Wes Duenkel
July 25, 2017

Growing up in the thick of the Fox-body Mustang days, a quick street Mustang ran 13’s in the quarter-mile. Now Ford’s turbocharged econobox front-drivers will run times that embarrass many muscle Mustangs of yore.

Take Ford’s latest Focus ST. Not only is it fast, it’s stupid-easy to make faster. Besides walking uphill (both ways) to school through hip-high snow, we old-timers also had to fill nitrous bottles, ice down intakes, and swap cylinder heads to gain a few tenths. All it takes to add nearly 90 lb-ft of tire-melting torque to a Focus ST is a few keystrokes on a laptop computer. Kids these days!

To sample this witchcraft for ourselves, we had the folks at Ford Performance send us their latest do-dads to make our 2014 Focus ST shred its front tires with ease. They responded with their Calibration and Spark Plug package, and their new Focus RS Cold Air Intake Box. Parts in hand, we headed out to the dragstrip to see what the hubbub was about.

How’d it go? Read the captions to find out. Now, get off my lawn before I call the cops!


The Tale of the Track

Race tracks aren’t dynos, and dynos aren’t race tracks. After visiting the track we found out how chassis dyno results don’t always translate to track performance. In our case, the dyno was only telling half the story.

With the OEM calibration, the Focus ST’s torque was limited below 5,000 RPM, and would ramp up more slowly after each gear shift. Additionally, the engine would nose over as it approached red line.

After installing the Ford Performance Focus ST calibration and spark plugs, more torque available down low - enough to break the tires loose from a roll in second gear! This is clearly visible in the chassis dynamometer graph. But those gains wouldn’t necessarily translate to faster track times. In fact, looking at the 60-foot times between the before and after best runs, the 60-foot time was slightly slower on the fastest run. However, by the 330-foot mark, the Ford Performance calibration starts to edge out the OEM tune, and by the eighth-mile, it’s no contest. If the engine is above 4,700 rpm during the rest of the run, where is the extra power coming from? Well, we certainly felt the torque hit harder after each gear shift, and the engine pulled hard to the red line. Clearly, the Ford Performance calibration adds power in ways that aren’t visible in a single-gear chassis dynamometer pull.


1. Our Ford Performance RS Cold Air Intake Box arrived with an OEM paper element air filter in addition to the included K&N reusable filter.

2. It may not seem like much, but you’re looking at 90 lb-ft of torque! The Ford Performance Focus ST Calibration with Spark Plugs kit includes a ProCal III voucher and vehicle interface, and special colder-heat-range spark plugs

3. We began our Focus ST performance upgrade by swapping out the filters in the RS cold air intake box. Note how the K&N filter is a direct replacement for the OEM paper element filter, including the hard plastic end cap that seals and retains the filter in the box.

4. To change the air boxes, we first disconnected the MAF sensor connector.

5. Then, we released the air ducting coupler from the radiator support.

6. Next we removed the cover from the air box, and removed the OEM air filter.

7. With the filter removed, we released the tabs on the cold air ducts and set them aside.

8. After loosening the MAF sensor hose clamp, we removed the OEM air box from our Focus ST.

9. With the OEM Focus ST air box removed, we compared it to the Focus RS air box. Note the added air intake area on the RS box compared to the completely sealed OEM design.

10. We continued installation of the RS box by transferring the MAF sensor housing to the Focus RS air box.

11. Then, we installed the Focus RS air box into the Focus ST using the OEM mounting grommets.

12. All of the OEM cold air connections are utilized with the Focus RS air box.

13. Finally, we reconnected the MAF sensor and tightened the coupler clamp.

14. Even though our engine compartment suffers from a bit of an ST/RS identity crisis, the RS air box looks right at home in the ST’s engine bay. While not as pronounced with the hood closed, the added “whoosh” noise from the turbo makes this modification worthwhile. Note how the upper portion of the air box seals against the hood liner, and the open area in the box gets air from the headlight area.

15. Before installing the spark plugs included with the Ford Performance Focus ST Calibration, we verified the gap (as Ford recommends).

16. We used compressed air to clear any debris from the cam cover to keep it from falling into the spark plug holes when the plugs are removed.

17. To gain access to all of the coils, we first removed the upper air duct from the engine and stuffed a shop towel in the opening leading to the turbo.

18. Then, we removed each of the ignition oils.

19. Using a spark plug socket, we removed each of the OEM spark plugs.

20. With the plugs removed we could compare the OEM plug (top) to the plug included with the Ford Performance Focus ST Calibration kit (bottom). Because detonation is the enemy of any boosted engine, the spark plugs Ford includes are of a colder, heat range. To transfer more combustion heat to the cylinder head, the center electrode is more recessed into the plug. This keeps the center electrode cooler, and less prone to trigger detonation that can damage the Focus ST’s hypereutectic pistons.

21. We resumed by installing the colder heat range spark plugs into the engine.

22. Then, we reinstalled the ignition coils and their retaining hardware.

23. We finished up the hard part installation by reinstalling the upper air intake duct and the engine cover.

24. Here’s where the magic happens: Ford Performance Focus ST calibration includes this “canelope” that connects a laptop computer to the car’s OBDII port.

25. We used the included voucher to download the ProCal III software onto our laptop (thankfully, Apple machines are also supported!) and followed the detailed instructions to reflash the cars PCM.

26. One of the many nice features of the ProCal III software is the simple manner in which changes to axle ratio, tire size, and other options are made. Out of an abundance of caution, we enabled Octane Adjust, which dials back the ignition timing slightly to compensate for each engine’s knock sensitivity.

27. To ensure the engine gets the fuel it needs, we affixed the included 91+ sticker to the inside of the fuel filler door, filled the tank with 93 octane, and headed for the track.

28. Ford supplied us with a chassis dynamometer chart showing the horsepower and torque gains with the calibration. Based upon our research, these gains are pretty typical of a Focus ST tune. Note how the OEM calibration is clearly holding back the torque from 2,000 to 5,000 rpm. While the calibration unleashes about 90 lb-ft of torque, it’s all on the low end. We certainly felt it on the street, but since the engine runs between 4,700 and 6,500 rpm at the track, would those low-end gains result in faster track times?

29. After three baseline passes (the best being a 15.264 at 92.12 mph) we swapped out the spark plugs and installed the Ford Performance Focus ST Calibration. The results exceeded our expectations. Our best of three runs after tuning was 14.684 at 96.12 mph, dropping nearly six tenths (!) and adding four miles per hour. Besides the added low-end torque, we could feel the torque ramp in more aggressively after each gear shift, and the engine didn’t lay over as much as it approached redline. Clearly, the dynamometer wasn’t telling the whole story.