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Any diesel engine can run a straight veggie oil. It's simply a matter of getting the oil into the engine, at the right viscosity. For most diesel engines the fuel must have a viscosity at or below 20 centistrokes (mm2/seconds). For veggie oil this viscosity is achieved at about 160 degrees F.
There are alot of ways to heat the veggie oil to the necessary 160 degrees. The most commonly used way is to run coolant lines from the cars radiator around the veggie oil. This method takes advantage of the waste engine heat to heat the oil. The problem with this method is that you have to wait until the coolant gets hot enough. This can take as long as 15min of driving! So if you have 10 min. commute to school or work (like me), don't plan on using much veggie oil because most of the time you'll be driving on diesel. To bridge this gap when the coolant is getting up to temperature, some SVO conversions have an electric heater that provides quick heat to get the oil flowing.
When we began designing our conversion system, we realized that there is another source of waste heat from an engine. Exhaust. Close to 42% of an internal combustion engine's thermal energy is lost in exhaust. Also exhaust is instantly hot, as it is produced by the combustion of fuel.
More than 25 different designs later, and over 20 hours of sitting in front of a computer with our eyes glued to a 3d modeling program, we developed our final design for the conversion. It would use both exhaust and electric heat to have our benz running on SVO within only a couple minutes of turning the key.
So, without further ado, I present to you...
The Process
The research, design, and assembly of converting our mercedes to SVO. From june 2006 to the present, Here is the process in journal form.
Finding a vehicle By: Josh Munson
My name is Josh Munson. I am the “head mechanic” for the Veggie-Benz conversion project. Ethan and I have been planning this project for close to six months, and during that process we have deliberated about what was the ideal vehicle to convert. I said that an older diesel pickup would probably be the best due to their simplicity and durability (and raw low end torque). Ethan agreed, but as we began looking for trucks he had a new idea: This project is also about being fuel efficient, so perhaps a small diesel car would be better. I agreed with him and the hunt for a mid eighty’s VW Rabbit began. A month went by, and Ethan had pinpointed a Rabbit up in Craftsbury. We were literally inches from that purchase when one night a few weeks later Ethan spotted a pristine ’81 Rabbit on ebay. We contacted the owner, went and saw it, the whole nine yards. Then on the final night of the auction the guy cancels it! Our hearts sank in disappointment. But just as hope faded, an ‘82 diesel Mercedes 300D popped up on the screen with 20 minutes to go, and nothing wrong with it (except maybe the color). We both said, “Well, why not?” Now we are converting a nice creamy-yellow 1982 Mercedes 300D Turbo diesel. Months of agonizing, searching and investigating ended in a twenty minute blaze of glory! And that’s the story of Ol’ Yeller.
Exhaust Heat By: Ethan Dreissigacker
The one major difference between our conversion, and the many other conversions out there will be the use of exhaust heat (hopefully). The advantage of exhaust is that nit gets hot very fast. we have a thermocouple on, and in our exhaust pipe. Within 10 seconds of turning on the car the heat of the exhaust gas is around 250-300 degrees F... And that's idling. when running the car at full throttle up a hill we have seen the exhaust temperature over 650 degrees. This leads me to the disadvantages of exhaust heat. It is extremely variable, depending on the load on the engine. It will jump from 300 to 600 degrees and back almost instantly. The vegetable oil must be maintained at 160-200 degrees to be injected properly. This means that the exhaust heat must be controllable to prevent the possible over heating of the oil. So far we have 4 different designs for an exhaust heating system. some are very complicated and some have obvious flaws. Here they are: Click on them to see full size.
All Show no Go By: Josh Munson
As you know we have a very beautiful ’82 Mercedes, but that was about all she had going’ for her at the time. Let’s just say you'd need a calendar to get the 0 to 60 time. As it turned out she was suffering from a case of having a hack artist for a previous owner. The car had very little power to speak of, and the transmission shifts were so hard, your foot came off the pedal. She just needed a little TLC. First, Ethan and I took a look at the 13 miles of star trek style throttle linkage, and sure enough, there was a hole drilled with a bolt trough it to hold the idle right, and you had to stomp a hole in the floor to get full throttle ( which is actually an important aspect for diesel engines).
In order to make room for the surgery on the linkage, we went to remove the stock airbox. In the process we discovered the methods of improper hardware and enough wire to hang an exhaust with, that had been used to “Secure” the airbox to the engine.
An array of lubricants, and the “Don’t force it, use a bigger hammer” method fixed the linkage, plus we set the idle Rpm the correct way, with success, and a slight increase in power. Now, she’s got a twinge more power, but it’s still about 6 G’s when she hit’s second gear so, an adjustment was in order. Once again the previous owner left us a surprise, and filled the tranny fluid about 1½ times too high, which raised the torque converter’s pressures a little two high to be comfortable. Well two down one to go.
