Injecting water into the engines SAAB

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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 conducts very promising experiments in this area. He is director of the department "
"Line Drive Concepts" in Sodertalje, Sweden. This department was responsible for work on Turbocharged engines for 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

"Water ice is already washer antifreeze with alcohol, which gives a (small) additional profit as a secondary fuel," says Mr Gilbrand. "In addition to cool the high-speed combustion chambers, the injection of water 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.

Water injection only occurs when the engine speed is greater than 3000 rev / min. The attached graphs show how it enables power gain while maintaining emissions at a reduced level. And without water injection, power would decrease rapidly beyond a certain point to keep pollution levels below certain values. The use of "windscreen washer" is shown on the graph 2ieme.

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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