Exhaust Terminology

Turbo-back Exhaust

This is the part of the exhaust system from the outlet of a turbocharger to the final vent to open air.

Cat-Back Exhausts

This is the part of the exhaust system from the outlet of a catalytic converter to the final vent to open air.

Rear Exhaust

(Back box / Rear Muffler)
This is the part of the exhaust system from the outlet of a centre section to the final vent to open air.

Exhaust Silencers

(Box / Muffler)
This is the part of the exhaust system that is usually positioned at the rear of the exhaust and can be known as the “volume box” this allows the manufacturer to determine the final volume of the exhaust, usually the bigger the box the more silent the exhaust.

Exhaust Resonator

(Silencer / Box / Muffler)
This is the smaller cylindrical box usually positioned towards the front / middle of the vehicle that removes the resonation sound that the engine produces, this box can be removed for a louder sound to the exhaust but can leave cabin drone a problem at motorway speeds for some people.


(Tips / Exhaust End)
This is the final stage of the exhaust gasses before it reaches normal air conditions, size and style of this part has little effect on volume, sound or power. Style is the main focus.


(Flex section / Flex)
One benefit of exhaust flex pipe is that it can reduce vibrations transmitted from the engine and exhaust into the chassis, which in turn can be felt by the occupants of the car. The flex pipe is used to connect rigid lengths of exhaust pipe, and the fact that it can flex and move reduces these undesirable vibrations.

Lambda Sensor

(Oxygen sensor)
This device helps to reduce carbon emissions. This monitors the percentage of oxygen present in exhaust gases and transmits information to the engine management system or electronic control unit (ECU).

Sports Cats

(Catalyst / Catalytic Converter / Cat)
All modern petrol car exhausts manufactured from 1993 are fitted with a catalytic converter and require one to enable the vehicle to be legal on the road. Cats contain precious metals and reduce harmful emissions of hydrocarbons, carbon monoxide and nitrogen oxides into the atmosphere. The catalytic converter works when it reaches its optimum working temperature, and converts the gases into water vapour and less harmful gases.

The difference between a standard cat and sports cat is that sports cats allow more gasses to pass through, while still allowing the same emission results.


(Catless / de-cat pipe)
Removing a catalytic converter by fitting a de-cat pipe can slightly improve your vehicles performance compared to using a sports cat, however it is illegal to drive on the roads with a de-cat pipe fitted (designed for race / track use only).