Mountune Ford Focus RS m520 review

513bhp? Surely not…

Oh yes, friend. We mean it completely seriously. The white Ford Focus RS shown here genuinely produces considerably more brake horsepower than a Porsche 911 or Audi RS4, to pick two extremely quick cars at random.

In fact, it has 100bhp more than the unquestioned power champion among mass-produced hot hatchbacks: the ridiculously fast 415bhp Mercedes-AMG A45.

And what does that feel like?

Utterly terrifying.

Mountune Ford Focus RS m520 performance

Is that the entire story?

Fine, let’s elaborate. Plant your right foot in Mountune’s RS and… nothing occurs. Truly nothing happens until roughly 3,000rpm, at which point it begins to consider doing something. To contemplate, you know, getting a move on. The odd whining and whooshing sounds beneath the bonnet grow louder, while the crossover sitting a few millimetres from your rear bumper starts to fall away.

At 3,500rpm, though, the world detonates and you are flung towards the horizon with unsettling force. Looking at the speedometer is out of the question. Your brain is too busy attempting to comprehend the turbocharged haymaker that the heavily reworked 2.3-litre, FOUR-CYLINDER engine has landed squarely on your cerebral cortex. And it is not coping well. At the same time, your arms are occupied with keeping the car travelling in a straight line as the steering wheel kicks and squirms beneath the strain of 513 Essex-spec horsepowers.

So, does it genuinely feel as though it has well beyond 500bhp and 500lb ft? Erm, yes. It absolutely does. This is properly serious pace from a properly serious machine.

So where does that power come from?

We will come to that shortly. First, some background.

Mountune began in the Eighties as a race-engine builder. That remains part of its business, but it is now perhaps better recognised among fairweather petrolheads for modest upgrades to Ford hot hatchbacks.

In years gone by, having your Fiesta ST Mountuned was an obvious choice. The tuner’s £599 package for the previous-generation ST brought a replacement airbox, air filter and ECU calibration to release extra power. More importantly, it did not invalidate the Ford warranty. You could even purchase the package and have your local main dealer fit it.

The same applied to the RS’s FPM375 upgrade. Priced at £899, it added 25bhp and 30lb ft through a recalibrated ECU, improved air filter, crossover duct and dump valve.

Although the kits are good, Ford no longer covers Mountune upgrades under warranty. Today, you can install them at home using only a dedicated phone app, which communicates with the car over Bluetooth, and a Philips-head screwdriver. Thirty minutes later, there is an additional 30bhp at your disposal.

However, the ‘m520’ package on this RS is not one for DIY installation, unless you are VERY sure of your mechanical abilities, can use a professional-standard workshop and/or happen to work for Mountune. It also costs rather more.

Ford Focus RS m520 upgrade and costs

How much more, exactly?

It is just under £14,000 before making any changes to the transmission, suspension, brakes or bodywork. In its current form, this RS, Mountune’s development car, carries comfortably more than £20,000 of modifications. These include carbon-fibre front wings, two-way adjustable KW dampers, a Quaife ATB differential and Michelin Cup 2 tyres.

“We initially thought if we do ten this year [2019] that’ll be great. But we sold the first ten in about a month,” Mountune boss Alec Pell-Johnson tells us. “A lot of the guys are going from standard, which is an enormous change. Also an enormous amount of work.”

The conversion requires the engine to be fully removed from the car and occupies the company’s technicians for around a week. They install the tougher parts necessary for the 2.3-litre ‘EcoBoost’ engine to deliver supercar-chasing power. “We source those parts from our race engines. And we already knew they could handle the power, because they run in the BTCC,” says Alec. “Quite a few of the bits are interchangeable.”

Central to the conversion are the crucial forged internals, alongside a larger and superior BorgWarner turbocharger with ceramic bearings, which is the most expensive single item. A high-pressure fuel pump is also fitted, as are innumerable new hoses and gaskets, a three-inch exhaust, and upgraded intake and intercooler systems. “You need the full air-cooling, oil-cooling, water-cooling kits,” Alec explains. “We haven’t ever had any overheating problems on ours, nor any we’ve ever done as far as I know.”

Once the mechanical team has rebuilt the engine and successfully put it back in the car, Mountune generally completes about 500 miles of testing before returning it to the owner, simply to confirm that everything functions as intended.

Living with the Mountune Ford Focus RS

That all sounds rather serious.

It certainly is, yet the Mountune RS is surprisingly tame when driven normally. Change up early and largely remain out of boost, and it is easy enough to potter about at moderately sensible speeds.

It is not dramatically thirstier than a standard Focus RS, though that is hardly an economical starting point, while the £2,083 KW coilovers are a complete triumph. They are firm, certainly, but sufficiently compliant that you will not need to marry a chiropractor merely to be checked over whenever you arrive home. They are unquestionably worth fitting. The only meaningful inconvenience is the race-style clutch, which can be slightly fiddly in traffic. Otherwise, the usual Focus RS shortcomings endure, especially the driving position being set a couple of inches too high and the mismatched interior.

The m520 does not feel like the sort of thing Ford in 2020 would sell itself, but Mountune has somehow retained its everyday usability, and that is genuinely impressive.

But I want to go quickly. Is it genuinely enjoyable on public roads?

Naturally, chances to deploy all of its power for any sustained period are scarce, although that applies to any car with more than, say, 300bhp. Even so, the Mountune RS is enormous fun, despite the experience being wholly dominated by an explosive punch of acceleration that makes mile-long straights seem around three feet in length.

It is the sort of car that makes you laugh out loud in a breathless, “thank God I survived” sort of way. Its cat-back exhaust crackles and bangs louder than any I have encountered, and it has a hard-edged, motorsport-inspired character. There is no sense whatsoever that it is delicate or highly strung; instead, it feels like a serious, robustly engineered object that has little patience for fools. Treat it carelessly at your risk: driving this machine fast demands your complete and undivided focus, unless you want it to land you in serious trouble.

Mountune offers milder RS kits, and the ideal balance of power, chassis ability and sanity may well lie with one of them. Yet for the hardcore minority, the m520 is among the wildest hot hatchbacks I have driven, and it feels thoroughly well assembled. Unhinged, but brilliant.

7/10