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The Honda 2015 F1 Power Unit explained


Honda Motor today gave the world a first look at an image of the power unit currently in development for the 2015 FIA Formula One (F1) World Championship. This article describes the Power Unit system that will be used.

Introduction: How can F1 machines, built for speed, be eco-friendly?

In 2014, the regulations for F1 engine and energy recovery systems were changed. The 2.4 liter engines were downsized to 1.6 liters, and environmental technologies such as energy recovery similar to conventional hybrid cars were introduced.

The technologies for F1 machines are far more complex than ordinary hybrid cars. The engine and energy recovery systems that provide the enormous power to machines to race at over 300 km/h need state-of-the-art technologies. F1 machines not only regenerate kinetic energy – like ordinary hybrid cars – but thermal energy as well.

Formula 1 recovery systems types

Competition is heating up for car manufacturers to make better environmental technologies. Honda will participate in F1 racing to meet these challenges to create revolutionary technologies. The technologies developed through participating in F1 racing will be fed back to production cars.

The Honda F1 Power Unit

The change in terms from “engine” to “power unit” signifies a shift in thinking, from developing engines for pure horsepower to the pursuit of energy-efficient power units, leading to the highest level of energy-efficiency through environmental technologies.

How do the two types of energy recovery systems, the kinetic energy recovery system and thermal energy recovery system, work?

Power Unit layout

The kinetic energy recovery system is an evolution of on KERS (Kinetic Energy Recovery System), the system used in F1 racing from 2009 to 2013, and works similarly to the hybrid system for the Accord Hybrid and Fit Hybrid, by using a motor and electrical generator to convert kinetic energy into electrical energy.

With an engine-powered car, kinetic energy through braking is lost into as it becomes thermal energy through the brake units. In other words, energy is lost through braking. With a hybrid system, this lost energy is recovered by the motor/generator unit as electrical energy, and is stored in the battery, which can then be used to power the motor during acceleration. The kinetic energy recovery system’s motor/generator unit is called “MGU-K” (Motor Generator Unit – Kinetic).

The second system, the thermal energy recovery system, captures the thermal energy generated from the engine’s exhaust. Hot exhaust from the engine’s combustion chamber is normally lost via the exhaust pipes. The thermal energy recovery system, a motor/generator unit, reuses this thermal energy to generate electricity. This unit is called “MGU-H” (Motor Generator Unit – Heat).

Power Unit configuration

Power units for F1 machines are located behind the driver’s seat (cockpit), where the batteries are also located.

Power Unit configuration

F1 regulations allow for one turbocharger with concise regulations for where it can be installed. The turbocharger increases the amount of air fed into the engine, which is cooled by the intercooler and fed into the engine’s intakes. The MGU-H has to be connected to the turbocharger.

The new 2014 regulations limit fuel usage to 100 kg, and fuel flow to 100 kg/h per race. Imagine Fuel usage as the capacity of the fuel tank, and fuel flow as the amount of fuel that flows from the fuel tank. Both the total amount of fuel and the maximum amount of fuel flowing at any time are limited per race. These regulations allow teams to use 30% less fuel compared to 2013 regulations. Due to fuel flow restrictions, it is harder to produce engine power, yet the smaller fuel tank capacities demand higher fuel efficiency.

F1 machines need to use the limited fuel carefully to be able to finish a race. Races cannot be won by driving slow, so the thin trickle of fuel needs to be efficiently converted into power. To win in F1 racing, the engine needs to be fuel efficient and powerful, and the two energy recovery systems need to be utilized wisely.

Every drop of gasoline must produce maximum power, and the machines must have absolute speed that is expected of an F1 Racing. These technologies from developing F1 power units will be valuable for production cars of the future.

Power Unit components


Energy storage devices (batteries) are used to store energy that would otherwise be lost. Regulations limit battery size to between 20 and 25 kg, to avoid excessive development costs. Battery development and control technologies gained through F1 development will also be beneficial to production hybrid cars in the future.

Power Unit Battery

ERS control unit

The ERS (Energy Recovery System) control unit is a computer that controls how energy in the power unit is used. It is the brains of the power unit, and its software determines how well the engine and two MGUs perform under constantly and rapidly changing environment and driving conditions.

Power Unit ERS control unit

The battery operates using direct current (DC), as opposed to the MGU-K and MGU-H which operate using alternating current (AC). The ERS control unit includes AC/DC and DC/AC converters to convert electricity between the battery and MGU-K / MGU-H. Technologies developed for conversion efficiency and heat management will most probably find their way to production hybrid cars.


The MGU-K converts deceleration kinetic energy into electrical energy, functioning similarly to motor/generator units in conventional hybrid cars. Maximum revs are limited to 50,000 rpm, and output to 120 kW. When powering the F1 machine by using electrical energy stored in the battery, the MGU-K adds 157 hp to the engine’s 592 hp. The MGU-K alone produces more power than the Fit Hybrid’s combined engine and motor output of 103 kW.

Power Unit MGU-K

The electrical energy charging the battery from the MGU-K is limited to 2 MJ (megajoules) per lap, and the maximum energy used by the battery to power the MGU-K is limited to 4 MJ per lap.


