Ford Focus ST225 Exhaust Systems & Downpipes

Which is the best exhaust for the Focus ST225?

Cobra Sport is our overall recommendation for the Focus ST225. Its systems are manufactured in the UK from stainless steel, offer exceptional build quality and are available in several configurations to suit different sound levels and power goals.

Most Cobra Sport exhaust systems include a lifetime warranty for the original purchaser, subject to the manufacturer’s terms. Sports catalysts, flexes and downpipes have separate warranty terms.

Resonated or non-resonated?

A resonated exhaust includes an additional silencer, making it quieter and more refined than the equivalent non-resonated system.

We normally recommend a resonated system for customers who regularly use their ST225 on the road or motorway and want a deeper exhaust note without excessive volume.

A non-resonated system produces a louder, more aggressive sound. It is better suited to customers who prioritise noise and character over refinement.

What exhaust is required for Stage 2?

For the best results from a Stage 2 Focus ST225, we recommend a complete three-inch turbo-back exhaust.

This replaces the system from the turbocharger backwards and should include either:

• 
  A high-flow sports catalyst for a road-going car
  
• 
  A de-cat pipe for off-road or motorsport use only
  

A three-inch system provides the flow capacity needed to achieve the best gains from a tuned Stage 2 setup.

Sports cat or de-cat?

A sports catalyst is the appropriate choice for a road-going vehicle. It retains a catalytic converter and is designed to offer improved exhaust flow while still controlling emissions.

An MOT pass cannot be guaranteed, as this depends on the condition of the vehicle, catalyst and complete emissions system.

A de-cat pipe removes the catalytic converter entirely and is intended for off-road or motorsport use only. It should not be used on the public road.

Will an ST225 exhaust drone?

All the exhaust systems we list are designed to minimise unwanted cabin drone, although the final sound will depend on the complete setup.

A resonated cat-back system with a sports catalyst will generally be the more refined option.

A non-resonated turbo-back system with a de-cat pipe will be considerably louder and may produce some drone at particular engine speeds.

How much power can a turbo-back exhaust add?

On a tuned Focus ST225, changing from the standard exhaust to a free-flowing three-inch turbo-back system can typically contribute around 10–20 bhp.

The exact improvement will depend on the exhaust configuration, intake system, intercooler, turbocharger and ECU calibration. The exhaust should be considered part of the complete tuning package rather than a guaranteed standalone power increase.

Is a remap required?

A remap is not normally required when fitting only a cat-back exhaust.

A remap should be carried out when fitting a de-cat pipe as part of a complete turbo-back system. Without suitable software, the removal of the catalyst is likely to trigger an engine-management warning light.

Although this may not immediately place the car into limp mode, we would not recommend running a de-cat setup without the correct ECU calibration.

Our recommendation

For a refined road car, choose a resonated Cobra Sport system with a suitable sports catalyst.

For a louder road setup, choose a non-resonated cat-back or turbo-back system, while retaining a sports catalyst.

For an off-road or dedicated motorsport build, a non-resonated de-cat system offers the most aggressive sound and unrestricted exhaust flow.

Contact Wayside Performance if you need help choosing a system based on your preferred sound level, current modifications and intended power target.