The Speedtail has the highest specific battery power of any production road car.

McLaren has lifted the lid on its new Speedtail hyper GT car after it achieved a top speed of 250 mph (403 km/h) in high-speed validation tests in the U.S.

The three-seater combines a supremely aerodynamic profile with low vehicle weight, and a race-bred hybrid electric drive system that incorporates pioneering battery technology to set a new benchmark for hybridized hypercars.

That hybrid drivetrain includes McLaren's trademark 4.0-liter V8, but with a new lightweight air-intake system, improved cylinder head cooling, and revised piston design to deliver 747 horsepower alone.

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On the electric side, engineers from McLaren Applied, the McLaren Group division that focuses on virtual product development, telemetry, electrification, and control, helped integrate motorsport-developed inverter and DC/DC converter technology to further enhance the car's performance.

A high power cylindrical cell, arranged in a unique array, delivers the best power-to-weight ratio of any high voltage battery available today, and has four times the power density of McLaren's only other hybrid hypercar effort, the P1

The battery design enables the Speedtail to deploy its energy in a smart way, because the cells are thermally controlled by a dielectrical cooling system and permanently immersed in a lightweight, electrically insulative oil which quickly transfers heat away from the cells – a first for a production road car.

Formula E-derived technology gives the Speedtail the highest performance installation ‒ including cooling and integration ‒ of any electric motor currently in use on a production road car. The electrification ups the overall figure to 1,055 horsepower thanks to a setup that's twice as efficient of any other road car, with a power delivery figure of 8.3kW/kg.

Gallery: McLaren reveals Speedtail electric secrets

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Secrets of the Speedtail: the race-bred electric drive and ground-breaking battery technology in McLaren's hybrid Hyper-GT

  • McLaren Speedtail has the highest specific battery power of any production road car
  • Hybrid Hyper-GT uses motorsport technology to supplement twin-turbocharged V8
  • Innovative battery cooling system enables electric drive to work harder for longer

Following the announcement that the Speedtail – the fastest McLaren ever – had completed high-speed validation tests in the United States and reached its maximum speed of 403km/h (250mph) more than 30 times, McLaren engineers have been asked one question more than any other: ‘How does Speedtail go that fast?’

The answer is that a combination of attributes, including aerodynamic excellence and low vehicle weight, delivers the hybrid Hyper-GT’s astonishing performance. Fundamental to this is a race-bred electric drive system that incorporates pioneering battery technology to set a new benchmark for hybridised efficiency. This unlocks the Speedtail’s intense acceleration from standstill to 300km/h (186mph) in a breath-taking 13 seconds and maximum speed of 403km/h (250mph).

The M840TQ powertrain comprises a 4.0-litre internal combustion engine and an electric drive unit, which together develop up to 1,070PS and maximum torque of 1,150Nm. The V8 engine features technology that has evolved from McLaren’s first hybrid hypercar, the legendary McLaren P1™.  A new lightweight air-intake system, improved cylinder head cooling and a revised piston design contribute 757PS and 800Nm of ‘traditional’ petrol-powered output to the Speedtail.

The electric motor, which uses Formula E-derived technology, generates more than 230kW. It gives the Speedtail the highest performance installation ‒ including cooling and integration ‒ of any electric motor currently in use on a production road car. Power delivery is 8.3kW/kg, which is twice the efficiency of an average sports car.

Engineers from McLaren Applied ‒ the McLaren Group division that focuses on virtual product development, telemetry, electrification and control ‒ worked with the Speedtail Electric Drive Technology team to integrate its ground-breaking motorsport-developed inverter and DC/DC converter technology into the electric drive system, ensuring the levels of control and power management required for the hybrid Hyper-GT to realise its extraordinary performance.

The high voltage energy storage system is where the Speedtail truly innovates. A high power cylindrical cell arranged in a unique array, the 1.647kWh unit is at the cutting edge of battery technology, being extremely compact and delivering the best power-to-weight ratio of any high voltage battery available today. As an indication of how McLaren technology has advanced, the power density of this battery is four times that of the unit in the McLaren P1™, providing 5.2kW/kg and an output of 270kW.

The design and integration of the battery system enables the Speedtail to achieve its maximum speed by intelligent energy deployment, with these headline figures achievable because the cells are thermally controlled by a dielectrical cooling system and permanently immersed in a lightweight, electrically insulative oil which quickly transfers heat away from the cells. This system, the first of its kind in a production road car, is highly efficient and allows the cells to run harder and for longer.