Water injection in SAAB engines

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Keywords: injector, anti NOx pollution, low Nox, Trionic, water, performance, power, Saab Ecopower, octane, detonation, Turbo

Water injection by SAAB

Written by David Scott in Automotive Engineer, translated and adapted by Christophe Martz.

 

Automotive Engineer
Automotive Engineer, Vol. 21, 1 No, from February to March 1996

According to Saab, the injection of water supports the cleanup.

The injection of water is nothing new, 2ième during World War it was used to increase the power of aircraft piston engine.

Now Saab has updated this old technology, not to increase power but to master emissions, especially during this demands heavy loads (high-speed or high acceleration).
It was requested that the engine cylinders 2.3L Ecopower of 4 walking stoichiometry (lambda = 1) in all driving conditions.

Dr. Per Gilbrand is conducting very promising experiments in this field. He is director of the department "
"Drive Line Concepts" in Sodertalje, Sweden. This department was responsible for the work on the turbocharged engines for the Saab manufacturer.

Mr Gilbrand claims that the injection of water can reduce fuel consumption in 15 25% this with a significant reduction in HC and NOx emissions. The installation on a vehicle is simplified by just using the tank washing ice, which limits the system installation to a single pump injector that supplies 4 cylinders.

System water injection
water injector system

"The water in the washer is already antifreeze thanks to the alcohol, which gives an additional (small) benefit as a secondary fuel" explains Mr Gilbrand. "In addition to cooling the combustion chambers at high speeds, the water injection also protects the catalytic converter from overheating."

The system is only operational during maximum acceleration phase and when the car exceeds 220 km / h. Water injection in the intake manifold is controlled electronically by the system Trionic 32 Saab control bits. Thus the system is directly related to the power demand.

Powers with and without water injection
Graph powers in limited emissions with and without water injection

Oxygen sensor measures the oxygen content of the exhaust and used to calculate the quantities of air and optimum fuel admitted to the engine. Its function is to keep the mixture at the best ratio.

The injection of water occurs only when the motor speed is greater than 3000 rpm. The graphs attached show what power gain it allows while maintaining emissions at a reduced level. Thus without water injection, the power would drop rapidly beyond a certain point in order to keep the pollution rate below certain values. Consumption of "washer" is shown on the 2ieme graph.

Water consumption seem quite important given the injected flow rates but Gillbrand replies that as the injection is done only intermittently (and high speed), the capacity of this reservoir is not a real problem.

Rates of injected water
water flows injected by the system

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