Centurion engine
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The Centurion is a series of diesel cycle aircraft engines for general aviation built by Thielert Aircraft Engines. So much interest was expressed in their 150 hp (112 kW) class engine for small aircraft that a much larger V-8 based on the same principles has since been introduced.
Centurion 1.7
The Centurion 1.7 was the first product introduced by Thielert, a 1689 cm³ (103 in³) engine aimed directly at the 135 hp (101 kW) target that makes up the vast majority of the general aviation world. It is in this power range that the popular Cessna 172 fits, and its popularity drove the entire market into the same general size range.
Unlike older designs, the 1.7 is water cooled, turbocharged and includes a one-control digital fuel control system (FADEC), dramatically improving reliability (many engine problems are caused by improper operation and power settings) as well as making the engine considerably easier to operate. It runs on either Jet A or diesel fuel, or any mixture of the two, allowing the operator to choose whatever is available and least expensive. The high compression ratio of the engine combined with the digitally controlled fuel injection system dramatically reduces emmissions as well, putting it on par with modern automobile engines.
The recommended propeller is a three-bladed constant speed model. Much of the sound of a light aircraft is generated by the tips of the propeller, which can approach the speed of sound. By using a smaller propeller with more blades, the same amount of power can be dissipated at a slower RPM and smaller radius, dramatically lowering the speed of the tips.
Some indication of the improvement in engine design can be seen by comparing the 1.7 to the engines it is aimed to replace, notably the Lycoming O-320, and to a lesser degree the Lycoming IO-360 and Continental O-300. The O-320 delivers 150 hp (112 kW) from 320 in³ (5.2 L), while the 1.7 delivers 135 hp (101 kW) from 103 in³ (1.7 L). This represents a dramatic increase in specific power, from the O-320's 0.47 hp/in³ (21 kW/L) to the 1.7's 1.31 hp/in³ (60 kW/L). The 1.7 is slightly heavier however, 294 lb (133 kg) vs the O-320 at 278 lb (126 kg). As a result of the greatly increased compression ratio of the diesel cycle, fuel economy is likewise improved, the 1.7 has a specific fuel consumption of 0.36 lb/(hp·h) (0.22 kg/(kW·h)), while the O-320 gets only 0.42 lb/(hp·h) (0.26 kg/(kW·h)).
For a slight drop in takeoff power, the 1.7 will instead deliver considerably greater power at altitude due to the turbocharger. This allows the aircraft to fly at higher altitudes where the thinner air reduces drag and increases performance. Combining the better fuel economy, higher performance at altitude, and the somewhat greater energy density of diesel fuel, aircraft range is dramatically increased. For instance, replacing the O-320 with the 1.7 in a Cessna 172 drops the fuel consumption by half, increasing range from 575 to 900 nautical miles (1100 to 1700 km). Fuel costs fall dramatically as a result, notably in Europe where avgas is much more expensive than in North America.
Centurion 4.0
The 1.7 generated intense interest in the aviation market, and many pilots were soon asking for a larger engine to replace the 300 hp (224 kW) class engines of the larger 4 seat aircraft making up the rest of the GA market. The result was a new V-8 design, the 350 hp (261 kW) Centurion 4.0, including a second turbocharger but remaining otherwise similar. The 4.0 is currently certified only Jet A.
External links
- [Centurion engines home page]
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