after the VW cheat-a-polooza, I doubt we'll see 4-cylinder diesels in the US ever again. DEF systems are too expensive for econoboxes.
Using DEF / Urea in the diesel exhaust system is like the old 2 cycle engines where you had to mix oil and gasoline. A truly efficient diesel engine should not need any type of Urea. So why is it if a diesel goes 60 miles on one gallon fuel it is a polluter so when the same diesel engine goes 40 miles on one gallon of fuel it is not a polluter. Help me on this one I went to public school and can't figure this one out....
One reason diesel engines are more efficient is that the peak temperature in the cylinders during combustion is hotter due to higher compression ratios. Unfortunately, that also means they produce a lot more compounds of nitrogen since there is nitrogen in the air and it'll react with oxygen at high temperatures to form NOX. If you run the engine rich, the extra fuel will cool the combustion and prevent NOX production but of course it uses a lot more fuel and pollutes more with hydrocarbons. Those can be dealt with another way.
To me it looks like the diesel engine is at the end of its useful ability due to pollutants. VW could only sell their diesel engine cars by fraud not by technology. I believe that current direct injection gasoline engines are the way to go as regular gas is less expensive than # 2 Diesel. Here in Warrenton Oregon, diesel $2.5999 / gallon, regular 87 octane, $2.039 / gallon. Prius (2016) est. 55 mpg on 87 octane, diesel 40 -45 mpg on expensive diesel. So where is the savings on diesel. Also lets not forget paying $3-5 / gallon of DEF/ Urea every 1,000 miles or so with the diesel. Again show me the savings with diesel...
not everyone lives in Oregon.... in Europe, diesel fuel is 10% cheaper, and TDI's cheat on emissions so they can be relatively affordable and fast, and get good mpg... thats why around 45% of EU drives a diesel.
They are also running lean much of the time, so there is more oxygen available to react with the nitrogen instead of burning with the fuel. VW cheated in regards to NOx emissions. The type of fuel has no bearing of how it is produced, but the conditions within the cylinder during combustion, and nothing to do to with efficiency. Well, that is is you want to use less fuel by making more NOx. The most efficient gasoline car available for sale was the original 2000 Insight. Its revised combined EPA rating is 53mpg; 65mpg under the old system, and many hypermilers have gotten over 100mpg in it. Part of its ability to sip so little fuel, and that of the older Civic VX and CRX HFE is that engine could use a very lean fuel mix. This results in high NOx production, as it will in any type of engine running the fuel mix lean. The Insight actually had a NOx trap like diesels now use. Current DI engines exceed the particulate emission limit that put a filter on diesel's exhaust years ago. It isn't all about money. My support for diesel stems from the current advantage it has in terms of sustainable, renewable fuels, and it is not just biodiesel. There is a vegetable oil based substitute that is a better replacement than biodiesel. It is already for sale in California. Audi has a pilot plant making a diesel heavy crude for excess wind power, exhaust CO2 from another plant and water. Not that there isn't research going into a renewable replacement for gasoline, but the field is further behind with most being done with alcohols that require different engines to be truly effective.
That's why I was surprised at the figures. But while the absolute rating may be off due to the difference in the testing cycle, the increase seems to indicate a pretty decent jump in efficiency. Very curious to hear what the ratings for the (various and as yet unclear) models are, including any possible 4/AWD version.
My bet is that the core 2WD model for the US (i.e. not eco) will achieve EPA rating of: 54 MPG highway. 58 MPG city 56 MPG combined. What is your bet?
I've been racking my brain to figure out how to poll this before the official numbers come out. In theory, two polls are enough, City and Highway as the combined is just a weighted average. But a single poll, combined is much easier . . . so many choices. Then the fourth poll is 0-60 times: > 9.8 sec. # That MPG better be my range 9.8-9.6 sec. # 9.7 is generally accepted number, no change 9.5-9.3 sec. # Ok, less bad 9.2-9.0 sec. # Humm, will be noticed 8.9-8.7 sec. # Hot Dog, we're having fun <8.6 sec. # Holy Carp! A full second shaved off!!! Bob Wilson ps. Perhaps all four polls but over in Fred's as a kinda of drinking contest. End them on November 17 and tally up scores: +1 for each correct guess. The "4" pointers get 'a toast' at our respective, local bars.
Maybe the Plug-in Prius until the battery is exhausted, but then one still has to figure out what to do with the human occupant(s).
