a. Engine position
The engine may be said to be the most important part of the car, and its arrangement for a motor vehicle having a significant impact on performance. For the car, the arrangement position of the engine can be simply divided into front, center and rear three. Most models currently on the market are based on a front-engine, center and rear engine used only in a few performance sports car.
Of course, in accordance with the engine placed in the form, can be divided into transverse, longitudinal engine
Front engine
Front engine, i.e., the front position before the engine shaft. Front engine advantage of simplifying the structure of the car is the transmission and the drive axle, particularly for currently mainstream absolute front-wheel drive vehicle, the engine delivers power directly to the front wheels, a long shaft is omitted, only reducing power transmission loss, but also greatly reduces the complexity of the failure rate and the power transmission mechanism.
Further, a driver facing the front of the engine, during a frontal collision, the engine can protect the driver from impact, thereby improving the vehicle safety.
The mid-engine
is set in the engine, i.e. between the front and rear axles of the vehicle engine, typically located in the cockpit before or after the engine. So to speak, mid-engine rear-wheel drive car is definitely or four-wheel drive.
car when cornering, the various parts of cars because of inertia are moved to the outside bend, the engine is the largest mass portion, due to inertia of the engine with a steering force to the vehicle body in the closed to the bending important influence. Mid-engine vehicle inertia feature is the largest in the center of the vehicle body of the engine, so that the body weight distribution can be made close to the ideal equilibrium state. In general, only those who pay attention to the super sports car or sports car was fun to drive mid-engined.
Of course, the mid-engine also has disadvantages, since the engine is set, resulting in a narrow cabin, the seat can not be arranged more, Further, since the occupants from fatMotivation too close, so noisy. However, only the pursuit of automobile driving performance of people, these are no longer peace, and even some people prefer to hear the roar of the engine roaring.
rear engine
was a classic Volkswagen Beetle and Fiat 126P models also rear engine.
transverse engine
refers to a transverse engine front axle parallel to the engine and vehicle. Simply say that you stand in front of the front of the engine, if the engine sideways in front of you, that is transverse engine.
In general, the precursor of the compact car, the majority of mid-size sedan and limousine few have adopted a transverse engine layout.
Advantages:
transverse crankshaft of the engine, the transmission and the axle input and output shaft are parallel, so that if a front-drive, it is most appropriate that the front transverse engine, the power short transmission distance, in the same direction, and therefore higher transmission efficiency.
On the other hand, due to the small longitudinal space occupied by the transverse engine, can greatly shorten the longitudinal extent of the space in the engine compartment, the result is large driving space, in particular a front passenger leg portion expand the space. This is especially important for the limited size of the compact car in terms.
Disadvantages:
before and after the imbalance in the weight distribution of the maximum defect of transverse engine, since the input shaft parallel to the transverse engine crankshaft of the engine gearbox coupled together, it may be arranged before the engine front axle, but the heaviest parts by weight of automobiles all concentrated in front of the front axle load is too large makes so prone understeering situation, the top-heavy front and rear axle weight vehicle will enable high-speed cornering the rear end of the lack of stress, some irrational distribution of axle load transverse engine cars and even up to 30 percentage percentage after the first 70, its performance can be imagined.
On the other hand, due to the transmission side of the transverse engine installation position biased too, a long drive shaft is a short, when a great driving force acting on the drive shaft of unequal length, there are two front wheels make the car speed difference, resulting in hard acceleration when the front left and right swing phenomenon, that is, we often say that the torque steer, which is particularly evident in the large displacement of FF models.
longitudinal engine
refers to a vertical longitudinal engine automobile engine and front axle, simply say that you stand in front of the front of the engine, if the engine is placed vertically in front of you, it is a longitudinal engine .
Generally after driving a longitudinal engine are used, because the power to be transferred to the rear axle, in a case where the transmission distance can not be shortened, it is necessary to reduce as much as possible in the direction of the force conversion. If then tapped, because the vertical direction of the crankshaft and the drive shaft, so first converting a direction to transmit power through the shaft, the shaft and the direction is perpendicular to the rear axle, the rear axle is required then conversion over the direction of rotation, which undoubtedly reduces the efficiency of the transmission system. The use of such longitudinal engine crankshaft and the transmission shaft can be parallel, reducing the drive direction conversion undoubtedly reduces the loss of energy.
