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1974 240d SVO Conversion

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monarchd's picture
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Hey Guys-

This is my first time posting, but I've already read through many posts and have gotten so much information already. Thanks!

I am looking to get a classic Merc diesel to convert to run on veggie oil. I have come across a 1974 240d which the seller is asking $1000. I have yet to see the car but before I even get my hopes up, has anyone attempted this conversion before? If so does anyone have any advice?

I know alot of people convert 80's s123/s124 but I am much more of a fan of the w115.

Any advice would be great!

Thanks,
Adam Sax

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redghost's picture
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Vehicles
2002 S430
1995 300D
1974 450SL
1972 220D

The old w115 is a great platform for a conversion. The OM616 engine is really simple and can run on just about anything you can get in the tank.

First consideration for running a VO car is outside temperature. Cold climate VO cars are not run in the winter. Just no great way to get the fuel to stay hot long enough without boogering up the engine and gelling in the lines.

Temperate climate cars are best done as a two tank system running VO as travel fuel and a bioD or petro tank (three gallon) as start and purge. Frybrid.com makes a really great system that will blend right in and looks oem in the cabin. You put VO in the main tank and have a small tank under the hood for non VO.

Hot climate cars are great for straight VO with no need for dual tanks or much of anything else. Just fill and go. Temps over 35 C are enough for your VO to flow wth ease. Deserts are not that good, because temp fluctuations from night to day will chill the fuel and might have gel issues. Tropics are the best for VO.

You can add VO to any tank of fuel you normally would run. I have run up to 80% VO in Gump during summer months. A gallon or two in the winter also works well.

Waste VO is another matter. There are many impurities that will screw up an engine if not removed. If you are going to get WVO, settle it out for at least a month, filter it down to 5 microns, 2 microns is better. Add a biocide to the VO so that algae do not grow, and dewater it as best you can. Try to get chinese or safflower/canola oil. Mexican and fast food oil is more garbage than fuel.

If you do run large amounts of VO in the engine, you will get some coking and glazing of the cylinders. There are sugars in the VO that need to be cleaned off. Best way to do this is to run petro tanks 100 gallons. It will disolve the gunk in the system and keep you running well. BioD is better, but not available everywhere.

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clay

2002 S430 - Victor, White Tie & Tails
1974 450SL Frosch, my little froggy prince, after meeting a bunch of toads
1972 220D - Gump - She was green, simple and ran and ran
1995 E300D - Cleo - Killed by a Suzuki Vitara
POS 1987 SDL - Beware Nigerian Scammers

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I built a system for my 1974 240D that will use the factory fuel tank for WVO, and a 5 gallon auxilary tank for startup/shutdown on biodiesel. There is a heat exchanger in the engine bay which transfers heat from the coolant into the WVO directly before it goes into the engine. I have not yet completed the installation, but I expect it to get the oil to a high enough temperature that it's viscosity is within the range of regular diesel fuels. My system is simpler and cheaper than most others, but it will be impossible to run 100% WVO when the ambient temperature is below the cloud point of the oil. Canola, Safflower, and Soy have a CP below freezing, and it rarely freezes where I live.

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Hi there,

Do you use filtered WVO? Can the existing filters take care of the impurities in the oil Clay mention? I was thinking of dumping down some waste vegetable oil for long trips along with ULSD.

Unfortunately, I do not have free space to filter waste oil.

W115nut

casioqv wrote:
I built a system for my 1974 240D that will use the factory fuel tank for WVO, and a 5 gallon auxilary tank for startup/shutdown on biodiesel. There is a heat exchanger in the engine bay which transfers heat from the coolant into the WVO directly before it goes into the engine. I have not yet completed the installation, but I expect it to get the oil to a high enough temperature that it's viscosity is within the range of regular diesel fuels. My system is simpler and cheaper than most others, but it will be impossible to run 100% WVO when the ambient temperature is below the cloud point of the oil. Canola, Safflower, and Soy have a CP below freezing, and it rarely freezes where I live.

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redghost's picture
Seattle, WA
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Vehicles
2002 S430
1995 300D
1974 450SL
1972 220D

The particulate matter will very quickly clog your filters, both in the tank and by the engine. There are also issues with organic matter disolved in the oil that is not best for long engine life. If you want to do small scale filtration, use a garbage can and silk to get the big bits out. Then use a commercial coffee filter and a five gallon bucket to siphon off what you want to put in the car.

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clay

2002 S430 - Victor, White Tie & Tails
1974 450SL Frosch, my little froggy prince, after meeting a bunch of toads
1972 220D - Gump - She was green, simple and ran and ran
1995 E300D - Cleo - Killed by a Suzuki Vitara
POS 1987 SDL - Beware Nigerian Scammers

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'74 240d Update

Hey guys-

Thanks for all the great info on the conversion.

So the 74 240d I am looking to buy to convert has a bad lower bearing. I know to repair this would involve a full engine rebuild. Is it worth it to rebuild the engine or should I try to find a new engine? I do not have access to a full garage and I have a limited budget (I'm just a college student).

Your insight is greatly appreciated,
Adam

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redghost's picture
Seattle, WA
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Joined: December 17th, 2001

Posts:
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Vehicles
2002 S430
1995 300D
1974 450SL
1972 220D

If you can get your hands on a known good engine for decent cash, you will be in much better luck. The rebuild will cost at least $1200. If you have time and cash, go ahead. For around $300 you should be able to get a rusted out 240D with an om616 in fine shape. All it would take is the time to get them swapped out.

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clay

2002 S430 - Victor, White Tie & Tails
1974 450SL Frosch, my little froggy prince, after meeting a bunch of toads
1972 220D - Gump - She was green, simple and ran and ran
1995 E300D - Cleo - Killed by a Suzuki Vitara
POS 1987 SDL - Beware Nigerian Scammers

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casioqv's picture
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W115nut wrote:
Do you use filtered WVO? Can the existing filters take care of the impurities in the oil Clay mention? I was thinking of dumping down some waste vegetable oil for long trips along with ULSD.

You will need to settle and filter the WVO or it will clog your fuel lines, filters, and tank. There is no way I know of to use WVO directly from the fryer in your car without settling and filtering externally. It may be possible, but you would need to engineer a very high surface area multi-stage flow through filter before the fuel goes into the tank. It would likely need to use a lot of heat and pressure to get reasonable flow rates. I plan on using virgin canola SVO when avaliable, which is still cheaper than diesel, and a much cleaner/easier to work with fuel.

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