The water injection system works by cooling the mixture entering the cylinders and ensuring more efficient, stable combustion. It’s similar in principal to the ones used on WWII aircraft engines, and quite commonly still in drag racing, albeit without the alcohol those cars use.
It injects water at high pressure into the V8’s intake plenum, which acts to cool the compressed air supplied by the supercharger to almost atmospheric levels. It also eliminates the need to throw extra fuel into the engine to ward off irregular combustion as many high-performance production engines currently do.
The injection system is governed by GMR’s own ECU, but the V8 engine operates under the standard, but remapped ECU – the latter allowing for the special fuelling. The system ensures the engine runs cool even under high loads without the need for extra heat exchangers. It prevents the build-up of carbon deposits inside the engine by effectively steam cleaning with every combustion cycle. When it’s out of water the ECU simply disables the supercharger, and a red warning light on the steering column tells you to top up the tank – ideally with 90 per cent water, 10 per cent methythelated spirit/denatured alcohol.
Heane has done 50,000 miles in his engineering prototype, which just happens to be his daily driver. “We wanted a reliable, drivable solution suitable for everyday use,” Heane says. “After every second fill of fuel, you just lift the bonnet and refill the injection system’s 5.5-litre water tank. And because the water acts as an anti-detonant, we can run much leaner fuelling than Aston itself does, so economy actually improves.” Automotive voodoo at work.
The GMR 600 has one of those accelerators you squeeze down gently at first. There’s a hint of softness in the pedal response below 3000rpm, but above 3500rpm the V8 is developing peak torque and behaves itself very well indeed, in smart proportion to your inputs. Outright performance is comfortably in the first-order super sports car league; hugely torquey in the mid-range, but still building nicely as the revs rise.
GMR doesn’t change the V8’s standard exhaust downstream of the catalytic converters, but it sounds like a different system all right: louder, harder edged but still cultured and tuneful. Especially over the last 1500rpm before the 7300rpm redline, where the engine retains the same pleasing elasticity of the standard tune.
The net result is a very fast car indeed, but a well-mannered one too – and which could be as discrete as you wanted it to be. Heane recommends you upgrade the factory brakes on your Vantage after you’ve had the engine overhaul. He offers a range of stoppers, but doesn’t offer a carbon-rich bodykit to accompany his work, nor an aftermarket suspension overhaul. Aston’s own optional sports suspension is firm enough he says, as fitted to his own car. We wouldn't disagree: body control’s excellent, ride quality is a little noisy but entirely acceptable. The car’s meaty, informative steering and chassis balance, meanwhile, are equally great.
And the GMR badging is optional, by the way. “One of our customers doesn’t want his wife to know he’s having the work done,” says Graham. “Assuming she doesn’t drive his car, he might even get away with it!”