AUTOMOTIVE ENGINEERING : Just switch off a cylinder

In order to reduce fuel and carbon dioxide, the car manufacturers are working on ever more economical engines.

Partially only two cylinders of a total of three, drive the Ford Fiesta ST.
Photo: Ford-Werke GmbH

For the first time Fiesta ST is offering a cylinder cut-off for a new three-cylinder engine. 
And suppliers such as Bosch are working on a water injection technology that is expected to save up to 13% fuel. The reason: Autoconzers face a dilemma. Many customers always want larger and heavier models. Demand for SUVs has grown rapidly. On the other hand, EU legislation forces car manufacturers to build fuel-efficient vehicles.
 The main focus is on the optimization of the motors. Some manufacturers rely on downsizing, that is, the use of smaller engines that are powered by turbochargers or other techniques to increase the performance of larger engines.VW, Audi and BMW prefer the direct fuel injection, which reduces fuel consumption by 15%.
 As the most attractive method for saving fuel, experts like the Viennese engine technician and university lecturer Fritz Indra see the temporary shutdown of cylinders in engines.The cylinder shutdown is comparatively inexpensive to achieve with little technical effort and has no influence on the stability of the engines, he says.
 Up to now, the cylinder cut-off is mainly used with eight-cylinder and four-cylinder engines. In the case of the Audi A 8, for example, four of the eight combustion chambers are shut down when little power is being obtained. As a result, the powerful eight-cylinder engine, up to 380 kW, consumes up to 23% less fuel compared to the V10 engine used in the previous model, despite its 74 kW more engine power.
Now this technology could also be used in the small car sector. Ford presented the first three-cylinder with cylinder cut-off at the Geneva car salon. The new Ford Fiesta ST runs in normal operation only partly on two cylinders. The EcoBoost petrol engine with a displacement of 1 l turns off a cylinder when only low engine power is required. The switching on and off of the injection and the opening or closing of the valves takes place within 14 ms. Drivers and riders therefore do not notice anything about the cylinder cut-off.
 The cylinder cut-off makes it possible to save fuel by 6%, says Ford. The new Fiesta is also fuel-efficient. "We have reduced CO 2 emissions from 137 g to 114 g per kilometer," says Chief Engineer Matthias Tonn. "An uncanny jump," Tonn enthused about VDI news.
The Ford engineers hope for further application possibilities of the EcoBoost with cylinder cut-off. Finally, the EcoBoost engine is already installed in models such as the Focus and the Kuga.
Cylinder shutdown, direct fuel injection and downsizing are not yet the end of engine optimization. Bosch recently introduced a new technology, which can also save up to 13% fuel: the water injection.Instead of gasoline, the cooling of the temperatures in the engine is to be carried out in the future by water, which is injected into the engine via a separate nozzle. According to Bosch, the water injection not only leads to lower CO 2emissions , but also to a 5% higher engine output. Bosch engineers expect a breakthrough of technology by 2019 at the latest.
First of all, compact cars could be fitted with Bosch water boosters. The BMW M 4 is the only series-produced vehicle to feature the water injection technology. Experts consider the water injection to be a useful application. However, an additional tank is needed for distilled water which must be refilled every 3 000 km so that the system works.Nevertheless, techniques like the water injection show that the good old combustion engine is still not at its end.