Power units and hybrid systems

Power Units and Hybrid Systems in Formula One

Modern Formula One cars are powered by complex hybrid systems that integrate high-efficiency internal combustion engines (ICE) with energy recovery systems (ERS). The 1.6L V6 turbo hybrid architecture, introduced in 2014, has evolved into the most thermally efficient engine platform in global motorsport, reaching over 50% thermal efficiency under race conditions.

Power Unit Architecture

A full power unit (PU) consists of six elements, as defined by the FIA:

1. Internal Combustion Engine (ICE)
2. Turbocharger (TC)
3. Motor Generator Unit–Kinetic (MGU-K)
4. Motor Generator Unit–Heat (MGU-H)
5. Energy Store (ES)
6. Control Electronics (CE)

Teams are limited to a finite number of each component per season. Replacements incur grid penalties under FIA Sporting Regulations.

Internal Combustion Engine (ICE)

The ICE is a 1.6-litre, V6, 90° configuration with direct fuel injection. It operates up to 15,000 rpm, though most engines are tuned for optimal thermal efficiency around 11,000–12,000 rpm.

Key parameters:

• Bore: 80 mm
• Stroke: ~53 mm
• Fuel flow limit: 100 kg/h above 10,500 rpm
• Compression ratio: ~18:1
• Max Brake Thermal Efficiency (BTE): ~50.1% (Mercedes, 2022)

Torque Output Model

Torque output \( T \) is a function of volumetric efficiency \( \eta_v \), cylinder pressure, and crank geometry:

$T={\frac {P_{mean}\cdot V_{d}}{4\pi }}$

Where:

• $P_{mean}$ = Mean effective pressure
• $V_{d}$ = Displacement volume

Turbocharging and MGU-H

The exhaust-driven turbocharger is coupled with the MGU-H, which:

• Converts waste heat from exhaust gases into electrical energy
• Controls turbo shaft speed (anti-lag system)
• Transfers energy directly to MGU-K or stores in ES

Eliminating turbo lag while minimising pumping losses is the core advantage of MGU-H systems, which are slated for removal in 2026.

MGU-K Functionality

The MGU-K acts as both a generator and motor:

• Harvests kinetic energy during braking (max 120 kW)
• Re-deploys under acceleration (limited to 4 MJ per lap)
• Linked to rear axle via transmission

$E=P\cdot t={\frac {1}{2}}mv^{2}$

MGU-K deployment is manually configured per driver using engine maps and controlled via steering wheel modes (Strat modes).

Energy Flow and Efficiency Map

A typical hybrid energy cycle:

→ ICE burns fuel → spins crankshaft → drives MGU-H (exhaust) → MGU-H sends electricity to ES or MGU-K → MGU-K deploys power to axle → MGU-K harvests energy during braking → returns to ES

Source	Energy Conversion	Efficiency Range
Fuel (Shell, Petronas)	Chemical → Thermal → Mechanical	48–50%
MGU-H	Heat → Electric	35–38%
MGU-K	Kinetic → Electric (regen) / Electric → Kinetic (drive)	~90% both ways
ES (Lithium-ion)	Storage → Discharge	~95%
Combined PU Efficiency	Overall (race average)	46–50% (peak)

Thermal Management

Heat rejection is one of the limiting factors in PU performance.

• Radiator surface area constrained by aero packaging
• Charge air coolers (intercoolers) used for intake temp control
• Waste heat from MGU-H and turbo routed via complex exhaust manifolds

Inlet air temperature and ambient density affect detonation risk and ignition timing—especially at high-altitude circuits (e.g., Mexico City GP).

Control Electronics and Engine Maps

The Control Electronics (CE) system includes:

• Energy management logic
• Anti-stall and clutch control
• Brake-by-wire calibration
• Real-time fuel/air mixture adaptation
• DRS interaction logic

Mode strategies include:

• Strat modes: Power delivery / fuel mix
• SOC modes: State-of-Charge control for ERS
• Harvest settings: Aggressive regen vs deployment bias

Regulatory Constraints

Per 2024 FIA regulations:

• Maximum fuel mass flow: 100 kg/h
• Total ERS deployment: 4 MJ/lap (MGU-K only)
• Total engine modes: Limited to non-adjustable maps per event
• Frozen ICE development since 2022
• MGU-H to be removed in 2026

2026 Power Unit Changes

Key differences in 2026 regulations include:

• Removal of MGU-H
• Tripling of MGU-K power (to ~350 kW)
• Increase in electrical energy share (~50% of total lap power)
• 100% sustainable fuels required
• More simplified and road-relevant hybrid architecture

See Also

• Energy Recovery Systems (ERS)
• Fuel flow regulations
• Turbocharger anti-lag system
• Thermal efficiency in internal combustion engines
• ERS deployment strategy modelling

References

• FIA Technical Regulations 2024, Sections 5–7
• Mercedes AMG HPP 2022 Power Unit Overview
• SAE Paper: “Advanced Combustion Modes for Downsized Turbo Engines”, 2023
• Honda Racing F1 PU Deployment Whitepaper, 2021
• AVL Simulation: Hybrid Drivetrain Efficiency Trends (2024)
• AMuS Tech Report: “ERS Deployment Maps Compared”, 2023