Helix SPX242

The Helix SPX242 is a scalable family of electric motors that has four variants: the -50, -94, -175, and -175D.  These are truly impressive offerings that reflect the state of the art in 2025.

I will report on the SPX242-94 because that is what's being used in the McMurtry Spéirling Pure, a track-only BEV that sells for a million pounds sterling.  McMurtry rates the “car” at 1000 horsepower because it uses two SPX242-94 drive motors.

The SPX242-94 is a 3-phase synchronous motor/generator that weighs only 34 kg and can run up to 17,000 RPM.  Its low-inertia internal rotor consists of six radial-flux permanent magnets.  The Helix datasheet reveals the following specifications:  

• Peak power: 400 kW (536 HP)

• Maximum continuous power: 278 kW (375 HP)

• Peak torque: 470 Nm (347 lb-ft) for 10 seconds

• Maximum continuous torque: 331 Nm (244 lb-ft)

Helix also makes a matching inverter (motor controller) that uses silicon-carbide MOSFETs and weighs only 10.5 kg.  Maximum DC voltage is specified at 950 V.  Maximum phase current is 773 Arms.

Both the motor and inverter are liquid-cooled with a 50/50 mixture of water and ethylene glycol.  Although the inverter is said to be over 99% efficient at 200 kW, that still means ~2000 watts of heat that must be carried off by the coolant just for one inverter.

The motor's architecture is considered scalable because the diameter remains constant and power increases come from additional rotor length.  In the case of the -175D, two inverters are required and this produces a 6-phase motor. 

The rotor position sensor is a Tamagawa TS2225 resolver.  I could not find that exact part number on the Tamagawa website, but similar resolvers can divide one complete motor revolution into 4096 parts.  

An efficiency map is shown below.  The shape of the torque curve is described by the envelope of the map.

Triumph TE-1 Motorcycle Prototype

The following information was distilled from a 2022 press release found on the Helix website.  Although the press release is short on technical details, we can glean the following: 

The power plant is considered “ultra-integrated” meaning the inverter is integral to the motor.  

The motor has a claimed peak power of 130 kW (175 bhp) and a peak torque of 109 Nm (80 lb-ft).

Peak power density is specified as 13 kW/kg (this implies the motor weighs 10 kg).

Continuous power density is 9 kW/kg (this implies the motor can make 90 kW continuously).

The vehicle's performance matches (or exceeds) Triumph's Speed Triple, a 1200cc 3-cylinder ICE sport bike.

The 0 to 60 mph time is given as 3.6 seconds.

The 0 to 100 mph time is given as 6.2 seconds.  

It has a 161 km (100 mile) range. 

Charge time is 20 minutes (from 0 to 80%).

The overall weight is 220 kg (485 lb).