In real life the gain in mpg for diesels is more than 25%. 

http://www.greencarreports.com/news/1019256_volkswagen-jetta-tdi-much-more-mileage-than-epa-admits

And yes, winter prices of diesel are obnoxious. 

And as for reliability, I put 200k miles on my Beetle TDI. I replaced the injection pump for $400 at 168k miles. Outside of regular maintenance and the  injection pump, all mechanics were original. Nothing else failed. Clutch, alternator, A/C and so on were original. At 47mpg during my commute it was tough to sell it. 

But I get your point. Diesels will never catch on on the US. They have brainwashed us for decades and most folks don't bother to look beyond the easy-to-digest label. 

Chris.

Wysłane z iPhone'a

Dnia Jan 21, 2012 o godz. 15:29 Dennis Haynes <d23haynes57@HOTMAIL.COM> napisał(a):

> -----Original Message-----
> From: Dennis Haynes [mailto:d23haynes57@hotmail.com]
> Sent: Wednesday, November 23, 2011 12:57 AM
> To: 'Mike S'; vanagon@GERRY.VANAGON.COM
> Subject: RE: Vanagon? Really? Gasoline vs. Diesel
> 
> Over the years there are a number of folks that somehow get convinced that
> Diesel is the way to go and consider ways to convert. There is always the
> question of why more diesels are not available. This may be more of a Friday
> topic but I'll try to shed some light. Of wonderful note we are starting to
> see some interesting technologies for both gasoline and Diesel engines but I
> see a number of forces that will keep Diesel use for small vehicles limited.
> 
> 
> For one thing the new clean fuel requirements and other forces are making
> Diesel fuel too expensive. Even home heating oil is going up. On this
> current trip from New York to Florida I have witnessed as much as a $.80
> price difference from regular unleaded to Diesel. That alone wipes out the
> 25% fuel economy improvement if that's what you get. Many Diesel vehicles
> 2007 and newer also require the use of a special Diesel Exhaust Fluid,
> (DEF). This is a urea based fluid used to mix with the exhaust in the
> catalytic converter to reduce the oxides of nitrogen (NOx) emissions. Due to
> high compression ratios and the excess air, diesels make a lot of NOx. An
> awful lot. This is a primary contributor to smog and why Diesel cars sales
> were not allowed in many Northeast states from 2003 to 2006.  I don't know
> how much DEF is used per mile but I see the truckers by it in five gallon
> pails.
> 
> Another big issue is both the increased purchasing and operating costs.
> Gasoline engine technology is now to the point that there is very little
> scheduled maintenance and almost any engine out there now can go 150,000 to
> 250,000 miles.  Diesels have very expensive injection systems and all have
> turbo chargers. The turbo alone can be a huge maintenance hit when it fails
> and many will at around 100,000 miles or less. Often a turbo failure will be
> the bearing assembly. This can allow engine oil to enter the intake track
> and when the engine sucks it in the engine can go into a run away. No way to
> shut it down until it blows. I have seen a number of Cat engines fail this
> way. The new Diesel injection pumps and injectors have very tight tolerances
> and any contamination will quickly destroy them. The final filters on many
> of them filter to 2 micron.
> 
> So why do Diesels get better fuel economy? There are three main advantages
> to a Diesel.  Diesel fuel has a higher BTU content than Gasoline, operates
> at higher compression, and the biggie is the lack of a throttle. Why does
> the throttle thing help economy? To begin with you do not have the vacuum or
> pumping losses. The inlet is always wide open so each intake stroke takes in
> as much air as can be sucked in or that the turbo can force in. With a gas
> engine when you lift your foot the engine and the vehicle slows down. With a
> Diesel the vehicle will only slow down if going uphill or going fast enough
> for wind resistance to slow you down. No energy is used to suck the air fuel
> mixture through a throttle plate. Now since an engine produces power by
> heating-expanding gases, having the cylinders fully charged with air, turbo
> pressurized air any fuel burn is going to produce a much greater pressure
> change, (power) than a partially charged cylinder would as in a gas engine.
> This really gives the Diesel an advantage at partial load, low speed
> operations. To add further to control emissions, modern Diesel injectors do
> not simply shoot fuel into the cylinder at the right time. They actually
> inject in steps to what is known as wave shaping. They start with a small
> shot to get a burn going, then go for a power shot and then an after burn to
> clean up soot. Yes for each cylinder power stroke the injector can fire
> three times are some variable amount during the full power stroke. This
> makes for complicated injectors as they not only operate electrically but
> the electric part operates a pilot or control  valve in each cylinder and
> then depending on the injector design either high pressure fuel or engine
> oil actually hydraulically operates the injector pin. This is often known as
> a Hydraulic Electric Unit Injector, (HEUI). On some engines these are
> calibrated so tight then when replacing them the replacements get stamped
> with trim numbers to reflect differences from the ideal standard. When
> installed you need to go into the ECU and program the trim numbers for the
> new injectors and the cylinders they were installed in.
> 
> A Gasoline, (spark ignition) engine has to run with a controlled fuel-air
> mixture. In order for the engine to run at a given RPM, it has to have a
> certain volume of air and that volume has to have a matching, (14 to1)
> amount of fuel go with. The Diesel does not need this. Note that in some
> applications Diesels are also run with propane or natural gas.
> 
> So where are we going with this. We are starting to see gasoline engines
> that will be direct injection and at some point we will see them going to
> compression ignition. The wave shaping technology described above will allow
> gasoline to be burned at much wider mixture ranges. So for idle and low
> speed we can use the spark ignition and normal mixture control for
> smoothness and when under way go to compression ignition, maximum air
> intake, and maximum power and efficiency.  This along with Hybrid technology
> is going to be the future for automobiles and light trucks. Diesels will
> still have their place for industrial and large truck, locomotives,
> generators etc. but the new stuff will be complicated and until these new
> technologies get refined somewhat expensive to maintain.
> 
> Dennis
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Mike S
> Sent: Saturday, November 19, 2011 11:25 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Vanagon? Really?
> 
> At 10:45 PM 11/19/2011, Dennis Haynes wrote...
>> As Gasoline engines go to
>> direct injection and dual mode, (spark ignition to compression
>> ignition) the
>> Diesel advantages will disappear.
> 
> Compression ignition _is_ Diesel. It's not a matter of what fuel it uses.