Produced from 2012 until 2018, the Ford Focus ST was equipped from the factory with the 2.0L I4 EcoBoost. As one of the smaller engines in the EcoBoost family, the 2.0 doesn’t always get the credit it deserves thanks to the 2.3L, 2.7L, and 3.5L versions which outsize and outpower the Focus ST’s engine.
The 2.0 turbo engine in the Focus ST produces 252hp and 270lb-ft. of torque bone stock. Fortunately, the turbocharged aspiration allows for some significant horsepower gains with just a few bolt-on mods. The Focus ST is capable of generating in excess of 300whp with the performance upgrades we are going to discuss in this guide.
1st Gen vs. 2nd Gen 2.0 Focus ST
The Ford Focus was discontinued in 2020, however, the Focus ST was left in the dust back in 2018. The only generation of Focus ST produced was the Focus MK3 (C436) models. However, in 2016 Ford made numerous updates to the 2.0L EcoBoost engine.
Before we dig into the best Focus ST mods, it’s important to understand the differences between the 2012-2015 models and the 2016-2018 models. The upgrades ultimately made the 2016+ Focus ST models more capable from a tuning and performance perspective.
Here are the updates made to the 2016+ 2.0L EcoBoost engines:
- Turbo upgraded to twin-scroll
- New stronger aluminum block
- Compression ratio increase from 9.3:1 to 10:1
- A redesigned cylinder head
- Various fuel and oil system upgrades
The updates made to the engine were to improve low end torque and overall engine and turbo efficiency. While stock power levels didn’t increase because of the updates, they do make the 2nd gen engines capable of producing more power.
With that being said, a Focus ST with second gen 2.0 EcoBoost with the same exact mods will probably produce somewhere around 15whp more than a 2012-2015 ST. While not extremely meaningful, it’s something to keep in mind if you are considering purchasing a Focus ST for performance purposes.
5 Best Ford Focus ST Engine Mods
- Flash Tuner
- Performance Intake
- Intercooler (FMIC)
- E85 Fueling
These 5 mods are the best starting point in our opinion for a Focus ST. One thing we did intentionally leave off of the list is turbocharger upgrades. Turbo upgrades require a lot of consideration and additional supporting mods so we’ll cover it later on in its own post.
These mods aren’t in any specific order although we would say that a tune and intake are the two best places to start. This guide will cover the above mods and go into more detail on the performance benefits, power gains, and costs.
1. Focus ST Flash Tuner
A flash tuner is one of the best modifications for a Focus ST because it offers the best bang-for-the-buck. Additionally, a tune is the foundation for further modification. When combined with the other mods on this list a tune can add up to 50whp and 70wtq.
We consider tunes the foundation to mods because without a proper tune the other mods on this list won’t offer their maximum benefit. Tunes adjust the fueling, AFRs, boost targets, etc. based on the other modifications on the car to maximize the power gains from the additional upgrades.
While custom tuning or dyno tuning is an option, we recommend starting with a flash tune. Every time you further modify your car you will need to have it re-tuned if you opt for custom tuning. On the other hand, flash tunes auto adjust when other upgrades are added and also come with a range of different prebuilt tunes. Custom tuning still requires a flash tuner as well unless you are getting it dyno tuned.
Best Focus ST Tunes
Since flash tuners have pre-built tunes programmed into them, picking a tuner from a reputable company is important. While there are a limited selection of tunes for the Focus ST, there are some highly reputable options available:
- Cobb Accessport
- SCT X4
Cobb and SCT are the two most popular Focus ST tuners. There are a few additional options you have when choosing a tuner. Companies, such as Stratified Tuning, sell the Cobb Accessport packaged with custom remote tuning services included. Other companies offer the same thing for the SCT as well, but pretty much every reputable custom tuning company out there uses either Cobb or SCT for the Focus ST.
We recommend buying the flash tuner itself first to start and then considering a custom tune once you have added all the mods you have planned. Both of the above options are completely plug-and-play and come with multiple prebuilt tunes.
Tuner Price: $350-$550
Focus ST Tune Power Gains: 20-50whp and 30-70wtq
2. Focus ST Upgraded Intake
An upgraded intake probably comes second on our list for best first mods, after a tune. Tunes primarily make more power by increasing the amount of boost that the turbo is running. Increasing boost requires more airflow. The stock intake is pretty good from the factory and usually won’t cause any issues for a Focus ST running a modest tune. However, once you begin running a more aggressive tune and further modify your engine the stock intake starts to become restrictive.
Since the stock system is pretty decent, you should only expect to get ~5whp from an intake on a stock ST with a modest tune. However, once you add the additional mods on this list and a more aggressive tune those gains can increase to about ~10whp.
The additional benefit of a tune is that it makes the turbo more efficient which makes it more reliable. The more air you bring into the engine the less work the turbo has to do pressurize it which takes stress off of it, increasing horsepower and reliability.
Focus ST Cold Air Intake Benefits
- 3-10whp and similar torque gains
- 40%+ increases to airflow
- Faster turbo spool and greater turbo efficiency
- Cool intake and turbo sounds
Open Air vs. Closed Box Intakes
The term cold air intake isn’t necessarily accurate for an upgraded Focus ST intake. Cold air intakes reroute the air filter to a lower part of the engine so that it sucks in more outside air and less engine bay air. Focus ST intake systems all use the factory intake location and don’t reroute the filter, so they aren’t truly cold air intakes.
There are two different intake designs: open vs. closed. With open intake systems the air filter is completely open and exposed to the engine bay air. Closed systems will put the air filter inside an enclosed box so that the intake isn’t sucking in hot engine bay air.
Open intakes will have higher airflow increases and therefore slightly higher power gains. Closed intakes will offer less airflow, less power gains, but slightly colder intake air temps. However, since the intake air gets heated up by the turbo anyways and then passes through the intercooled, the benefit of colder intake air temps is pretty much zero.
Therefore, our preference is open air systems since they provide the biggest increases to air flow and are the least restrictive.
Best Focus ST Intakes
- AF Dynamic – true open air system offering the best bang-for-the-buck price wise
- K&N – one of the most reputable brands on the market, good price for trusted quality
- Roush – while this appears to be an open system it actually seals with the hood making it enclosed. Doesn’t void warranty
3. Focus ST Upgraded Downpipe
Downpipes are unique to turbocharged engines and are the first component of the exhaust system in turbo cars. The downpipe connects directly to the turbo and also houses the primary catalytic converter. Since the downpipe is catted it is highly restrictive. This restriction creates a lot of backpressure for the turbo which reduces turbo efficiency.
The stock downpipe is great for emissions but bad for performance. You want the least amount of backpressure possible behind the turbo which is why upgrading your downpipe is a fantastic performance mod. Outside of producing power gains it also improves turbo reliability.
Upgraded Downpipe Benefits
- 5-15whp gains
- 10-20wtq gains
- Faster turbo spool
- Improved turbo efficiency and reliability
- Slightly louder exhaust note (not as obnoxious as a cat-back)
Less backpressure creates lower exhaust gas temps and reduces the stress on the turbocharger allowing it to spool more quickly. You might read on forums or other blogs that you should upgrade your cat-back exhaust system and that the downpipe doesn’t matter as much. This is completely false. Virtually all of the exhaust backpressure is created by the downpipe which is why it offers such great power gains.
Don’t expect to get anywhere near these level of power gains with a cat-back or even full exhaust system unless you also upgrade the downpipe.
Focus ST Catless vs. Catted Downpipes
A catless downpipe is simply a hollow exhaust pipe with zero restriction inside it. Therefore, it provides the biggest power gains since it eliminates virtually all of the backpressure created. However, the downside being that it removes the catalytic converter, making it illegal.
The legal option is going with a high-flow catted downpipe. These downpipes keep the exhaust legal and emissions friendly while still improving exhaust flow and reducing backpressure by using a less restrictive internal structure inside the piping. They still offer great performance benefits and better exhaust flow, but expect a high-flow downpipe to produce about 5whp less than a catless downpipe on the Focus ST.
The other downside to high-flow options is that they are more expensive. Catalytic converters use rare earth metals inside them which makes them a lot pricier than a catless downpipe that is literally a hollow piece of stainless steel.
Best Focus ST Downpipes
- Cobb – $695
- cp-e – $635
- Accelatec – $500
- Whoosh Catless – $175 (not sold online anymore)
No one sells catless downpipes online anymore due to EPA crackdowns. The best options above are all catted high-flow downpipes. If you are also wanting to upgrade your full exhaust system, Cobb offers a full turbo-back exhaust system for $1,425 that includes their catted downpipe and cat-back system. We really only recommend choosing a full system if you want the louder exhaust note since you won’t get that much additional performance benefit for the extra $730 the turbo-back systems costs.
