 The turbine wheel and compressor impeller of the Saab turbocharger are small and lightweight. So the turbocharger begins to boost the intake air pressure at very low engine speeds. After the air has been compressed in the turbocharger, it is cooled by abouit 60 degrees centigrade in the intercooler, which reduces the thermal stresses on the engine. | Intercooler
When the engine intake air has been compressed in the turbocharger, its temperature will rise. But the air is then routed through an intercooler between the turbocharger and the engine, and its temperature is reduced. As a result, its density increases, and the air admitted into the engine therefore contains more oxygen. This enables more fuel to be injected and burned efficiently, and the engine power thus increases. The intercooler has been developed by Saab and is designed to perform efficiently, even at veiy low temperatures. An intercooler may become blocked by ice in very cold and humid weather, and it will then perform unsatisfactorily. In the Saab intercoooler, this is prevented by a safety valve which by-passes the intake air across the intercooler in the event of icing. |  The turbine wheel is induced to rotate at up to 120,000 rpm. Under heavy loads the turbocharger can glow with the effect of heat and pressure from the exhaust gases passing through it. |  The small, minutely balanced turbine wheel is made from specially developed lightweight materials that can take the extreme temperatures generated |
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