Milltek Seconday Cat Delete - BMW F8X M3/M4

The delivery time for products in stock is 1-3 business days.

If the product is not in stock and it is a pre order product, the average delivery time is 5-21 business days. If the product has a longer delivery time than previously announced, we will be in touch.

Terms for product returns:

• You must return the ordered products within 14 days of receiving
• The products must be unused and without damages
• Commission fee for handling returns is 21,90€
• For product returns, the customer is in charge of the return costs. Only door to door service (Express)
• Shipping costs are not refunded

For international orders (outside of Europe) sales are final and non-refundable. Once an order is placed, it cannot be canceled or returned. By placing an order, you acknowledge and agree to these terms.

Return address: QT Parts, Vasarakatu 8B, 37150 Nokia, Finland.

Pre order / made-to-order products

If the product you have ordered is a pre order or made-to-order item, it is not subject to the 14-day right of withdrawal or return under consumer protection laws, as the product is manufactured or sourced specifically based on the customer’s individual order.

If you wish to cancel your order before receiving the product, we will refund 50% of the total order amount.

This condition applies to the following product categories:

• Suspension
• Engine Tuning
• Engine Parts
• Exhaust Systems
• Fueling
• Turbochargers/superchargers
• Drivetrain
• ECE-approved Downpipes

All of the above products are manufactured or sourced individually based on the customer’s order, and therefore cannot be returned after delivery, unless the product has a manufacturing or material defect.

In the event of such a defect, the standard liability for defects as provided by consumer protection legislation shall apply.

The Milltek Sport Secondary Catalyst Bypass is designed to maximize exhaust flow, power delivery and sound on F8X generation M3 and M4 models. By removing the factory-installed secondary catalysts (while leaving the primary catalysts in place), the system provides a significant improvement in airflow and sound permeability – resulting in a wider, deeper and more aggressive sound profile that is ideal for track and performance-oriented use.

This upgrade is especially popular with F8X enthusiasts who want more sound and dynamics without the need to change the entire exhaust system.

Better flow and more intense sound

Secondary Catalyst Bypass Solution:

• Improves exhaust gas flow rate and reduces back pressure

• Deepens the sound and increases the transparency of engine tones

• Provides an aggressive, motorsport-style exhaust note

• Retains optional compatibility with the original Cat Back system

The S55 engine's familiar metallic high-rev sound comes through cleaner and stronger than before, especially during sporty driving.

Bolt-on installation to original mounting points

Milltek's design ensures:

• direct compatibility with the factory exhaust system

• bolting without welding or structural changes

• precise fit and high-quality finish

Bypass tubes integrate seamlessly with either the standard or Milltek Cat Back system.

304L grade stainless steel

Milltek's 304L Aircraft Grade stainless steel offers:

• excellent heat resistance

• long service life even under high thermal loads

• high-quality TIG welding

• flow-optimized internal structure

Pipes made from this material can withstand even the most demanding operating conditions.

Compatibility: BMW F8X M3/M4 (non-OPF/GPF)

This secondary catalytic converter bypass kit fits the following 2014-2018 models:

• BMW M3 F80

• BMW M3 Competition F80

• BMW M4 Coupe F82

• BMW M4 Convertible F83

• BMW M4 Competition (F82/F83)