What is it?
Mountune’s M520 belongs back in time, when no-name electric cars with 2000bhp didn’t show up out of nowhere and we thought supercars making barely one-third of that were pushing the boundaries of what normal humans could handle. If you want a date, try March 2000, which was the month Porsche showed a concept version of the Carrera GT in Geneva.
This is the era you need to mentally revisit to fully appreciate such an outrageous take on the Ford Focus RS. We’ve become worryingly immune to big numbers, so let's be clear: 513bhp is an unhinged degree of power for any hatchback, and has been achieved by the company that, while Porsche was formulating its V10 supercar, was supplying four-cylinder turbo engines for the works Focus WRC cars of Sainz and McRae.
The M520 also uses a four-cylinder turbo engine, though one based on the 2.3-litre Ecoboost that still serves in the latest Focus ST. Following the M375 and M400r kits, the M520 is the most thorough reworking of the package yet. Mountune fits a new BorgWarner turbocharger with low-friction ceramic bearings and a low-inertia turbine.
There are then upgraded camshafts and valvetrains, a more powerful fuel pump and a host of new gaskets, hoses, studs and nuts. Any car due for conversion also needs, as a prerequisite, to use Mountune’s own intercooler and air-intake, big-bore exhaust and forged engine internals, to take the strain.
Elsewhere, the front driveshafts have been beefed up and there’s a Quaife torque-biasing differential to replace Ford’s open differential. Interestingly, the rear axle, which in the standard Focus RS is never asked to cope with more than 240bhp of the engine’s 345bhp total, has been left untouched.
From scratch it all costs around £15,000, but the promise of Nissan GTR-troubling performance with Mountune’s trademark drivability (not every member of the household wants 300bhp per tonne) has meant no shortage of orders.