ENGINE

The B4 flat-four shares a massive number of components with its turbocharged flat-six sibling — you know, the one found in the back of the 911! The list includes the high-pressure direct fuel injection system, the timing chain, almost the entire auxiliary drive, connecting rods and bearings. The flat-four also uses the same technology when it comes to materials and manufacturing of the crankcase and cylinder liners. There are, however, some significant differences. For example, all 718s make use of adaptive engine mounts, replacing the previous singular forward engine mount with two hydraulic items. As standard, they use engine vacuum to switch between two levels of stiffness, though this can be upgraded to more sophisticated magnetorheological operation through the Sport Chrono Package. By way of a centrifugal pendulum, the 718's dual-mass flywheel has also been designed to balance out the vibrations of the engine at lower speeds.

The 718’s oil sump is aluminium, while the part is plastic on the 911's B6 engine, a difference dictated by the former’s hotter exhaust routing. Then, while the variable demand oil pump in the B6 is taken as a basis for that of the flat-four, the smaller engine’s part features two levels of delivery to the B6’s three, reducing the number of components and, consequently, weight. Porsche went the other way when it came to the control of valves and camshafts, adding sophistication: the flat-four gets Variocam Plus for complete control of valve timing, as well as two switchable cam profiles for the intake. This is the same as the 911, but in 718 flat-four applications, there’s are also two switchable cam profiles for the exhaust side, allowing calibration to optimise performance or economy, as conditions demand. Nifty stuff.

And what of the engine’s efficiency? Well, when it was launched, Porsche quoted a significant thirteen percent improvement in economy and emissions over what came before. Interestingly, that measurement was given on the old NEDC test regime, which has been shown to vary considerably from real-world conditions. Many miles have been driven in turbocharged four-cylinder 718s since that time and it’s generally accepted the newer powerplant is only marginally more economical than its six-cylinder predecessor when driven in normal traffic. Push on and the flat-four is just as thirsty, though! It’s worth mentioning, however, that despite a weight decrease in the engine department, the 718 models weighed slightly more than their predecessors, chiefly due to added luxury equipment and beefing up of the brakes.