Published on February 5th, 2019 | by Subhash Nair0
What Porsche Changed on the 911’s New Boxer Engine
The new 911 is Porsche at its absolute finest. Some time has passed since its introduction, so we thought it best to talk about that new turbocharged flat six engine that it brings.
Porsche’s goal with the motor has been to meet the latest emissions standards while enhancing performance.
Compared to its predecessor, this flat 6 puts out 30 PS more power (450 PS) at 6,500rpm and offers 30 Nm higher torque too (530Nm) between 2,300 rpm and 5,000 rpm.
Here’s what they’ve done to achieve those figures.
The new six-cylinder engine features forced induction by an almost completely new intake system. Two mirrored turbochargers replace the previously used identical parts. In addition, the compressor and turbine wheels are now arranged in mirrored configuration in relation to the engine, and therefore rotate in opposite directions. The diameter of the turbine wheels has been increased by three millimetres to 48 millimetres, while the 55-millimetre compressor wheel is now four millimetres larger. Thanks to a newly developed lightweight cast manifold and the adapted turbine housings, it has been possible to improve the air flow conditions on the turbine inflow and outflow. This contributes to increasing efficiency, responsiveness, torque and power.
Wastegate valves are now controlled electrically using stepper motors, making boost pressure control faster and more precise overall. The maximum boost pressure of the 911 Carrera S with GPF is around 1.2 bar.
Further downstream in the intake section, compressed air flows through the two newly positioned charge air coolers, which were previously installed in the location of the air filter – they have now swapped places. Instead of being located at the sides in the rear wings, the charge air coolers are now located directly over the engine in a central position under the rear lid grille. This new position permits improved air inflow and outflow of the cooling air and the dethrottling of the process air path, while the increased size of the charge air coolers significantly boosts their efficacy.
The entire basic engine has been targeted for further development, and numerous details have been optimised. For the first time, piezo-controlled injectors directly inject fuel into the combustion chambers. Piezo injectors open and close even more rapidly than the previous solenoid-operated components, meaning that the injection volume can be divided across up to five injections per cycle. In addition, the injector opens outwards so that fuel is distributed better and in finer droplets into the combustion chamber. Without the new piezo injectors, the only way to implement these improvements would have been by increasing the injection pressure; the chosen method has made it possible to retain the pressure level of 200 bar.
The VarioCam Plus variable valve control system uses asymmetrical intake camshafts with a small valve stroke to control gas exchange for the first time. In this arrangement, the two adjacent valves of a cylinder open in this partial load position at different partial strokes. Where previously both intake valves had a uniform 3.6-millimetre small valve stroke, on the new engine the lift is at 2.0 millimetres and 4.5 millimetres. This dethrottling in the partial load area and various other detail optimisations have improved fuel management and therefore combustion – reducing consumption and emissions. Smoother running at low engine speeds and loads also increases comfort on the road. When full stroke is selected for higher engine performance, both inlet valves of the cylinder open with parallel strokes.