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While we realised early on that forced induction was the key to unlocking the Aston Martin V8 full potential, we had to determine which means of supercharging to take. Turbochargers and centrifugal superchargers are not compatible with the characteristics of the Aston, instead better in small high-revving vehicles. This meant exploring Positive Displacement superchargers, the twin-screw and roots. The twin-screw consumes power and generates a high-pitched whine beyond 10psi, making it a prime choice in race cars but not fitting for the Vantage. Instead, we favour a roots design, common choice for numerous road car manufacturers for their prodigious levels of boost at low engine speeds. In particular, we use the Twin Vortices Series (TVS) by Eaton. This is combined with our innovative Geyser Cooling System, to create a truly state-of-the-art engine upgrade like no other. Contact us to find out more.
The Eaton roots has been the blower of choice for road cars, not only due to the boost levels at low engine speeds, but also because they are reliable and quiet in operation and, when off-boost, they do not generate heat or significant drag on the engine. Unfortunately, they are also the least efficient type of blower, being only on average 55% thermally efficient compared to other superchargers (75% for centrifugal and 70% for twin-screw) with a typical turbocharger boasting 75% thermal efficiency.
Like the twin-screw, roots feature rotors, but the key feature is a bypass valve which directs the air away from the rotors when not needed. When the accelerator pedal is depressed, a partial vacuum is generated in the manifold, causing the bypass valve to close and direct air through the rotors, which compresses the air to generate boost. But, because of their relative efficiency ratings, the roots design had always had to give way to the twin-screw when boost beyond 10 psi was required… until now!
Things have now changed, with the introduction of the Twin Vortices Series (TVS) supercharger by Eaton. Whilst still a ‘roots’ this range of blowers features a pair of screws not dissimilar to those of the twin-screw. However, the design of the TVS screw is revolutionary! It features four blades instead of the usual three, and each blade ‘twists’ 100 degrees further. These two innovative design alterations have allowed Eaton to do the apparently impossible, creating a supercharger that beats the twin-screw on efficiency, noise and power consumption. It has a thermal efficiency of no less than 76% over most of its operating range, and is far quieter in operation than the previous designs. It also only uses 0.3 of a BHP to drive when off boost. This is why it is the one we use in GMR systems!
Our Geyser Cooling System is a modern version of the water injection process developed for aircraft engines during the Second World War. The process was developed in order to lower the temperature of the charge (i.e. the fuel/air mixture), whilst at the same time acting as an anti-detonant (i.e. avoiding ‘pinking’ or ‘knock’).
It works in three ways:
1) Water is injected into the manifold as a very fine mist through nozzles at over 100 psi.
2) The water changes state by evaporation into vapour, absorbing heat as it does so. This process instantly cools the air within the manifold (compression of air by a supercharger also, inevitably, heats it). The system is so efficient that the compressed air can be introduced at almost normal atmospheric temperature.
3) In the combustion chamber the remaining vapour turns into steam. The effect on the engine is to reduce cylinder temperature. This improves the dynamics of the ‘flame front’ which means that the fuel/air mixture burns in a slower, more efficient manner, giving the piston a less violent ‘shove’.
In conventional engines, the only way to achieve the equivalent cooling effect as the Geyser system, is to add more fuel. This is exactly what manufacturers of modern production cars do: more fuel is added to enrich the air/fuel mixture under load, purely in order to reduce the in-cylinder charge temperature. Our Geyser system acts as an advanced version of water injection, precisely calibrated by our own software for any given engine. The water is pressure and temperature controlled precisely by the system, so there is no danger of excess water entering the cylinders and thus risking corrosion.
Water is cheaper and more effective than fuel for cooling and generates a leaner air/fuel mix underload, for more efficient performance. The steam generated also helps reduce carbon build-up within the system. This can enhance fuel economy as it is not being wasted via use as a coolant. Not to mention, thanks to our Geyser system, the supercharger runs at an exceptionally low boost pressure of only 6.5 psi!
For more information or to discuss your engine upgrade requirements with a member of the team, contact GMR Design today.
