2017 Ford Focus St Modified – The Ultimate Roadmap For Power
A 2017 ford focus st modified with the right components transforms from a fun daily driver into a track-ready performance machine. By prioritizing cooling, chassis rigidity, and a refined engine calibration, you can unlock significant power while maintaining the reliability Ford built into the platform. This guide breaks down the essential upgrades that provide the best “bang for your buck” while keeping your car safe and enjoyable.
You likely bought your Focus ST because you wanted a practical hatchback that could still put a massive smile on your face during a canyon run. However, once the “mod bug” bites, you quickly realize that the factory left quite a bit of performance on the table to satisfy a broad range of drivers. Choosing to drive a 2017 ford focus st modified for your specific needs means you are ready to address those factory compromises.
I promise to walk you through the exact steps needed to sharpen your handling, increase your horsepower, and ensure your engine stays healthy for years to come. We will explore everything from basic bolt-ons to advanced tuning strategies, ensuring you have a clear path forward for your build. Let’s dive into the world of the Mk3.5 ST and see what this 2.0L EcoBoost is truly capable of.
The Foundation: Addressing the Rear Motor Mount
If you have ever launched your car or shifted hard from first to second gear, you probably heard a loud “bang” coming from the engine bay. This is not your transmission falling out; it is the engine hitting the firewall because the factory rear motor mount (RMM) is incredibly soft. Upgrading this mount is arguably the most important first step for any 2017 ford focus st modified project.
A high-quality aftermarket RMM uses a stiffer polyurethane bushing to limit engine movement. This modification significantly reduces wheel hop and improves shifting feel by keeping the drivetrain stable under load. While you might notice a slight increase in cabin vibration at idle, the trade-off in traction and shift precision is well worth it.
When selecting an RMM, look for brands like Cobb, Mountune, or JBR. Most enthusiasts find that a 70a to 80a durometer rating provides the perfect balance between performance and comfort. Installing this part is a simple DIY job that requires only basic hand tools and a set of jack stands.
Unlocking Power Through Thermal Management
The 2.0L EcoBoost engine is notorious for “heat soak.” The factory front-mount intercooler (FMIC) is barely adequate for stock boost levels and quickly becomes a bottleneck during spirited driving. If you want consistent power, you must upgrade your cooling system before chasing higher boost numbers.
An aftermarket intercooler features a much larger core and better internal fin density. This allows the car to maintain lower charge air temperatures (CATs), which prevents the ECU from pulling timing and reducing power. In many cases, simply swapping the intercooler can gain you 10-15 horsepower on a hot day without even changing the tune.
While you are working on the cooling system, consider a “sound symposer delete.” The factory symposer pipes engine noise into the cabin through a plastic diaphragm. These are known to leak boost as they age. Replacing it with a simple block-off plate simplifies the engine bay and ensures every ounce of boost reaches the intake manifold.
Upgrading the Intake System
The factory airbox is actually quite efficient, but it is quiet. Most owners of a 2017 ford focus st modified want to hear those intoxicating turbo flutters and induction noises. A high-flow dry filter or a full “cold air intake” system will provide that sound while slightly improving throttle response.
If you are on a budget, simply replacing the stock paper filter with a green filter and removing the airbox lid provides a great sound. For those looking for maximum aesthetic appeal, a full 3-inch intake pipe from companies like 27WON or Mishimoto cleans up the engine bay and pairs perfectly with a larger turbo down the road.
How a 2017 ford focus st modified for Performance Changes the Driving Experience
The magic happens when you combine hardware upgrades with a custom engine calibration. The Focus ST uses a speed density fueling system, meaning it is very receptive to tuning. Using a device like the Cobb Accessport allows you to flash new maps that optimize boost, timing, and fueling for your specific modifications.
A “Stage 1” tune typically focuses on smoothing out the power band, while “Stage 2” (intercooler required) and “Stage 3” (full exhaust required) push the factory K03 turbo to its limits. You will notice a massive surge in mid-range torque, making the car feel much more aggressive during highway passing maneuvers.
However, power is nothing without control. A 2017 ford focus st modified for the track needs to handle the corners as well as it handles the straights. The ST is famous for its “lift-off oversteer,” but you can further refine this behavior with a few key suspension tweaks.
The Impact of a Rear Sway Bar
One of the best-kept secrets in the ST community is the rear sway bar (RSB). The factory bar is relatively thin, allowing for a fair amount of body roll. Upgrading to a thicker, adjustable RSB helps the car rotate more predictably and reduces understeer.
For a daily driver, the Steeda or Whiteline bars are excellent choices. Set the bar to the “medium” setting for a balance of stability and agility. This modification makes the car feel much more “planted” when you are carving through tight corners or navigating an autocross course.
