BMW's water injection system gives turbo engine a boost



BMW is using an old-school trick to improve the performance of one of its newest cars.

The twin-turbocharged six-cylinder that powers the M4 coupes it employs as a safety cars for the Moto GP motorcycle racing championship is fitted with a water injection system that sprays a cooling mist into the intake air, and it will be offered in showrooms soon.

It’s a century-old idea that reduces the temperature in the cylinder, which improves combustion and allows a turbocharged engine to run at higher boost by reducing knocking and heat related stress.

In the M4, three injectors are installed in the intake plenum of the inline-six-cylinder motor, each supplying two cylinders with fine droplets of H2O. They’re fed by a 5.0-liter tank installed in the rear of the car that needs to be refilled with each tank of gasoline during track use, but just once every five stops on the road.

BMW says that during less enthusiastic driving, the system can also help reduce emissions and improve fuel economy by approximately 8 percent. And it will work without the water if the tank runs dry, the engine simply adjusting itself to run at a slightly less extreme tune until you top it off.

BMW has promised that the technology will be coming to one of its M products, and Car and Driver reports that the first car that will get it is the M4 GTS, a hardcore version of the sports coupe due later this year. It won’t be the first production car with a water injection system. The 1962 Oldsmobile Jetfire used a water-alcohol-corrosion inhibitor mix called Turbo Rocket Fuel, and the Saab 99 Turbo S got an extra boost out of water injection, as well.

Will 21st century drivers think it’s cool? It won’t be long before we find out.