Ford Focus ST Mk2 (ST225) Tuning Guide

Ford Focus ST Mk2 (ST225) Tuning Guide

The Ford Focus ST Mk2 (ST225), produced from 2006 to 2010, is a popular choice for car enthusiasts looking to unlock more performance from their vehicle. Equipped with the 2.5-litre turbocharged Duratec engine, the ST225 offers a solid foundation for tuning. Whether you're looking for a moderate increase in performance or an all-out upgrade, there are several key areas to focus on. This guide will cover the essential aspects of tuning your Focus ST225, common boosting issues, and an important engine modification to consider before tuning.

If you're looking to tune your Focus ST225, check out our wide range of tuning parts here. 

1. Engine and Performance Tuning

The Focus ST225’s 2.5-litre turbocharged engine is capable of delivering impressive power, but there’s always room for more. Here are the most common tuning modifications:

• ECU Remapping: One of the most popular tuning options for the ST225 is an ECU remap. A remap can provide significant gains in power and torque by adjusting the engine’s fuel, air, and timing settings. After a remap, the ST225 can easily reach around 250-270 horsepower, depending on supporting modifications and the quality of the remap. Many tuning companies offer stage 1 and stage 2 remaps, with stage 1 usually being a simple plug-and-play remap, and stage 2 requiring additional upgrades (such as a larger intercooler or a high-flow exhaust).
• Turbocharger Upgrades: While the stock turbo is fairly capable, many owners opt for larger turbochargers or hybrid options to significantly boost power. A bigger turbo can provide more air to the engine, allowing for higher levels of boost and, in turn, more power. However, it’s important to ensure that the rest of the engine can handle the increased performance, so supporting mods (like the fuel system and intercooler) are often necessary. Consider building your engine if you are adding a hybrid, or big turbocharger, check out out engine build parts here. 
• Intake and Exhaust: Upgrading the intake system and exhaust is another common tuning route. A larger, more efficient intake system can improve airflow to the engine, while a high-flow exhaust system helps to remove exhaust gases more quickly, allowing the turbo to spool faster and improve overall engine efficiency. Many ST225 owners opt for a larger downpipe and a sports exhaust to improve both performance and sound.

2. Boosting Issues

The Focus ST225 is equipped with a turbocharged engine, which means boosting issues can sometimes arise, particularly when tuning for more power. Here are the key components to check when experiencing performance issues related to boosting:

• MAP Sensor (Manifold Absolute Pressure Sensor): The MAP sensor monitors the pressure inside the intake manifold and helps the ECU adjust the fuel-to-air ratio. If the MAP sensor becomes dirty or fails, it can send incorrect information to the ECU, causing poor performance or hesitation under acceleration. Cleaning or replacing the MAP sensor can resolve many boosting issues.
• MAF Sensor (Mass Air Flow Sensor): The MAF sensor measures the amount of air entering the engine and ensures the correct air/fuel ratio. A faulty or dirty MAF sensor can result in the engine running poorly, affecting the turbo’s performance. Regular cleaning or replacement of the MAF sensor is recommended, especially if you notice a drop in power or fuel economy.
• Boost Solenoid: The boost solenoid controls the turbo boost levels. If the solenoid fails, you may experience inconsistent or lower-than-normal boost, leading to a lack of power. Inspect the solenoid for any signs of wear or damage and replace it if necessary.

If these components are in good condition and you're still experiencing boosting issues, it's worth datalogging the car using Forscan or a similar diagnostic tool. This can provide more detailed information on the car’s performance and highlight any other potential issues with the turbo system.

3. Block Mod (Engine Block Shim Mod)

A critical modification that many Focus ST225 owners opt for before tuning is the block mod, which involves inserting shims into the engine block. This mod is specifically designed to prevent issues with the engine block becoming oval or warped under high boost pressures, which can lead to catastrophic engine failure.

The problem stems from the fact that the stock block on the ST225 can sometimes deform when subjected to the high power levels produced by tuning. The block mod prevents this by providing additional reinforcement to the block, ensuring it maintains its shape even under higher boost levels. It’s highly recommended to carry out this mod before performing any major tuning work, particularly if you plan on running higher boost pressures.

The block mod is not a complicated process, but it should be performed by a professional who has experience with these engines. It’s a relatively affordable modification compared to the cost of a potential engine rebuild, making it a smart investment if you're looking to tune your ST225 for more power.

4. Supporting Modifications

If you plan to take your Focus ST225’s performance beyond stock levels, there are several supporting modifications to consider. These upgrades can help ensure that your car runs smoothly and reliably with the increased power.

• Upgraded Intercooler: When you increase the boost, the temperature of the intake air rises, which can cause performance issues. A larger, more efficient intercooler can lower the intake air temperature, improving performance and preventing heat-related issues. JXL Performance recommends AIRTEC Motorsport
• Upgraded Fuel System: With higher performance, the stock fuel system may struggle to provide the necessary fuel to the engine. Upgrading the fuel pump, injectors, and fuel pressure regulator ensures that the engine gets the fuel it needs to support increased power levels.
• Upgraded Clutch: As power increases, the stock clutch may begin to slip, especially if you’re running higher torque. A performance clutch kit with increased holding capacity is a worthwhile investment to ensure that your car can handle the additional power without slipping or damaging the transmission. JXL Performance recommends LUK Ford Focus RS Mk2 Clutch Kit
• Brakes and Suspension: Upgrading your brakes and suspension should be considered to handle the increased performance. Performance brakes with larger discs and upgraded suspension components, such as coilovers or adjustable shocks, can help you manage the car's handling and braking under high-speed driving.

Check out our full range of aftermarket and tuning parts for the Focus Mk2 ST225 here

5. Conclusion

The Ford Focus ST Mk2 (ST225) is an excellent base for tuning, thanks to its robust engine and well-balanced chassis. Whether you’re looking for a modest power increase or a full-blown performance upgrade, there are numerous tuning options available, from ECU remaps to turbo upgrades. However, before you start pushing the limits of the engine, it’s essential to address common boosting issues and consider performing the block mod to prevent engine damage.

Remember, tuning should be done carefully and progressively, with supporting modifications to ensure that the car can handle the increased performance. Always consider professional advice and work with experienced tuners to make sure your Focus ST225 remains reliable and enjoyable after modifications.