Although a relatively small car manufacturer, Saab has always been among the forerunners in meeting the stiffening exhaust emission requirements.

Exhaust gas emission control

All Saab cars are fitted with a device which ensures that any excess fuel will be burned before the exhaust gases are discharged into the atmosphere. Most models are also equipped with an Exhaust Gas Re-circulation (EGR) system.

Saab 900 cars are equipped with a breakerless ignition system. Since this system has no moving parts that can sustain wear, it will perform efficiently for a very long time-with no service whatever. This ensures better running economy, consistently high performance and cleaner exhaust gases.

Catalytic converter
Since way back in 1976, Saab has been manufacturing cars with catalytic converters and the Lambda system for the USA, Canada, Japan and other countries. Saab cars with catalytic converters are now also available on certain European markets. Many other manufacturers are developing catalytic converters for the European market, although few of them have as much experience of the system as Saab.

Saab cars are equipped with three-way catalytic converters which remove unburned hydrocarbons, carbon monoxide and nitrogen monoxide from the exhaust gases. The active part of the catalytic converter is a ceramic core with small square holes, coated with a thin film of precious metals. The catalyst converts most of the toxic substances to more innocuous gases, i.e. carbon dioxide, steam and nitrogen.

To ensure the best possible performance from the catalyst, the fuel/air ratio supplied to the engine must be carefully controlled. The fuel injection system is therefore controlled by signals from a Lambda sensor which senses the oxygen content in the exhaust gases. A car equipped with catalytic converter and the Lambda system must be run on lead-free fuel, and is therefore equipped with a special fuel filler pipe, so that it cannot be filled with leaded petrol by mistake.

Lambda control of the fuel injection system is essential for the satisfactory performance of the catalytic converter, so that carbon monoxide, unburned hydrocarbons and nitrogen oxides will be eliminated.

1. The Lambda sensor monitors very accurately the oxygen content of the exhaust gases and applies electrical signals to the electronic control unit of the fuel injection system.
2. The electronic control unit regulates the fuel! air ratio, so it is as close as possible to the ideal Lambda value of 1.
3. The catalytic converter is mounted in the exhaust pipe, under the floor below the centre console. The catalyst is heated by the exhaust gases and operates at temperatures between about 300 and 800°C. A heat shield between the converter and the floor eliminates the heat that would otherwise be radiated from the converter into the interior.