More power for less fuel. What sounds absurd is sometimes quite simple. You just have to have the nerve to question principles that are seemingly written in stone.
The 911 Turbo and 911 Turbo S models have an innovative expansion intake manifold that was used for the first time on the latest 911 GT2. Its unique operating principle is unlike anything ever featured on existing induction systems. Our ‘expansion’ intake manifold is a radical development that is the polar opposite of the resonance principle used on conventional turbocharged engines.
A resonance manifold increases engine output by forcing additional air into the combustion chambers. To do this, the manifold is designed in such a way that the air – which vibrates due to the action of the valves – is in a compression phase as it passes through the inlet ports.
Unfortunately, compression not only increases air volume, it also increases air temperature and this has a negative effect on ignition.
Our expansion manifold simply turns that principle around. The internal geometry is radically different from that on a resonance intake system. Key modifications include a longer distributor pipe, with a smaller diameter, and shorter intake pipes. As a result, the air is in the expansion phase as it enters the combustion chambers. Since expansion always cools, the air/fuel temperature is lower and ignition is significantly improved – thereby increasing performance.
Of course, the amount of air that enters the engine under expansion is less than it would be under compression. To compensate for this, we’ve simply increased the boost pressure. The resulting increase in temperature – again through compression – is immediately offset by the uprated intercoolers.
Instead of hot compressed air entering the combustion chambers, we now have cooler air generating more power and torque. As a consequence, there is a major improvement in engine efficiency and therefore lower fuel consumption even under heavy loads and at high revs.
As we said, sometimes you just have to question established ideas.