(credit: Getty Images | Joe Klamar/AFP)
It's no secret that we're fans of using the racetrack to improve road car technology here at Ars. It's also no secret that we believe the discipline of endurance racing (Le Mans and the like) to have far more relevance to making our road cars better than Formula 1. But it would be incorrect to say that no such tech transfer happens within the ultra-specialized world of F1. And a perfect example of that is a clever engine development being used by Mercedes-Benz and Ferrari that's pushing the envelope of energy efficiency. It's called turbulent jet ignition (TJI), and not only does it do wonders for fuel efficiency, it also results in a cleaner exhaust.
As you probably know, gasoline engines combust fuel with air within each cylinder, and that combustion moves the pistons—and therefore the crankshaft, powering the car. But most of the energy released during combustion is wasted as heat. In fact, the average road car engine wastes between 70 to 75 percent, meaning its thermal efficiency is around 25 to 30 percent. That comes down to the way that the fuel combusts after it's injected into the cylinder, which normally happens around the center of the cylinder by the spark plug (the bit that ignites the mixture). If you can control ignition so that it happens more homogeneously throughout the cylinder, with more air per given amount of fuel (i.e. a leaner burn), less energy is wasted as heat and more of it is converted to work.
But this process can be improved. Take Toyota's latest generation of Prius hybrids, for example. These cars use what's known as an Atkinson-cycle (most engines work via the Otto-cycle). The current Prius engine is supposed to have a thermal efficiency of 40 percent, which is quite an achievement. But there are other options, too, like a technology that's already used in some road cars called direct injection. Rather than traditional fuel injection, which squirts fuel into the engine upstream of the cylinder in the intake port (the bit that the air gets sucked through on its way from the outside of the car into the engine), direct injection uses a high-pressure system to add the fuel into the cylinder itself. This makes it possible to more accurately control the fuel-air mix, whether that's to achieve a stoichiometric air-fuel ratio (14.7:1) or even an ultra-lean mix (useful when cruising with the engine under a light load).
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