In a motor vehicle, the powertrain or powerplant comprises the main components that generate power and deliver that power to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive. Hybrid powertrains also include one or more electric traction motors that operate to drive the vehicle wheels. All-electric vehicles eliminate the engine altogether, relying solely on electric motors for propulsion. A motor vehicle's driveline or drivetrain consists of the parts of the powertrain excluding the engine. It is the portion of a vehicle, after the prime mover, that changes depending on whether a vehicle is front-wheel, rear-wheel, or four-wheel drive, or less-common six-wheel or eight-wheel drive. In a wider sense, the powertrain includes all of the components used to transform stored energy into kinetic energy for propulsion purposes. This includes the utilization of multiple power-sources and non–wheel-based vehicles.
Developments
The most recent developments in powertrain are driven by the electrification of it in multiple components. Electrical energy needs to be provided, usually this leads to larger batteries. Electric motors can be found as isolated component or as part of other elements, e.g. the axle. In hybrid powertrains the torque generated by the combustion engine and the electric motor have to be brought together and distributed to the wheels. The control of this process can be quite involved but the rewards are greatly improved acceleration and much lower emissions. Powertrain development for diesel engines involves the following: exhaust gas recirculation, and advanced combustion. Spark ignition engine development include: fuel injection, including the gasoline direct injection variant, as well as improving volumetric efficiency by using multi-valves per cylinder, variable valve timing, variable length intake manifolds, and turbocharging. Changes also include new fuel qualities to allow new combustion concepts. So-called "combined combustion systems" or "diesotto" cycles are based on synthetic fuels or gas to liquid ). BEVs, FCEVs and PHEV powertrains are expected to reach cost parity with ICE powertrains in 2025.
Manufacturing
The manufacturing of powertrain components and systems is important to industry, including the automotive and other vehicle sectors. Competitiveness drives companies to engineer and produce powertrain systems that over time 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 requirements have led to designs involving higher internal pressures, greater instantaneous forces, and increased complexity of design and mechanical operation. The resulting designs in turn impose significantly more severe requirements on parts shape and dimension; and material surfaceflatness, waviness, roughness, and porosity. Quality control over these parameters is achieved through metrology technology applied to all of the steps in powertrain manufacturing processes.
Frames and powertrains
In automotive manufacturing, the frame plus the "running gear" makes the chassis. Later, a body, which is usually not necessary for integrity of the structure, is built on the chassis to complete the vehicle. Commercial vehicle manufacturers may have "chassis only" and "cowl and chassis" versions that can be outfitted with specialized bodies. These include buses, motor homes, fire engines, ambulances, etc. The frame plus the body makes a glider.
