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reprinted from Automotive Engineering, February 1996

Windshield washer water for greater engine efficiency

rotary engine
Mazda's prototype, naturally aspirated, side-intake,
side-exhaust twin-rotor Wankel engine produces high
power and torque, while assuring good fuel economy.

Windshield washer water would seem to have only one use--for cleaning the windshield. But researchers at Saab have other ideas: they see it as perfect for lowering combustion chamber temperature. Per Gillbrand, the company's Head of Engine Concept Development and the man who pioneered Saab's long association with the turbocharger, says use of the washer water also allows the company's four cylinder turbocharged engine to be run at Lambda 1 (the ideal air/fuel ratio for emissions and fuel economy) under all operating conditions, not just steady state--even at high engine speeds. The water injection system is triggered when full throttle is used or when speeds above 200 km/h are reached or maintained, as they may be on German autobahns. Fuel consumption is said to be reduced to 20-30% at such high speeds, the water being injected through nozzles in the intake manifold. Development of the system is now under way. Gillbrand says it is necessary to determine if anti-freeze or other washer additives might influence the effect of water injection; indications so far are that they do not. "In fact it provides a multi-fuel engine," quips Gillbrand. Only if the car were cruised at very high speeds for long distances would there be any likelihood of the washer water being exhausted, he believes. "Why should we not use something like this which is readily available instead of trying to develop something far more complex?"

Gillbrand believes there is an enormous amount of development potential remaining in the gasoline engine for cars, and is equally convinced of the continuing efficacy of the turbocharger. Saab is now developing an asymmetrical turbocharger installation which will be applied to a 3.0-L V6 engine also under development (AE December). More details of this have now been released. Saab says one small (42 mm) turbocharger will be mounted on the front cylinder bank and driven by the exhaust from that bank. "But the turbocharger then delivers a charge of air to both cylinder banks, also eliminating the need for a wastegate to control the boost pressure. The entire turbocharger is integrated into the exhaust manifold instead of being a separate unit. It works at a "light" pressure, yielding high torque at low revs, allowing higher gear

Jack Yamaguchi