BMW has been producing some very tasty turbocharged cars lately, and one of our favourites — the BMW M4 — has received a major upgrade. We’re not talking some sort of fancy ECU wizardry, or a larger engine; we’re talking about some good old fashion import-tuning water injection. No, not water/methanol injection, as that would prove too costly — the team at BMW decided water-only would be the go. The new model, has been dubbed the GTS, a suitable badging for something of this nature.
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When the M4 was released, it was a mind blaster. Its three-litre, in-line, six-cylinder produced an impressive 317kW (425hp) at the flywheel, and could hit the signposted speed limit here in New Zealand in 3.7 seconds. This was thanks to a pair of beefy turbochargers hanging off the straight-six — something BMW has been seriously working on for a good decade now — with excellent, and very tunable results.
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So, how does an auto manufacturer improve on such luxury greatness? Well, they do something turbocharged tuners have been doing for years — add water into the mix. Water? Won’t that hydrolock my engine? The simple answer is no — it will do the complete opposite, in fact. When water is injected into the intake tract of a turbocharged engine in an atomized form, it can significantly reduce intake-charge temperatures. This has very obvious benefits with a turbocharged engine that produces extremely high intake temperatures, thanks to its air being compressed. Usually, intercoolers are employed to reduce intake temperatures, but water injection takes things to a whole new level. With cooler intake temperatures, the boost pressure through the turbochargers can be increased, and much more aggressive ignition timing can be run — enough that without the water injection, serious detonation would occur.
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With the water injection added into the mix, BMW were able to get a staggering 51kW (68hp) more out of the twin-turbo six. An impressive number indeed, considering that if the vehicle were to be re-flashed and tuned on an ethanol-based fuel, power would increase yet again. Although the newly found power figure is impressive, what is more admirable is the BMW’s extreme weight reduction. A factory M4 weighs in at around 1600kg (3530lbs), yet the M4 GTS weighs only 1510kg (3329lbs), and this is thanks to a serious CFRP (carbon-fibre reinforced plastic) diet. The hood, and even the driveshaft, is made from CFRP.
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The GTS has also received an upgraded suspension and braking package better suited for circuit work, when compared to the factory M4 — three-way M-coilover suspension, upgraded carbon-ceramic brakes, and a new set of wheels have been added. To aid in grip, the front 19-inch wheels are wrapped in 265/35R19 Michelin Pilot Sport Cup 2 tyres, and the 20-inch rears measure a staggering 285/30R20, in the same Michelin compound. Just in case you catch on fire, you have a factory-fitted fire extinguisher, and a roll bar to keep you safe. What do these upgrades translate to? A predicted seven minutes and 28 seconds around the Nürburgring Nordschleife — that’s if they’re allowed to take part in a shoot-out that is.
As soon as pricing becomes available for this water-injected GTS, we’ll let you know.