An auto's drivetrain or powertrain consists of all the 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.
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, ie. ICEs have limitations regarding efficiency but it is not said that the well to wheel efficiency of alternative propulsion systems are better. This refers to fuel cells with additional reformer losses, electric vehicles powered from the grid with low hydraulic energy share and also vehicles using energy storage with high losses (some battery types, ultra- or supercaps).
Restricting to today’s powertrain development the trends comprise for Diesel engines:
- modular injection
- electronic valve control
- low pressure EGR
- advanced combustion
For spark ignition technology the focus is on
- de-throttling (in part load where the low efficiency of Otto-engines is defined)
- downsizing (lower displacement, electronic valve control EVC)
Rinaldo Rinolfi, today's Vice-President at Fiat Powertrain Technologies (FPT): The Future of Powertrain Technology, Barcelona, May 2005
Last but not least new fuel qualities (no sulphur and aromates) allow new combustion concepts. So called "combined combustion systems" CCV (VW 2003) or "diesotto" cycles (Mercedes) are based on synfuels (synthetic diesel, biomass to liquid BTL or gas to liquid GTL). They promise to combine clean combustion with high efficiency.
The energy management inside the powertrain decoupling energy transformation and propulsion demand is in its infancies - especially in Europe industry doubts that customers may adopt vehicles where RPM may not change if the accelerator pedal is pushed or even if the acceleration is adapted automatically to follow minimal energy consumption and minimal environmental pollution. The right term for this type of riding would be "de- emotionalization".