.:VRS:. Emissions

Company & Fleet Login
Live Webcam

Emissions

Failed a MOT? Need a CAT? At VRS we can help! Book online today!

The most common part of the exhaust system to become defective is the rear silencer as moisture gathers inside the box and attacks the metal. Corrosion from the inside results in hole, which causes the exhaust to blow. A defective exhaust will mean the vehicle fails the MOT test. It also causes excessive noise and thereby rendering the vehicle illegal which could lead to a fixed penalty fine. An unchecked exhaust may also result in fumes entering the car, which can lead to headaches, sickness and drowsiness. The catalytic converter can be damaged if the engine is not properly tuned and excess fuel or oils enter the component. If your catalytic converter or exhaust does become defective and requires replacing, VRS can provide high quality replacement parts at significant saving to dealer prices.

With regular servicing, VRS can keep your exhaust system legal and prevent any fumes from entering the vehicle. With our fully skilled technicians we can diagnose any current faults or any faults that may occur in the near future and cause the exhaust or the catalytic converter to become defective.

ABOUT THE CATALYTIC CONVERTER
There are millions of cars on the road that are potential sources of air pollution. In a major effort to reduce vehicle emissions, carmakers have developed an interesting device called a catalytic converter, which treats the exhaust before it leaves the car and removes a lot of the pollution.

In order to reduce emissions, modern cars have been designed to carefully control the amount of fuel they burn. The goal is to keep the air-to-fuel ratio very close to the "stoichiometric" point, which is the calculated ideal ratio of air to fuel.

The main emissions of a car engine are nitrogen gas, carbon dioxide and water vapour. These emissions are mostly benign (although carbon dioxide emissions are believed to contribute to global warming), however because the combustion process is never perfect, some smaller amounts of more harmful emissions are also produced in car engines:

Carbon monoxide: A poisonous gas that is colourless and odourless.
Hydrocarbons or volatile organic compounds (VOC's): Produced mostly from unburned fuel that evaporates. Sunlight breaks these down to form oxidants, which react with oxides of nitrogen to cause ground level ozone, a major component of pollution.
Oxides of nitrogen: Contributes to smog and acid rain, and also causes irritation to human mucus membranes.

These are the three main regulated emissions, and also the ones that catalytic converters are designed to reduce. A check of vehicle exhaust emissions is part of the MOT test for all 4-stroke spark ignition-engined vehicles with 4 or more wheels in Class IV and VII. Two of the exhaust gases are included are Carbon Monoxide and Hydrocarbons.

How does a CAT work?
The operating temperature of a cat is between 350 to 400 degrees Celsius. Once the cat has reached this temperature a chemical reaction occurs as the exhaust gases flow through the coated monolith. The harmful gases are oxidised and converted as shown in the diagram opposite.

Components of a CAT
A honeycomb monolith coated with precious metals (usually Platinum, Palladium and Rhodium) is encased in a steel can. Between the monolith and the can is matting. Upon running a cat in, this matting expands when subjected to heat. Once expanded, the matting holds the monolith in place.

Comments or Questions? Webmaster
(c) PSH - 2008