The MGU-H converts heat energy from exhaust gases into electrical energy, and is yet to be used in conventional hybrid cars. MGU-H technologies developed in F1 racing may find their way to production cars in the future.

Power Unit MGU-H

Unlike the MGU-K, F1 regulations do not place energy usage restrictions on the MGU-H. Electricity generated by the MGU-H may be fed directly into the MGU-K, effectively bypassing the MGU-K restrictions and tapping the full 157 hp, highlighting the importance of developing a system to fully utilize the MGU-H. The new F1 power unit heavily depends on how effectively the MGU-H performs.

Internal combustion engine

The 2013 2.4-liter normally-aspirated V8 engine was replaced under the new 2014 regulations with a 1.6-liter V6 turbo engine with direct fuel injection. The engine is one-third smaller, and there are two-less cylinders, following the global trend of downsizing.

With a smaller capacity and less cylinders, the engine alone cannot be as powerful as before. Forced induction devices, such as turbochargers, allow the engine to be more compact, and produce the same power as before. The aim of engine downsizing is to reduce the size of the engine and increase fuel efficiency while producing the same power as a larger, normally-aspirated engine. Turbocharged engines can be built smaller, with higher fuel efficiency.

Power Unit engine

Until 2013 F1 engines were limited to 18,000 rpm, but from 2014, the rev limit is reduced to 15,000 rpm, with the maximum fuel flow capped at 10,500 rpm.

Output increases proportionately with the amount of fuel burned, so higher revs burn more fuel, and increase output, in a shorter time. By capping the maximum fuel flow at 10,500 rpm, only the same amount of fuel flow is available at higher revs, increasing mechanical resistance, and decreasing the merits of revving higher.

F1 engines of the past were designed to maintain higher revs to create higher output, but the new restrictions shift the focus to designing engines that use energy more efficiently.


The 2014 F1 regulations re-introduced turbocharged engines, a form of forced induction, to increase thermal efficiency. Turbochargers were allowed in F1 racing in the 1980’s, and in 1988, Honda’s turbocharged engines won 15 out of 16 grands prix. Turbocharged engines were banned the following year, in 1989, but after 25 years it has been re-introduced.

Power Unit turbocharger

The turbocharger, a device to efficiently utilize the engine’s exhaust energy, comprises of a turbine and compressor supported by bearings on the same axis. Exhaust gas energy turns the turbine powering the compressor, which in turn compresses and increases air fed into the engine’s combustion chamber, thus allowing for more combustion and higher output. Conventional turbocharged V6 engines are generally equipped with two turbochargers, but F1 regulations limit the engine to one turbocharger, requiring power to be found by other means.

Energy flow in race conditions

How does energy flow within the power unit? Depending on what the F1 machine is doing on the track, energy is recovered, or is used to assist the engine.


The energy flow is similar to a conventional hybrid car: The MGU-K recovers (or generates electricity from) part of the kinetic energy lost when the F1 machine is braking, and stores the electricity in the battery. The MGU-K’s maximum output is 120 kW and the amount of energy allowed to be stored is 2 MJ per lap, so the F1 machine needs to brake for around 16.7 seconds per lap to reach this maximum charge.

Energy flow during braking

Acceleration out of corners (using MGU-K)

The F1 machine can accelerate faster out of corners by adding the output of the MGU-K to the engine’s output.

Accelerating out of Corners (with MGU-K Power-assistance)

Acceleration out of corners (solving turbo lag)

When turbocharged cars decelerate, the flow rate of exhaust gas decreases which delays the turbine to perform and hence the acceleration requires additional time. This small time-lag is called “Turbo Lag”. The MGU-H solves this problem by using a motor to power the compressor, without needing the turbine to wait for the exhaust gas.

Acceleration out of corners (solving turbo lag)

Full-acceleration (with MGU-K and MGU-H Power-assistance)

The turbocharger uses its compressor to send compressed air into the engine. Under full-accceleration, the exhaust energy fed to the turbine can increase to a point where it exceeds the amount of air the compressor can handle to feed the engine.

Full-acceleration (with MGU-K and MGU-H Power-assistance)

The MGU-H converts the excess exhaust energy into electricity, which it then sends to the MGU-K. There are no rules on how much electricity the MGU-H is allowed to generate, so the MGU-K’s output can be added to the engine’s output without worrying about the rules on the amount of electricity that the battery can charge or discharge. Unused exhaust energy can be efficiently used to accelerate faster.

Under full acceleration out of corners, the battery can also send electricity to the MGU-K. This way, full-acceleration can be achieved at the maximum output allowed for the MGU-K, at 120 kW.

Source: Honda


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    […] The Honda 2015 F1 Power Unit explained – Honda Motor today gave the world a first look at an image of the power unit currently in development for the 2015 FIA Formula One (F1 … do the two types of energy recovery systems, the kinetic energy recovery system and thermal energy recovery system … […]

  2. allan bonnick12-03-2015

    I am author of a book called “Automotive Science & Mathematics” and it is designed for the BTEC Level 3 unit for Motor Vehicle studies – it was published in 2008. I am considering writing some additional material to cover the Further Maths for the BTEC level 3 in Motor Sport. I have been looking at your website and I would like you to give me permission to use some of the pictures to illustrate some maths examples and exercises.
    Allan Bonnick
    BSc CEng MIMechE.

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