Anyone else make biodiesel?

I'm on my 3rd processor right now. The first one was made out of a water heater. It made 25 gallons at a time. The second one was made out of a 55 gallon barrel that I cut the bottom off, and welded a cone onto. It made 45 gallons per batch. Now I'm on to the 3rd itteration. It is made out of a 90 gallon pressure vessel. I can make about 70 gallons at a time.

I haven't kept track exactly how much they cost to build, but I'd say probably around $300. My fuel cost me about $1/gallon now, so my ROI is pretty quick with 3 big diesels in the fleet.

I know all about SVO. My first experiment into biofuels was an 85 Suburban with a 2-tank SVO system. I logged about 40K miles on that thing on veggie before I sold it. The only issue I have with it is that now that I have 3 vehicles, the initial investment to run them on SVO would be a lot higher than to run them on bio, since I would have to buy 3 of everything. It's a big chunk of change to drop right now, especially since I already have the bio equipment up and running. I'm planning on eventually installing veggie systems to my trucks, but it will have to wait for a while, as cash is tight around here right now.

j427x said:

i had been running it. but murphy oil started going around collecting all the used cooking oil from the fast food joints and cut off my supply of used oil.

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Same thing here, with big stickers on the tanks telling how it belongs to the waste company and they'll prosecute you for theft.

I've run up to 20% vegetable oil mixed with regular gasoline in my 1980 Malibu. Smelled a bit odd at idle, but started and ran fine, mileage went up about 1.5mpg, probably because the factory smog calibration in the carburetor is very lean, so it was closer to stoichiometric with the SVO.

I'd still be using it if it was still available for free.

I used to run about the same proportion of Diesel to gasoline, back when Diesel was cheaper than gas. Been a long time now.

Diesel mixes fine with gasoline, but you have to premix vegetable oil, which is a pain in the ass. Once it's stirred and mixed, it stays that way - I let test burets sit for a week in the freezer, and a month out in the shop, with no separation. But if you just pour it into the tank it'll run to the bottom and get sucked up by the pickup tube, the carburetor will fill with straight oil, and you'll find that gasoline engines *really really* don't like that. Fortunately the engine was fully warmed up and I was on a long straight road after dumping some oil in after refuelling. I moved along wide open at about 25mph for twenty miles or so before it cleared, limped back home, and had to put new plugs in. On old G-bodies like that you have to either have prehensile hands or you jack the car up, take off the front wheels, and access the plugs through the fenderwells. <sigh>


I also tried 25% nitromethane/alcohol (model air plane fuel) injection through a spraybar in the air cleaner lid. The nitro dissolved the plastic on a couple of windshield-washer pumps I tried. I thought the nitromethane would work like a poor man's nitrous oxide setup, but the car actually lost power when I hit the switch. I figure the 75% alcohol part cost me more power than I gained from the nitro, and I was probably airflow-limited by the ~200CFM Rochester DualJet carburetor anyway.


"Diesel-Kleene" or other Diesel fuel additives work great in gasoline engines. To simplify things considerably (for detail, get Glassman's "Combustion, Third Edition" from the library) the additives make fuel easier to light. In Diesels, it increases the cetane number. In gasoline engines, it makes the fuel easier to light and faster to burn, without making it more sensitive to detonation. Running is noticeably smoother and gas mileage goes up. However, after checking mileage through several tanks, I came to the reluctant conclusion that, price-wise, it was a wash. Plus the additive stinks to high Heaven, and even the empty funnel will stink up a station wagon.


Uh... I've played with fuels a bit.

Smokey Yunick. He had some of the OEMs looking at it for a while, blamed failure to sell his invention to them for Big Bucks on the "Not Invented Here" mentality, then got sour over the whole thing.

I acquired both the original and revised patents, which are beautiful examples of the patent application lawyer's art. They lay out the various claims while giving a minimum of useful information. Still, it wasn't *that* difficult to figure out.

Basically, I think Yunick's method would have been unable to pass the EPA's cold start emissions cycle. It would also have been a dog to drive until fully warmed up. Also, I think throttle response would have been... strange, at least to people used to carbureted cars with direct throttle linkage (as opposed to many modern cars, where the pedal and engine RPM are only related by software). Finally, the whole "Hot Vapor Engine" thing went away about the same time the EPA cranked down hard on NOx emissions. Oxides of nitrogen are generated primarily as a factor of temperature, and though some new catalyst technology can *partially* deal with them, it wasn't available back then.

Combustion of gasoline is fairly complex. The fuel-air mixture starts off stable, like a rock at the top of a hill. The spark kicks the rock downhill. The fuel-air combustion creates a dozen-plus-odd intermediate compounds. The first several-odd ("gasoline" is a complex and variable product, so you can't nail things down precisely) reactions take more energy to complete than they release; that is, they're self-extinguishing. So you need a big spark to provide energy to kick the rock out of the hummocky area and down the slope.

During this time the piston is moving down the cylinder. As this happens, temperature and pressure start to drop more rapidly than combustion proceeds. Combustion depends on temperature and pressure; at some point, the combustion process basically stops. On most engines, this happens somewhere around 2/3 of the piston's way down the bore.

