The coolest new old idea
If you are of an age to remember the JC Whitney catalogue or have ever scanned the ads in the back of Popular Mechanics magazine, circa 1960s, chances are you’ve heard of water injection.
Available in either kit form or as do-it-yourself plans, its over-the-top ads promised dramatic improvements in both engine performance and fuel economy.
But it was given the same level of credibility, in most quarters, as the 100-mpg Fish carburetor — and, like that device, it was rumoured to have been suppressed by Big Auto/Big Oil/Big Government, take your pick.
But now, rumours suggest that water-injection may soon find its way into production models, from BMW, no less.
Just as its name implies, a waterinjection system sprays a fine mist of water into the intake airstream entering the engine or directly into the combustion chamber itself.
The water helps cool the incoming charge — just like an intercooler does — improving both performance and efficiency. But it also helps limit the onset of engine- damaging spark knock, allowing use of a higher compression ratio. Consequently, it is particularly beneficial for turbocharged engines.
Water injection gained its currency in the Second World War when it was employed in the engines of fighter aircraft to help augment power under high-load conditions, such as during short takeoffs and in dogfights.
Apart from its aftermarket automotive applications, water injection has also seen some limited use in production cars. It was standard equipment on the 1962 Oldsmobile F85 Jetfire, which along with the Corvair Spyder of the same vintage made history as the first turbocharged production car.
Water injection was later offered on the Saab 99 Turbo S, adding an additional 15-to-20 horsepower to its output. The advent of intercoolers stifled further interest in the technology, however — until now.
BMW first revealed its experimentation with the concept in an M4 Safety Car support vehicle for MotoGP racing. That car was fitted with a separate water tank that had to be refilled with every tank of gas — a potential inconvenience in a production car.
A1-Series prototype that was revealed more recently keeps the water supply for the injection system topped up by recovering condensed water, which drains into the tank whenever the engine is switched off. The engine itself is a turbocharged, 1.5-litre, three-cylinder with water injection that sprays a fine mist into both the intake manifold and directly into the combustion chamber.
As a result, the compression ratio was increased from 9.5:1 to 11.0:1, power was enhanced by 10 per cent and efficiency improved by 8 per cent, according to BMW.
Even better, the efficiency rate improves the harder the car is driven, because the added cooling effect reduces temperatures sufficiently to avoid the usual need to inject excess fuel for cooling under those highload conditions.
BMW is expected to reveal a trackfocused M4 GTS concept car at the 2015 Pebble Beach Concours d’Elegance next weekend, with a production version to follow next year. Expect them both to feature water injection. And don’t expect that to be the last you hear of water injection. Gerry Malloy is a frequent contributor to Toronto Star Wheels. For more Toronto Star Wheels stories, go to thestar.com/ autos. To reach Wheels Editor Norris McDonald: