In our 5 Best Ford Focus ST Mods guide, we covered an upgraded intercooler as one of our favorite performance upgrades. Intercoolers not only provide solid power gains but also allow for more consistent performance and a healthier engine via lower intake air temps. The stock intercooler on the Focus ST is great when you’re running stock boost levels, but it is easily overwhelmed once boost is increased and more air is entering the engine.
This guide is going to discuss the performance benefits of upgrading your intercooler, important considerations like intercooler design and sizing, and provide recommendations on our favorite Focus ST FMICs.
Focus ST Intercooler Basics
Turbocharged engines, like the 2.3L EcoBoost in the Focus ST, produce a lot of heat. The turbo itself operates under very high temperatures and therefore heats up the air it compresses significantly. Since hot air is bad for combustion, the air is passed through the intercooler before entering the combustion chamber. This cools the air down after it has been heated up from being compressed by the turbo.
The Focus ST has an air-to-air intercooler. It sits within the front bumper and uses outside air to cool the compressed air within it. Intercoolers have “air galleries”. Outside ambient air passes through these air galleries as you drive which cools down the air inside the intercooler, which is then sent to the combustion chamber.
The stock intercooler is totally sufficient for stock STs and those running stock boost levels. However, once a tuner is added and more air is being compressed by the turbo, the stock intercooler becomes inefficient. This can lead to increased IATs and various performance issues like heat soak, knock, and misfires. Upgraded intercoolers increase efficiency and cooling capacity which leads to lower IATs, consistent performance, power gains, and a healthier engine.
FMIC Sizing & Design
Not all FMICs are the same. There are two different aspects we look at when choosing a performance intercooler. The first is the design, which can come in the form of bar and plate or tube and fin. The design impacts how the air galleries are constructed which in turn impacts efficiency and cooling capacity. The second is the intercooler sizing. Larger intercoolers are more effective and can cool larger volumes of air. However, there is a such thing as going too big.
Bar & Plate vs Tube & Fin
This topic is a bit more nuanced, but important to consider. Any upgraded intercooler will outperform the stock intercooler, but not all are made equal. As we discussed, air-to-air intercoolers use air galleries to cool charge air. These air galleries can be designed in a bar and plate or a tube a fin layout.
Bar and plate intercoolers have more rectangular air galleries which increases the amount of ambient air that passes through the intercooler. They also tend to be more durable, albeit this means they also weigh a bit more. One of the best features of bar and plate designs is that they tend to have less of a pressure drop, meaning they can hold more boost (psi).
Tube and fin intercoolers have more curved air galleries. They have slightly less capacity but are also more efficient. They are lighter which is good for weight savings, but they are also less durable and can easily be damaged from rocks and other things that might hit the intercooler while driving. Additionally, tube and fin intercoolers also have more pressure drop and can’t handle as much boost.
Overall, we recommend bar and plate intercoolers. Despite being heavier they have more cooling capacity and less pressure drop which results in better performance.
The second differentiating factor for intercoolers is their sizing. Intercooler sizing has two different components: core size, and surface area size. The core refers to the internal part of the intercooler and the volume of air it can hold. Surface area is the exterior part of the intercooler that faces outwards from your front bumper. Larger surface areas catch more ambient air and therefore result in lower IATs.
A larger core means the intercooler can hold more air, which is important for people also running an intake along with a tune. When more air is brought into the engine, the small size of the stock intercooler can’t always hold enough air which results in hotter IATs. Also, the larger it is, the longer the air path is inside the intercooler which means it gets cooled down more effectively. Core sizes for the Focus ST range from 60%-200% larger than the stock intercooler.
With surface area, the larger the better. More surface area means more outside air can pass through it which improves effectiveness. Most aftermarket Focus ST intercoolers have 20%-50% larger surface areas.
Can an Intercooler Be Too Big?
Absolutely. I like to think of intercoolers in stages, similar to tunes. You have “Stage 1” and “Stage 2” intercoolers. Your typical stage 1 intercooler will have a core volume of about 100%-130% larger than stock. Comparatively, stage 2 intercoolers will be closer to the 200% larger mark. Surface area sizing will be 20%-30% larger compared to 40%+ larger.
If you don’t have an upgraded turbo, you should stick to the smaller stage 1 intercooler. Using a larger intercooler when you aren’t pushing that much air will cause for greater pressure drops inside the intercooler and will also increase turbo lag.
Most stage 1 intercoolers can handle over 500whp. Considering you can’t make these power levels without a built engine and upgraded turbo, there is no need for a larger intercooler if you are simply tuned and full bolt-on.
