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Irvine 20 ABC Diesel
Design History:-Designed and manufactured as a dieselized version of a nitro glow engine in England in the mid 1980's
Design Features:-Front through the shaft induction; ABC piston/cylinder technology; advanced design carburetor and bolt on muffler without pressurization tap.
Specifications:-Displacement 2.5 cc
"This is the latest and, perhaps, the most significant example of the diesel-ization of an existing glow plug engine, in that it was initiated and developed by the engine's manufacturer. Ever since they began producing their own motors in 1977, Irvine Engines have specialized in glow engines (the sole departure being their production of the Mills 75 replica) and the fact that Ron Irvine decided to press ahead with the production of this diesel version of the well-liked and very successful Irvine 20 series, obviously indicates considerable faith in its capabilities.
The Irvine 20 has not been extensively redesigned for diesel operation. It has a new crankshaft; otherwise, dieselization is confined to the cylinder head assembly, plus small modifications to the carburettor and silencer".
After describing the reduced-choke carburetor, the author continues....
"The reason for having this much reduced choke area is to enable the engine to be operated without the assistance of an exhaust pressurised fuel system, which is the reason why the diesel version of the silencer has the usual pressure nipple replaced by a screw-in plug.
Why no exhaust pressure feed ? Simple! Exhaust gases condense to form a certain amount of H2O when they come into contact with the cool fuel in the tank. A little water in the fuel does not matter in a glow engine; it is miscible with methanol-based fuel and a small amount can be tolerated...Diesel fuel, on the other hand, is petroleum based (usually kerosene, occasionally DERV). Ergo, the water remains separated and, having a higher specific gravity than that of the fuel, settles in the bottom of the tank, where it may be sucked up by the clunk weight. Not even diesels like running on water. Result: malfunction of one kind or another...".
The author was Peter G.F. Chinn.
Although it is generally regarded as a fine engine it is not my favorite by far. Looking for a practical RC Diesel to power a Kitty-Wake sport float plane, I settled upon the Irvine 20 ABC diesel to do the job. After a short ground run I made a very bad decision and decided to opt for a first flight. As I recall the flight did not last very long, nor did the poor Kitty Wake. The Irvine suddenly quit and I was faced with the worst of all situations for an RC flyer; a down wind dead-stick landing on a new model. Needless to say the landing didn't go well, ripping away the floats on impact.
Irvine 20 Glow Engine
That Irvine it's self never ran again. All attempts to start it proved unsuccessful and the reason was obvious. There was almost no compression, the once tight engine had gone from lots of compression to none in the matter of a few short minutes (unbelievable!). The engine was thrown into a corner and forgotten for a number of years, until one day I got around to disassembling it for a close examination. What I found was the engine had eaten it's self. The piston and sleeve were severely scored, with deep vertical groves running full length in each. All attempts to find replacement parts (matching piston and sleeve) proved to be impossible so, I thought if I could find a used Irvine 20 engine for parts that would be the answer (not!). The other used Irvine 20's that I managed to find were ringed engines, with marginal compression and I knew from the beginning that they would never start as a diesel.
Watch the video below showing my attempts to start and run these engines.
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