There are still flammable compounds in the cylinder, it's just that it's too cold for them to burn. What Yunick did was to raise the starting temperature - make the hill higher - so that more of the fuel would react before the charge hit the freezing point. Yunick used an "interheater" between the intake and exhaust to raise the charge temperature.

Yunick's patents went over this in detail; it's basic engine design stuff you can get from many textbooks.

Generally, when you raise the starting temperature you increase the chance of detonation or "knock." That's bad for the mechanical bits of the engine. At the temperatures Yunick was describing, his engines should be been like Diesels, if not just hammering themselves to bits in short order.

What was cleverly mentioned but not explained in the patents was the method by which he controlled knock. EGR. The nasty smog-control method that made so many '70s and '80s cars run like crap. Particularly bad examples would keep on running even after you turned them off and removed the key, like the Family Truckster on "National Lampoon's Family Vacation."

What Yunick did was to use a *lot* more EGR than Detroit was using; enough to reduce the tendency for the engine to knock. Yunick used so much EGR that the engine needed a turbocharger to make the same power it did before.

What Yunick did *not* disclose was the method by which he controlled the EGR in relation to engine load, etc. Nowadays you'd do it all with the engine computer. Yunick kept his method a secret. It was probably quite a trick - he would have to do it with mechanical linkages and vacuum doodads, electronic engine controls not being around when he did his first demo cars.

It's an interesting system.

MaadiMan said:

I did install an HHO (one of those hydrogen/oxygen scams) on a friends vehicle.

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Hydrogen works as a combustion accelerant, like throwing gasoline onto a barbecue grill. A little bit goes a long way. Unfortunately, its effectiveness falls off rapidly.

Spare hydrogen atoms move throughout the combustion process like dancers at a square dance. Swing your partner, do-si-do, swap those electrons around all the carbon bits. Once there's enough hydrogen to match all the available slots, more hydrogen doesn't do much.

Providing a snort of hydrogen can really perk up performance, particularly at low RPM or part throttle, where combustion can be weak or unstable anyway. It's much less effective at WOT.

Despite the massive propaganda, hydrogen is a piss-poor motor fuel (knock sensitive, among other things), and its combustion byproduct is not "just water" as the enviro-dweebs like to claim. It would be just water if you were dragging along your own oxygen supply, but if you burn ordinary air, you output lots of nasty oxides of nitrogen and come other byproducts, all regulated by the EPA.

Like the man said, "There Ain't No Such Thing As A Free Lunch."

Lunyfringe said:

would think that would drop the octane

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Octane and cetane are different things, not opposites.

Any kind of knock rating is very slippery to define, which is one reason the gas companies opposed mandatory octane ratings for decades before the Fed ordered a standardized test and pump labeling.

Octane is determined as a fuel's resistance to knock, as compared to a chemical called iso-octane, as tested in a standard variable-compression test engine. It's made by Waukesha, operates at low RPM, and has a hockey-puck shaped chamber.

What the Feds didn't know, or didn't want to hear, was that their "octane rating" only applies to engines of similar geometry. Quench, swirl, and tumble, among other things, greatly affect an engine's knock tendencies, along with spark plug placement, bore size, and exhaust valve cooling. If you've ever owned a vehicle that ran just fine on regular or mid-grade but pinged on premium, that's what can happen.

My Bandit 1200 has slightly over 13:1 CR, runs fine on most regular gas, and pings on some "premium." This isn't because the fuel is bad or the gas company is ripping people off, it's that it's compounded to pass the octane test in a very different engine. In most cases, though it's close enough, particularly with modern closed-loop engine management systems.


There are fuels like methanol or propane that have high octane ratings, but don't always perform well in unmodified gasoline engines. That's because those fuels have a much narrower range of acceptable temperature and spark advance before they start to knock. Back in the old days keeping the engine tuned to propane's sweet spot was often quite a trick - people like Ak Miller and Rite Autotronics made a living doing that sort of thing.

TRX said:

Octane and Cetane are different things, not opposites.

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They're measured different ways, but it's impossible to have a fuel that's high in both.. Diesel has an research octane number of 15-25.. I found this at my favorite diesel site:
Mixing Gasoline And Diesel
this is from the perspective of putting gasoline into Diesel in a Diesel engine- not in a gasoline engine.. I would think Diesel wouldn't be as much of a problem in a gasoline car, but would absolutely lower the octane, while at the same time increasing the amount of energy (BTUs per gallon, Diesel is significantly higher, while alcohols are lower) This has me wondering if putting a bit of diesel into a tank of E85 would help the cold start ability, and increase the mileage..

Pump octane rating is an average of research and motor octane..(RON+MON/2) Both are measured by the variable-compression engines as you describe, but the motor octane test involves pre-heating and more ignition advance..

They don't normally publish octane numbers for E85, but those that run turbocharged engines into ever-increasing boost levels love the fuel.. main problem is getting big enough injectors, and still being able to idle (banks of injectors?) the latent heat of evaporation of ethanol really cools the intake charge well, making it denser & decreasing the knock sensitivity..