GMR 600 Aston Martin V8 Vantage first drive

The GMR 600 is an Aston Martin V8 Aston Martin Vantage given special powers by Taunton-based engineering outfit GMR Design. 

Company owner and former aero engineer Graham Heane has been working on an engine conversion for Aston’s early 4.3-litre V8 Vantage since 2010. Identifying the strong supply of affordable used Vantages that currently exists, sharing the same appreciation of the baby Aston’s charms that so many feel, but aware of the limitations of early cars too, Heane has developed a low-impact, low-pressure supercharger installation with a twist: a proprietary water-injection system.

Running with just 6.5psi of boost pressure, a special ECU and a leaner fuel-to-air mixture than standard, the 4.3-litre GMR 600 Vantage trumps even the new Aston V12 Vantage S for power – developing a peak 573bhp along with 445lb ft of torque from 3500rpm. The conversion on newer 4.7-litre engines puts peak power above the 600bhp threshold.

Aston’s 0-60mph claim for the last V12 Vantage was 4.1sec. For the current one, it’s 3.7sec. This V8 will do it in 3.6sec; less on an absolutely perfect run. And the conversion costs £20,000 including VAT - on cars widely available used from just £30,000.

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.