Technological Revolution: The Power Unit
2014 introduces what is widely recognised as the biggest technical revolution since the first Formula One season in 1950. The significance of this change cannot be underestimated in terms of the challenges presented to both teams and drivers, as they embark upon a voyage into a relative unknown following eight years of stability from 2006 to 2013 in what has become known as the ‘V8 era’.
Here, we break down the new 'Power Unit' into its component parts to examine just what has changed, and what it all means. The engine is no more, long live the Power Unit!
In regulatory terms, the Power Unit comprises six different systems: the Internal Combustion Engine (ICE), Motor Generator Unit-Kinetic (MGU-K), Motor Generator Unit-Heat (MGU-H), Energy Store (ES), Turbocharger and the Control Electronics . The change in terminology reflects the fact that this new powertrain is far more than simply an Internal Combustion Engine. Where the previous V8 format utilised a KERS hybrid system which was effectively ‘bolted on’ to a pre-existing engine configuration, the Mercedes-Benz PU106A Hybrid has been designed from the outset with Hybrid systems integral to its operation.
The Internal Combustion Engine (ICE) is the traditional, fuel-powered heart of the Power Unit; previously known simply as the engine. For 2014 this will take the form of a 1.6 litre, turbocharged V6 configuration, with direct fuel injection up to 500 bar of pressure. Where the V8 engines could rev to 18,000 rpm, the ICE is limited to 15,000 rpm from 2014. This reduction in crankshaft rotational speed coupled with the reduction in engine capacity and number of cylinders reduces the friction and thus increases the total efficiency of the Power Unit. This down-speeding, down-sizing approach is the key technological change at the heart of the ICE structure.
The turbocharger is an energy recovery device that uses waste exhaust energy to drive a single stage exhaust turbine that in turn drives a single stage compressor via a shaft, thereby increasing the pressure of the inlet charge (the air admitted to the engine for combustion). The increased pressure of the inlet charge offsets the reductions in engine capacity and RPM when compared to the V8 , thus enabling high power delivery from a down-speeded, down-sized engine. The turbocharger is the key system for increasing the efficiency of the ICE.
For 2014, the notion of hybrid energy recovery has shed a letter (KERS has become ERS) but become significantly more sophisticated . Energy can still be recovered and deployed to the rear axle via a Motor Generator Unit (MGU), however this is now termed MGU-K (for ‘Kinetic’) and is permitted twice the maximum power of the 2013 motor (120 kW or 161 hp, instead of 60 kW or 80.5 hp). It may recover five times more energy per lap (2 MJ) and deploy 10 times as much (4 MJ) compared to its 2013 equivalent, equating to over 30 seconds per lap at full power. The rest of the energy is recovered by the MGU-H (for ‘Heat’); an electrical machine connected to the turbocharger. Where the V8 offered one possible ‘energy journey’ to improve efficiency via KERS, there are up to seven different efficiency enhancing energy journeys in the ERS system.
The Motor Generator Unit-Kinetic (MGU-K) has double the power capability of the previously used KERS motors and operates in an identical way. Some of the kinetic energy that would normally be dissipated by the rear brakes under braking is converted into electrical energy and stored in the Energy Store. Then, when the car accelerates, energy stored in the Energy Store is delivered to the MGU-K which provides an additional boost up to a maximum power of 120 kW (approximately 160 hp) to the rear axle for over 30 seconds per lap.
The Motor Generator Unit-Heat (MGU-H) is a new electrical machine that is directly coupled to the turbocharger shaft. Waste exhaust energy that is in excess of that required to drive the compressor can be recovered by the turbine, harvested by the MGU-H, converted into electrical energy and stored in the Energy Store. Where the MGU-K is limited to recovering 2 MJ of energy per lap, there is no limit placed on the MGU-H. This recovered energy can be used to power the MGU-K when accelerating, or can be used to power the MGU-H in order to accelerate the turbocharger , thus helping to eliminate ‘turbo lag’. This new technology increases the efficiency of the Power Unit and most significantly provides a method to ensure good driveability from a boosted, down-sized engine.
The Energy Store (ES) does exactly what it says on the tin; storing the energy harvested from the two Motor Generator Units (MGUs) for deployment back into those same systems. It is capped in terms of maximum and minimum weight: the maximum (25 kg) setting engineers an aggressive target, while the minimum (20 kg) means weight reduction will not be chased at all costs.
kJ / MJ / kW
A joule (J) is a unit of energy; (kinetic, heat, mechanical, electrical, etc.) A kilojoule (kJ) is equal to one thousand joules, whilst a megajoule (MJ) represents one million joules. To put this into context, kJ is a unit often used to describe the energy present in nutritional goods, while 1 MJ represents the approximate kinetic energy of a one-tonne vehicle travelling at 160 km/h. Meanwhile, a watt (W) is a unit of power that quantifies a rate of energy flow; with a kilowatt (kW) equal to one thousand watts. This unit is commonly used to express the power output of an engine, where 1 kW is equal to 1.34 hp.