propjobbill

Now this may be a dumb question, but here goes. You run diesel engines and all they need is compression to start. Would it be possible to use diesel fuel in a glow engine with a glow plug. I know that a normal engine would not have enough compression to fire, but if a glow plug were to be used it should be able to fire at lower compression. Has anyone ever tried it or even toyed with this idea?

Thanks for any info or ideas you might have.

[email protected]

propjobbill, over the years many of us have used our model diesel fuel in a stock glow plug engine and started the engine with a glow plug hooked to a battery. A glow engine set up for no nitro usually works best as it has higer compression than an engine set up to run with some percentage of nitro in the fuel. Some engines run pretty well this way but most lack power and need more compression. I am sure you will get a number of responses to this question as it comes up from time to time. Jack

qazimoto

My Feedback: (1)

It should also be pointed out (just in case) the the diesel fuel isn't pump diesel, it's a mixture of ether, oil, kerosene and some cetone booster. As the poster above suggests it can work, but really it achieves little.

bogbeagle

I've emboldened the erroneous assumption in your post. Some standard engines run pretty well on diesel.


The glow plug has no effect upon diesel fuel, as far as I know. It is useful for starting, though.

Hobbsy

My Feedback: (102)

Bill, there are many engines that will run on Davis Diesel fuel but without a conversion head you're locked into one prop. Here is my older high compression Saito .80 running on Davis ABC mix turning a MasterAirscrew K-14x8 at 8,790 rpm and idling at 1,492. It has 14.4 to 1 compression, (uncorrected) so probably 12.5 to 1 in the real world. It will fire up and run unaided, no glow heat required in fact I drilled the glow plug coil out of the Fox Miracle that is in it.

Mr Cox

It helps when the engine is running too, remove the glowpower and it runs much rougher from the low compression.

Hobbsy

My Feedback: (102)

How are you Mr. Cox, I think that bog is referring to the lack of catalytic reaction in the presence of Diesel fuel, Thanks, Dave

AMB

Your best bet for info is the Davis diesel site for for conversions for a lot of modern glow engines and info too, Also go back on this site and read the previous pages saves a lot of repetitive posting after that, please ask the guys here on the site are quite helpful on any other questions and will be happy to respond to assure your success martin

Mr Cox

Maybe I read too much into the original question. There is no catalytic reaction as have been pointed out, but what about keeping a low voltage on the plug the whole time?

There is heat from the combustion once it is running so presumably a lower voltage than 1.5V would be enough to just maintain a smooth run. So a regular separate battery with a voltage regulator way well last several flights...

earlwb

Many glow engines will run off of model diesel fuel. But how well is a different story. Some run pretty good, others not so good, and some barely run at all. it might be possible for some engines to run with the glow plug powered the entire time, but you have to be careful, some engines may get preignition or detonation problems. the other issus is the engines are fixed on compression, so you cannot adjust the compression (allows you to advance or retard the timing) to use different propellers. Installing a Davis diesel adjustable head or other head is the way to go most of the time, as you can change compression to adapt the engine to different props easily. 

Then most diesel engines work best with smaller bore carbs on them, not the big bore high performance types of carbs. the air fuel mixture ratios are more lean with model diesel fuel than glow fuel. it is where the diesels get their low fuel consumption fame from. so the small carbs offer easier adjusting and running and fuel draw. That is why certain glow engines are more popular than others when converted to diesel use. But still a engine with a large bore carb can work well, you just maybe cannot run the larger props on them.

Jim Thomerson

I have run a couple of K&B 4011's on diesel fuel. On glow the engine turned an 11 x 5 APC at 9,700 , Tuned about like I would turn it loose on a control line stunt airplane. Tried some Eric Clutton diesel fuel. Hooked up the glow plug and started the engine, After about 20-30 sec. disconnected the battery, and turned the ST needle in one and a half tuns. Engine sounds good, 9,700 RPM, Tried another K&B. It would run undercompressed. Heat up the glow plug and it ran smooth, 9,700. I think the second engine had a thicker head gasket. I've seen a glow plug engine running on diesel fuel pull a control line stunt airplane through the AMA pattern.

Recycled Flyer

Ihave heard of engines like the MVVS 49 that has a standard of 12:1 compression (and that is fairly high for a glow engine due to being set up for FAIfuel only - 80% methanol and 20%castor) being used for control line stunt by simply switching fuels.

The plug was attachedand alight for starting because what a diesel needs is heat to initially fire off (this heat comes about by compressing the fuel/air charge) and when stone cold it will usually need a little help to warm the combustion chamber until the combustion cycle can self support itself.

The reason for the diesel fuel switch in this case was flying at higher altitudes, this needs the largest prop the engine can stand in order to grab the thinner air all the better, and the larger the prop the less the compression you will need for good running so hieght above sea level can be a factor here.

Cheers.

Hobbsy

My Feedback: (102)

Here is the very engine of which you speak, it wears an AJCoholic conversion head, it is turning a Graupner 12x7, I'll have to look up the rpm. RPM==9,775, it has a MVVS 7mm carb and MVVS 3245 Quiet Muffler.

Recycled Flyer

Yes thats the beast there Dave but I was talking more about a stock standard glow engine with zero changes on it - seems possible to run glow engines with LARGE props from about a 12:1 compression ratio up but it also seems that a heat source will be needed (from a lit glow plug) to get it started initially.
Once warm remove the clips from the plug and you are good to go.

Itoo have an MVVS with a A.J. Cohoilc head on it and its wonderfully made and of a very, very soild construction with two 'O' rings on the contra (I am assuming that this is not the norm here.)

Cheers.

P.S. Another help with starting any diesel is the use of a heat gun or hair dryer to firstly warm the head, that and a high ether and/or oil content (if the engine is worn) will also benefit in that regard.

AMB

Recyled flyer MVVS are great conversions have a 40 and a 61 davis heads,

Hope the electric guys do not see the heat gun thing since we are always ribbing them about extra batteries, chargers etc
May be a comeback, AH but you need a generator to run the heat gun at the field ( could not help myself on this one)
The glow plug thing works on a few high compression engines from what I gather, but we are still stuck with a fixed compression engine, cheers martin

On a really positive note either you or fiery came up with a crank for his irvine 20 so he will be back in biz with that one
that is strange never heard of any irvine breaking a crank

Hobbsy

My Feedback: (102)

In about 21 years of flying and running Diesels that is the first thing I have had to break.

AMB

Dave, think you have to write it off as a bad piece of steel they of course do not magnaflux these things, bet it was it would have
shown up martin

KidEpoxy

I dont want to ruffle any feathers here in the Diesel forum,
but couldnt one run a stock glow engine on a diesel fuel cut with methanol to catalyst the glowpug?

The engine conversion guys have a HUGE thread on GGL gas-glow,
they found 2gas:1glow* gives the 20-25% methanol required to fire glow plugs.... cant we just cut Diesel fuel with methanol to give that 20% for firing on the plug? Or a lower share of methanol for having the plug just 'help' the engine diesel fire.

I know it wouldnt be a true 'Diesel running engine' if we use methanol and a plug to fire a kero fuel,
but in the world of practical exercise, its worth a shot to test it out... right?




*for gasoline engines, they use rc car 10nitro 10 oil, for this exercise we would want a different oil content

qazimoto

My Feedback: (1)

The issue of miscibility between the methanol and the kero would likely be a problem here. They simply don't mix together IIRC. The ether might help to a certain extent but really what's the point?

Ray

Recycled Flyer

I have no idea if it would work but my gut is telling me that its bound to fail.

Easy enough to check I suppose, just doctor a small container of fuel and away you go.