Ford Focus RS MK3 Intercoolers & Cooling Upgrades

Does the MK3 Focus RS need an upgraded intercooler?

The standard MK3 Focus RS intercooler is adequate for an unmodified road car. Once the engine is remapped, however, charge temperatures can increase very quickly during repeated acceleration, hard road driving and track use.

As charge temperatures rise, the ECU may reduce ignition timing and power to protect the engine. An upgraded intercooler therefore provides two important benefits:

• Increased peak performance with suitable tuning
• More consistent performance during repeated hard use

For a Stage 1 Focus RS, we recommend an intercooler upgrade, although it is not an essential hardware requirement.

For a proper Stage 2 setup, an upgraded intercooler is essential and should be fitted before the car is calibrated.

AIRTEC intercooler upgrade for the Focus RS

The AIRTEC Motorsport Focus RS intercooler upgrade uses a large 100mm bar-and-plate core with cast end tanks and an air-ram scoop designed to direct airflow through the core.

It is suitable for:

• Standard Focus RS models
• Stage 1 cars
• Stage 2 cars
• Stage 3 and larger-turbo builds
• Fast-road and track use

The larger intercooler does not introduce any noticeable additional turbo lag in our experience.

How much cooler is the AIRTEC intercooler?

AIRTEC publishes its own three-run test data for this intercooler. With an ambient temperature of 16°C, AIRTEC recorded:

• Charge temperature entering the intercooler: 155°C, 157°C and 160°C
• Charge temperature leaving the intercooler: 18°C, 18°C and 19°C

These are AIRTEC’s test results rather than figures recorded by Wayside Performance, and results will vary with boost pressure, vehicle specification, ambient temperature, road speed and testing method.

They do, however, demonstrate the cooling capacity available from the larger core during repeated testing.

Intercooler capacity and construction

AIRTEC lists the following intercooler capacities:

• Original Ford intercooler: 9.8 litres
• AIRTEC intercooler: 19.7 litres

The AIRTEC unit therefore offers approximately twice the internal capacity of the factory intercooler, together with a wider, taller and deeper core.

Its main features include:

• 100mm bar-and-plate core
• High-flow cast end tanks
• Single-pass core design
• Air-ram scoop to direct airflow through the core
• Pro-Series black finish
• Optional AIRTEC logo

How much power can an upgraded intercooler add?

On a tuned Focus RS, approximately 10–15 bhp is a reasonable real-world contribution when the intercooler is combined with suitable ECU calibration.

The exact gain will depend on:

• The car’s existing tune and hardware
• Starting charge temperatures
• Ambient conditions
• Boost pressure
• Whether the original intercooler was already heat soaked

The benefit should not be judged only by a single peak-power figure. The larger improvement is often the car’s ability to repeat its performance without rapidly losing power as temperatures increase.

Focus RS intercooler recommendations by tuning stage

Standard Focus RS

The factory intercooler is generally sufficient for an unmodified road car.

An upgraded intercooler can still be fitted to a standard car and may be worthwhile where the vehicle is driven hard, used on track or being prepared for future tuning.

Stage 1 Focus RS

An upgraded intercooler is recommended at Stage 1, particularly for cars used for repeated acceleration, fast-road driving or track days.

It is not essential for a normal Stage 1 road car, but it will help control rising temperatures and maintain performance more consistently.

Stage 2 Focus RS

An upgraded intercooler is essential for Stage 2.

The higher boost and additional airflow create more heat, so relying on the original intercooler can result in rapidly increasing charge temperatures and inconsistent performance.

Stage 3 and larger-turbo Focus RS

The AIRTEC intercooler is suitable for Stage 3, hybrid-turbo and larger-turbo builds.

For these applications, we strongly advise considering the complete intercooler and big boost pipe package to improve airflow throughout the charge system.

Intercooler only or big boost pipe package?

The standard intercooler upgrade connects to the original boost-pipe system and is sufficient for most Stage 1 and Stage 2 cars.

The AIRTEC intercooler and 2.5-inch big boost pipe package replaces the restrictive original 2-inch boost pipes with larger 2.5-inch alloy pipework and silicone hoses.

Choose the intercooler only if:

• The car is standard or Stage 1.
• The car is running a typical Stage 2 setup.
• You want the main cooling benefit at a lower overall cost.
• You are happy to retain the original boost pipes.

Choose the intercooler and boost pipe package if:

• The car is running Stage 3 software.
• A hybrid or larger turbo is being fitted.
• You want to improve airflow through the complete charge system.
• You are building the car for higher future power.

Are 2.5-inch boost pipes required for Stage 1 or Stage 2?

