How Does a Formula 1 Power Unit Work?
All F1 fanatics will be familiar with the ‘power unit’ that allows the cars to reach such incredible speeds, but how exactly do they work?
Before we start, I’ll warn you that this is a loooong read. If you’re still interested to learn how modern Formula 1 engines work, pull up a chair and let’s get cracking!
In some respects, the power plant of a Formula 1 car could not be more similar to your everyday road car. In others, the technology is alien in comparison. To fully understand the magnitude of the task at hand for Formula 1 engine manufacturers, it’s important to step back and gain some perspective on exactly what they’re trying to build.
In the ever-changing world of Formula 1 the cars can no longer refuel during the race, so must start the race with all of the fuel it needs to reach the finish line. A full fuel tank means a lot of weight which slows the car down, so the most efficient engine minimises the amount of fuel the car needs to complete the race, providing a weight advantage and more speed. Not only is a minimal fuel load important, but the materials used in the power unit components must also be as light as possible. The engine weight is also proportional to its size. The larger it is, the heavier it is and the more space it consumes in the car. A large power unit (PU) will restrict the freedom of the aerodynamicists to design around it, so a compact PU is advantageous.
Upon their return to Formula 1 in 2015, Honda revealed their 'Size Zero' directive, an attempt to make their engine as compact as possible without sacrificing power.
Lightness can mean weakness, though. Aside from the risk of retirements due to component failure, there are penalties for exceeding a maximum number of each PU component used throughout a season. The materials in the power unit must therefore have incredible strength and durability as well as being light. In their efforts to shed pounds while maximising structural integrity of their parts, Formula 1 teams have pioneered exotic materials in manufacturing like carbon fibre and metal alloys. In short, the teams can achieve north of 1000 horsepower from an engine lighter and more compact than the one found in your daily runner, that can also run at full capacity for over 1500km without failing.
The world’s answer to both the depletion of natural resources and climate change has universally been the introduction of hybrid and battery technology in motoring, in a bid to reduce consumption of fossil fuels and greenhouse gas emissions. By the end of the ‘non-hybrid’ Formula 1 engines in 2013 a simple hybrid system was already utilised but, because of minimal research into hybrid technology, the peak output was much lower than today and the engines were limited in their longevity. In 2014, the Formula 1 engine regulations changed to make more fuel-efficient turbo-hybrids mandatory for all teams.
The level of research and development this demanded from the manufacturers was unprecedented and building an F1 engine had never been so complex or costly. Only the world’s biggest car manufacturers can now justify shouldering the costs of designing and manufacturing F1 engines. Although all manufacturers are now pushing for breakthroughs in clean and sustainable power, it is these rising costs that are also pushing businesses away from Formula 1. Where it became a common sight to see seven or eight different engine manufacturers competing on one grid, now we are reduced to just four. However, the directive has now produced the most energy-efficient engines ever built. Let’s take a deeper look to see how these incredible feats of engineering work.
Internal Combustion Engine (ICE)
At the heart of the PU is the Internal Combustion Engine, or ICE. The power plant of choice for almost all road cars for more than 100 years, the ICE is the most mainstream component of a modern Formula 1 PU.
A mixture of fuel and air is injected into a cylinder, which is then compressed by a piston. The compressed mixture is ignited by a spark plug and the rapid expansion of gas pushes the piston downwards with great force. The output gases from the combustion are expelled through the exhaust and the cycle begins again. The pistons are connected via connecting rods to a crankshaft, which rotates as the pistons are pushed downwards by the combusting fuel-air mixture. The rotating crankshaft is connected to a gearbox and differential, converting the longitudinal engine rotation into lateral drive at the wheels.
This is what’s known as a ‘reciprocating engine’ – the crankshaft continually rotates as it is powered by certain pistons, enabling the other pistons to rise back to the top of the chamber to start new strokes. Each chamber is referred to as a cylinder, and the cylinders must fire in a defined sequence to keep the crankshaft rotating smoothly and reliably.
ICEs produce horsepower in abundance, with generations of knowledge and refinement making them efficient and reliable. Before the turbo-hybrid engines were introduced in 2014, ICEs were the one and only power source for Formula 1 cars. Today, they still produce the majority of the car’s power, but are smaller and more energy efficient than ever.
Formula 1 engines now commonly use pre-chamber ignition, pioneered by Mercedes. In a normal combustion chamber the spark plug ignites the fuel-air mix and the flame created spreads outwards to the edge of the chamber, burning all the fuel-air mix in the process. This is fine when there is sufficient amounts of fuel and air to mix in the right ratio throughout the combustion chamber. When there isn’t, it can be hard to achieve full combustion. With fuel consumption now a key issue, the engines run leaner (a lower proportion of fuel in the fuel-air mix) than ever but with the demand for power output remaining the same. This creates a problem as the fuel-air mix can often be too weak to achieve full combustion through normal means.
