For years car makers have boasted about the number of horsepower per litre they can squeeze out of petrol and diesel engines, but there's now a new arms race. In the EV field it's all about power density – how much 'go' that can be squeezed out of the smallest motor. Thanks to two British firms, the arms race just went nuclear.

Like all the best weapons projects, the work between electrification experts, Equipmake, and materials and thermal specialists HiETA even has a codename. Dubbed AMPERE, it uses additive manufacturing (more on that in a minute) to minimise weight, alongside some electrical wizardry to hit a targeted 295bhp in a package that weighs about as much as a half-decent road bike. This represents a power density that is around four-times that of a regular EV motor.

What's more, both companies are working to make AMPERE as cost-effective as possible.

The explosive power comes thanks to Equipmake's experience in making high-power, low weight EV motors. Whilst the company's main outlet for trade is in electric buses as well as working with Ariel on the forthcoming HIPERCAR, its compact APM series of motors is among the most power-dense in the world. Its APM 125, for example, offers a peak power of nearly 168bhp at 12,000rpm in a package that weighs just 14kg – the equivalent of 9kW per kilo.

Even some of the best permanent magnet EV motors hitting the roads today – such as the 362bhp Tesla Model S motor – sit below that 9kW per kilo figure. So the question is how on earth can the teams at Equipmake and HiETA find more than double this power-density for the AMPERE?

Fairly obviously, to increase power density the motor needs to shed some weight and gain some oomph – and find a way of dissipating the heat created in the process. HiETA's expertise comes into play here, as the company has significant expertise in additive manufacturing – better known as 3D printing. Rather than milling a motor housing from solid billet steel, the metal structures in the AMPERE will be printed.

According to the companies, this has several advantages. First of all there's no excess metal. Secondly, the thermal properties of the design can be very tightly honed, removing the need for multi-part structures and replacing them with a single structure that offers the necessary cooling. Finally, because the moving parts are lighter than could be achieved through regular manufacturing techniques, rotational mass is minimised so higher rotational speeds can be achieved.

Andy Jones who heads up Innovation at HiETA, reckons that typically, they can reduce the size of heat management components by five times through 3D printing – and if you've ever taken a good look at an EV motor the cooling side of things is typically quite bulky. All of these little improvements are also designed to bring down production costs.

Thanks to all of these manufacturing innovations, the 10kg AMPERE is designed to crank at up to 30,000rpm at which speed it'll be pushing out that target power of 295bhp.

Ian Foley, MD of Equipmake, is excited by the potential that the development of AMPERE has to offer: “This exciting project has the potential to totally change our concept of what an electric motor can offer – and with such a huge amount of performance in a such a small package at as low a cost as possible, this motor is set to further revolutionise e-mobility, whether that’s in automotive or aerospace. We are grateful to Innovate UK for their support and are looking forward to getting the very first AMPERE prototypes up and running very soon.”