diesel fuel vs nitro fuel for RC airplanes

by Joe
(riverview,florida)

i keep seeing people use and talk about using diesel fuel instead of nitro fuel in their RC airplane engines. Whats the deal here?

Can you just buy diesel and put it in just like nitro or is there a different carb or something you need.

thanks

Joe

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diesel fuel vs nitro fuel for RC airplanes

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excellent post!
by: Matt

Wow Michael,

Thanks again for another excellent post!

Model diesels are really compression ignition engines.
by: Michael from Oz

G'day Model diesel fuel is not the same as the stuff used in trucks (and my car). It is a mixture of kerosene (the fuel), ether (the ignition source) and oil (often castor oil). It may also contain a small amount of an ignition improver such as Amyl Nitrate (nearly impossible to get), Isopropyl Nitrate (difficult to get) or one of the ignition improvers used for auto diesels.

Model diesels do not have glow plugs but usually have some means of varying the compression of the engine - usually via a contra-piston in the top of the cylinder which is pushed down by a screw or key. (It is pushed up by the exploding fuel after the screw has been released a bit). The key allows you to vary the compression ratio and this affects the ignition timing. As you increase the compression, you are advancing the ignition timing. Larger props need the timing retarded.

Fuel mixtures can cover a wide range of formulas from the very basic 1:1:1 where equal parts of the three main ingredients are used or my old racing mixture of 20% oil, 30% ether and 50% kerosene plus 1 to 2% ignition improver and many many more variations.

Being able to vary the igntion timing makes it possible to run quite large props on model diesel engines.

Model diesels were once very common in Europe and the UK and Australia but these days, glow engines are more common. PAW is one brand still available. Enya also makes some excellent diesel engines including a four stroke.

Most diesel engines these days are glow engines with a diesel head such as those sold by Davis Diesel in the USA. A very good basic starting point is the OS LA 40 or 46 with a Davis Diesel head. It is often an advantage to use a smaller carby on a diesel converted engine as the diesel engine will use about half the fuel that the glow engine uses and the glow carby may be too large. The LA engines have a relatively small carby for their size and usually work OK. My diesel converted Magnum 46 has a 25 size carby and works very well. My original Irvine 40D has quite a small carby.

And then there is the tuning of diesel engines but that is a whole new game but in short, they work best a bit under compressed and a little rich.

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Submitted by: Michael from Oz

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G'day Model diesel fuel is not the same as the stuff used in trucks (and my car). It is a mixture of kerosene (the fuel), ether (the ignition source) and oil (often castor oil). It may also contain a small amount of an ignition improver such as Amyl Nitrate (nearly impossible to get), Isopropyl Nitrate (difficult to get) or one of the ignition improvers used for auto diesels. Model diesels do not have glow plugs but usually have some means of varying the compression of the engine - usually via a contra-piston in the top of the cylinder which is pushed down by a screw or key. (It is pushed up by the exploding fuel after the screw has been released a bit). The key allows you to vary the compression ratio and this affects the ignition timing. As you increase the compression, you are advancing the ignition timing. Larger props need the timing retarded. Fuel mixtures can cover a wide range of formulas from the very basic 1:1:1 where equal parts of the three main ingredients are used or my old racing mixture of 20% oil, 30% ether and 50% kerosene plus 1 to 2% ignition improver and many many more variations. Being able to vary the igntion timing makes it possible to run quite large props on model diesel engines. Model diesels were once very common in Europe and the UK and Australia but these days, glow engines are more common. PAW is one brand still available. Enya also makes some excellent diesel engines including a four stroke. Most diesel engines these days are glow engines with a diesel head such as those sold by Davis Diesel in the USA. A very good basic starting point is the OS LA 40 or 46 with a Davis Diesel head. It is often an advantage to use a smaller carby on a diesel converted engine as the diesel engine will use about half the fuel that the glow engine uses and the glow carby may be too large. The LA engines have a relatively small carby for their size and usually work OK. My diesel converted Magnum 46 has a 25 size carby and works very well. My original Irvine 40D has quite a small carby. And then there is the tuning of diesel engines but that is a whole new game but in short, they work best a bit under compressed and a little rich.

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Here's a link about diesel heads
by: Matt

Hi Joe,

Conde is right, you need to buy a special head in order to burn diesel fuel in a glow engine.

You may find this article interesting.

need diesel head
by: CONDE

Hi i know people used to fly with diesel motors and they just change the head of the engine for special one and the plug is different.

The actual engines are made for glow. I think the ports, the carb and the header are designed for this. if you put diesel in a glow engine with factory head you damage the engine.

And the diesel engines are really dirty ones.