Four cylinders, direct injection, a thumpin’ great turbocharger, and lots of reliability problems. The 2.3-liter EcoBoost in the Focus RS has its ups and downs, but in the hands of Mountune, this fellow is capable of 684 horsepower at the crankshaft.
Complemented by a BorgWarner EFR 8374 turbocharger and the MRX cylinder head from Mountune, the engine on the dyno in the following video has also 566.5 pound-feet of torque. That’s 768 Nm if you were wondering, which is almost a match for the 4.0-liter twin-turbo V8 that McLaren uses in the 720S supercar.
The automotive engineering company from Maldon, Essex didn’t mention if there’s an official upgrade in the pipeline, which means that the m520 MRX Package remains the most hardcore option from Mountune for the third-gen Focus RS. At £5,975 including value-added tax in the United Kingdom, it’s also expensive.
Every penny is worth it given the incredible performance without too much of a problem in terms of reliability, and yes, the m520 MRX Package includes a turbocharger assembly from BorgWarner. The EFR 7163 is joined by professional calibration, new hoses and coolant lines, a v-band downpipe, gaskets, inlet and outlet water supply, performance camshafts and valvetrain, oil and filter, and an uprated fuel pump. The parts which are not included are the upgraded intercooler, full intake system, 3.0-inch exhaust system, and forged engine internals.
Turning our attention back to the 684-horsepower build, Mountune mentions E30 fuel. That’s a combination of 30-percent ethanol and 70-percent gasoline. Premium fuel is a must in the Focus RS as per the owner’s manual, 98 RON to be more precise. Even the Mustang with the 2.3-liter EcoBoost needs 93 octane instead of 87 to develop the advertised performance numbers and fuel economy figures.
On a slightly different note, Ford is currently developing the fourth-gen Focus RS with know-how from the Focus ST. European models feature the 2.3 with 280 PS on tap, and chances are the Focus RS will level up to 400-ish ponies thanks to 48-volt electrical assistance.
After a 1:43 scale model of a Ferrari 250 GTO sparked Mircea's interest for cars when he was a kid, an early internship at Top Gear sealed his career path. He's most interested in muscle cars and American trucks, but he takes a passing interest in quirky kei cars as well. Full profile
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