How to Modify the Ford Focus ST: The Ultimate Guide

The Ford Focus ST has quietly become one of the best budget performance cars you can buy. Powered by the turbocharged 2.0L EcoBoost engine and paired with a 6-speed manual transmission, the Focus ST delivers everything enthusiasts love about a hot hatch. Even years after production ended, aftermarket support is stronger than ever. From daily drivers making 280 horsepower to fully built big turbo cars pushing over 400 wheel horsepower, there's no shortage of ways to build one. The trick however, is knowing where to start. So how do you build a Focus ST the right way? Let's get into it.

The First Mod Every Focus ST Needs: Rear Motor Mount

If you ask one hundred Focus ST owners what your first modification should be, you'll hear the same answer over and over. Upgrade the rear motor mount. The factory rear motor mount is extremely soft and allows excessive engine movement under acceleration. That movement contributes to things like wheel hop, a sloppy feel when shifting, and inconsistent launches.

Popular upgrade options include:

1. Mountune Rear Motor Mount
2. cp-e Rear Motor Mount
3. Damond Motorsports Rear Motor Mount

Many owners also pair this with upgraded shift bushings and a short throw shifter.

Important Reliability Issues To Know Before Modding

The 2.0L EcoBoost is a solid engine overall, but there are a few things worth keeping an eye on. Specifically a little thing called Low Speed Pre-Ignition.

Low Speed Pre-Ignition (LSPI)

If you've spent any time on Focus ST forums, you've probably heard people talk about LSPI. Sounds scary, and kind of is if you don’t know how to avoid it. Essentially what you want to avoid is lugging the engine in higher gears at low RPM while trying to make a sudden amount of boost. If you’re looking to stomp on the throttle, make sure your RPMs are sitting above 3K. Otherwise. BOOM.

Best Suspension Upgrades For The Ford Focus ST

The Focus ST chassis is already playful from the factory, but suspension upgrades make it feel significantly more planted.

Coilovers

Some of the most common setups you'll find on Focus ST builds include:

1. BC Racing BR Series – Affordable, adjustable, and extremely popular.
2. Fortune Auto 500 Series – Excellent ride quality with strong street and track performance.

Lowering Springs

If coilovers aren't in the budget:

1. Eibach Pro-Kit
2. H&R Sport Springs

Rear Sway Bars

One of the best upgrades for improving body roll and reducing understeer in the corners. Popular choices include:

1. Whiteline Sway Bar
2. COBB Sway Bar

What Wheels And Tires Fit The Ford Focus ST?

The Focus ST uses a 5x108 bolt pattern. Which is a bit unfortunate since it is a bit of an oddball bolt pattern. However, more wheel brands have started supporting it as the Focus ST has gotten so popular.

Recommended Wheel Sizing

Diameter: 18"

Width: 8.5"

Offset: +38 to +45

A very common enthusiast setup:

18x8.5 +42

Recommended Tire Size

235/40R18

245/40R18

A quality tire makes a huge difference on these cars.

Recommended Wheels

The Focus ST pairs well with lightweight motorsport-inspired wheels.

1. Konig Ampliform– Lightweight, affordable, and a community favorite.
2. Fifteen52 Turbomac – Classic turbofan style for the Focus platform
3. Enkei NT03+M – Multispoke design that looks incredible on these cars.

Recommended Tires

1. Nitto Neo Gen 
2. Continental ExtremeContact Sport 02
3. Falken Azenis RT615K+

Bolt-On Performance For The Ford Focus ST

The 2.0L EcoBoost responds incredibly well to simple bolt-ons. Here is what we recommend.

Intercooler Upgrades

If there is one power modification almost every Focus ST owner recommends first, it's the intercooler. Heat soak is one of the biggest limitations of the factory setup, making this upgrade noticeable even on a stock tune.

Popular options include:

1. COBB Front Mount Intercooler
2. Mishimoto Inctercooler
3. Depo Racing FMIC
4. Mountune Intercooler

Intake Systems

Popular choices include:

1. COBB Redline Intake
2. Mountune High Flow Intake
3. Mishimoto Performance Intake

Exhaust Systems

A quality 3-inch exhaust helps improve flow while giving the EcoBoost a much more aggressive sound.

Popular systems include:

1. AWE Touring Exhaust
2. COBB Catback Exhaust
3. MBRP Catback Exhaust

Tuning

This is where the Focus ST really wakes up and makes the most out of your bolt-ons.

The most common tuning platform is:

1. COBB Accessport

For custom tuning, the community consistently recommends:

1. Stratified Automotive
2. Edge Autosport
3. JST Performance

With a quality tune, intercooler, intake, and exhaust, 280-320 horsepower is very realistic while still being reliable.

The Biggest Mistakes When Modifying the Ford Focus ST

This platform is incredibly rewarding, but there are a few common mistakes.

First: Skipping The Rear Motor Mount

It’s a comfort mod, but it’s worth it.

Second: Ignoring The Factory Intercooler

Heat soak kills consistency. Upgrade it as soon as possible.

Finally: Buying Power Before Tires

Front-wheel-drive cars are a blast to drive, but only go as fast as their front tires will allow.

Conclusion

The Ford Focus ST remains one of the best all-around enthusiast cars ever sold in North America. It's practical enough to daily drive, capable enough for weekend autocross, and responds incredibly well to thoughtful modifications. Build it smart, choose quality parts, and you'll end up with one of the most entertaining front-wheel-drive cars ever built.

Mod your car with your friends at MartiniWorks.