gas to deisel conversion

topic posted Fri, April 21, 2006 - 9:48 AM by  Lost Sailor
I have a dodge dakota with a 318 v8 gas guzzling machine. I would love to drive a different vehicle, but dont know if I can afford to buy something different at the moment. Does anyonoe know if I can convert my gas engine into a diesel, to eventually run on biodiesel?
I know I can swap out the engine all together, but would like to explore other options if there are any.
posted by:
Lost Sailor
  • Re: gas to deisel conversion

    Fri, April 21, 2006 - 11:41 AM
    i don't think the existing engine is strong enough. if i recall correctly diesels use higher compression and therefore things would likely break fairly quickly.

    Best bet is to buy a diesel engine and tranny that will fit (or can be made to fit), install those and sell your existing engine and tranny to recoup some of the cost.

    or just buy a diesel and sell the Dakota.

    personally i'm going to drop diesels into all of my Scouts. but i'm crazy and i have the time and energy to bang my knuckles and swear incessantly.
    • Re: gas to deisel conversion

      Fri, April 21, 2006 - 12:00 PM
      I've been in a conversation much like this once before.

      Ultimately, the conclusion drawn is that there is no practical way to convert a gasoline ENGINE to a diesel. You can sometimes convert a gasoline VEHICLE to diesel, if you can find a diesel engine that will fit the vehicle, and are willing to take the time and effort to make it happen.

      The problems with converting an engine are:

      1. The two fuels have radically different properties. Diesel detonates readily; gasoline is specifically designed not to.

      2. Gasoline is far more volatile than diesel.

      3. Resulting from points 1 and 2, gasoline and diesel engines have different ignition systems, gasoline using spark ignition, diesel using thermodynamic ignition.

      4. Resulting from point 3, gasoline and diesel engines need different valve and injection timings.

      5. Diesel has a higher energy density, meaning that a smaller amount of fuel is needed to do the same work.

      6. Diesel produces far more torque, in turn requiring a more heavily built engine (as Pigboy was alluding to in the previous post in this thread).

      Could it be done, theoretically? Sure, but it's probably not worth the effort. I would think that the most effective method would involve melting down the gasoline engine, adding more metal to make up the difference, and re-casting it. It's that much of a stretch.
  • Re: gas to deisel conversion

    Fri, April 21, 2006 - 12:03 PM
    Unfortunatly there is no practical way to convert a gasoline engine into a diesel engine.

    This is for a few reasons, but i'll give the most popular reasons.

    * Compression Ratios - Diesel engines often use compression ratios of 22:1 or higher, while this is technically possible in a gasoline engine, there are not very many outside of the racing world that operate here.

    *Diesel engines are built with sturdier parts. Basically a diesel engine is a large high pressure air compressor. What happens with air when you compress it, is that it heats up if you add fuel to the compressed air it will ignite, thereby causing a small contained explosion. Whereas a gasoline engine compresses a fuel/air mixture that then is ignited by the heat energy of a spark, causing the same explosion. The fact that the power in the diesel engine comes from the actual compression of the air and not ignition of the fuel by spark flame means that all of the components in the engine have to be built sturdier.

    *ECU or Engine Control Unit. I'll assume that you have a fuel injected vehicle. Everything in the propulsion end of your vehicle from the fuel pumps to the sometimes transmission control programming is handled by the ECU. This whole computer would have to be replaced or maybe somehow frankensteined into a controller for a diesel engine. Sounds like a headache because it is. Having a computer modified or R&D' would cost as much as a new diesel crate motor and ECU.

    Some other issues you may not have considered is that diesel engines [for the most part depending on what engine package you chose] have much higher torque ratios at far lower positions on the powerband. Or in plain english, even a moderatly sized diesel [something with similar accelleration properties that your used to] engine stands the good possibility of turning your gas powered tranny into shredded wheat.

    The tranny issue is a big one when you start talking diesel trucks because modern diesel engines can put out incredible amounts of horsepower and torque, that can lead to premature transmission failure. Especially if you havent driven diesels before and you find yourself mashing the go pedal all the way to the floor, way more than you realize. Trust me the torque is very addictive!

