For all its shouty wings and other aero bits - not to mention the enormous price - the big headline with the BMW M4 GTS is the water injection tech under the bonnet. It’s a simple concept: a mist of water is squirted into the intake manifold, lowering the engine temperature and decreasing engine knock. That means better efficiency, more power, and in the case of the M4, the ability to crank up the boost pressure on the turbos to give a massive hike in power to 493bhp. When we spoke to BMW M boss Frank van Meel earlier this year he remained coy on the prospect of the Bosch co-developed tech appearing on other BMWs, but it’s now looking like we’ll be seeing water injection appearing on cars from multiple brands.
Speaking to Autocar, Bosch global project manager Fabiana Piazza said: “We’re launching it [water injection] into the market now as tighter legislation and new real driving emissions tests are increasing the importance of this technology in all cars.”
The system in the M4 uses a five litre tank, which is drained at the same rate as the fuel tank during hard track driving. In a more normal application under more gentle driving, Bosch reckons you’d manage 1800 miles between fill-ups - something done using special distilled water. The engine would function just fine if you ran with the tank empty too - just a little less efficient.
On the subject of efficiency, we’re looking at a 13 per cent reduction in fuel consumption, and a four per cent decrease in CO2 emissions. Not a bad innings for the simple price of filling up a little tank of water every now and then.