An introduction to water injection production
When BMW revealed the M4 GTS, celebrating the 30th anniversary of the BMW M3, it used some vague wording to imply its seven-and-a-half minute Nordschleife lapping hardcore coupe was the first production car to utilise a water injection system. In actual fact, the automotive industry has seen several flair-ups over the last eight decades, with manufacturers adopting water injection in various guises but, until recently, none succeeded in creating a system that would expand to a larger ecosystem of cars.
Although the idea of water injection has been around since the early 1900s, the practical origins can actually be traced back to the aircraft of WWII, with the German Focke-Wulf 190D-9 making use of a rudimentary water/methanol system to add another third to its existing horsepower in 1942.
From there, Chrysler dabbled briefly with their own interpretation during the sixties, but water injection seemingly hit its stride towards the end of the seventies and in the early eighties, unsurprisingly coinciding with the development and widespread availability of turbochargers.
The iconic Saab 99 Turbo took the system to new heights in the car world, with an optional water injection add-on for its turbocharger unit that resulted in more power (145bhp to 160bhp) and improved cooling. Unfortunately, compressor erosion was a common fault among these ‘Sport’ 99 Turbos due to atomised water being dispensed in front of the turbocharger. A fault BMW rectified for the M4 GTS system.
As is often the case with areas of development for the automotive industry, water injection found a home in the Formula 1 paddock during the eighties. The likes of Renault and Ferrari were among the first to champion the system that introduced a 12-litre tank into the side pod. The additional power more than made up for the weight deficit meaning that soon the rest of the field followed in their footsteps, with water/methanol injection becoming increasingly popular up and down the grid before turbochargers were banned in the sport in 1989.
The premise has continued to play a prominent role in drag racing and rallying ever since, with the latter yielding the commemorative road-going Impreza 22B STi that housed the same system. But the automotive industry abandoned the concept from that point on, with the rise of the contemporary intercooler signalling the end of the road for the concept. That was until 2015 and the M4 GTS.
The lack of production models to feature water injection in the wider industry has resulted in a thriving aftermarket appetite for car modders and although the performance implications are a topic of heated debate, BMW clearly saw potential where no one else did and began development of their own newfangled system.
Originally introduced to the world as a prototype serving as the Moto GP Safety Car in the 2015 season, the production M4 GTS was announced to the world in October of that year, with just 30 arriving in the UK. Despite the ambiguous language in BMW’s announcement suggesting its the first production water injection system, the German marque’s pioneering new approach is certainly the first of a new breed, that enhances the power output and economy of the turbocharged straight-six engine.
In contrast to the aforementioned Saab 99 Turbo’s defective system, BMW’s refined method produces a fine spray that evaporates in the intake manifold plenum chamber, thus reducing the temperature of the air around it, which in turn reduces the risk of knock and allows for higher boost pressure.
The alleged five per cent increase in boost power is a key figure for many, but that’s not where Bosch – the mastermind behind the contemporary water injection apparatus – is focusing its attention. A significant boost in fuel efficiency and a reduction in CO2 emissions by 13 per cent and 4 per cent respectively could have dramatic implications in the modern world in which greener and greener motoring is most definitely the name of the game. As a result, Bosch has made the system available for other manufacturers to purchase.