The MSO HS is a specially commissioned supercar based on the 666bhp 675LT, but it features a host of weight-saving and bespoke aerodynamic features, as well as a blueprinted and optimised edition of McLaren's M838TL twin-turbocharged V8 engine that produces 679bhp and 516lb ft, the latter available from 3000-7000rpm, in all drive modes.
To mark out its additional power, the reworked V8's carbonfibre engine bay is finished in clear gloss, while the engine's header tank and plenum cover are bespoke MSO HS parts.
The engine's exhaust ports are hand-polished, while the exhaust system itself features a crossover muffler, which gives more length to optimise gas flow. The system ends with two circular exhaust pipes, forged from titanium, which exit through the centre of the car's rear bodywork underneath the rear wing. McLaren says due to the high temperatures of the engine's waste gases, the exhausts will change colour over time.
To go with the power increase the MSO HS gains its own unique exterior bodykit which is capable of generating 220kg of downforce at 150mph. The additions include a new front bumper and splitter, dive planes and an air induction scoop on the roof, all of which are made from carbonfibre, as are full length side skirts, the side intakes and a P1 GTR-inspired rear wing.
Like the GTR's wing, the HS's rear wing can also act as an airbrake and can be adjusted electrically through settings fixed by McLaren’s chief test-driver, Chris Goodwin, to tweak the car's aerodynamic balance.
Each MSO HS cabin is finished to its customer's requirements. Alcantara trim with contrasting stitching saves a combined 3.5kg compared with leather - although full Nappa leather is available - and a further 15kg is saved with a pair of lightweight carbonfibre racing seats, complete with racing harnesses and identical to those fitted to the P1.
MSO has also ditched the usual door-mounted heating controls by moving the settings into the car's infotainment system, saving more weight. Also integrated into the system is McLaren's Track Telemetry package, which features F1-influenced timing software with GPS technology and data logging.
Three cameras are built into the cabin and work in conjunction with the data logger, recording track running to offer additional analysis. One camera is mounted in the front bumper and one in the rear, while a third looks over the driver's shoulder in the cabin.
F1-style shift lights that change from red to blue are placed in the driver's eyeline to encourage manual operation of the gearbox, further emphasising the model's track focus.
Just 25 examples of the MS HSO are being built by McLaren's Special Operations (MSO) department, and all have been assigned to customers. The model will not go into general production.
The car that the MSO HS is based on, the 675LT, was revealed in 2015 and remains the top McLaren Super Series production model. The range also includes the 650S, 650S Spider and the Asia-only 625C. The 675LT produces 666bhp from a twin-turbocharged 3.8-litre V8 engine and costs £259,500.