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Date:         Sun, 22 Jan 2012 13:04:17 -0500
Reply-To:     "Chris S." <szpejankowski@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "Chris S." <szpejankowski@GMAIL.COM>
Subject:      Re: Vanagon? Really? Gasoline vs. Diesel-again.
Comments: To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
In-Reply-To:  <BAY152-ds31F50F19C8BC260DCA300A0840@phx.gbl>
Content-Type: text/plain; charset=utf-8

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.


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