Mercedes' clever pre-ignition idea helps the engine ignite all of the fuel-air mixture. Image: CAR Magazine
Mercedes’ trick splits the fuel-air mix into two places; the standard weak fuel-air mix in the combustion chamber, with a richer mix held within a small chamber around the spark plug. With this pre-chamber set up, the spark plug fully ignites the rich mix. As this expands, it’s directed through small slots between the pre-chamber and into the combustion chamber below. These jets of flame fully ignite the rest of the lean mix, delivering full combustion and maximum power while using less fuel in total.
The turbo hybrids use 1.6-litre combustion engines which, at full power, can produce around 850bhp on their own. That’s a power output comparable to the fastest petrol-powered road cars from an engine as small as the one you’d find in a Ford Fiesta. Combined with the hybrid system which is capped at 161bhp, that figure ticks over 1000bhp at maximum capacity.
The output of the modern ICEs may not be much different than most Formula 1 engines since the 1980s, but not only are they more compact than virtually anything that has gone before, they use around 33% less fuel than the 2.4-litre V8s of the previous generation. The newest engines have a thermal efficiency of over 50%, so more than half of the energy in the fuel is converted into useful work to drive the car forwards. From 2022 onwards, Formula 1 will use E10 fuel which contains 10% biofuel, naturally sourced from living matter. Despite offering lower carbon emissions, biofuel is less energy-dense than standard fuel so a reduction in power is expected, unless the teams can recover it through other means.
Formula 1 engines through history have featured as few as four cylinders and as many as twelve. Now, they must use six. While some engine manufacturers have experimented with flat and inline cylinder configurations in the past, they now must be arranged in a V-configuration at a 90-degree angle. The engine valves open and close in time with the pistons to allow the fuel-air mix into the combustion chamber and the exhaust gases to leave it. Since the mid-1980s, these have been opened and closed pneumatically (with pressurised air), replacing traditional metal springs. This valve technology has since enabled engines to rev faster and achieve higher power outputs.
The engine block, pistons and crankcase are traditionally made from cast or wrought aluminium alloys, the crankshaft and camshafts are iron-based alloys, and the valves can be alloys based on iron, cobalt, nickel or titanium. The ICEs are connected directly to an eight-speed gearbox. Teams are allowed to use three ICEs freely throughout the season without penalty.
To prevent a return to the crazy 1500bhp beasts of the 1980s, the engines are capped at 15,000rpm and have a fuel flow meter to regulate consumption. The engines are short-stroke to allow them to operate at high speed without catastrophic failure, meaning the bore of the cylinder is unusually large for the displacement. Due to the fuel flow restrictions, there isn’t enough fuel to optimise the engine past 12,500rpm so drivers will change gear before hitting the rev limiter. For perspective, the naturally aspirated engines of old would rev to around 20,000rpm. Fuel is injected at a maximum pressure of 7,250psi – this sounds like a lot, but normal petrol engines inject at around 5,000psi while modern diesel engines regularly exceed 30,000psi.
Turbocharged monsters from the 1980s, including this BMW inline-four engine from the 1986 Brabham BT55, could produce around 1500bhp at peak output.
Intricate oil and water systems lubricate the moving parts and prevent the engine from overheating. The oils themselves and ideas used in Formula 1 tend to be mirrored in road cars, as the oil companies prefer to bring their findings into the mainstream to improve reliability and cooling efficiency of your daily motor. The ideal operating temperature of the engines are also similar to your everyday road car (between 100 and 120 degrees Celsius), just below the point at which the coolant fluid turns from liquid to gas.
The turbocharger has been a common component on road car engines for several decades. Some Formula 1 teams dabbled with the technology in the 1980s and managed incredible power outputs, but they were banned from 1989 onwards before their reappearance in 2014. The turbocharger boosts power by reusing the outgoing exhaust gases. The fast-flowing gas spins a turbine at incredible speeds (around 120,000rpm). The turbine is connected to a compressor which draws in air as it enters through the air box above the driver’s head, compressing it before it reaches the combustion chambers of the ICE.
Compressed air contains more particles in a given area than atmospheric air. More oxygen means better combustion and more power. However, compressing the air does mean that its temperature increases, which will decrease its density and reduce power. Turbos therefore come with an intercooler to reduce the temperature of the air from the compressor. Intercoolers can either use colder atmospheric air to cool the compressed air, or a water-based cooling system.
Most manufacturers opted for tightly packaged, conventional turbo designs which had been tried and tested on road vehicles for many years. However, this compact turbo design can lead to heat bleeding from the turbo to the compressor, increasing combustion air temperature and reduces the effectiveness of the intercooler.
Mercedes pioneered the ‘split turbo’ design, where the compressor sits on the front of the engine and the turbine at the rear. The two are connected by a much longer shaft than usual, but efficiently use the space in the middle of the ‘V’ of the engine which would otherwise remain empty. Not only does this reduce heat bleed and allow a smaller intercooler to be used, there are also much greater packaging benefits by using this setup including shorter piping for intakes and the exhaust. All of these things lead to greater power, less lag and more driveability.
The split turbo design pioneered by Mercedes improves intercooler efficiency among many other benefits. Image: CAR Magazine
The longer shaft used to connect the compressor to the turbine exacerbates even the smallest oscillation significantly, and greatly decreases the tolerance of the turbo. Reliability is therefore absolutely paramount and difficult to achieve, perhaps explaining why only Honda have managed to exploit Mercedes’ split turbo idea to date and Ferrari will only do the same in 2022, eight years after its first use. It has quickly emerged as the preferred turbo layout for a Formula 1 engine. Teams are allowed to use three turbochargers freely throughout the season without penalty.
Motor Generator Units
Now we can look at the first of the hybrid parts working to power the car electrically. The Motor Generator Units, or MGUs, are capable of both regenerating electricity and deploying charge to either provide more power for the PU or improve its responsiveness. Electrical power delivers instant torque, unlike the power from combustion of fuel which has ‘torque bands’ in different rpm ranges. The MGU is split into two key components – the Kinetic (MGU-K) and Heat (MGU-H) components. Teams are allowed to use three of each MGU component freely throughout the season without penalty.
The MGU-K is geared to the front of the engine’s crankshaft so that it can both drive and be driven by the ICE. It recovers some of the kinetic energy that would otherwise be lost as the car decelerates, converting it to electrical charge that can be stored and deployed again later. It does this through the use of permanent magnets and coiled wires, which I will explain in more detail a little later.
In deployment mode, the MGU-K generates a maximum of 161bhp, deploying it directly through the crankshaft to aid acceleration. As the car decelerates, its Electronic Control Unit (ECU) switches the MGU-K from deployment to recovery, allowing the motor to rotate with the drivetrain. The motor has permanent magnets which, when rotated through a coil, produce electrical current which is transferred to the battery. This concept is crucial for both MGUs as they regenerate.
The resistance that this generates also slows down the rotation of the drivetrain, otherwise known as ‘engine braking’. This action means the rear brakes are barely used at low speed and can be reduced in size as a result. In generator mode, the MGU-K is only allowed to save 2mJ of energy to the battery.
A failure of the MGU-K could destroy the engine, but at minimum would mean a reduction in energy recovery and the tiny rear brakes would be put under more load to slow down the car. At most circuits it would lead to retirement, but we saw Daniel Ricciardo win the 2018 Monaco Grand Prix with a failed MGU-K due to the circuit’s reduced need for straight-line speed. Ricciardo could not use his two highest gears as the engine was no longer producing sufficient power to sustain them. He also had to force his brake bias forwards to take some strain away from his tiny rear brakes.
The MGU arrangement on a Formula 1 engine. Image: CAR Magazine
The MGU-H is a more complex component which connects to both the hybrid battery and the MGU-K. The motor is also connected to the turbo and, like the MGU-K with the ICE, can drive or be driven by it. The MGU-H can use power from the battery to keep the turbine spinning at maximum speed when not at full throttle, acting as an anti-lag system to maximise the engine’s power when it would otherwise bog down. This electrical system is much more efficient than other fuel-hungry anti-lag solutions used elsewhere.
In generator mode, the MGU-H can be used in several ways. Conventional turbos can produce too much boost as the high-pressure exhaust gases spin the turbo too quickly on the throttle. This is controlled by a wastegate, which slows the turbo and expels the high-pressure gas through a separate exhaust pipe. This wastes the useful exhaust gases, so Formula 1 engines use the MGU-H to slow the turbo, again using a magnetic field, generating electricity.
There is no cap on how much energy can be recovered through the MGU-H and the battery has capacity for 2mJ from each of the MGU-K and the MGU-H. So, the more they can use the MGU-H in generator mode, the more energy can be deployed. The obvious use would be to keep the turbo spinning off-throttle for the anti-lag benefits, but the energy generated by the MGU-H is also permitted for use by the MGU-K. The regeneration can therefore be used to extend the 161bhp boost delivered by the MGU-K, that would otherwise only last for around 30 seconds.
However, simply recovering energy through the MGU-H as an alternative to a wastegate isn’t enough. Conventional turbos house the components in one package, so the parts have to be compact. In 2014, Mercedes realised a gain could be made with their split turbo setup by running an enormous compressor. This was not necessarily for extra boost, but rather that a larger turbo needed more ‘wastegate time’ to prevent it over-boosting the engine. The MGU-H would therefore be spun for longer and regenerate more – although the back pressure effect all of this regenerating creates will reduce peak ICE horsepower, the increased regeneration and subsequent battery deployment led to faster lap times. Ferrari and Honda, meanwhile, missed this trick after prioritising raw horsepower over regeneration. They soon realised their mistake but took a couple of years to perfect their new MGU-H strategy.
