THIRD-GENERATION DFI ENGINE

Porsche has used direct fuel injection in its flat six since 2009, but today’s units are vastly different to those early engines. Here’s how…

Last issue we focused on how Porsche has developed what is now its third generation of PDK gearbox for the 992, after the technology originally debuted on the 911 back in 2009. Alongside the introduction of PDK for the 997.2,

Porsche also brought in a new flat six engine boasting direct fuel injection (DFI) which, in principle, still remains in the 911 today. However, much like that PDK transmission, much has changed in the 12 years since.

The biggest change was perhaps the adoption of turbocharging for the 991.2 in 2016, with a reduction in capacity to 3.0 litres for both the Carrera and S variants (mapping rather than capacity now determining the power difference between the two). This was now coded the 9A2 engine rather than 9A1. The 9A2 Evo-coded flat six used in the 992 remains a 3.0-litre, twin-turbocharged engine with direct fuel injection, but the latest tweaks means it is more efficient, powerful and responsive over old.

A new, aluminium crankcase is used, with flow-optimised inlet and exhaust ports – the valve lifts are now configured to be different on each cylinder, with an asymmetric valve lift ensuring air intake is “displaced at low speeds and loads into an additional swirl flap” to improve mixing with the injected fuel, reducing consumption and emissions.

Piezo injectors have also been used, as covered in this section previously, which improves efficiency, and the turbocharger on each bank has also been redesigned, the compressor and turbine sides having been expanded. The chargers are also now arranged symmetrically, with the compressor and turbine wheels on the right and left charger turning in opposing directions, which optimises gas flow as well as the charger’s response. Electric flaps then help widen the opening angle of the 9A2 EVO’S wastegate valve, the diameter of which has been increased, designed to optimise catalytic converter heating. Most notably in terms of visuals, the twin intercoolers have also been expanded and moved directly above the flat six engine, increasing efficiency and cooling.

These key changes, along with an increase in maximum boost pressure to

1.2 bar, means the latest DFI flat six outperforms its predecessors, while proving more efficient than ever before.