Powertrain

In a vehicle, the term drivetrain or powertrain refers to the group of components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, driveshafts, differentials, and the final drive (drive wheels, caterpillar track, propeller, etc.). Sometimes "powertrain" is used to refer to simply the engine and transmission, including the other components only if they are integral to the transmission.

A vehicle's driveline consists of the parts of the drivetrain excluding the engine and transmission. It is the portion of a vehicle, after the transmission, that changes depending on whether a vehicle is front wheel drive, four wheel drive, or rear wheel drive.

Broader definition

In a wider sense, the powertrain includes all components to transform chemical, physical or nuclear energy into secondary energy and deliver it to the interface to the outer world for propulsion purposes. This includes the utilisation of multiple power sources and non wheel based vehicles. From an energetic standpoint the weakest point is the first step: internal combustion engines have limitations regarding efficiency, but the "well to wheel" efficiency of alternative propulsion systems are not considered any better. This refers to fuel cells with additional reformer losses, electric vehicles powered from the grid with low hydraulic and renewable energy share and also vehicles using energy storage with high losses (some battery types, ultra- or supercaps).

Developments

Powertrain development for diesel engines involves the following trends: modular injection, electronic valve control (EVC), low pressure exhaust gas recirculation (EGR), and advanced combustion. Spark ignition technology has focused on de-throttling (in part load where the low efficiency of Otto engines is defined) and downsizing (lower displacement, EVC).

Attention to new fuel qualities (no sulphur and aromates) allow new combustion concepts. These promise to combine clean combustion with high efficiency. So-called "combined combustion systems" (CCV) (Volkswagen, 2003) or "diesotto" cycles (Mercedes-Benz) are based on synthetic fuels (synthetic diesel, biomass to liquid (BTL) or gas to liquid (GTL)).

The energy management inside the powertrain decoupling energy transformation and propulsion demand is in its infancy, especially in Europe. If acceleration is adapted automatically to follow minimal energy consumption and minimal environmental pollution, performance may suffer. The motor vehicle industry doubts that customers may adopt vehicles in which acceleration responsiveness is reduced. This type of riding has been called "de-emotionalization".

Manufacturing

The manufacturing of powertrain components and systems is a key factor in the competitive position of companies in the automotive and other (truck, motorcycle, tractor, construction equipment…) vehicle industrial sectors. Global economic and environmental factors have led to the requirement to engineer and produce powertrain system that are more economical to manufacture, higher in product quality and reliability, higher in performance, more fuel efficient, less polluting, and longer in life expectancy. In turn these trends have led to designs that involve higher internal pressures, are subject to greater instantaneous forces, and are more complex in their design and mechanical operation. The resulting advanced powertrain designs in turn impose significantly more severe requirements on the shape, flatness, waviness, roughness, and porosity,of powertrain subsystems, as well as limitations on the allowed presence of potential defects in the surfaces and other dimensional characteristics of the system components and assemblies. In addition to improved materials and material forming methods, these requirements have led to advanced metrology technology that more thoroughly and accurately measures and enables improved control of all of the steps in powertrain manufacturing processes.

See also

• Gear train