by P Sanchez
Whether it’s appliances, smartphones or automobiles, the high-end market is the proving ground of market-readiness for many technological advancements. Consumers in this segment are often first adopters and enthusiasts, willing and able to afford the expense of new technology that had not yet benefited from the economies of production scale. Remember when variable valve timing and turbos were still exotic options? Now those technologies have tricked down to the masses, seen standards even in the entry-levels of some car makes.
Today we’re looking at a few updates made to the venerable internal combustion engine as found in high-end models and luxury brands, each new tech promising better and more sophisticated performance for the everyday cars of tomorrow.
Variable Compression Engine
Infiniti, the luxury division of Nissan, has introduced their variable compression engine last year, much to the excitement of automotive enthusiast and engineering geeks everywhere. Called the VC-Turbo, it has a neat trick of changing the geometry of the piston assembly to vary the effective cylinder length.
Instead of the piston connecting directly to the crankshaft, the VC has its piston rods connected to a linkage that in turn connects to the crank and then to an electro-mechanical control assembly. By changing the angle of the linkage, the piston assembly can be positioned further up the cylinder (shrinking the compression space, raising the compression ratio at top dead center), move the piston assembly further down the cylinder for lower compression ratio, and everything in between. Advance system management changes the ratio on the fly depending on variables like speed, acceleration demands, load conditions, boost levels, and engine knock avoidance
Interestingly, Infiniti is not the first manufacturer to come up with an engine that changes its compression ratio by repositioning its internals. Back in 2000, Swedish manufacturer, Saab has come up with its own variable compression engine it called SVC. Instead of changing the position of the pistons relative to the cylinder just like in the VC-Turbo, Saab’s SVC did just the opposite by changing the position of the cylinder relative to the pistons. It achieved this by having the cylinders, valve and head assembly as one unit on a tilting platform separate from the rest of the engine block. The cylinders would tilt away from the pistons for low-compression and high-performance situation, or tilt back for efficiency.
Cooling lines, belt-assemblies and induction systems had to be specially designed to move with the tilting head assembly. Finally, it was deemed too complex and costly to produce and the very promising SVC was scrapped. The whole company followed in its demise a decade later. Infiniti’s VC-Turbo is a simpler more straight-forward design compared to Saab’s and hopefully, we’ll see variable compression technology as a staple feature with our daily drivers.
VTEC, CVVT, IVT...er...FreeValve KICKED IN, YO!
During the induction part of a 4-stroke gasoline engine, restricting the valve opening at lower engine speeds causes incoming air to tumble which makes for better air-fuel mixing while fully opening the valves at high-RPM allows the cylinders to breathe better. At its most basic, variable valve timing (let’s call it VVT for short) allows for both valve configuration and a few variations in between.
Honda’s VTEC has successfully proven the efficiency benefits (and mass marketability) of variable valve timing. They’re not the first to play with the idea, one of the earliest to implement it was Alfa Romeo in 1980. But we have Honda to thank for coming up with a reliable system that became the standard of the last few decades. Today, any step that car manufacturers have to do to make their engine more efficient must include some form of VVT.
Most VVTs are tied into the crank via belts and pulley, gearing and a camshaft, with the variation in valve positions achieved through mechanical adjustments in the cam assembly. This increases the complexity of the system, decreasing long-term reliability, and limits the number of valve position variations possible. Enter legendary hypercar manufacturer Koenigsegg and its Freevalve technology.
The idea of using an electrically-actuated valve system is not new and engineers have been trying to implement the use of solenoids (a device that uses electromagnets to make mechanical actions) to control the opening and closing of engine valves. There have been engineering companies (such as this) that have developed such technology for ready application to car engines, but it is Koenigsegg that has the technology standard in its new cars.
In a camless design, the valves are fully independent of each other and of the engine itself and can be individually controlled. The number of valves in use, amount of valve lift, and the timing can all be programmed to achieve a host of benefits like changing intake profiles and compression ratios, advancing exhaust and even cylinder deactivation.
Advancement in materials sciences (like neodymium magnets), battery technology, and computer systems have made this technology not just feasible but ready and reliable enough for the mass-market application. But for now, if you want to get a first-hand feel of how the technology works, set aside a couple of million dollars for one of Koenigsegg’s handcrafted marvels.
We’ll be rounding out our talk of car technologies that are just taking their first step out of recent car conventions and into the real world. We’ll cover BMW’s water-injection technology and Nissan’s Extroid toroidal CVT comeback. So stay tuned!