definative cat laws????

[gavinvr6 0]

thought some of you guys ru ning slightly older cars might like a bit of clarification as to cat laws. it gives a date which being the times newspaper im leaning to taking as pretty much gospel.

9th November 2003

The aim of the catalytic converter is to dramatically reduce the three most harmful exhaust emissions — carbon monoxide, hydrocarbons and nitrogen oxides — hence the term “three-way catalytic converterâ€. The device is required on unleaded petrol-engine passenger cars first used on and after 1 August 1992.

It’s called a converter because the emissions that go into the catalyst are converted to more benign substances such as carbon dioxide, nitrogen and water vapour. The device is fitted in the exhaust system just under the driver or passenger footwell and looks like a conventional silencer box, albeit flatter and squarer.

The converter has two sections: a reduction catalyst and an oxidisation catalyst. Each is made of a ceramic honeycomb with a metal coating. The honeycombs create the maximum surface area for exhaust gas to pass over.

Inside the reduction catalyst, the honeycomb is coated with platinum and rhodium, which are used to reduce nitrogen oxides in emissions. As the gas passes over the platinum and rhodium, a chemical reaction takes place that splits the nitrogen atoms from the oxygen. Both are harmless in their separate forms.

In the second stage, hydrocarbons (from fuel) that have passed unburnt through the engine, together with carbon monoxide, are oxidised (burnt, basically) on a catalyst coated with platinum and palladium.

It is because so many rare and precious metals are used that a replacement converter costs so much (between £100 and £500) but without it, your car will not pass the MoT test. Eventually, a converter will wear out (three to four years would be typical), though it can be physically damaged by knocking it on a kerb, or by an engine backfire. Mistaken use of leaded petrol will also ruin a converter.

http://www.timesonline.co.uk/

The Sunday Times, 9 November 2003

[gavinvr6 0]

here's another bit i found but dont know if its from a worthy source.

All petrol-engined class IV vehicles first used on or after 1st August 1992 (i.e., K prefix registrations onwards) will have to go to a catalyst MoT station.

Not all petrol-engined class IV vehicles first used on or after 1st August 1992 had to be fitted with a catalyst. However, the catalyst station will be able to identify whether or not a catalyst should be fitted and apply the appropriate emission tests. Vehicles fitted with catalysts and first used before 1st August 1992 are not subject to the catalyst emissions test.