BMW Injects Water to Cool Engine, Boost Performance

BMW AG says its new direct water injection (DWI) system can lower engine temperatures by as much as 160 F from the typical 750 -930 F operating range during combustion. Such reductions can improve a turbocharged gasoline engine's efficiency by 3%-8% and increase power by 5%-10%, according to the carmaker.

BMW demonstrated the concept this week in its 1 Series small car powered by a 3-cylinder gasoline engine. Media reports say DWI boosted the engine's output to 215 hp from 201 hp and improved the compression ratio from 9.5: to 11.1, while significantly reducing fuel consumption during hard acceleration.

During the process, water is sprayed into the inlet manifold to cool the engine. The fine spray evaporates before combustion begins.

The system uses a 7.0-liter water reservoir mounted in the engine bay. Water is supplied from otherwise wasted condensation from the air conditioning unit. Injection is triggered by temperature and engine speed.

DWI reduces thermal stress on various engine components and minimizes emissions, according to BMW. The company says the technique also can prevent engine knocking during high engine loads.