Test Car Specifications
Model tested: BMW 1 Series Direct Water Injection (DWI) prototype
Pricing: not yet in production
Engine: 1.5-litre turbocharged three-cylinder petrol
Transmission: eight-speed automatic, rear-wheel drive
Body style: five-door hatchback
CO2 emissions: reduced by up to eight per cent over non-DWI equivalent
Combined economy: increased by up to eight per cent over non-DWI equivalent
Power: 218hp, as opposed to 204hp without DWI
Torque: improved by up to ten per cent (depending on model)
What's this?
A rather innocuous-looking BMW 1 Series five-door with some very clever - and brain-fuddling - technology hidden under the bonnet. BMW has already had a go at water injection with its M4 Safety Car, said to be a precursor to an M4 CSL or GTS for next year. In the Safety Car, that system was indirect; a fine spray of water is fired into the inlet manifold ahead of the cylinder in order to further cool intake air, thus increasing combustion efficiency. But this 1 Series has Direct Water Injection (DWI), in which the water is sprayed into the cylinder itself. If, like the author, you have only the loosest grasp of how a combustion engine actually works, you might be dimly aware that water in the cylinders is usually catastrophic to a motor's health.
But not for this BMW. The Munich firm claims that DWI ups a turbo- or supercharged petrol engine's fuel economy by between three and eight per cent in regular driving (we'll expand on that in a moment) while simultaneously unleashing between five and 10 per cent more power. DWI requires a seven-litre reservoir tank to be mounted in the engine bay, which is fed by condensation from the air conditioning unit that would otherwise go to waste by dripping onto the road. So minimal is DWI's use of water that BMW reckons 80 per cent of owners worldwide would never need to top the reservoir up; the other 20 per cent, made up of people living in areas where they don't use air conditioning regularly and track-day drivers who want to save every last horsepower for circuit work, would have to do some refilling.
Once the engine is up to optimum temperature and a certain point in the rev range is surpassed, water from the tank passes through a filter and then is fed to one of two places. The first is the same indirect water injection as the M4 Safety Car, with fluid sprayed into the inlet manifold, but the clever part of DWI is the second method: the water is mixed with the petrol in a high-pressure fuel pump just ahead of the injector, forming an emulsion. This emulsion is then squirted directly into the cylinder during the compression phase of suck-squeeze-bang-blow, with the spray of water so fine that it has totally evaporated by the time the spark for combustion occurs. But its work is already done - intake air temperatures, according to BMW, have been slashed from their usual 400- to 500 degrees centigrade by around 70 degrees, leading to an air/fuel mix that's as cool as 330 degrees C. In layman's terms, BMW likens this to 'driving the car on a cold winter's day, every day'.
How does it drive?
Other than a tablet plugged into the diagnostic port (and we're guessing a BMW engineer with an iPad won't be standard fit on any production DWI models) to show us when and how the 1 Series is using its resources, there is nothing to mark this water-injected model out compared to a regular One. Which prepares you for the driving experience, because it too is no different to any regular three-cylinder 1 Series, despite BMW upping the compression ratio on the 1.5-litre triple from 9.5 to 11.0:1. DWI's undetectable nature is a good thing, as it shows how much effort BMW has put into making the hardware viable.
On the scorching hot Miramas test circuit in southern France, cooking at a heady 36 degrees C during the late June European heatwave, we conducted three full bore acceleration tests around the 2.5-mile loop from the following speeds: 0-80mph, 50-120mph and 50-80mph. Hard acceleration is where DWI does its best work, as not only is it helping to prevent knocking (when combustion of the air/fuel mixture does not take place at the correct time according to the spark of ignition, a potentially ruinous problem for petrol engines), but its secondary charge-cooling effect has a more pronounced impact on the larger volumes of intake air; hence why BMW only claims three to eight per cent efficiency gains overall as that's the more likely return for less frenetic, day-to-day driving. So, in the baking French heat, the 1 Series' fuel efficiency was increased by an incredible 19 per cent over 2.5 miles, while DWI used 0.04 litres of water to enact that saving. This is a remarkable set of stats, considering it's just plain water scavenged from the air conditioning that's conjuring up these increases.
Verdict
Indirect water injection will most likely be seen on that rumoured M4 CSL/GTS next year, so in some form this ingenious BMW technology will make it to market. However, at the time of writing, the DWI system has not yet received official backing from the BMW board. Until it does, the test track will remain its only home but we're hopeful that this device will be green-lighted soon. Given BMW's petrol range is entirely turbocharged now, the benefits would be considerable and most welcome.
Exterior Design
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Driving Dynamics
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