Focus ST Intercooler Piping Kits
In addition to upgrading your intercooler, you can also upgrade your intercooler piping, or chargepipe. There are two different pipings: hot-side and cold-side. Hot side refers to the piping that carries the air from the turbo to the intercooler. It’s called hot side since the air hasn’t been cooled by the intercooler yet. The other is the cold-side which carries the air from the intercooler to the engine. This side is also frequently called the chargepipe since it carries charged (compressed) air.
Upgrading the piping will increase air flow to the intercooler and to the engine. It also allows you to add a blow-off valve for the cool “pssshh” noises. These are decent upgrades if you can afford them, but they really aren’t necessary unless you are pushing big power, want the blow-off valve sounds, or want meth injection.
We have a full guide on Focus ST Chargepipe Upgrades if you want to dig further here.
Focus ST Upgraded Intercooler Benefits
- 5-10whp and torque gains
- 40+ degree reduction in IATs
- Consistent performance
- Reduced heat soak
- Knock and misfire prevention
Intercooler performance gains tend to be linear to existing power and tuning. The more power you have and the more aggressive the tune, the more performance benefits you’ll get from an intercooler. Gains up to 10whp and even greater are possible with an aftermarket intercooler.
Not only will an intercooler help add power, but it will also prevent power loss. When you’re driving aggressively, like on a track, the constant high rpm, high boost nature can cause heat soak. This can cause the Focus ST to actually lose 10-20whp. An upgraded intercooler will not only add power, but also prevent power loss from heat soak providing more consistent performance.
The other important benefit of an intercooler is reliability. Heat is the killer of all engines. Hot air can cause the engine to pull timing, misfire, knock, or pre-detonate. Cooler IATs result in lower engine temps, lower exhaust gas temps, better timing, and less chance of knock. Therefore, an intercooler is one of the best reliability mods for tuned Focus ST’s.
Best Focus ST Intercooler Upgrades
There are plenty of upgraded intercooler options for the Focus ST. Important considerations are the design and sizing. Just remember, the biggest intercooler isn’t always the best intercooler. I’m guessing the majority of readers here don’t have an upgraded turbo, so our first recommendation is probably the best bet for the majority of you.
Additionally, you can also upgrade the intercooler piping, although it’s not really necessary unless you are pushing past 500whp. While any upgraded intercooler is better than the stock one, we stay away from the Cobb intercooler as it’s a bit small, and the Mishimoto one since it is a tube and fin design and pricey for its value.
Our Top Pick – Focus ST CVF Street Intercooler
CVF offers our favorite Focus ST intercooler as it provides the best combination of price, quality, and performance. Their street intercooler has a core volume 115% larger than the stock core, and has a surface area about 30% larger. Testing has shown a decrease in IATs by 41 degrees. It is a bar and plate intercooler so it offers the least pressure drop, highest boost capacity, and is extremely durable. Additionally, it has high-flow end tanks to improve airflow to and from the intercooler.
CVF claims the intercooler is capable of handling up to 670hp, which is plenty enough for any highly modified ST. Additionally, they offer piping and chargepipe kits for anyone looking for additional flow, meth injection, or the cool blow-off valve noises. All in all, CVF is our favorite brand on the market and also comes in as one of the most affordable Focus ST intercoolers.
2.3L Ford Focus ST Intercooler Upgrade Summary
Upgrading your Focus ST intercooler is one of the best performance and reliability mods for tuned STs. In addition to offering solid 10whp power gains an intercooler will also allow for more consistent performance and prevent pre-detonation, knock, misfires, and heat soak. This creates not only a more powerful, but also a more reliable engine when tuned.
We recommend looking at two things when choosing an intercooler: design and sizing. We prefer bar and plate intercoolers since they hold boost better and have larger cooling capacity. Also, they are a lot more durable and less likely to be damaged from rocks while driving. Sizing-wise, we recommend sticking to an intercooler in the 100%-130% larger range, unless you have an upgraded turbo. Sticking to a smaller intercooler will prevent boost pressure drops and increased turbo lag. If you are shooting for 500whp+ or frequently track your ST, then we recommend going as big as you can get.
CVF makes our favorite intercooler on the market. It is 115% bigger so it provides ample cooling capabilities but also isn’t too big to where it will create lag or allow for pressure drop. It’s the best bang for the buck and can handle beyond 600whp. cp-e is our favorite intercooler for anyone looking for the biggest option on the market.
If you are interested in other mods, check out our 5 Best Focus ST Mods guide.