Many people read the configuration parameters will say that this car xxx car is SOHC, no XXX DOHC good, etc., may be a lot of people understand the only stay in the "car has a few cam", recently talk about this The working principle and characteristics of the two are also the actual use of the pros and cons.
In the market common large displacement performance models have basically rarely use this SOHC engine, because the motorcycle is commonly used in the common speed are higher, only some cruise car retro car despite the large displacement but still in the use of two valves Or ordinary SOHC engine, this engine is more seen in the 250cc within the small displacement models.
SOHC structure compared to DOHC more simple, but although only one camshaft, but through the two valve arm to the four valve, which control the valve opening and closing.
Advantages: Since there is only one camshaft, driven by the timing gear, the engine is less affected by the resistance of the camshaft itself when the speed is rising, and the output of the low speed part can be done more lightly. Maintenance and maintenance costs lower, simple structure, in the commonly used low-speed road fuel will be more economical.
Disadvantages: In the high speed, due to the existence of a certain degree of flexibility of the valve arm itself, reciprocating parts more, resulting in inertia, so the high turn when the valve stroke control will be the lack of stability and precision, there will be some unnecessary vibration or noise The
DOHC (double overhead camshaft) As the name implies, the double overhead camshaft naturally has to drive two camshafts, because it is two camshafts that can be directly driven by the camshaft under the pressure of the valve, no valve rocker this medium, but need Longer timing of small chains or belts to drive.
The mainstream of the larger displacement models are used in the DOHC engine, especially high-performance models! Due to the complex structure of the DOHC also requires a higher cost to create maintenance.
Advantages: the structure of the engine for high stability of the stability of the gas to be more accurate, is conducive to play the engine's maximum performance, because there is no too much moving parts and transmission media, in the vibration control better. The use of two independent cams can be used V-type combustion chamber, the valve angle can also be more flexible in the design, the spark plug can be placed in the middle of the combustion chamber, for the full uniform combustion have a certain contribution.
Disadvantages: due to the two cams to drive, for the engine's low speed acceleration range of torque will be lost, due to the complex structure, maintenance and repair costs and difficulty than the SOHC higher.
DOHC seems to be more competitive in use than SOHC, but for motorcycles, not all cars with DOHC must be good.
DOHC low twist shortcomings of this shortcoming, enough to make a car within 250CC headache, a small displacement of the engine a stroke is not much work, but still have to drive two camshaft, so even if you want to make a small displacement Performance engine, but also need to take care of the torque of the solid, or you are still not easy to get an ideal acceleration results.
The SOHC in daily use, both to have a more refreshing low-output, but also have an ideal fuel consumption. In the large displacement, put aside those retro cruise, most of the engines are using DOHC, because the structure for the large displacement of the engine driving quality can make better performance, and large displacement of a single stroke work The ability is also very strong, the loss ratio for low torsion will be smaller.
As in the case of cars, if the small displacement of small cars with DOHC hard to compress costs to improve cost-effective to better use SOHC to make the user experience more perfect.