I'm impressed. I did not know the difference was that high. I didn't believe it either, but looked it up here just for a quick resource.
EPA/DOE 2005 Fuel Economy Guide
Initially I thought "why are we not all driving diesels?" But it is the primary reason people buy fuel efficent vehicles in the first place: money. In 2005, the price adder the diesel engine was ~$3,500. (2005 Volkswagen Jetta, TestDrive.com) A seven year investment to break even, longer when you consider time/value of money. Do you think an "ethanol tuned" engine would carry this type of premium? (I recognize, that is a hard question to answer, but critical to the success of a producer of such engines.)
I appreciate the links on the Miller engine. Good reading for me later. And "engineering gobblegook" is what pays my bills. Thanks. A while back a read an article by a Saab Automotive Engineer talking about a new line of engine built specifically from ethanol. He was stating the lower energy content was going to produce a lower MPG but expected people to break even because of the lower price of ethanol. If I can find it again, I'll ping you to it.
The Saab article isn't the same thing you are talking about. They were adjusting timing and Turbo to better use E85 with a 104 Octane. Ping to you none-the-less.
http://www.edmunds.com/insideline/do/AutoshowArticles/articleId=108748
Yes, diesel engines cost more. But there is also a marketing component WRT diesels in passenger cars in the US.
In the EU now, over 40% of all new cars sold are diesels -- small, highly-efficient turbo'ed, common rail or "Pump Duese" (pump injector -- aka 'piezo injectors'), getting mileage like those VW products I'm using for illustration. So customers like the performance. So customers in the EU like diesels and they like the performance they're seeing from tiny little diesel engines (1.8 to 2.2 liter displacement).
In the US, however, GM and others have made such a hash of diesel engine products for the consumer in the late 70's that an entire generation of consumers instantly says "Oh, not this crap again!" when you tell them about diesels. To sell these people on diesel cars, you need to bodily grab them, sit them down in the driver's seat of a prospective car, and force them to drive it.
The fault for this is GM's. GM had some atrocious products in the late 70's -- in particular, a 350-cid engine that they made into a diesel by changing the crank, pistons, heads, etc -- and the result was a roaring piece of crap. It was unreliable, trouble-prone, smoked like it was burning soft coal, you name it.
The second perception of diesels in US consumer's minds comes again from GM, or rather, the Detroit Engine division, who used to make these smoke-belching two-stroke diesels that used to be used in muni bus fleets all over the US. People saw how these things belched smoke, knew they were diesels and it is implanted in their minds that "diesel means thick black smoke."
The first thing we US consumers need to do is start pressuring Detroit to make modern products - and by "modern" I mean "Look at the European engine manufactures, particularly in Germany, and use that as a starting point. Don't try to cheap out of this."
The second thing we US consumers need to do is become informed about what is possible with diesels. With today's computerized fuel injection systems, they no longer smoke -- either at idle or under hard acceleration. They're highly fuel efficient. And they're not slow. The problem of perceived "lack of get up and go" again comes from the 70's -- GM didn't put a turbo on that piece of crap 350-cid V-8 morphadite diesel, which means that until it got up in RPM and "breathing", the performance just sucked the chrome off a bumper hitch.
Today, there are no diesels in cars without a turbo. Period. It is just naturally assumed that "diesel needs a turbo" and that's the truth. They do, to get the highest efficiency and performance out of them.
Next thing diesel cars need: better transmissions. Diesels have a characteristic of developing their torque at low RPM's, and in a narrow band of RPM's. This is why big diesel trucks have 9 to 18 gears in them -- to keep the engine in the RPM range where it is most efficient and developing the best torque. If you can do that, a diesel engined car can fly off the starting line.
You're starting to see ads for 8-speed trannies on luxury cars now, even with gasoline engines. The recent turbodiesel cars being released by MBZ and others are up to six speeds. Want to see the optimum efficiency from a diesel? Get a 10 to 14 speed transmission in the car, and keep that engine within a narrow 200 RPM "power band" and not only will you see your fuel mileage go up, up, up, but the car will fly off the starting line.