On the other hand allows the longitudinal engine position of the transmission back extension as far as possible, the center of gravity of the power train located behind the front axle, the vehicle body weight would allow more evenly.
in the longitudinal engine platform, there is a more specific example, the use of which is longitudinally mounted engine front-drive Audi. Although Audi longitudinal engine used to take care of more Quattro this tradition, but longitudinal engine layout engine front-wheel drive can also bring a good front-rear weight ratio. Such an arrangement may be disposed before the engine longitudinal front axle, gearbox and engine directly connected to the engine compartment space will be limited, it is necessary arranged behind the front axle, the input shaft of the gearbox and the engine crankshaft rotation around the same axis , to bear the weight of the engine and gearbox of the vehicle front axle, he like the balance point, the engine and gearbox located in front and rear sides of the front axle, so that the engine and gearbox front bearing weight more evenly distributed the center of gravity ratio is more reasonable, although they are still before the drive will Tuitou phenomenon, but its weight ratio is much better than ordinary transverse engine models such as the Audi A4 before and after the precursor of the weight ratio reached a more perfect 55:45.
However longitudinal engine also has disadvantages, since the vertical position causing the engine nacelle take a long space, resulting in some loss of the driving space.
trans-engine
ldquo; inverted rdquo; is a special arrangement of the transverse engine, usually the front transverse engine exhaust manifold, the intake manifold in the arrangement, simply means that ldquo; rdquo ;, if backward before the intake transposes the exhaust gas, the intake manifold to the front, rear manifold placed into ldquo; rdquo ;, after an advance is called ldquo; inverted rdquo; of. Only transverse engine only ldquo; positive and negative home rdquo; said, longitudinal engine intake and exhaust manifolds on left and right ends, interchangeable and there is no difference, so there is no such argument. The use of anti-engined cars around us are many, such as: the use of the Ford Focus, Mondeo, Mazda, Lancer wing of God, and the new Regal 2.4 and other models are anti-mounted engine.
advantage that the inverted engine intake manifold at the windward side, and better able to reduce the intake air temperature, the temperature drop of the air density is increased, the oxygen content per unit volume are increasing, it is possible the combustion more fully, improve efficiency, reduce fuel consumption. For non-direct injection engine, is arranged such that the trans-mounted supply line but also with the intake manifold is moved to the front of the tube, it has a better cooling effect. After shifting the design of the exhaust manifold, the exhaust pipe is no longer pass under the engine, the engine can be shifted downward position, the effective center of gravity to enhance handling performance, and further with an exhaust pipe from the engine, the cooling system to reduce thermal load, avoiding the impact on the oil pan, exhaust gas no longer ldquo; tortuous rdquo; exhaust conduit such that the resistance is greatly reduced, the exhaust gas smoother, more efficient, the engine can be output at high speed higher power.
However, the engine is not perfect inverted, after the first exhaust pipe so as to shift the position closer to the passenger compartment, and the high-temperature exhaust noise easily penetrate into the passenger compartment, the temperature in order to reduce the influence of noise and , you need to spend more of the cost of doing handle noise insulation in the firewall and other locations. Another disadvantage is inverted smooth engine exhaust line is reduced back pressure in the exhaust pipe, so that the reduction in exhaust efficiency of the engine speed is low, thereby affecting the efficiency of the intake air, the intake air-fuel mixture in the intake manifold is often can not be completely sucked into the cylinder, it is likely to cause uneven density of mixed gas, insufficient fuel combustion, etc., without adsorbed into the cylinder wall on the intake valve and also fine dropletsCarbon easily formed under high temperature environment. That’s why anti-mounted engine power output is usually weaker at low speeds, but also a lot of use of anti-engined models one of the main factors likely to produce coke.
However, with the variable-length intake manifold and the current mainstream variable valve timing technologies, applications, engines inverted vulnerable are gradually emerging direct injection technology is being gradually improved. VVT technology enables ldquo; gas flow valve switch and rdquo; greatly reduce the adverse effects of conventional multi-air mixture concentration EFI engines, direct injection and the application is further weakened the switching valve and the manifold for mixed gas stream adverse effects of concentration, fuel directly into the cylinder, capable of more accurate calculation and control the amount of fuel injection, compared to the outer-cylinder injector reduces the loss of fuel, to improve efficiency and reduce fuel consumption purposes. It can be said, the engine inverted vulnerable in this regard has been effectively compensate, higher efficiency can be achieved in the whole section of the rotational speed, and better characteristics which exert a high speed output.