Suspension and Stance: Springs vs. Coilovers
Most owners want to get rid of the factory “wheel gap.” You have two main paths: lowering springs or coilovers. Lowering springs are cost-effective and work with your factory struts. Brands like Mountune or Eibach offer a modest drop that improves the look without ruining the ride quality.
If you are serious about performance, coilovers are the way to go. They allow you to adjust ride height, damping, and sometimes even camber. This level of adjustability is crucial if you plan on corner-balancing the car for competitive driving. Look for options with adjustable damping so you can soften the ride for the commute and stiffen it for the track.
Remember that lowering the car changes the suspension geometry. You may need adjustable rear camber arms to keep your alignment within spec and prevent premature tire wear. Always get a professional alignment after performing any suspension work on your 2017 ford focus st modified.
Stopping Power: Brakes and Tires
Speed is expensive, but crashing is more expensive. Do not neglect your brakes. The 2017 Focus ST comes with decent brakes from the factory, but the stock pads are prone to fading under heavy use. Upgrading to a high-performance street pad, such as the Hawk HPS 5.0, provides a much better initial bite and higher heat resistance.
For those who track their cars, stainless steel braided brake lines are a must. They eliminate the “mushy” pedal feel caused by factory rubber lines expanding under pressure. Pair these with a high-boiling-point fluid like Motul RBF600 to ensure your pedal stays firm even after multiple laps.
The Importance of Quality Rubber
Tires are the only part of your car that actually touches the road. You can have 400 horsepower, but it means nothing if you are running cheap all-season tires. A 2017 ford focus st modified deserves a dedicated summer performance tire like the Michelin Pilot Sport 4S or the Continental ExtremeContact Sport.
If you live in a climate with cold winters, do not try to “tough it out” on summer tires. The compound becomes hard and brittle in low temperatures, significantly increasing your stopping distance. Invest in a second set of wheels with dedicated winter tires to keep your pride and joy safe when the snow starts to fall.
Reliability and Preventative Maintenance
Modifying a car increases the stress on its components. To keep your ST running strong, you must be diligent with maintenance. The most critical issue to be aware of is Low Speed Pre-Ignition (LSPI). This occurs when the engine is under high load at low RPM, which can lead to catastrophic piston failure.
To avoid LSPI, never “lug” the engine. If you need to accelerate while in 5th or 6th gear, downshift to 4th to get the RPMs up before applying heavy throttle. Additionally, always use a high-quality full synthetic oil and change it every 5,000 miles or sooner if you are driving the car hard.
Spark plugs are another vital maintenance item. Most tuners recommend “one step colder” spark plugs (like the NGK 6510) gapped to roughly.026 or.028 inches. This helps prevent misfires under high boost and ensures a clean combustion cycle. Check your plugs every 10,000 to 15,000 miles to ensure they are in good condition.
Frequently Asked Questions About a 2017 ford focus st modified
Will modifying my 2017 Focus ST void my warranty?
In the United States, the Magnuson-Moss Warranty Act protects consumers. A dealer cannot void your entire warranty just because you have modifications. However, they can deny a specific claim if they can prove that your modification caused the failure. For example, if you have a tune and your engine fails, they likely won’t cover it. If your power window stops working, they still have to fix it.
What is the best first mod for a Focus ST?
The Rear Motor Mount (RMM) is widely considered the best first modification. It solves the most glaring factory flaw—engine movement and wheel hop—without breaking the bank or requiring a tune. It immediately makes the car feel more solid and connected.
How much horsepower can the stock turbo handle?
The factory K03 turbo is relatively small. With full bolt-ons and an E30 (ethanol) blend tune, most owners see around 270-280 wheel horsepower and over 350 lb-ft of torque. To go beyond 300 wheel horsepower, you will typically need to upgrade to a “big turbo” kit.
Is the Focus ST a good platform for DIY mechanics?
Yes, the Focus ST is very DIY-friendly. The engine bay is relatively easy to work in, and there is a massive community of owners who have created step-by-step guides for almost every modification imaginable. Most bolt-on parts can be installed with a standard metric socket set and some patience.
Final Thoughts on Your Build Journey
Building a 2017 ford focus st modified to your liking is a rewarding experience that teaches you about mechanical engineering and vehicle dynamics. Start with the basics: fix the motor mount, upgrade the cooling, and get a solid tune. From there, let your driving style dictate your next moves, whether that means better brakes for the track or a louder exhaust for the street.
Always prioritize safety by using the correct tools and high-quality parts. A well-modified car is a reflection of its owner’s attention to detail and passion for driving. Take your time, do your research, and most importantly, enjoy the process of making your Focus ST uniquely yours. Stay safe, keep the shiny side up, and enjoy every mile on the open road!
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