage of the V-shaped cylinder is compared to the absolute advantage of the V-six-cylinder, in fact, the V6 engine is unparalleled, second only to the operation of the V12 engine.
To understand why the straight six-cylinder engine is smooth, let’s first understand how the engine’s vibration is coming. For a qualified engine, the vibration is mainly from two points: one is the vibration generated when the piston is up and down, referred to as a first-order vibration of the engine; the other is the vibration generated when the crankshaft is rotated, called Second-order vibration.
Among them, the first-order vibration generated by the piston up and down movement is actually very easy to solve. Because when a piston moves down, only one other piston is moving upward motion, the vibration generated when the two piston movement can be canceled. It can also be concluded that as long as the number of cylinders of the engine is double numbers, and the piston is moving in the opposite direction, it can effectively avoid the effect of first-order vibration.
However, the second-order vibration generated by the crankshaft is more difficult to avoid. The second-order vibration is produced because the engine used by the piston crankshaft link structure, which has a characteristic, that is, the angle rotation of each stage of the crankshaft, the distance movement with the piston, is not a time, etc. Simply, in one stroke, the crankshaft is 180deg; the rotation process, the first 90de; the corresponding piston moves up and down, and the post 90deg; the corresponding piston corresponding to the rotation moves the distance, not equal.
Among them, according to the physical principle, the motion speed of the piston in the upper half of the cylinder is to be significantly faster than the piston in the lower half. Motion speed. So in practice, the crankshaftFigure Blue Parts) From any one of the starting positions, such as inhalation, a 12-point position of the work stroke (12:00 on the left side of the figure below), the crankshaft passes through 90deg; rotation runs to 3 points; or compressed, 6 points started from the exhaust stroke, passing through the crankshaft 90deg; rotating to 9 o’clock, the piston is at the bottom of the cylinder. Instead, it is in this piston up and down, and the acceleration is asymmetrical, eventually triggeting the second-order vibration of the engine.
Therefore, in order to completely eliminate the second-order vibration, it is necessary to determine the work of each cylinder as a crankshaft like a three-cylinder engine. The rod rotates 120deg; (as shown the relative position of the crankshaft linkage of the three cylinders represented by the blue cylindrical in the “1 cylinder in the inner view” above. When the engine is running, the crankshaft connecting rod of the No. 1 cylinder is in the process from the 12 o’clock position of the above to 4:00 (the left green sector shape on the image), the piston will experience a downward movement from the vertex to the cylinder. The process of the lower half (as shown in the “1 cylinder integral angle” on the right side of the above figure). According to the above, the piston runs faster on the upper half of the cylinder, so the moving speed of the piston in the cylinder will present a tendency from a quick to slow.
Ingenious, at this time, the crankshaft connecting rod of the No. 3 cylinder will undergo a position from 7:30 to 12 points. Process (left green fan shape above), is a process of running from the lower half of the cylinder to a vertex (as shown in the right “3-cylinder integral angle” above), which will present a slow to fast process. And this slow to fast acceleration, it is exactly from the No. 1 cylinder from fast to slow acceleration. Thereby eliminating the second-order vibration of the No. 1 cylinder and No. 3.
And we discussed the V-type six-cylinder engine, although it consists of two three-cylinder engines, but due to V6 engines The crankshaft does not use an aliquot 360deg; it is still a second-order vibration. That is, when one of the piston movements, the acceleration generated is unable to be offset by the acceleration of other pistons.
Although the straight six-cylinder engine can also be considered as two three cylinders The machine works together, but is different from the V6 engine, the inquiry six-cylinder engine is composed of two three-cylinder engine mirror. Therefore, during the operation, the left and right of the straight six engine, 1-6 cylinders, 2-5 cylinders, 3-4 cylinders, are also two mirrors. So the straight six engine will have a second-order vibration like a three-cylinder engine. At the same time, the 6-cylinder is used as an even cylinder, and there is no one-stage vibration. Therefore, the six-engine has a self-balance function, which is also not available.
[123 Although the inquiry six-cylinder engine has the advantages of self-balance and low cost. But its shortcomings are also very obvious, the main problem is that the engine is too long. Since the six cylinders of straight 6 are arranged, it is much longer than the length of V6, the length of the six-engine will grow, and the overall length is only slightly shorter than the V12 engine, which is obviously within the cabin. Longitudinal space proposes high requirements.
Simultaneous The cabin has been ranked. This leads to that if the model of the horizontal platform wants to carry a six-cylinder engine, it will eventually select the length of the V6 engine close to the straight four-cylinder machine.
In addition to the volume, the height of the straight six-cylinder engine will be higher than The V6 engine, so the height of the center of gravity of straight 6 engine models is usually higher than V6 models. At this time, if the V6 engine is 60DEG; angle, it will be around 14% lower than the in-line six-cylinder engine, about 5-8cm. And if the V6 engine uses a lower 90deg; angle, it will be about 30% lower than the inner six-cylinder machine, that is, 10-15cm.
Therefore, for a model of manipulation, V6 engine is obviously a better choice. The performance car using a straight six-cylinder machine needs to reduce the center of gravity from other parts, such as using carbon fiber roof like BMW M3. 
With the development of the times, the number of the engine’s cylinder has also occurred. big change. The V8 engine that once “can not be” begins with lower fuel consumption, more environmentally friendly V6 engine, like Ford F150 Raptor, a new generation of land trips, Audi RS4 and other models from the 8-cylinder downgrade for 6-cylinder .
At the same time, it is benefited from the relationship between the volume of the car, and the shortcomings of the inner six-cylinder size is no longer as fatal. At this time, the straight six cylinder cost is lower, cheaper, and the advantages of more smooth operation will be amplified. So is a luxury such as Mercedes-Benz, Lu JunBrand, have also embarked on the road to replace V6 with straight 6. In this way, the high-end position of the V6 engine showed a significant decline signs. After all, there is only a rear driver, and there is a sufficiently long cabinet space to accommodate the same distinguished straight six-cylinder engine!