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VSS
Joined: 14 Jan 2007 Posts: 2845 Location: Llyn Peninsula, North Wales
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skedone
Joined: 19 Oct 2006 Posts: 351 Location: essex inbetween a blue bit and a green bit
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dougal
Joined: 15 Jan 2005 Posts: 7184 Location: South Kent
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Posted: Wed Aug 08, 07 7:23 pm Post subject: Re: biofuel |
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VSS wrote: |
... Once started it runs like a dream, only smells like a barbeque. The problem it getting it started. |
The smell is from the unburned hydrocarbons in the exhaust.
Not terribly clean.
The starting problem with *oil* is a clear indication that you are using a fuel that doesn't meet the manufacturer's specification!
Biodiesel (and fossil diesel for that matter) vapourises much more easily than straight veg oil, and so starting (with glowplugs) isn't a problem with the type of fuel the engine was designed to use.
Starting on Veg oil gets even more difficult in cold weather.
A dual tank system should also include an oil heater, so that with the engine started on 'proper' diesel/bioidiesel, it changes over to run on warm oil.
The human part of the control system (yes the bit that gives problems) must remember that (a minute or so) before *stopping*, you should change back to diesel so that the injector system is properly primed with the right stuff, ready for the next start.
/mounts hobbyhorse
Rudolf Diesel didn't 'invent his engine specifically to run on veg oil'.
That is an internet myth, repeated over and over again.
Sadly it isn't true.
The first ever independent performance figures for one of his engines were reported using *fossil* petroleum fuel. (1897 Prof Schroter at Augsburg)
Diesel demonstrated his engines running on various fuels - including milk *powder* and *powdered* coal, oh yes and veg oil too. But his original engine was not specifically designed for these fuels.
The miniature high pressure fuel pump that made possible the first road vehicle with a 'diesel' engine wasn't even *invented* until about 20 years after Diesel's death.
-- source of these statements: Encyclopedia Britannica 14th (1929) Edition
It means that that pump, and its injectors, simply are not designed to run on veg oil (or pulverised coal).
Apart from starting (vapourisation) difficulties, there is a longer term problem, with the injectors being, quite literally, "gummed up".
Veg Oil (and esp used cooking oil) has rather a lot of gums. (You know how sticky a chip pan gets? Then you know what I'm on about.)
Vehicle 'veg oil' conversions do nothing about the gums.
Different injector/pump designs have different tolerances for oil and its gums.
Old Mercs reputedly have few problems but modern ultra high pressure injectors (like VW's "pd" models IIRC) gum up quickly. And are damn expensive.
Biodiesel is a very good solvent (hence its reputation for loosening gunge that then bungs up filters). Running biodiesel occasionally should help to control the gum buildup.
But for a modern diesel engine, it'd be better to run on biodiesel all the time - it really is a much more suitable fuel for a modern engine than veg oil. That's why anyone bothers with it.
/ gets off hobbyhorse |
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Hairyloon
Joined: 20 Nov 2008 Posts: 15425 Location: Today I are mostly being in Yorkshire.
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vegplot
Joined: 19 Apr 2007 Posts: 21301 Location: Bethesda, Gwynedd
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RichardW
Joined: 24 Aug 2006 Posts: 8443 Location: Llyn Peninsular North Wales
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maryf
Joined: 25 Oct 2009 Posts: 341 Location: suffolk
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mousjoos
Joined: 05 Jun 2006 Posts: 1986 Location: VERY Sunny SW France
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Hairyloon
Joined: 20 Nov 2008 Posts: 15425 Location: Today I are mostly being in Yorkshire.
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mousjoos
Joined: 05 Jun 2006 Posts: 1986 Location: VERY Sunny SW France
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brettgilbert77
Joined: 09 May 2014 Posts: 13
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brettgilbert77
Joined: 09 May 2014 Posts: 13
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