This entire time, the car was running with no air filter of any sort so that was next. Ethan and I were contemplating the purchase of an aftermarket High Performance intake. After we deliberated the cost, I figured a trip to NAPA could produce the same results a lot cheaper than 150 bucks. Sure enough, we picked up a cone filter for 26 bucks, a 3 dollar pipe adapter and a piece of the old intake, then we had an intake to rule them all! ( Pictures in the photo gallery)
One test drive after the improvements and we thought we were flying! If that was’t enough I mixed in some fuel additive in with what was in the tank, so she’s a cookin’ now. It just goes to show what a little time and effort can do for a car, and we hope to keep doing just this type of work until we have our eco-efficient work of art.Parts By: Ethan D
Here is a list of all the parts we've used so far... It will grow as we continue to experiment.
- 2x electric 12v soleniod valves. 3 port.
- 20' annealed aluminum tubing- 1/4 inch I.D, 5/16 O.D.
- 6' viton rubber fuel line- 5/16 inch I.D
- a bunch of hose clamps.
- zipties - 6 inch
- 25' high temperature fiberglass insulation- 1/4"x2"x25'
- approx. 6' foam tubing insulation. for 5/16 tubing.
- 2x brass barbed tee fittings- for 5/16 hose
- 1 brass barbed reducing tee- 5/16 > 3/16 > 5/16
- 1 compression to compression coupling- 5/16
- 1 compression to barbed fitting- 5/16
The Three Port Solenoid Valve By: Josh Munson
The main component of a veggie oil converted car is the three port solenoid valve. This allows two different fuels to be run into the same engine. This type, manufactured by Greasecar™ features a mounting plate, three barbed fittings and Viton seals that can withstand high temperatures of heated veggie oil, and the corrosive properties of bio-diesel. The valve is powered electronically by a 12 volt source, being your cars battery, allowing it to be wired to an ON/OFF switch which controls the flow of the fuels. When the valve is in the OFF position, it allows whatever fuel is in the cars’ stock fuel tank (usually regular Diesel) to flow through the valve. When switched to the ON position, the Diesel is cut off and now Veggie oil is being pulled through the system. A fuel system requires two valves because of the diesels injector return setup. This takes any unused fuel from the injectors and places it back into the tank and main fuel supply line. Not only do you need to supply veggie going in, you need to get rid of the veggie flowing trough the return to prevent any stoppages in the lines. You must purge the lines with diesel again. So another valve supplies diesel directly to the return line purging out any diesel.
Car Troubles By: Josh Munson and Ethan Dreissigacker
Things were going pretty well, it was a sunny day in Morrisville, and Ethan and I had just emerged from the rear bay of concept 2 in a running Mercedes with two newly installed and solenoid valves. We thought, hey, while we’re in the area let’s bring it to the car wash! So we do, we give her a “class A” wash down and head out.
We were about 1 mile from my house when a sudden humming noise emerged from underneath the hood. We pulled over for a quick inspection. Sure enough, the injector pump oil supply line had blown off and we had single handedly and efficiently pumped every ounce of oil out of the engine, and blown it all over the newly cleaned car.
We added more oil and proceeded on home.
Now, we are pretty well back on track, and it’s time to install the fuel line that runs from the bottom of our exhaust coil into our fuel pump. We also have to swap out a fitting in the top of the diesel filter, and plug the hole where it was. We get the car inside and operate. A few hours later its time to test it out. IT LIVES! For about………..2 minutes. The car would start, run for a bit, and then shut off, as if it was starved of fuel. We finally gave up, leaving the car in the school parking lot for vacation. After two weeks of going over every scenario that would cause a lack of fuel. Clogs, and lines and pumps and injectors, the circle was continuous but to no avail. Now that I had almost convinced Ethan into buying an injector pump, we tried one last idea. Hey, why don’t we buy some clear fuel line so we can see what’s going on? Well, it worked. The problem turned out to be the way in which our fuel system was set up. The stock setup pushed fuel through the filter where as our system pulled it through. That means if there is an air bubble present in the filter, the liquid connection between the filter and the lift pump is gone, essentially sucking air. The car had run fine before with our setup, but hen we changed the fitting on the filter we got a nice big air bubble in it. Well anyway, at that point we just wanted to get the thing back home, so we reset the fuel system back to the stock setup, and drove home.
On the way home we were reminded of another problem. Remember that humming noise that appeared when we ran low on oil? Now it’s a raging growl and the runs like its being dragged with a noose around it’s neck so that means we completely fried the turbocharger’s main bearings, but don’t worry. There is a used turbo in the mail right now so things are looking up.
