The First 10-second Focus RS in the World…
Mountune USA built the fastest MK3 Focus RS over 3 years ago and still holds the title today.

The very first North American Mk3 Focus RS vehicles began arriving in customers’ hands in June of 2016. Mountune USA took delivery of our development car on June 28, 2016. From the outset, the purpose of purchasing the Mountune Focus RS was to design, manufacture, and validate a suite of aftermarket upgrades to turn the car into the ultimate Focus RS. This was not to be a one-trick pony. The car had to accelerate, stop, and handle significantly better than stock; yet retain the character and refinement it had from the factory.



Not all cars are drag cars, but all cars can be drag raced. Drag racing is a universally known form of racing and a great measuring stick of a vehicle’s acceleration performance. It is accessible to most with hundreds of drag strips across the United States. Some will argue that a Focus RS is not meant to be a drag car but that doesn’t mean a Focus RS can’t be a ton of fun and impressively fast at the drag strip. What Mountune did not want to do was compromise responsiveness in the name of making a certain horsepower number or trying to run a specific time at the drag strip. Mountune has decades of experience with turbocharged 4-cylinder engines. Huge horsepower numbers may sound impressive on the internet, but with the associated trade-off in lag and response, this can easily ruin a great car and make it a bore to drive. A reliable and extremely responsive 500+ hp AWD monster was exactly what we had in mind.

In 100% factory trim, a Focus RS could be expected to run the 1/4-mile in about 13.4 seconds at 103 mph. Drag racing is fairly predictable in that you are basically accelerating a known mass (the car) with a known amount of horsepower. Various online drag race calculators confirm that a 3500 lb (Focus RS + driver) would need about 300 hp to run 103 mph through the 1/4 mile. It just so happens that most stock Focus RS's will make somewhere around 300-310 hp at the wheels when tested on a chassis dyno. If you start playing with these online calculators, you can get an idea of what 400 or 500 hp might do in a Focus RS. Removing some weight from the equation would further improve the predicted performance. None of these theories really matter until proven in the real world on the race track, but it's interesting to juggle the variables and get an idea of what it might actually take to put a Focus RS in the 10's. We can definitively say that throughout the development and testing of the Mountune Focus RS, the laws of physics have always held true. Our dyno numbers have always correlated with the car's resulting trap speed through the 1/4 mile. What does your favorite tuner's dyno sheet actually trap through the 1/4 mile?

Way back in 2016 when the Focus RS first came out, there was a ton of excitement surrounding it. It was the first time the RS badge was offered in North America, fans wondered if it would live up to the hype. Ford had stated some impressive acceleration figures for the turbocharged AWD platform. Turbocharged 4-cylinders have historically responded well to aftermarket tuning. New owners were anxious to test Ford's claims, and then set out to immediately improve on them. Just a few months after the car's initial release, a couple videos popped up on YouTube of a white Focus RS out of Connecticut running high 11's! For a brand new platform to come out and knock 1.5 seconds off of it's stock 1/4 mile time, that is a huge accomplishment. The quickest video we saw was 11.7 at 118 mph. Running that through those same calculators, assumptions could be about how much horsepower it might have been making. With our knowledge of the limits of the stock Focus RS turbo, we think that car had a lot of weight removed from it as well. But that guy took a brand new car, cranked the boost up to the max, pulled a bunch of weight out, added sticky tires, and took it to a good track with favorable weather conditions; the result was no doubt impressive.


If these cars were already into the 11's in just the first few months, surely there will be a Focus RS in the 10's in no time... and then things went really quiet. No word of that white car improving upon its time. A rash of mid-13 second Focus RS's flooded the online lists and registries tracking the top Focus RS 1/4 mile results. Most were casual drag racers, taking their bolt on tuned cars to the track to test out and have some fun. Some were more determined to improve on their times, but only one or two others ever got into the 11's on a stock turbo. Yet nobody was able to beat that 11.7s. It started to become apparent just how much of a unicorn that white car out of Connecticut really was.

Knowing that the majority of Focus RS owners were not merely looking for outright ¼ mile performance, Mountune embarked upon developing a logical progression of aftermarket upgrades for the Focus RS. A few essential durability upgrades were the first out of the gate- an uprated turbo recirculation valve, billet PTU brace, sound suppression chamber, and oil breather plate. The Mountune Quick Shift and roll restrictor (rear motor mount) ensure the shifts are fast and precise. Mountune was the first in the US to install a prototype model Quaife ATB limited slip differentials and soon after sourced the required bearings, seals, and hardware to sell an installation kit for these diffs to other shops and installers.

Focus RS essential mountune upgrades:

• Uprated Recirculation Valve
• PTU Brace Upgrade
• Sound Suppression Chamber
• Oil Breather Plate
• Quick Shifter
• Roll Restrictor

The next step in increasing performance was to optimize the airflow into and out of the 2.3L EcoBoost engine. The Mountune full high flow induction system eliminates any restriction of the air being drawn into the turbocharger. This system includes a reusable high flow air filter, a custom molded high flow silicone intake hose, and upper/lower crossover ducts leading directly to the turbocharger. The crossover ducts feature a unique cast aluminum construction that is unmatched in flow, durability, appearance, and fitment.

