Anyone here know of any recent experiments with converting gasoline engined vehicles to run on diesel fuel? I’m thinking seriously of doing this with my ’91 Toyota pickup. It has the 22RE (electronic fuel injection) engine, 9:1 compression. Some older tractors had this ability – what is done is that there are two fuel tanks, a small one for gasoline, the larger for kerosene, and the engine is started (and stopped) on gas, then switched to kerosene when warmed up. The only real differences, at least in the garden tractor I have (BCS) which has these optional parts available, are the larger jets in the carb and hotter plugs. I’ve read that some also heated the fuel line with the exhaust to thin out the fuel. I’m thinking of doing essentially this — including heating the diesel fuel line — and also installing larger flow injectors, which are easily available and also am thinking of adding a turbo. The 22RE engine was offered in a turbo model from ’85-’88, but it had lowered compression (7.5:1). I’m thinking that the burning rate of the diesel will be greatly enhanced by the turbo boost, effectively increasing compression for better combustion. I’d have to add an exhaust temperature gauge, of course, to ensure it wasn’t getting out of hand, but since the fuel will be diesel (actually biodiesel) instead of gasoline, I don’t think there will be a problem with knock and precombustion as you’d see in a boosted gas engine. I’ll probably just try it w/o the turbo at first, since I haven’t found one yet, and new/rebuilt ones are rather expensive.

You can’t run straight diesel, but you can mix diesel with gasoline with no  modifications to your engine or injectors.  Try one gallon per tankful, increase until the engine either smokes, or is  hard to start, then back off on the diesel per tankful.  This will not harm your engine, there is the possibility of mixing too much  diesel with the gas, then you’ll either foul the spark plugs, (Clean or  replace them, do not use a hotter range plug) or it just won’t start, you see  diesel is not as volatile as gasoline (Gasoline evaporates easily, diesel  will not evaporate like gasoline, so it remains a liquid fog instead of a  finer vapor.  If you insist on a fuel changeover system, preheating the diesel in the line  is a good idea, do it as close to the injectors as practical, but don’t get  it too hot or you get vapor lock, use a water heat exchanger, (Available in  the Northern states where it really gets cold) and that should be enough, but  only on the diesel line and the Diesel will then vaporize easier, it will run  on straight diesel (Poorly, but it will run) when the engine is hot, but not  when cold starting.  Be aware that the fuel systems today are intended to recirculate fuel back to  the tank, so you will not only need a return line (Also switched over) but  the recirculation is designed to cool the fuel, the tank mounted fuel pump,  and also the injectors, you may get a burned out injector or fuel pump by  heating the diesel  The idea of starting on gasoline, then switching to kerosene, is a good one,  and has been used since the 30’s, but the added expense of a second tank,  fuel pump, lines, and changeover switch make this a costly refit.and the cost  of diesel is not enough different to recover the cost.  If you’re thinking that running diesel will be more efficient (Better gas  mileage) you will be disappointed, the diesel engine is very different from a  gasoline engine, and it’s the difference, not the fuel, that makes diesels  more fuel efficient.

You have a few misconceptions about diesel running in a gas designed engine.  First of all, the higher compression of a diesel is designed to raise the  compressed air’s temperature above the “Flash Point” of diesel fuel (Where  the fuel ignites spontaneously) This allows the diesel to be injected  directly into the combustion chamber where it ignites immediately from the  heat of compression without any spark plug needed to “Light the fire”.  Note the injectors on diesels are in the combustion chamber itself, and squirt the diesel against about 600 PSI of back pressure from the initial compression, this requires high pressure pumps, fuel lines and different injectors.

But in gasoline engines the injectors are in the intake manifold, and squirt the gasoline not into the combustion chamber, but into the intake manifold very near the intake valve. This only requires a low pressure injector, most work around 14PSI, although 40PSI systems are on some cars.

This difference, though seemingly minor, is really a very major difference, you see, as the diesel is compressing the air trapped in the cylinder, IT IS CRITICAL TO KNOW THERE IS NO FUEL IN THE COMPRESSED AIR, then when the fuel is squirted into the hot air, it ignites.

A gasoline engine compresses both fuel and air mixture, this is why the compression ratio is lower THE AIR MUST NOT BE COMPRESSED TO THE FLASH POINT TEMPERATURE, if it is, you light the gasoline from the heat of compression and destroy your engine through detonation, also called knock, spark rattle, pre-ignition, and other names.

Gasoline engines use lower compression to prevent this ignition by air heat,   then at the correct time the spark plug lights the warm (Not hot) fuel-air mixture, and away you go.

In diesels the injector timing replaces the spark timing, by squirting the diesel at the Top Dead Center (Actually slightly before TDC) the engine cannot knock, detonate, pre-ignite, etc. Remember there’s no fuel until injection occurs.

So when you tell me you intend to increase the compression of a gas engine, and/or add a turbo (Same thing) and run diesel, you’re forgetting that you are now raising the engines compressed air above the flash point of gasoline and of diesel, and are now compressing a air-fuel mixture, not just
non-flammable air.

You will destroy your engine.

I note that your tractor “Is offered with this option” the wording suggests that a factory conversion is possible, actually that is another, entirely different engine, not simply a carburetor conversion.   Your garden tractor is a low compression, far more “Forgiving” engine, than any automotive engine. What works in a 6 to 1 compression, air cooled engine, will not work in a 8.5 or 9 to 1 automotive engine (Diesels commonly run 22 to 1compression ratio or higher.)

As an aside, when you increase the compression, you install colder spark plugs, not hotter ones, “Colder,” or “Hotter” refers to the spark plug’s ability to transmit the heat of combustion to the engine’s head (A heat sink) so the plug will not melt. (Yes they can and do melt.) “Colder” spark plugs can transmit more heat, allowing the plug to survive higher combustion chamber temperatures.

You worry about the EFI’s ability to handle diesel? no problem, it’s slightly thicker than gas, but automotive fuel injectors are designed for variable flow, the injector “Meters” fuel by the time it’s allowed to stay open, (richer mixture, longer “Open” time, leaner mixture, shorter time)

The system really doesn’t know or care just what fluid is flowing through it’s system, it works on a series of sensors that tell the car’s computer how hot the engine is (Coolant sensor) and whether or not there’s any free oxygen in the exhaust (Oxygen Sensor), If Oxygen is present in the exhaust stream the mixture is enriched until there is none, then leaned again until Oxygen is again detected, and repeat many times per second, the whole idea is to attain the “Perfect” fuel mixture where all fuel is burned and none is left in the exhaust.

Note, I said “Fuel” , your engine’s computer doesn’t care if the burnable stuff is gasoline, alcohol, diesel, veggie oil (I would thin it with alcohol to avoid plugging the injectors, and be sure to filter it heavily, a very tiny french fry particle will stop up an injector) or any other burnable fluid, the only thing you need to worry about is a fluid that is too thick to allow enough flow through the injector for the engine to run, and that will burn at a fast enough speed to support combustion.

While a bit extreme, an example is motor oil, you can’t use motor oil, even though it will burn, and is a liquid, it simply cannot flow fast enough, to allow enough through the injector, thin it with, any more volitile fuel, such as alcohol, gasoline, propane/butane (Bet you didn’t know propane/butane is mixed in gasoline to make gas evaporate faster) then it will burn just fine.

Was your tractor by any chance a Semi-Diesel, those engines are designed from the start as a hybrid gas/diesel engine.