Mk2 Ford Focus ST225 Engine Tuning (Complete Guide)
Updated: Feb 8
✔ This article has been fact checked.
The Mk2 Ford Focus ST (2005-2010) comes as standard with 225hp. The Volvo 2.5L 5 cylinder engine found under the bonnet is a capable engine with lots of power potential.
There are usually 4 stages of tuning for an ST225:
Each tuning stage requires a different set of modifications and upgrades to reach the power output listed.
In this article, we will explain what modifications it takes to achieve certain power levels with the Mk2 Focus ST225 and the power you can expect at each stage of tuning.
Stage 1 (~260-275hp)
A stage 1 upgrade is usually as simple as a remap. It'll usually provide around 260-275hp and 360-380 ft-Ib of torque.
Some tuning companies and manufacturers recommend installing a couple of extra mods for provide a better result, including the following mods.
Performance air filter (typically a foam filter)
Induction kit
De-cat exhaust
While these modifications are not required for a stage 1 tune, they will enhance the results, allowing your Ford Focus ST to be closer to the upper end of the range (around of 275hp).
It's also advised to upgrade your clutch since the clutches on the ST225 are prone to failing when tuned.
Note: When de-catting your car, it will not pass it's MOT as it will fail emissions testing, making it illegal on the road, it will also be slightly louder. Also, a decat exhaust may be required for pop and bang maps.
Stage 2 (~300-320hp)
Tuning your Focus ST225 to stage 2 will require some additional modifications, such as the following. The modifications below are usually required to see 320hp and around 420 ft-lb of torque on the Mk2 Focus STs'.
Performance air filter (typical a foam filter)
Induction kit
De-cat exhaust
3-inch exhaust system (cat-back and down pipe)
Larger intercooler
While you could get away with not installing a de-cat or down pipe, it'll limit the power output and you'll likely only reach around the 300hp mark on a stage 2 tune.
Stage 2+ (320-340hp)
A stage 2+ (oftentimes called stage 3) tune on the mk2 Focus ST will typically see a maximum of around 340hp.
At about 320hp, the fuel system is the limiting factor and needs upgrading to see a higher power output.
To reach the maximum power of the stock KO4 turbocharger you will need the following modifications on your ST225.
Upgraded wastegate actuator (Turbosmart IWG75 unit)
Ford Focus RS 440cc or 550cc fuel injectors
The upgraded actuator has a stiffer spring, allowing it to handle a higher boost pressure without opening the wastegate. You may notice a drop in boost pressure and power at high rpms without upgrading the wastegate actuator.
340hp seems to be the limit of the stock turbocharger on the Mk2 Focus ST.
Stage 3 (340hp+)
Stage 3 is also sometimes referred to as a stage 4 tune depending on the tuning company and manufacturer. It's usually what comes next after you've maxed out the stock turbocharger and need to upgrade to a larger hybrid turbo.
There are a few types of st225 turbocharger upgrades: