Tim - Yes it is done, but is unwise, especically if no modifications are made to the injectors, etc., and it is most often done on older Mercedes with the oil-fed inline Bosch pump and percussion balls in the prechamber. That combination and the engine's durable design, and the use primarily of new rapeseed oil (thinner, cleaner, and better combustion than waste cooking oil, and cheaper than petrodiesel in Germany, where most of this is done), allows people to get away with it to some extent.
However, for most engines (and I have the Mercedes and still do not use the single tank idea), even if one has a design that heats the fuel sufficiently on a cold day at startup (alternator output becomes an issue, you are really asking a lot to pre-glow the engine and pre-heat the fuel, all electrically, and at about the same time, prior to startup), you would still be injecting SVO into a cold combustion chamber at startup, and allowing SVO to cool in the combustion chamber at the end of the cycle. This leads to excessive coking of the injector tips, poor combustion characteristics, upper cylinder deposits, ring sticking, excessive wear in the engine. It might take a while, and this is where people fool themselves into thinking its ok and all is well. Given the above, and the need for considerable electric heating in the sort of design you propose (both 12V and mains overnight, probably), it is easier and less expensive to use other techniques, the foundation of which is the two-tank arrangement. Then you can use return fuel heat, glycol heat, electric heat and/or combinations to do the job quite easily. The down side of installing an extra tank is a bit of lost space, but the positive is also added range. We have two-tank systems that use just electric heating, and also glycol+electric for colder climates, and they start at $299 US. They are quite straightforward installations, usually installed by one or two people in under a day. If someone shows me good studies that use single tanks longer term and no problems in terms of coking, I'd take a look at it, but the other issue is that new rapeseed oil is probably superior to most other oils, and yet around the world, many people will be using a range of new and used oils that are not as fit, have higher cloud points, less favourable combustion properties, etc. So, studies showing acceptable longer term results on single tank but on rapeseed oil, and on Mercedes engines as described, would not be helpful. Edward Beggs www.biofuels.ca > From: Tim Helweg-Larsen <[EMAIL PROTECTED]> > Reply-To: biofuel@yahoogroups.com > Date: Thu, 20 Dec 2001 12:27:00 +0000 (GMT) > To: biofuel@yahoogroups.com > Subject: [biofuel] SVO without a diesel start/purge > > Hello, > I have been looking at your archived postings and > researching different designs of VSO conversions. I > have yet to come across any that overcome the use of > diesel or biodiesel as a startup/purging fuel. > Does anyone know of cars that have been rigged to > start on VSO even on cold days? > > I have the outlines of a possible design here, and I > am keen to hear what you think of it. > > SVO/WVO only design: > - Single fuel tank and delivery system (SVO) > - Fuel lines and possibly tank heated with engine > coolant (pipe in pipe) and insulated > - Electrical heating element (wire) inserted inside > fuel lines close to the engine, near to the fuel pump > and injectors. Also electrical heat tape wrapped > around the outside of pump and injectors. > - A small reservoir installed just before the fuel > pump. This would consist of a collapsible bellows, > also heated from the inside with heating wire. > > So with all this in place, it would be operated as > follows: > The electrical heaters would be turned on, as you > might with glow plugs. These will bring the fuel that > first needs to get to the engine up to temperature. > In the worst case example, you might find all your SVO > fuel solid in the morning. In this case the electrical > heaters would melt and heat up the fuel close to the > engine and the engine would begin to use up this and > the fuel in the reservoir bellows, collapsing it as it > did so. With the engine now running however, it could > start to melt the rest of the fuel supply and > replenish the reservoir. The electrical heaters would > be controlled thermostatically to cool down and shut > off as the fuel supply heats up sufficiently. > > The practicality of it all would depend to a great > extent on how quickly the electrical heaters generally > took to bring the SVO up to temp. Bear in mind that > the volume of fuel contained in these ãend of the > lineä components isnât very big and that the specific > heat capacity of Veg oil is probably quite low. I > would hope it could heat up quite quickly. > > You then have to weigh up waiting for a veg oil only > car to heat up or the slightly cumbersome procedure of > switching fuels in an SVO/diesel. I suppose in part I > am trying to find a design that is easy for Joe public > to buy and not think twice about. > > Anyway, I would appreciate any feedback on this, > > Thanks, > Tim. > > > __________________________________________________ > Do You Yahoo!? > Everything you'll ever need on one web page > from News and Sport to Email and Music Charts > http://uk.my.yahoo.com > > > Biofuel at Journey to Forever: > http://journeytoforever.org/biofuel.html > Please do NOT send "unsubscribe" messages to the list address. > To unsubscribe, send an email to: > [EMAIL PROTECTED] > > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ > > ------------------------ Yahoo! Groups Sponsor ---------------------~--> Send FREE Holiday eCards from Yahoo! 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