Our Focus RS intercooler upgrade features a durable “bar & plate” construction along with cast aluminum end tanks. The cast aluminum end tanks again offer performance, installation ease, and appearance that is superior to the fabricated end tanks offered by many other intercooler brands. The V2 and V2X cat-back exhaust systems feature full 3” piping throughout the system for unobstructed flow supporting power levels well beyond 500 hp. The Mountune V2 cat back exhaust was the first aftermarket exhaust system to employ the genuine OEM exhaust valve as found originally on the Focus RS, with the V2X version deleting the valve completely.

The best bang for the buck modification for a factory turbocharged car like the Focus RS is ECU tuning. Mountune set out to serve Focus RS customers’ needs in several different ways. The M380 Performance Upgrade is not only 100% street legal (CARB E.O. #D-727-3), but more impressively, was certified by Ford to not void the vehicle’s factory powertrain warranty coverage. The popular COBB AccessPort is also sold and supported by Mountune, with the custom Mountune optimized calibration included as part of the very popular Mountune B7 performance upgrade package. For full on race car conversions, Mountune became factory certified and the first Syvecs ECU distributor in the US to specialize in the Mk3 Focus RS standalone ECU kit.

With this wide range of performance upgrades available, Mountune was already well positioned to service the vast majority of Focus RS enthusiasts. Yet Mountune continues to push the performance envelope for those brave few who are determined to set records and be the best. The limits of the stock turbocharger were quickly reached. In designing the Mountune MRX turbo upgrade kit, the Borg Warner EFR line was selected for its extremely low inertia and fast response. Remember, we’re not intending to build drag cars here. Lag had to be minimized and the MRX turbo kit is hands-down the quickest spooling 500+ hp turbo kit available for the Focus RS. Period. We’ve tested several other turbo kits on the Focus RS for ourselves. If you’re making 500 hp on a 2.3L Focus RS with a different turbo, the Mountune MRX turbo will spool significantly faster, have a more usable power band, and be a lot more fun to drive. Not all 500+ horsepower Focus RS’s are created equal.

It may be possible to make over 500 hp on a stock engine, but for how long?

Some tuners brag about big hp numbers on stock components. It’s curious that you never hear about subsequent real world performance results to back up those big numbers. That’s not the Mountune way. Mountune would much rather brag about the fact that not a single engine failure occurred during the entire development and testing of the Focus RS platform. Countless torture tests on the dyno, drag strip, and road course. Dozens of experimental components tested. Pushing the engine platform into uncharted territory on gasoline, ethanol, direct injection, and auxiliary injection. We built a solid foundation before any failures occurred because we see the R&D process as a significant investment. It’s far more important to have a solid foundation to validate our entire line up of performance parts, rather than gain temporary internet glory with a one-time dyno pull on a stock engine ticking time bomb. The Mountune forged engine program for the 2.3L EcoBoost was born from this need. Brand new RS 2.3L blocks and cylinder heads are used as the foundation for these engines. We then install a keyed and lightened crankshaft (9lb less than stock!), forged connecting rods, and forged pistons. Tri-metal race bearings and performance fasteners are utilized throughout. While a built engine doesn’t add any more horsepower on its own, this stout foundation gave us the confidence to push every other component to their limits and has yet to let us down.

On April 4 of 2018, we decided to take the Mountune Focus RS to the drag strip to see where it would stand in the online rankings. On it's very first pass, the Mountune RS ran 11.61s at 118 mph. We had built the fastest Focus RS in the world on it's very first trip down the 1/4 mile!

Being that this was the very first pass on the car, we knew there was much more potential in it. The internet would undoubtedly snub their nose at a record that was only 0.1 seconds quicker than that old video they'd been bragging to their non-RS friends about for the past two years. So we kept it quiet. Our test day was cut short with a silicone hose problem on our prototype MRX turbo kit. Which was not a big deal because it is part of the development process. We test all Mountune products on our own car before selling it to customers. The prototype kit on the car was fabricated with off the shelf components, but we already had our custom designed 5-layer reinforced silicone hose first articles on the way from the factory. There was a solution in the works and we would soon be back on track.



With our production MRX turbo kit hose installed, we returned to the track on May 2, 2018. We ran four 11 second passes, the best being an 11.632s at 123 mph. That day was cut short by a broken front drive shaft. Still being in the 11.60's, we weren't quite ready to make any public announcements yet. We knew there was still so much untapped potential in the car, especially with that 123 mph trap speed. The only word that got out was this video that popped up on YouTube from a car that had been in the lane next to us on one of the 11.6s passes. According to the video's description, it was filmed from a 6.1L Hemi that runs in the 11’s itself. It's really evident how the Mountune Focus RS really puts down the horsepower in third and fourth gears (not to mention the flames from that no lift shift!).