4. Intercooler (FMIC) Upgrades
Front mount intercoolers are not only important for performance but also extremely important for reliability. Intercoolers don’t provide the biggest power gains but instead provide more consistent power delivery and healthier engine temps.
The stock intercooler is effective on the stock engine but once you add a tune and increase boost it quickly becomes overwhelmed. The stock intercooler begins to experience heat soak where it cannot efficiently cool the large amounts of air before entering the engine. The end result is passing a lot of hot air into the combustion chamber.
Hot air is less dense and causes the engine to pull timing to prevent misfires and pre-detonation issues. When you are consistently hitting the throttle, whether just driving aggressively on the streets or during track days heat soak can can cause you to start losing power quickly. On the stock intercooler you can lose about 20whp when the intercooler is experiencing a lot of heat soak.
An upgraded intercooler will add about 5-10whp but will also prevent the engine from losing power during aggressive driving.
Focus ST Upgraded Intercooler Benefits
- 5-10whp gains and similar torque gains
- Lower intake air temps
- Consistent performance through heat soak reduction
- Lower chances of misfires or pre-detonation
Best Focus ST Intercoolers
5. Focus ST E85 Fueling
First of all, make sure you are running 91 or 93 octane if you are tuned. Higher octane allows for better timing and reduces the chances of engine knock. While race gas is an alternative option it is very expensive and not always readily available. Therefore, the best option for the Focus ST is E85 ethanol fuel.
The stock fueling system on the 2.0 EcoBoost can handle a blend of E85. While running 100% E85 will require some fueling upgrades, you can safely run an E30 blend with the proper tune.
Ethanol or E85 has an octane rating of 108. Additionally, it burns cooler and cleaner than traditional gasoline which allows for more aggressive timing and more boost. Running an E30 blend with a proper ethanol tune can add 10-15whp to the Focus ST.
Power gains are even higher when you run 100% E85 especially alongside an upgraded turbo but this will require fuel pump upgrades, port injection, etc.
E85 Fuel Benefits
- 10-15whp and similar torque gains
- Allows for more aggressive timing
- Allows for more boost
- E85 is cheaper than pump gas
An additional alternative to running E85 is using methanol injection. However, this requires a standalone methanol injection kit and is a more advanced fueling mod that we won’t go into depth about in this guide.
6. Focus ST Motor Mounts
This is a bonus “mod” that we recommend to all owners who are adding additional power to their 2.0L Focus engines. The Focus ST engine shakes a lot. This creates a lot of wheel hop and bounciness between gears.
The stock motor mounts are way too soft which allows the engine to shake too much. When you throw mods and extra power at the ST it makes the engine shake even more resulting in more wheel hop. This causes less power to get sent to the ground and ultimately makes your car feel slower than it should under hard acceleration. It also makes the car a bit more difficult to control under acceleration.
Stiffer motor mounts cost about $150 and will help provide way better traction and grip on the road when you want to floor it.
Ford Focus ST Power Potential
We consider the 5 mods listed here to be “full bolt-on”. While there are additional mods you can perform like a full exhaust system, an intake manifold spacer, etc. we left these off the list as these mods don’t provide enough power gains to justify the costs. With only these mods mentioned, your Focus ST will produce 300-320whp and 340-360wtq. Considering all of these mods can be made for sub $2,000 makes the Ford Focus ST a very mod-friendly car.
While the 2.0 EcoBoost can handle more power getting to those levels will require an upgraded turbo, advanced fueling mods, and eventually internal upgrades.
To recap, a tune is the best place to start when modifying your Focus ST. Providing up to 50whp gains a tune is the most effective upgrade for power gains. Next, adding an upgraded intake is recommended to help the engine and turbo get enough air for the added boost. An upgraded downpipe is the only exhaust mod that we recommend unless you want a louder exhaust note. Power gains from a cat-back exhaust system aren’t good enough to warrant the cost. Next an intercooler is recommended to provide more consistent power, prevent power loss, and improve engine reliability. Lastly, the best “free” mod is running E85 fueling alongside a proper ethanol tune.
Ford underrated the Focus ST power numbers from the factory with bone stock cars dyno’ing in the 240-250whp range. These 5 best mods will get you to 300-320whp meaning you can achieve up to 80whp gains for less than $2,000 in mods. Keep in mind the differences between the 1st gen and 2nd gen EcoBoost engines. First gen engines will likely be on the lower end of all the quoted figures.
Let us know what Focus ST mods you are running and the power levels you are making.