For most of the 130 years that hydrocarbon-fueled, internal-combustion engines have been around, they have been the first choice for automotive propulsion. Recently electric alternatives have been gaining popularity but they are just a small fraction of current automotive sales. The internal-combustion engine is going to be difficult to de-throne because it offers high power density, practicality and low cost. For these reasons and others, it’s not going away anytime soon. However, these engines continue to evolve under federal and market pressures to pollute less and deliver better gas mileage. To meet these challenges, a number of new technologies are currently under review. Let’s look at three of them.
Electric Accessory Drives
Most of today’s engines drive alternators, coolant pumps, air-conditioning compressors and other accessories mechanically via a belt, and they generally run continuously. An obvious solution would be to drive these accessories via more-efficient electric motors. The problem is that standard 12 volt systems make this difficult because not enough power is available to drive typical accessories.
A solution to this problem is to step up the voltage used in cars (12 Volts) to 48 Volts. This allows two things: the construction of more efficient electric motors and the ability to shut them off when not needed. A system such as this will eliminate belt-related parasitic loads and this could lead to a boost in fuel efficiency of 10-15 per cent. One manufacturer, Kia, showed a 48 Volt prototype diesel Hybrid at the at the 2014 Paris Autoshow. According to Metro Kia of Atlanta, a local Kia dealer in Atlanta, GA, this model is not available for sale just yet.
Advanced Cylinder Deactivation
Sometimes car manufacturers put technology in their cars before it is ready for primetime. Example: for the 1981 model year, Cadillac introduced an innovative new V8 engine technology that could automatically switch off two or four cylinders when cruising. A real good idea but when Cadillac attempted it with throttle-body fuel injection and crude electronics, the “V-8-6-4 System” was far from a success.
Today, cylinder deactivation has been almost perfected. Soon, additional sensors and more accurate control algorithms will enable engines to run more of the time on less than their full banks of cylinders. By the end of this decade, it is forecast that the technology will have advanced to the point where V6 and V8 engines will be able to cruise on just two cylinders. Estimates suggest that fuel consumption could be cut as much as 20 per cent with this technology.
Internal combustion engines use intake valves to allow fuel and air into their cylinders and exhaust valves to purge exhaust gases. The opening and closing of these valves is generally actuated by rotating camshafts, a process that is quite energy intensive. That may soon be an old-school technique. Several manufacturers are working on the opening and closing of engine valves via electric solenoids. This allows two advantages: first, it takes far less energy for a solenoid to open and close a valve than a camshaft requires. Second, engineers can fine tune the opening and closing timing to match engine loads and speeds more accurately.
While research is quite promising, it’s looking like this technology is going to require the 48 volts systems that we discussed before. This because opening and closing engine valves requires very powerful solenoids and this necessitates voltages higher than the 12 volt systems we have today. This technology is a few years away from implementation.