While the cap on the MGU-K means it only generates enough energy for just over 30 seconds of full deployment, the MGU-H produces enough in addition to virtually provide this 161bhp boost for an entire lap. Rather than permanently trying to deploy the full battery charge and draining the supply, the engine’s ECU software decides when to apply the energy based on information from ‘engine maps’.
The maps can be configured by the teams to pinpoint areas on the circuit where the power unit will deploy some charge or start ‘clipping’, another word for regenerating. You’ll often see the lights on the back of the cars flashing as the drivers reach the end of the straights. This means the car is regenerating, sacrificing a bit of top speed as it approaches the braking zone to maximise the amount of energy recovered.
Drivers will switch between maps throughout a race, with each map providing a different combination of deployment and clipping throughout the lap. Engine braking can also be adjusted, altering the regeneration and deceleration that is experienced as the MGU-K regenerates.
The Energy Store is essentially a fancy way of saying ‘battery’. As the MGUs generate electricity, that energy is stored as direct current (DC) in the battery to be deployed later. The battery uses Lithium ion (Li-ion) technology, something which even the most mainstream batteries have been using for years. These batteries are effective, but also one of the heaviest individual components of the cars. Teams therefore try to minimise the size of their battery packs without costing capacity or performance, also placing it strategically in the car to reduce the effect this weight has on balance.
The maximum capacity of the battery for racing is 4mJ, however most teams will push beyond this capacity for their battery even if they’re not allowed to use it. The reason for this is simple – a battery capable of storing 4mJ will be at 100% capacity on a full legal charge, but a battery capable of storing 8mJ would only be at 50%. As with the batteries in everyday items, fully charging the battery to its maximum capacity reduces its lifespan compared to partially charging it, so it is best to build more capacity into the battery and cap the charge to minimise wear. Teams are only allowed two Energy Stores throughout the season, so longevity is key.
While most parts of the power unit are cooled traditionally by water or air, the battery uses dielectric fluid to prevent the risk of electric shock should it be damaged. You’ll often see mechanics wearing large insulating gloves while working on the PU or while recovering a crashed car, again to minimise their risk of an electric shock. The fuel is stored in a malleable Kevlar-rubber bag and, like the battery, is positioned strategically low down across the chassis for a low centre of gravity. The high-strength flexible tank minimises the risk of a puncture leaking fuel onto the hot engine or near the live battery, which could result in a catastrophic explosion.
Crashed Formula 1 cars have to be handled with extreme care, with a potentially damaged battery and fuel tank in close proximity.
The Control Electronics of the car manage all electrical components in the PU, namely the MGUs and the battery. Teams can use two sets of Control Electronics throughout the season without penalty.
The main job of the Control Electronics is to convert the alternating current (AC) generated by the MGU-K and MGU-H into direct current (DC) which can be stored in the battery. Likewise, it can invert this process using battery power to spin the MGUs. There are different sets of electronics for each system, dubbed the Control Unit Kinetic (CUK) and Control Unit Heat (CUH).
Capacitors are the storage components used to switch the power between the MGU and the battery, while IGBTs (insulated gate bipolar transistors) switch the current from AC to DC and vice versa. The process of converting AC to DC and back creates heat which is lost. Keeping the electronics at working temperature is key to reliability so removing this heat is important. Like the MGUs, the electronics have a water-cooling circuit with a pump and radiator stored in the car’s sidepod.
CE positioning changes depending on the manufacturer’s philosophy, but they’re often housed with the battery in a recess under the fuel tank or in the sidepods. It all depends on the team’s fuel tank strategy and its impact on the length of the wheelbase, the size of the sidepods and cooling. Bigger sidepods can allow the CEs to be positioned there strategically and are preferred for air-cooled turbos, but do create drag and are restrictive for the aerodynamicists. Smaller sidepods do the opposite, improving aerodynamic effectiveness but forcing the teams into a water-cooled turbo system and having to think more about compact packaging and cooling in general.
Formula 1 has always been at the forefront of technological innovation in motoring, and the hybrid powertrains they’ve utilised since 2014 are no different. With an output of over 1000bhp, engines more energy-efficient than any other on the planet and durability good enough to run a whole season on just a few PUs is nothing short of incredible. While full-electric power is the direction for mainstream motoring, it’s unlikely Formula 1 will be giving up on combustion any time soon so it’s important that they put effort into maximum sustainability through other means. It may be costly and complex, but these power units certainly push the realms of possibility for a good cause. They really are one of the most amazingly intricate and precise pieces of engineering the world has seen.