Toyota's Direct Injection Four-Stroke Superior version (D-S4) engine combines direct injection (which injects fuel into the combustion chamber) with port injection (which injects fuel into the intake ports). It controls the two types of injectors in accordance with driving conditions. Under heavy load, direct injection is employed. Under medium or high load, both types are used. In the drawing on the left, the engine uses both types of injectors (port injection is marked as "1" at the top). On the right, the engine uses direct injection only. (Source: Toyota)
Talking about automation, what we need also are more intelligent cruise control systems. For electrics/hybrids it makes a big difference if power is constant rather than speed is constant. Allow the cruise control system to slow down the car on climbs and speed ups on descents. With a definable window of speeds for the cruise control, highway efficiency can improve further.
Based on the following government site, bad driving habits can affect milage as much as 33%.
Although I'm not an agressive driver so my milage wouldn't improve dramatically from an optimal pattern, I can hardly wait for autonomous vehicles. Let the machine do the driving! Traffic lights won't even be necessary.
I suspect even our most optimistic forcasts of improved traffic flow and milage will ultimately prove to be pessimistic.
Absolutely right. The more efficient the car, the more carefully the driver has to drive to extract this performance. A 10mpg car is not going to see too much degradation in performance when the driver drives badly. Hybrid and high fuel efficiency vehicles will see dramatic reductions in fuel efficiencies by poor driving technique. The car must be intelligent enough to be able to help these poor drivers while not compromising safety.
Finally! Someone else sees this as a big picture issue. Traffic patterns in this country have severly degraded over the last 30 years (since the big recession in the '70s). Traffic lights have reverted from sensor oriented back to timed lights, and they are no longer timed together. Traffic circles, or round-abouts are non-existant. Stop and go traffic is a problem the government needs to resolve. Not tearing apart working, flowing interstate exits and replacing them with traffic light ramps that stop traffic as they are currently doing in my community. We seem to be going backwards in this area.
If this country is serious about improving fuel economy then we need to invest in things like traffic circles and timing for stop lights. It's no secret that city fuel economy is nominally 30% less than highway economy. btwolfe mentions start/stop habits ... the best solution is to avoid the stop altogether since it takes far less fuel to maintain velocity than to accelerate to the same velocity from a stop.
The real gorilla is simply size and weight. All these admirable technologies simply allow us to extract incremental improvements in efficiency but as long as we use heat engines we are stuck with fundamental physics and the Carnot cycle. The physics of physical size on aerodynamics is pretty much fixed for practical vehicles that people can use for real transportation. Weight is the other one. There will be compromises. Vehicles will have to get smaller and lighter. Cutting weight is where the money is. Vehicle manufacturers have done very impressive work on making engines more fuel efficient, reduced emissions, and have kept performance pretty reasonable. I remember the gutless wonders that came out the the late 70's, early 80's. Chevy Citation anyone? Celebrity with the iron duke 2.5L? K-car? Remember throttle body fuel injection? <<shudder>>. Some of these cars had 0-60 times measured in minutes.
Cars are going to become more focused in their marketing/deployments. For instance, if you do mostly highway driving or country roads with few to moderate stops, a hybrid car becomes a liability because of the extra weight and complexity. Hybrids and start-stops make good sense for city cars and lots of in-town driving but their advantages disappear on the open road. Light weight, good aerodynamics, and simple, fuel efficient engines will yield very good results when the driving is biased towards the open road. Parasitic drag is another area that will yield significant improvements. Power steering and water pumps are prime for electrical replacements.
With all the customer and market interest in fuel efficient vehicles, why does the government feel it needs to drive this market? I can understand to some degree safety and emissions mandates as those are less tangible to the average consumer. But mileage? That's on virtually every one's mind.
The real gorilla in the room is the driver. I don't know what kind of efficiency improvement optimal acceleration and decelaration would garner, but I bet it's significant. I'm always amazed at how many people gun it at the green light only to hit the brakes 500 meters farther down at the next light.
As for the technologies presented in this article, it looks like the engineers are doing their part.
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