Multi Fuel vs Diesel Only Questions

[mdl06g]

What is it that makes a multi-fuel different than an old diesel only engine, like the early Cummins that came in the Dodge trucks or the pre-turbo International diesels in Ford trucks?

What is it about the injection system or the combustion chamber/process that allows the engine to run on any old petroleum product?

Maybe another way to ask the same question... if I wanted to make an old Cummins into a multi-fuel what would have to be done to it? Or, if I wanted to make my multi-fuel Deuce into a diesel only, what would I have to do to it?

Thanks,
MDL

 

[avengeusa]

going from multi to diesel is only, just use diesel

the other way around is a big expense, we had a recent thread about this, i will look

 

[Ferroequinologist]

First,
Welcome to the site!

The thing that makes a multi a multi is the design of the pistons and engine as a whole. There is a Fuel Density Compensator (FDC) on the engines, it was to adjust the amount of fuel used to even out the engine output no matter what you were burning. Most are bypassed, as it was common to leak into the crankcase. The Army put Diesel only on the trucks after the bypass, but it will still burn most anything.

There are lots of threads on this topic, the search button is a great tool.

Again, welcome! and don't forget to search first, and if you can't find it, then post. Thanks!

 

[Ferroequinologist]

Is that a little hunting blind trailer as your avitar? pretty cool idea BTW.

 

[Ferroequinologist]

helpful links:
http://www.steelsoldiers.com/deuce/32930-fdc.html
http://www.steelsoldiers.com/deuce/30821-all-dueces-multifuel.html
http://www.steelsoldiers.com/deuce/26917-fuel-density-compensator-pass.html

Hope those help some!

you can usually run any diesel engine off an oil if it is filtered properly and/or blended. I would never even mix gas in anything other than a multi though. Just my

 

[mdl06g]

Thanks, I struggled to find the answer via search. I'm still learning to use the tools, so I appreciate your patience.

I'm guessing that the multi-fuels are indirect, low-pressure injection engines. I'm just curious, mainly.

The avatar is an M104. My sons and I built it in the driveway (my neighbors love me) and we call it The Buckshack. It's a hunting blind that has 8 windows, a locking door and I can stand up inside it in the center. It has two layers of carpet laid on the floor and six chairs that some school was throwing away. It's the most luxurious hunting I've ever done.

MDL

 

[gimpyrobb]

To make a non multi into a multi, it COULD take alot of money. I have seen that some people are using WMO in non-electric diesels. Like the old ford 6.9 and chevy 6.2. There is alot of info on the web, just search "waste motor oil" & "fuel", on google to find some info.

 

[mdl06g]

A few pics of the build... off topic, but entertaining all the same.

MDL

 

[crazyplowboy]

MDL that is a neat hunting outfit you got there! Good to see you are letting the young ones help you out, believe me they will thank you some day.

 

[bottleworks]

I'm guessing that the multi-fuels are indirect, low-pressure injection engines. I'm just curious, mainly.

I believe it's the exact opposite.

 

[Jake0147]

What is it that makes a multi-fuel different than an old diesel only engine...

The multi-fuel ability comes from a fairly high compression ratio (but not unheard of in straight diesels), a specific and slight change to the combustion chamber (which resides within the piston crown, like many straight diesels), Fuel injectors that do NOT atomize the majority of the fuel charge so it burns from a liquid state (which really doesn't work out so good in a regular diesel engine), and timing settings to accommodate all of the above. Look up or search here for "hypercycle" for more information about it's origins and processes.
The later and more common multi-fuel engines also have the "fuel density compensator" attached to the fuel pump. Since your right foot tells the pump what volume of fuel to inject, different fuels with different energy content yield different horsepower at that given volume. The FDC will (in theory) reset the pump based on the viscosity of the fuel, which among the authorized fuels will compensate such that the same throttle input will result in the same horsepower output regardless of what fuel is used.

As far as converting a regular diesel to multi-fuel... That's a tough one, as there's a lot of stuff to be adapted. Including the fact that "turning up" the multi fuel process to even conservative modern horsepower per displacement standards gets the exhaust awful hot, awful quick. Diesels will run on more than just diesel fuel, just not such a wide variety of fuels. I'd be inclined more to look into the direct or mixable fuels that work out for a conventional diesel engine. Used petroleum lubricating (engine oil, tranny oil, gear oil, etc) is not out of the question. Not straight, but 50/50 is reasonably doable, and higher percentages are possible depending on the weather and your ability to start the engine on straight diesel. The medium and heavy truck folks don't do much more than dispose of oil from an oil change, but pickup truck sites have loads of information on what burns well in what type of injection mechanism and how much you can get away with at what temperatures. I'm sure you could relate some of that information to your engine.

 

[tm america]

yes they are direct injection hi pressure.alot of the modern diesels are .but the older non electric one are mostly indirect injection.

 

[m16ty]

The multifuel could be called a indirect-injection engine. It's not like any I've ever seen but it does have a pre-combustion chamber built into the pistion that the injector squirts into.

 

[mdl06g]

So, the multi fuel probably runs a higher compression and higher injection pressures than my 06 Cummins?

By the way, I greatly appreciate all who have taken their time to share their knowledge with me. Very generous.

MDL

 

[m16ty]

So, the multi fuel probably runs a higher compression and higher injection pressures than my 06 Cummins?

By the way, I greatly appreciate all who have taken their time to share their knowledge with me. Very generous.

MDL

The multifuel does have higher compression than the cummins.

Don't know about the injection pressures. Does that really make any difference? I could understand more volume of fuel or the injector design would make a difference but I can't see how the pressure would.

 

[Sumoman]

All I know is this, I can burn liquid crap and dinosaur snot in mine, I doubt a regular diesel could

 

[Floridianson]

22/1 ratio and 2800 3000 pop off pressure

 

[roger-wilco-66]

I'm guessing that the multi-fuels are indirect, low-pressure injection engines. I'm just curious, mainly.

I would say they are a direct, since the nozzles inject directly in the combustion chamber, and to my understanding the cavity in the piston is part of it.
Compared to modern commonrail-diesels they have a very low-pressure injection. The pressure in the railsystem is about 10 times as high compared to the pop off pressure of the multifuel Bosch injector nozzle.


Mark