After a call to our friends at The Driveshaft Shop, we had a set of their Heavy Duty front drive axles on the way. Another example of products that we have tested and proven in house on our own car, that we then go on to offer to our customers with firsthand experience of the installation and durability.

With the new driveshafts installed, we produced the consistent results shown below:

  • May 9th: 11.71s @ 118 mph
  • May 16th: 11.69s @ 119 mph
  • May 30th: 11.65s @ 119 mph

We had a consistent and reliable car, it was then time to really turn up the boost.


June 19th, 2018: 540 hp, 535 lb-ft

We take the Mountune Focus RS back to the chassis dyno with a tank full of E85 to turn up the boost with the Syvecs standalone ECU. Being the Mountune development car, we've tested all of the different ECU and fuel delivery combinations on it. Direct injection, port injection, reflashed OEM ECU (via COBB AccessPort), and full standalone Syvecs ECU. While the COBB AccessPort is adequate for the vast majority of customers, the Syvecs standalone ECU is unmatched in an R&D scenario like this where we are testing and developing our own hardware (intercoolers, turbo upgrade kits, camshafts, intake manifolds, etc.). The data logging capabilities, real time tuning changes, and total control over every aspect of the engine are essential to efficiently proving out new components. With the Borg Warner EFR-7163 pumping out just over 30 psi, the Mountune Focus RS put down 540 hp to the wheels.


June 20, 2018: 11.413s @ 123.7 mph

We return to the drag strip yet again. It is summer-time weather in sunny Fontana, CA. The track opens in the evening for test and tune runs on Wednesdays. It's still over 85F at 6:30 pm and the density altitude is above 3,800 feet. In spite of these less than ideal conditions, the Mountune Focus RS put down a handful of 11.4s second runs, with a best of 11.413s @ 123.7 mph. At the time, we were three-tenths of a second quicker than the previous record and over 5 mph faster. That's a pretty significant difference at this level of performance. We weren't even reaching the same boost pressure as we were on the dyno and the wastegate duty is at 100% for nearly the entire run. Density altitude is a killer, even on turbocharged cars. With the weather conditions only going to get worse through the summer, we figured this was the best we'd do for a while. We uploaded a video to YouTube the next day proclaiming it the "World's Quickest Focus RS" and it has held the title ever since.



Development continued on the Focus RS platform throughout the summer months. We had been testing a Quaife sequential transmission at the time, along with carbon synchro upgrades for the standard H-pattern transmission. The transmissions went in and out of our RS several times over a period of years. With cooler autumn weather approaching, we expected other RS's would be out looking to improve on personal bests and break records. It was time to improve upon our 1/4-mile time and put that Quaife sequential transmission through some durability testing.


October 24, 2018: 11.022s @ 124.72 mph

The weather has cooled off a bit in Fontana, CA, but the DA was still nearly 3,000 feet in the evening. The Mountune Focus RS was able to run deep into the low 11's, with a best of 11.022s @ 124.72 mph. So close to a 10 second pass! We had improved our previous record by four-tenths of a second and there was still no other Focus RS even close. A lot of excuses could be made, but the fact remains it is undeniably a very fast Focus RS. We believe it to be the fastest in the world and nobody has yet come forth disputing that claim.



We were proud of our accomplishment, but the internet was not shy about telling us why they shouldn't be impressed. It has a big turbo upgrade, the engine internals are forged, it has a sequential transmission, Mountune is a company with lots of money, Golf Rs are faster, Mustangs are faster, Honda K20s are better engines, my RS is being built by XXXX and has 800 hp... Some people think those are valid reasons to detract from the performance of this car. While Mountune has invested a lot of money in this car, the result of that has been the development of products and solutions for the Focus RS community. We don't believe in experimenting on customers' cars or selling untested parts, only to turn around and blame the manufacturer when things don't work out. Our products have the Mountune name on them, are designed to work together as a package, and have proven that their performance is unmatched. It's been nearly three years since we ran those 11.0's and still nobody has come close.


April 14, 2019: 11.016s @ 125.8 mph, OEM H-Pattern Transmission

After breaking no fewer than five prototype Quaife sequential transmissions, we decided that the sequential transmission was not suitable for sale. It just did not meet our standards for performance and durability. Mountune has a huge investment in time and labor installing and resting each one of those, plus we even designed and manufactured components specific to that transmission's installation. Once we determined those transmissions were not going to become a reality, we went back to the OEM H-pattern transmission. On April 14, 2019 (still with 2300' DA), the Mountune Focus RS ran 11.016s @125.8 mpg with an OEM H-pattern transmission. It actually went quicker and faster than with the sequential!



This was the result. - A nearly 10-second Focus RS built with parts that anyone can buy from Mountune USA and install themselves. Is this the first 10-second Focus RS in the world? It could be argued it is not. What can't be argued is that Mountune USA has had the quickest and fastest Focus RS in the world for three and a half years, and has been on the cusp of the 10's for nearly three years now. Where is everybody else? Should we take our car back to the track in search of that elusive 10-second pass to make it official?