Water injection? Hang on; I'll go get my son's Super Soaker out of the wardrobe.

Erm, it's all a bit more high tech than that. You see, BMW reckons that water injection is a clever way to get more power out of its new family of turbocharged engines while also improving emissions and full economy.

So how does it work? Do the windscreen washers turn around?

No. No, they don't. This is the 16th year that BMW has been involved with the MotoGP series and has provided the likes of Z8s, X6s and M3s as safety cars, medical cars and more. This year, the M4 Coupé is being used as the safety car and with the bright red LED lights on the roof, the carbon boot spoiler and the swoosh of M red, blue and purple on the sides it looks like the only police car you'd ever be happy to be pulled over by.

The interesting bit is under the hood though.

You mean the nerdy bit.

Yes, OK, the nerdy bit, but if a simple-yet-clever system that increases performance while also improving efficiency is nerdy, then pass me the glasses and the pocket protector.

The whole issue here is heat. Turbo engines are becoming hugely efficient but the problem is that they tend to run hot. Passing air through a turbo compresses it, which helps the engine to release more power, but it also heats it up, which is not so good. An intercooler helps cool the charged air back down, of course, but it's only so effective and once that ambient air temperature is above 20 degrees Celsius then you are starting to approach problems with knocking - that's when the temperature in the combustion chamber gets too high and the fuel starts to burn in an uncontrolled fashion. It's something that the engine's electronics can usually cope with but it does mean essentially reducing power.

The water injection gets around that. There's a five-litre water tank in the boot that connects to a system that sprays fine atomised droplets of water into the intake manifold to cool down the charged air as it enters the cylinder. That means the turbo can be cranked up a notch higher without the risk of knocking and you can get more power from the engine.

There's a side benefit too. Cooler air means a more efficient fuel burn so not only does that help to reduce overall consumption it also means you get fewer of the nasty exhaust by-products such as nitrous oxides (NOx). It also helps reduce mechanical strain on components like the turbo, the cylinder walls, the pistons and the catalytic convertor. It even helps high performance engines like this run better on lower octane fuel, meaning you don't have to go searching around for 98 RON.

There is no officially-official word on fitting the system to production cars yet but a spokesperson did say: "The letter 'M' is not only synonymous with success on the racetrack, but also with uncompromising high-performance, street-legal sports cars. The BMW M4 MotoGP Safety Car allows BMW M Division to underline its innovative prowess and to follow the brand's philosophy of bringing motorsport technology to the streets." Which sounds pretty much like 'give us a week and we'll confirm it' to us.