Workshop Activities

What is Lambda 1?

When the engine is operating at normal running temperature a Lambda sensor or Exhaust Oxygen Sensor, situated in the exhaust close to the engine, is used to control fuelling. This sensor for 95% of engine operation is in total control of the fuel mixture settings.

For the cat to operate successfully this sensor tries to hold the fuelling around Lambda = 1. Operating at this point the converter will reduce all the exhaust emissions to, Carbon Dioxide, Oxygen and Water. Whilst the specifications for vehicles may vary a Lambda measure outside values of 1.03 to 0.097 may result in a failure of the MOT test.

Modern fuel injected vehicles operate at Lambda = 1. For a quality engine the catalytic converter does very little, however it is that little bit which is an MOT pass or fail. As the engine wears and produces more undesirable gas conversion becomes more important and the converter has to work overtime.

At this point a successful but poor converter on a new car would fail on a high mileage vehicle.

• A poorly maintained engine

• A high mileage vehicle

• A defective lambda sensor

• A poor exhaust pipe, leaking a bit

• Engine electronic control systems

Any of the above can result in an MOT failure, the sort of problems Pratt’s Garage regularly resolve.

If you think a cat is the answer to global warning, think again! The cat does nothing to reduce the Carbon Dioxide produced by the engine, if anything it will increase this gas a little.

A partnership established 1983

Telephone 01443 231135

Pratt's Garage, Unit 5 Cambrian Ind. Est. Coed Cae Lane, Pontyclun, CF72 9EW

The web site sets out typical work undertaken and some technical topics which may interest you.