    Personally I wouldnt reccomend a swap out of motors unless your are willing to do a motor/tranny swap out. This is a daunting task for a non-mechanic and unless you have disposable income or your own fully stocked shop (including lifts) I would not reccomend paying to have the job done. People that ususally do this type of thing, are usually making a shop truck, a magazine article or a multi-thousand dollar off road monster (aka sponsor money).

    Just to give you an idea of how involved this is, I found a website of someone that has done a 1999 Dodge Dakota conversion from a gasser to a diesel.

    Dodge makes a fine line of Cummins powered diesel trucks, even one in a Dakota. If you are sersiously interested in trading up to a diesel, I'm sure there is a dealership near you that has a pre-owned diesel that will more than satisfy your needs.

    I'm not really a big fan of buying new diesels either. Because they are built heavier duty, so long as you keep up on the oil change and maintenance schedule, there is no reason that you can't go 300,000 miles before your ready for a overhaul. Its not uncommon for some heavier diesel to go 1 million or more miles! I have seen a peterbuilt with 3 million miles on it!

    Diesels do not depreciate very fast, and in fact some classes of diesels are appreciating according to Kelly Blue Book!

    If you decide to buy a diesel person to person. I reccomend you have a *GOOD* impartial DIESEL mechanic check it out (ie a dealership or equivalent), as well have the mechanic send the engine sump oil and transmission fluids off for testing. These test are very indicitave or certain problems in diesels as you will find in the truck sector that most diesel trucks are bought for work purposes more often and less often as personal vehicles....unless your one of those nutty biodiesel people. I'm a nutty biodiesel person so no groans people;-P

    Having said that you want to make sure the reason your getting the steal of century is not because, the previous owner used crappy fuel that has contaiminated the tank, worn valve seals, trumpeting on injector nozzles, an out of calibration injector pump, poor compression on a couple cylinders, coked exhaust valves, a wonky glow plug controller and a rats nest in one half of the exhaust manifold. Just to name a few problems. None of them are fatal problems, but just about all of them will cause you to burn fuel poorly and you want to make sure you have a good running diesel for maximum reliability.

    You must realize that a diesel is not gasoline engine. Their are special issues that you must consider with being a diesel owner. These issues will directly affect your overall happiness with your diesel. A happy well maintained diesel will run practically forever and makes for a happy diesel owner.

    I definetly reccomend checking out the DIESEL FAQ, and let me know if you have any other questions, wether they are on the FAQ or not.
    BTW thanx for the question I'll add it to the next revision of the FAQ.

  • Re: gas to deisel conversion

    Fri, April 21, 2006 - 1:48 PM
    I agree with the other posters - there is no way without a swap. Which would probably cost you more than buying a used diesel would.

    You *can* convert your gas engine to run on propane, ethanol, etc. though.
    • Re: gas to deisel conversion

      Sun, April 23, 2006 - 5:35 AM
      "You *can* convert your gas engine to run on propane, ethanol, etc. though."

      Yes, ethanol is sufficiently volatile, and propane and methane are alread gasses, thus these fuels lend themselves to being burned in spark-ignition engines. They are also less energy-dense than gasoline, making the engine sturdiness issue a non-issue (i.e. a gasoline engine is more sturdy than necessary for these fuels).
      • Re: gas to deisel conversion

        Wed, September 6, 2006 - 8:10 AM
        Oh, I so want to convert my 85 Dodge Xplorer Camper (the one that looks like a space shuttle). It has a 318. Is it expensive to run on propane? I already have a smallish propane tank for the heater and stove.

        I'd like to go biodiesel, too, but don't know who'd be able to pull off the conversion.

        Just yammering.

        • Re: gas to deisel conversion

          Wed, September 6, 2006 - 9:56 AM
          A conversion to biodiesel is much simpler than a conversion to propane. Ultimatly cheaper as biodiesel has more energy than propane does.... although propane makes a lovely supplemental fuel.... kinda like nitrous for a diesel.

Recent topics in "Diesel"