Abstract
This article is about two types of engines; the rotary engine and the piston engine. It examines the differences between the two types of engines and their different areas of application. This refers to the specific cars where the two types are used, as well as the market response with reference to the cars in question. Furthermore, the disadvantages and advantages of the two are closely looked into, where it is determined why the piston engine is most preferred by the auto manufacturers and car enthusiasts. Besides, the article concludes with which engine type is suitable depending on the needs of the car owner.
Introduction
Since the invention of the first vehicle to date, technology has been rapidly changing and upgrading. Different mechanisms have been invented or improved from time to time. The automobile industry has not been left behind on this. With the rapidly rising competition among vehicle manufacturers, the pressure to make more efficient vehicles has constantly been rising in order to win the largest shares of the ever expanding car market (Davis, 1999). This includes fuel consumption, engine torque as well as efficiency. This led to the upgrade from the rotary to the piston engine.
Mazda Rx-7, a miraculous car enthusiast’s dream
The Mazda Rx-7 is a Japanese sports car that was manufactured from 1978 to 2002. The car came after the Mazda Rx-3 before it was upgraded to the Mazda Rx-8. Perhaps the most inviting thing about this car is that implements the rotary engine. While other car manufacturers quickly disposed of the type rotary engine, a few, however, stuck to maintaining and improving the rotary engine. One of these companies is notably Mazda, which applies this engine in their Rx series automobiles (Whitney, 2003).
Before the manufacture of the Rx-7 Series came to a halt in 2002, the car had evolved through three notable generations, while undergoing a series of improvements and modifications. This car had conquered the market, with a total of 811,634 RX-7s having been produced (Whitney, 2003). The popularity of this model is so notable through the use in various famous Hollywood films such as the Fast and Furious series, Need for Speed and Forza Motorsport. This made it become a classic vehicle sensation that became a dream car to many car enthusiasts.
In terms of engines, the RX-7 originally included a twin-rotor Wankel rotary engine with a rear-wheel drive and a front-midship design (McCOSH, 2002). Despite the major shift from rotary engines and the worldwide advisories against this engine-type about the inefficiency, Mazda proved the world wrong about it with their classic masterpiece.
Thesis: Rotary combustion engines failed to achieve what piston engines did because of high maintenance engines, the heat problems, and the heavy carbonization problems.
The rotary engine is well known for its high horsepower, better handling as well as its immunity to catastrophic failure. However, this type of engine has often had its downside. The point of discussion, therefore, is whether the rotary engine has failed to match the qualities of the piston engine. This is argued using reported problems such as high maintenance engines, the heat problems, and the heavy carbonization.
How do rotary engines work compared to piston engines?
The rotary engine was an early internal combustion engine with an odd number of cylinders in each row, arranged in a radial manner. The crankshaft remains stationary in operation while the crankcase connected to the cylinders rotates about as a single unit. This type of engine was embraced in the World War 1 era, where the main area of application was aviation. Besides, it was also preferred in a number of the early cars and motorcycles (Hege, 2001).
On the other hand, the piston engine, also referred to as a reciprocating engine, is a type of engine that transforms pressure into rotary motion. Most of these reciprocating engines are usually heat-based, although there also exists pneumatic and hydraulic piston engines. The motor vehicles in the current world mainly use an internal combustion engine that includes either a spark-ignition system or a compression–ignition system (Davis, 1999).
The combustion process
Rotary engine combustion process
A rotary engine does four main different jobs: intake, compression, combustion, and exhaust. Each happens in its own part of the engine housing. This is similar to having four different dedicated cylinders for the four processes. The rotary engine uses the pressure that is created when fuel and the air are burned together. This pressure is contained in a chamber formed by a part of the engine housing that is sealed by a face of the triangle-shaped rotor. This rotor follows a destined path that keeps every single peak of the rotor in contact with the housing. Thus, this creates three different and separate volumes of gases. While the rotor is in motion, each of the three gas volumes expands and contracts, which draws air and fuel inside the engine. It is then compressed and generates power as the gases expand (Hege, 2001).