No. The larger boost pipes are not required for Stage 1 or Stage 2, although they can still provide an improvement.

The standard boost pipes have not caused reliability problems in our experience. The reason to upgrade is primarily to replace the original 2-inch pipework with a larger and less restrictive 2.5-inch system.

For a Stage 3 or larger-turbo car, the big boost pipes are strongly advised because the engine is moving considerably more air.

Benefits of the AIRTEC big boost pipes

The AIRTEC boost pipe system uses lightweight alloy hard pipes connected by reinforced silicone hoses.

The benefits include:

• Increasing pipe diameter from 2 inches to 2.5 inches
• Reducing airflow restriction
• Supporting increased airflow on higher-powered cars
• Swaged pipe ends to help prevent hoses moving under higher boost
• Compatibility with the original Ford and common aftermarket intercoolers

The boost pipes are a direct replacement and do not require permanent modification to the car.

Does the AIRTEC intercooler require cutting?

No. AIRTEC states that the intercooler fits behind the original front bumper without cutting or trimming.

The front bumper must be removed to gain access, but the upgrade can be returned to standard in the future.

The kit includes the required fixtures, fittings and installation instructions. AIRTEC quotes an approximate fitting time of one to two hours, although the actual time will depend on experience, workshop equipment and the condition of the vehicle.

Does a Stage 1 or Stage 2 Focus RS need an uprated radiator?

No. The original Focus RS radiator is more than adequate for a normal road-driven Stage 1 or Stage 2 car when the cooling system remains in good condition.

An intercooler and radiator perform different jobs:

• Intercooler: Cools the compressed air entering the engine.
• Radiator: Controls engine-coolant temperature.

A remapped road car commonly benefits from an intercooler upgrade without requiring the main engine radiator to be replaced.

When is the AIRTEC radiator worthwhile?

The AIRTEC Motorsport Focus RS radiator is most relevant for:

• Cars used regularly on track
• Vehicles subjected to prolonged hard driving
• High-output builds producing sustained additional heat
• Cars operated in particularly hot climates
• Replacing an original radiator that has already failed or become damaged

If the standard radiator needs replacing, the AIRTEC unit is a sensible opportunity to upgrade rather than fitting another original unit.

AIRTEC states that its radiator uses a 40mm aluminium core and increases capacity from 11.34 litres to 12.99 litres, approximately 15% more than the original Ford radiator.

It uses the original mounting points and connectors and does not require cutting or trimming.

Intercooler versus radiator upgrade

For most tuned road cars, upgrade the intercooler first.

The intercooler directly controls the temperature of the compressed air entering the engine and becomes increasingly important as boost pressure and power are raised.

The radiator should generally remain standard unless the car is used regularly on track, experiences cooling problems, produces sustained high levels of heat or requires a replacement radiator anyway.

Frequently asked questions

Is the standard Focus RS intercooler good enough?

It is adequate for a standard road car. Once the engine is tuned, it can become hot quickly during repeated hard use.

Is an intercooler required for Stage 1?

No, but it is recommended. It will improve temperature control and performance consistency.

Is an intercooler required for Stage 2?

Yes. We consider an upgraded intercooler essential for a proper Stage 2 setup.

Will an intercooler add power?

Approximately 10–15 bhp is a reasonable contribution on a tuned car with suitable ECU calibration. The result will vary between vehicles and conditions.

Does a larger intercooler cause more turbo lag?

We have not experienced any noticeable increase in lag with the AIRTEC intercooler.

Is the AIRTEC intercooler suitable for a bigger turbo?

Yes. It is suitable for standard-turbo, hybrid-turbo and larger-turbo builds.

Do I need the 2.5-inch boost pipes for Stage 2?

No. They are not required at Stage 2, although they can improve airflow. They are strongly advised for Stage 3 and larger-turbo builds.

Are the original Focus RS boost pipes unreliable?

We have not experienced a common reliability issue with the original pipes. The upgrade is mainly fitted to increase pipe diameter and improve airflow.

Does the intercooler require bumper cutting?

No. The bumper must be removed for access, but AIRTEC states that no cutting or trimming is required.

Does a Stage 2 Focus RS need an uprated radiator?

Not for normal road use. The standard radiator remains more than adequate when it is in good condition.

When should I upgrade the radiator?

Consider it for regular track use, prolonged hard driving, high-output builds or when replacing a failed original radiator.

More MK3 Focus RS parts and tuning advice

Browse our complete range of MK3 Ford Focus RS performance parts, or read our MK3 Focus RS tuning guide for power figures, tuning stages and supporting hardware advice.