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Mk2 Focus ST 225 Tuning Guide (Stage 1, 2 & 3)

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Last Updated on: 7th September 2023, 12:45 am

The mk2 Focus ST 225 utilises the 2.5L 5-cylinder Volvo engine, it is a powerful platform with significant horsepower and torque increases available with simple bolt-on modifications.

There are many levels of tuning for the mk2 Ford Focus ST and some things you should be aware of at specific levels of tuning, which we discuss in this article.

mk2 focus st 225

Block Mod

When it comes to modifying these cars, the “block mod” (steel shims between the cylinder liners) is a controversial topic, some people swear by it, while others without it have no issues.

The 2.5 Volvo engines used in this car have an increased risk of the cylinder liners cracking, shimming between the liners can help increase the strength of the engine.

Installing the block mod is recommended, although it does not ensure that cylinder liner cracking will not happen, it does reduce the chance. It usually costs between £600 and £900.

Clutch

The clutch used in the mk2 Focus ST is not ideal for increased power. Sometimes even standard cars can experience clutch slippage.

Although not every Focus ST has clutch issues, it is likely to happen on higher powered cars, usually beginning to appear above 280 hp.

Many owners decide to fit the clutch from the mk2 Focus RS, although any clutch upgrade would work.

Stage 1 (up to 280 hp)

A stage 1 Focus ST 225 only requires a remap which will see up to around 280 hp.

If you wish to see higher power, simple bolt-on modifications such as a decat, induction kit or performance air filter can help.

Recommended Mods

  • Block mod
  • Upgraded clutch
  • Performance air filter
  • Decat or sports cat

Stage 2 (up to 320 hp)

A stage 2 Focus ST 225 with the appropriate modifications should see about 300-320 hp. Without an upgraded clutch you may see more clutch slippage.

It’s also recommended to install the RS or an upgraded oil cooler to help keep oil temperatures within optimum range.

Required Mods

  • Performance air filter
  • Decat or sports cat (3 inch diameter)
  • Upgraded intercooler
  • 3 inch diameter exhaust

Recommended Mods

  • Performance induction kit
  • Big boost pipes (2.5 inch diameter)
  • Upgraded clutch
  • Block mod
  • RS or upgraded oil cooler

Required mods are needed to run the stated power figure, recommended mods improve reliability and may see higher power output.

Stage 2+ / Stage 3 (up to 340 hp)

A stage 2+ (sometimes referred to as stage 3) mk2 Focus ST will see between 320 and 340 hp.

It involves the installation of larger 440 cc fuel injectors, the Turbosmart or Forge wastegate actuator along with the usual bolt-on modifications for stage 2.

Required Mods

  • Same mods as those from stage 2
  • 440 cc or 550 cc fuel injectors
  • Turbosmart or Forge wastegate actuator

Recommended Mods

  • Performance induction kit
  • Big boost pipes (2.5 inch diameter)
  • Upgraded clutch
  • Block mod
  • RS or upgraded oil cooler

Required mods are needed to run the stated power figure, recommended mods improve reliability and may see higher power output.

Stage 3 / Stage 4 (typically 380 hp or more)

A stage 3 (sometimes referred to as stage 4) involves the installation of a more capable turbocharger, typically a hybrid turbo.

This will usually take the vehicle to around 380 hp, though it could be more or less depending on the turbocharger used and the supporting modifications.

At this power level you will almost certainly experience clutch slippage so an upgraded clutch will be required.

Sustained throttle input will also cause the oil temperature to rise possibly to a dangerous level, requiring the need for the RS or upgraded oil cooler.

Larger fuel injectors (typically 550 cc) will be required depending on the level of power you desire.

Engine Forging

The standard engine in the mk2 Focus ST 225 is usually fine to about 400 hp, after this power level will require forging the engine internals (forged pistons and rods).

References & More Information

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  • Andy Lewin

    Andy Lewin is a senior mechanic, ASE qualified master technician, and an experienced automotive engineer. He's passionate about serving the automotive community with the highest-quality and trustworthy information on all things automotive. He loves to write about car repairs, maintenance, car modifications and tuning, faults, and much more.

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