Explain Multifuel

[David_4x4]

I'm still working on getting me an M35a2 and hopefully will bring something home this weekend.

Anyways Im sure this question has been drug out many times etc, but I couldn't narrow anything down from a search and my computer is to slow to go through any online manuals and IM waiting on my paperbacks.

How does "multifuel" work? I'm sure 99.9% of the time I'll be running on No. 2 diesel, but what else would it run on. I'm sure Kerosene, Jet Fuel, etc. But could it run on regular gasoline?

I understand some principal of fuels and motors. But a motor running on most any fuel is new to me. Especially when diesel uses compression and gas requires a spark. And I've always heard these things will run on anything that burns...

But if anyone could point me to some good links or previous threads. I'd be more than greatful.

 

[jwaller]

anything but avgas 100LL

 

[rmgill]

You can get a compression ignition engine to work on a lot of fuels. It just takes tuning the engine for that fuel. The first Diesel Cycle engine ran on peanut oil as I understand it.

The Multi fuel works on two points.
1. the Combustion head. Aka the Hyper Cycle Combustion head process. It has to do with the shape of the head, the swirl patterns it generates as it compresses and how it's very efficient in getting the fuel to do what it's supposed to do on compression ignition.
2. the fuel density compensator. This adjust the fuel delivery such that the quantity of the fuel matches what the engine needs for a good burn. More fuel needs to be delivered in the case of low octane gasoline, less in the case of diesel. More viscous fuel means more power per quantity of fuel, so the FDC dials back the fuel the thicker it is.

Those two items allow the engine to burn low grade gasoline, kerosine, oil, diesel, alcohol, and any mix of that.

 

[ken]

There are a few features that help this engine run on a mutltiude of fuels. First it has a fuel density compensator on the injection pump. It's main job is to adjust the rate of fuel entering the injection lines. When you have a thicker fuel it allows less fuel in. When you have a thinner fuel like gasoline it allows more fuel in. This is sopposed to keep engine performance the same no matter what fuel your using.Thicker fuels generally have more BTU's per gallon. The pistons also have a sphere shape in them. This is so thin fuel "gasoline" will puddle. As the piston travels down the gas will evaporate and burn slowly. So that you don't get preignition. Fuel is also sprayed on the cylinder wall to burn the same way. It's main fuel is #2 diesel and it will run smoother on it.
I've ran gasoilne through mine "It was a emergency" and i don't recomend it. It looses a lot of power and drinks it like crazy. I currently mix used motor oil with diesel in mine. It cuts my fuel costs quite a bit. But it does stink pretty bad.

 

[Jones]

We had Multifuelers in Nam and the motorpools quickly put out a bulletin that said that gasoline was an emergency, get out of harm's way alternative only; because of the lack of lubricity for the injection pump. Their advice was to add motor oil to a tankful of gasoline to try to keep the IP alive. I think the ratio was 1gal per tankful. Otherwise the engines didn't seem to mind just about anything that could be poured into the tank.

 

[WillWagner]

I'm running FedEx's mix of gas and diesel. Put around 800 mi on with it with no issues. I figure it's about a 50/50 to 60/40 mix, more toward the gas side. The only thing I notice is that if there is too much gas in it, the engine will have a tendency to "hunt" at a hot idle, so, i just add a couple gallons of #2 or oil.

 

[Westech]

I have seen that in mine too. I have been running diesel and ATF in mine for the last 1000 miles and the pump will "turn up" a bit and then back down wile driving. I think Im going to bypass the compensator

 

[M35A2]

A few guys I know that own deuces have run them on contam. Thats the fuel at the petrol station that people have put the wrong fuel in, either petrol into a diesel or diesel into a petrol engine. Some fuel depots store this fuel as the petrol station has to pay to get rid of it.

These two guys have run their truck on that mixture and have burnt their pistons out and had to get another engine. So does this mixture only apply in an emergency, or has another aspect come into play on their blown engines???

 

[rmgill]

They may have poorly adjusted FDCs or pumps. Gasoline/Petrol will have LESS heat per unit volume, so it should not burn pistons. More likely it should cause problems for the fuel pump as it's working on dryer fuel with little lubrication. but with Diesel in it, it should be fine. I'd see about adding some ATF or motor oil.

I previously added 5 gallons of used motor oil and on this latest fillup, it's still quite dark and oily. A little oil goes a long way.

Speaking of contaminated fuel, I've called around to a bunch of gas stations to see if they have any and gave my number as a person that'd provide them with a free source of disposal vs a service to come get the fuel.

 

[David_4x4]

Great info you guys. Every little bit helps.

Keep it coming

 

[TBigLug]

Sorry to dig up an old post, but I'm new to the whole multifuel thing and wondered if anyone could help me out a little. Do you have to manually adjust anything when you switch fuels? Is it better to mix oil in with your diesel for lubricity purposes? Does mixing in used motor oil shorten fuel filter or IP life (metal flakes or dirt in oil, etc.)? What is the usual longevity of these motors in a fairly light duty application? Approx. mileage for say a '69 ish Deuce w/ 46" SS tires not doing alot of heavy hauling (compared to the actual payload capacity)? Are these engines durable or do they have a breakdown tendency due to the variety of feuls? Sorry for the newbie questions but I figure if I can find any straightforward, plain english explanations it'd be here.

 

[TBigLug]

Also, I was wondering how the multifuels will hold up to ULSD and bio diesel? I've heard of some diesels losing IP's due to a lack of lubrication.

 

[G744]

The injection pump and injectors used with the multifuels all have hardened parts internally so as not to gall when buring fuels like gasoline or arctic mixes for extreme cold weather. The new ultra-low sulpher fuels are righht at home in a mil-spec engine.

Just about anything that burns short of alcohol will be fine.

I have run mixtures of Diesel, used motor oil, used ATF, transformer oil, biodiesel, gasoline, kerosene all with no problems. It all makes power.

If you have problems with burnt pistons as mentioned before, I suspect water in the fuel. If too much goes in, the filters can't hold it all and it goes to the injectors. When in an injector, water will turn to steam just before the popping point and burst the tip open so it now is a flamethrower ready to melt aluminum.

dg

 

[TBigLug]

That's good to know. So used oil doesn't plug up filters? Good to know. Easy way to get rid of post oil change waste.

 

[bottleworks]

I believe those who run UMO are filtering it before adding it to the tank.

 

[TBigLug]

Would you use a 5 micron filter or is everybody using a super fine strainer in a funnel? What kind of filter would work?

 

[bottleworks]

I would suggest three things. You can find a fair bit of info with the Search feature of this web site. Two: Check out the Alt fuels section of the fourm. ...and three... Check out this thread:
http://www.steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=8668