AdamB wrote:Interesting. I current own 2 direct injected cars, and I can say that they haven't increased efficiency over their normal throttle body/upstream of the valve injected by 50%.
CVT transmissions on the other hand...
Only a portion of the increased efficiency in the Delphi-Hyundai engine was from the direct injection. Another big part was getting the cylinders to fire off with compression alone, no spark plugs. Like a diesel engine. And combining direct injection with a turbo, like the Ford ecoboost engine. There were numerous other areas that added a small efficiency gain here or there as well. And Hyundai is targeting more modest fuel savings than the original Delphi article: 25% better fuel economy.
In conventional gasoline-powered engines, a spark ignites a mixture of fuel and air. Diesel engines don’t use a spark. Instead, they compress air until it’s so hot that fuel injected into the combustion chamber soon ignites. Several researchers have attempted to use compression ignition with gasoline, but it’s proved challenging to control such engines, especially under the wide range of loads put on them as a car idles, accelerates, and cruises at various speeds.
Engine Could Boost Fuel Economy by HalfHyundai has revealed an ultra-efficient diesel engine, and although it’s a compression-ignition internal combustion engine — gasoline is its fuel. It has a common-rail fuel system, uses both a supercharger and turbocharger, and has diesel-like high compression. What it does not have is a spark plug or even a glow plug. According to Hyundai’s Nayan Engineer, “What we have is an ultra-efficient IC engine, a diesel compression-ignition engine running on gasoline.” What’s at stake is creating internal combustion engines that are clean, efficient, powerful and cost-efficient engines for the next 10 to 30 years.
Then there’s the turbos. While gas engines have toyed with turbos, and in the last decade about 15% of engines passenger car engines became turbocharged, modern diesels always use at least one, and often two turbos or an expensive variable-geometry turbocharger. You can see turbochargers gaining use as smaller engines nabbed the turbo advantage, then direct injection, to make a compact gas engine punch far above its weight. Ford’s EcoBoost engines are a great example, as are Hyundai’s GDI motors.
According to Engineer, “Gasoline doesn’t want to auto-ignite, diesel fuel does. Gas is locally slow (burning), locally lean.” The Hyundai chief says that to make this engine work there are several critical technologies, all enabled by modern turbos, injectors, and above all, modern engine computers.
In every phase of development, the team has also focused on friction reduction. This engine accomplishes many tiny efficiency gains, like 1 percent from a rollerized camshaft, 3 percent from rollerizing the cranktrain, 1 to 2 percent by recovering waste heat. They’ve optimized the two-stage oil pump and lowered the rpm limit to 5,000, coated piston rings with low-tension oil control rings, and coated the piston skirts. Even cooling the EGR offers a 3 percent improvement in efficiency.
If you’re wondering why all the bother to create a new class of engine you need look no further than the emissions regulations set to phase in next year. We’re betting we will see similar technology for small engines emerging from many automakers. For one, it makes sense, and we know clean-burning engines are needed globally as well as at home. This research also opens whole new avenues in diesel engine technology, and we’re darn thankful. Hyundai is not the only company working on gasoline fuel use in a diesel engine environment. We’ve also seen early examples of a similar setup from Audi and Aragon National Labs. In both cases, the goal is to reduce the emissions in a gasoline-burning engine. As technology marches on, we’ll see more of these hybrid engines and most likely other new technologies as well.
DIESEL HYBRID ENGINE: NEW HYUNDAI DIESEL RUNS ON GASOLINE
The oil barrel is half-full.