Piston engine combustion process
The piston engine works in a combustion cycle that incorporates a number of strokes depending on the type of car. The most common mechanism in the modern world is the four-stroke combination cycle; intake stroke, compression stroke, combustion stroke and exhaust stroke. A part called piston is attached to the crankshaft using a connecting rod (Davis, 1999).
Intake stroke: As the piston rotates, it starts from the top, where the intake valve opens as the piston goes down to allow the engine to take in a cylinder containing air and gasoline
Compression stroke: When the piston pulls back upwards, it compresses the air-fuel mixture thus creating pressure
Combustion stroke: The moment the piston reaches the top of the stroke, the spark plug emits a spark which ignites the gasoline mixture. The pressure increases rapidly and explodes, thus pushing the piston down
Exhaust stroke: The piston hits the bottom of the stroke, where the valve opens, and the exhaust leaves the cylinder towards the tailpipe. The engine is then ready for the next cycle, where a fresh mixture of air and gas is taken in, and the cycle is repeated.
The rotary engine has fewer moving parts compared to the usual four-stroke piston engine. This is because of numerous components in the piston engine such as valves, crankshaft, and piston while the rotary has just a single triangular rotor. Minimizing of these parts transforms into better reliability. Furthermore, all parts in a rotary engine rotate in a continuous manner in one direction unlike violent and sudden changes in direction like piston engines. This translates to better power delivery. Besides, the rotary engine is slower. This is because the rotors spin at a speed which is a third of the speed of the output shaft (McCOSH, 2012).
Real life examples
Rotary engines are not so common in the current world compared to the beginning of the 20th century. This is not a big surprise comparing its efficiency to the piston engines. However, Mazda, being the only car manufacturer applying rotary engines is a leading example through their RX-series vehicle (Whitney, 2003). Furthermore, this engine-type also finds use in other areas such as motorcycles and aeroplanes. Most aeroplane manufacturers prefer rotary engines due to fewer rotating parts and smoother power transmission (Hege, 2001).
Daily use problems.
One major complaint concerning the rotary engine is the huge fuel consumption (Vance, 1999). This is because this engine does not burn oil out of the fault; rather, it uses oil squirters which take small amounts of oil into the fuel to lubricate the engine seals. Less gas mileage is a huge problem due to the high costs incurred by the car owner (Vance, 1999).
Rotary engines have a high torque, which is quite advantageous. However, this develops into a huge problem due to wearing out of certain parts e.g. seals as a result of the friction. This mainly happens in case the driver lives in a cold climatic environment. Since the parts are rare, they tend to be more expensive than the usual piston engine spare parts. Besides, rotary engine mechanics are also rare to find due to the isolated nature of this technology. This massive torque and resultant friction also increases the chances of damaging the engine (Hege, 2001).
The rotary engine runs at an approximate 200-400 degrees Fahrenheit more than a piston engine (Vance, 1999). This excessive heat has at times been reported having melted down parts of the rotary. A combination of this heat with the fragile apexes in contact with the housing often leads to meltdown. More so, the oil squirters that spray oil on the apex seals generate carbon deposits which close the existent gaps that ease the movement of the side seal and the apex. This leads to motor failure and could also cause huge engine damages.
Conclusion
Despite the reliability of rotary engines in terms of smoother power transmission, weight reliability, and high horsepower, these engines require constant maintenance and regular checkups. However, the notable success by Mazda in their RX-series proves that the engine type is not that bad. Therefore, rotary combustion engines have not failed to achieve what piston engines did because of high maintenance engines, the heat problems, and the heavy carbonization problems.
References
Davis, T. (1999, March 5). This motoring century; ROTARY HYSTERIA. Sydney Morning Herald (Australia), pp. 5.
Hege, John B (2001). The Wankel Rotary Engine: A History. Jefferson, NC: McFarland.
McCOSH, D. (2002, March 29). The return of the Wankel engine. The New York Times, pp. 1.
Vance, B. (1999, July 16). Innovative NSU doomed by engine problems. The Ottawa Citizen,
Whitney, T. (2003, February 28). Mazda's RX-8 revives the rotary engine: Automaker is the only one in the world to offer engine. Ottawa Citizen, pp. C8.
