Can a Propane Onan be Converted to Diesel?

[Depewtee]

Hi All,

I have been searching for a new generator for some time.  Currently have a 15Kw.  I do not need anything that big.  I have yet to find a decent used generator under $5,000.00.  I have limited my search at this point to diesel generators, but I have seen a few propane models that seem to be selling for less.  Can a propane generator be converted diesel?  If so, is it cost prohibitive?

Thanks in advance,
Brian S.

P.S. - I know I could just add a propane tank.  Not wanting to do that.

[gcyeaw]

  A propane engine is basically a gasoline engine. It has a carburator that mixes the air and fuel which is pulled into the cylinder. It uses a spark plug to ignite the fuel. It cannot be converted to diesel fuel.

A diesel engine pulls air only into the cylinder and injects the fuel directly into the cylinder via an injection pump. The high compression ratio of the diesel heats the compressed air in the cylinter hot enough to ignite the fuel. You can inject propane into a diesel engine air input to get more power, but with that comes more strain on the engine components.

[bevans6]

It's almost a question of "can" and "should".  A propane generator can be converted, but should you?  No - it means basically replacing the engine, either literally, or replacing virtually every part except the block. 

Brian

[TomC]

A dedicated propane engine will have a compression ratio of around 10 to one.  A small pre chamber Diesel for generator will have twice that compression ratio. It's the same analogy as the infamous 350 V-8 that was converted from an Oldsmobile gasoline engine into a Diesel (ultimately it was a totally different engine, but GMC ruined the thought of having a Diesel engine in a car for many-yet my Mercedes Turbodiesel is pushing 400k miles with the original engine).  You can convert a propane engine back into a gasoline engine-mainly changing the intake system.  But-you'll get almost Diesel longevity out of a propane engine since propane is such a clean burning fuel-it doesn't contaminate the oil like gasoline does.  Good Luck, TomC

[artvonne]

  Anything can be done, but like Brian said, should it? I have this 94 Jeep, and I really been thinking of putting a diesel in it. But everything I could use is either much too small or just impractical. For example I could put a Mercedes motor in it, but I dont like their automatics very much.

  I was standing their looking at it one day, and suddenly imagined injectors in the spark plug holes. Immediate thoughts of GM's 350 fiasco ran through my head, but I reminded myself of how stout AMC six bangers are. If you didnt try to push too much fuel into it it would probably work.

While I was never much of a GM fan ( though I LOVE their Buses), the majority of the problems with the Olds 350 Diesel were the the result of owner and technician abuse and incompetence, and not necessarily in that order nor mutually exclusive to one another. Turning a diesel loose on a world of inexperienced people without a water separator in the fuel system was quite the recipe for disaster. It actually shared very little with their gas engine, but much of it was too little, too late.

[Depewtee]

Thanks for the replies fellow nuts.  Looks like I will keep looking for a diesel unit.

Brian S.

[viento1]

I feel your pain, I have an ONAN QD 10000 and currently selling it... hint hint to anyone wanting one.

Nothing on my Bus is rated for 50Amps so I only run half a leg. I was looking for 30amp solutions and came up with:

In the small diesel department I have narrowed it down to
Onan 3200 expensive $6500 and only puts out 23Amps - but it has a built in kind of quiet box
PowerTech 3sv2 only puts out 25Amps - Nice little kuboto engine.
Next Gen 3.5 $4100 without the Marine enclosure but actually puts out 29Amps - same kuboto engine.

I choose the Next Gen and it will delivered in 4 days. I will let you know how the install goes but I am excited about it. I am putting it in the spare tire compartment - he he he. I am not sure what to do with all the extra space and 700lbs of storage bliss.

[viento1]

Oh ya, to answer your question... yes.

good luck 

I imagine this Frankenstein project would require recasting, sleeves, pistons... a full time machine shop would be handy.

It would be fun to watch and maybe help for  a few hours now and again.

[Mex-Busnut]

Maybe Brian a.k.a. Depewtee is thinking along these lines because a lot of diesels ARE converted over to natural gas, not propane/butane gas. City buses and others wishing a clean-burning fuel.

[TomC]

If you have a split 120/240v output from your generator, many times, if you have a four wire output, you can rewire it so it is a straight 120v.  My 12kw is wired straight 120v.  You have to use both positives and both commons when wiring this way to carry the load.  But it is so much simpler then having to balance the loads between legs.  Good Luck, TomC

[artvonne]

Nothing on my Bus is rated for 50Amps so I only run half a leg. I was looking for 30amp solutions and came up with:

  My understanding is generators need to deliver power equally on BOTH legs. I have been told by many that unbalanced loads, which occur when taking more off one leg than the other, will overheat the windings and shorten the life of the generator. This is the reason most RV generators are set up for 120 volts.

  Many 4 pole 1800 rpm generators have 12 taps, and these taps can be re-configured multiple ways to change the output to both 2 and 3 phase and many different voltages, 120, 240, 208, 440, 660 etc..

  With the ever downward spiraling economy, the old Bounder keeps losing value. I dont know what its worth today, probably not a great much, but its got an Onan/Kubota 3 banger diesel 1800 rpm liquid cooled Genny. I keep thinking I should yank it out and keep it and sell the Bounder gennyless.
 

[viento1]

The ONAN apparently has some sort of system that allows you to simply pull off half the load without messing things up.

I have been trying to sell this ONAN for 4k but no luck so I am not sure if the Bounder is better off with or without??