Engine Downsizing Technology For Improving Engine Efficiency
Most construction vehicles and equipment are powered by diesel engines. Diesel engines are also used frequently in other kinds of equipment found at construction sites such as generators and compressors. Because of diesel's unmatched and unique combination of power, performance, reliability, fuel efficiency and now low emissions, it is the technology of choice and the workhorse of the construction sector, powering more than three-fourths of all heavy construction equipment.
In spite of the stringent emission norms and green initiatives, diesel power is projected to remain the dominant technology for heavy machinery operations. Over the years, the diesel engine technology has evolved slowly with a steady increase in power density and gradual weight reduction. Diesel engines have greatly increased in power density with similar-sized engines pumping out incredible horsepower and torque with respect to their early counterparts. This is achieved through technology known as engine 'downsizing'.
Due to increasingly stringent emissions norms and the need for improved fuel efficiency, one option that equipment OEMs are increasingly going in for is engine downsizing. Engine downsizing is a trending concept for vehicle / equipment engine manufacturers to provide efficient yet powerful engines. Engine downsizing can result in lower fuel consumption, lower exhaust gas emission and reduce the costs of the engine.
Downsizing is a simple concept in which a larger engine is replaced with a smaller version, with a lower displacement. The downsized engines have fewer, smaller cylinders, so the volume swept by pistons as they pump up and down inside is reduced. This leads to mechanical and thermal loss reductions, the lower weight of the engine, which results in a equipment lower weight and leads to lower fuel consumption, cutting carbon dioxide emissions, and reduced material cost of the engine. However, to ensure that smaller engines are still able to deliver the kind of power and performance that larger equivalent engine delivers, manufacturers often use forced induction – turbocharging, supercharging or even both.
The concept of downsizing allows the design of compact combustion engines that are comparable in their power output to naturally aspirated engines with considerably larger displacements. A reduction of engine displacement from a six-cylinder naturally aspirated engine to a four-cylinder naturally aspirated engine results in a loss of both power output and torque, while the fuel consumption will be reduced due to the smaller number of cylinders. However, to keep the power output and the torque at the same level as the six-cylinder engine, the smaller four-cylinder engine requires charging of the intake air. With a certain level of either supercharging or turbocharging, or both, the six-cylinder naturally aspirated engine can be replaced by a four-cylinder boosted engine. Due to the higher specific power output of downsized engines, it is possible to modify the overall transmission ratio, yielding to a shift of the engine operating point towards lower engine speeds. This is commonly defined as downspeeding, which is generally combined with the downsizing concept.
Downspeeding is about making diesel engines operate at low speeds with high torque – thus resulting in higher efficiency with reduced fuel consumption, due to reduced engine friction from low piston speeds, reduced relative heat transfer and increased thermodynamic efficiency.
Downsizing using a Turbocharger and Supercharger
Turbochargers and Superchargers are used throughout the automotive industry to enhance the output of an internal combustion engine without increasing the cylinder capacity. The application of such a mechanical device enables equipment manufacturers to adopt smaller displacement engines.
Despite of its lower displacement, the performance of a downsized engine can be maintained by injecting more air into the combustion chamber to burn additional fuel. Turbocharging and supercharging provides the engine with the mass of air needed to ensure highly efficient and clean combustion.
Both turbochargers and superchargers are simply different types of forced induction technologies and adopt slightly different ways of achieving the same objectives. Both are used to pressurise the intake tract, thereby achieving better combustion and volumetric efficiency. The key difference between a turbocharger and a conventional supercharger is that the latter is mechanically driven by the engine, often through a belt connected to the crankshaft, whereas a turbocharger is powered by a turbine driven by the engine's exhaust gas.
One of the main problems with the use of only a turbocharger is that they do not provide an immediate power boost when you accelerate. It takes some time for a turbine to get up to the speed before boost is produced. This results in a feeling of lag when you accelerate. While, the main advantage of supercharger is better throttle response, as well as the ability to reach full-boost pressure instantaneously. Engine-driven superchargers apply boost in direct proportion to the engine rpm. However, the thermal efficiency of supercharger is less when compared with a similar turbocharger, because turbochargers use exhaust gas energy that would normally be wasted. The economy and the power of a turbocharged engine are usually better than the engines with only a supercharger.
To overcome the disadvantages of turbocharger and supercharger, twincharger can be adopted. Twincharger is a combination of an exhaust-driven turbocharger and an engine-driven supercharger. A supercharger offers exceptional response and low-rpm performance as it has no lag like that of the turbocharger whereas a turbocharger provides better thermal efficiency using exhaust gas energy. Both the components work together to give maximum output mitigating the weaknesses of the other.
Use of Turbocharger or Supercharger alone has now become obsolete. The reason is that the use of them without any supplementary device has comparatively lesser advantages. Newer technologies like Turbocharged Direct Fuel Injection, Advanced exhaust gas recirculation and Variable Valve Timing are widely used in recent times to support downsized engine in increasing its performance
Current Issue
02-2026
