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Old Jul 01, 2004, 09:31 PM
Rocky Mountain High and Higher
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Question
2.5cc MAPP3 Diesel, prop size?

Very easy question for someone in the know.

What would be the recommended prop sizes for the 2.5cc MAPP3 diesel?

Thanks.
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Old Jul 02, 2004, 03:21 AM
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Try 10x6 maximum; 9x4 for running in; 7x4 minimum. Diesels are versatile and cope well with larger props than an equivalent glow but at lower revs generally.

The rest in between depend on the use you want it for. High pitch for speed, low pitch for power in climb. Go for 6 in. pitch for general use.

What sort of model is it for?
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Old Jul 02, 2004, 03:59 AM
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If I recall correctly, the MAP3 is considered a "team race" diesel (used primarily in CL Speed events) and as such is ported/timed for high RPM. You will want to run a prop from a 7x3 to an 8x4 on it to keep it in its optimum power delivery RPM range. I have one but received it without any instructions about 10 years ago so I am going by the manufacturer recommendations of similar Russian engines of the same displacement and construction (rear intake, radial exhaust, radial porting, etc.). Oil content and composition is important for it so I would contact Dr. Diesel (Eric Clutton) or Carlson Engine Imports (Ed Carlson) to source some fuel. Make sure to mention what engine you need it for. I did run mine and unless my memory fails me, it was quite impressive (and messy).
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Old Jul 02, 2004, 07:24 AM
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I deliberately suggested the more conservative (ie larger) props as it sounded from your post that you may not be very familiar with diesel operation. Larger props will give some confidence and experience in starting with less risk.

As Lomcevak has pointed out, the engine is a 'racing' type for FAI team race. Be very careful not to use the small props initially as the engine is very likely to be 'snappy'. That is, it needs a much harder flick to start than a glow and any misfire will catch you out and cause injury Also, you need to guard against flooding and it locking up towards compression if too much priming has been used.

I also agree that you could do a lot worse than get in touch with Eric Clutton - his experience and knowledge of diesels will be very helpful.
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Old Jul 02, 2004, 03:40 PM
Rocky Mountain High and Higher
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Thank you very much for the information.
I am considering using this diesel in a HOB R/C T-6 Texan I want to pylon race. Just to have something different. I really don't need the throttle as long as I can cut the engine by timing the fuel burn.
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Old Jul 02, 2004, 05:02 PM
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I don't know the particular model, but the Texan's radial cowl could do with having a larger prop anyway.

I'd fit some sort of radio operated fuel cut-off if possible.Diesels are much more frugal with fuel than glows, so there's a problem timing fuel burn accurately.

Don't forget that you need diesel resistant fuel tubing. The normal glow type is useless in a few minutes after exposure to diesel fuel.
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Old Jul 02, 2004, 06:00 PM
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I have heard that the black gasoline line will work. I don't know about silicone or neoprene.
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Old Jul 02, 2004, 08:51 PM
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Neoprene or Tygon tubing is gasolene or diesel fuel resistant.
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Old Jul 02, 2004, 10:38 PM
It flies? I like it!
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Proper props for this engine will not protrude much beyond the coke bottle cowl... but it might be fun to try anyway. At any rate, avoid using an electric starter on this motor. It will destroy it in very short order.
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Old Jul 03, 2004, 03:27 AM
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Neoprene is the type used by most diesel users for many years, but it does harden over time and can eventually split (again, over a number of years, not a short term thing).

I got a clear yellow, thin walled tubing, very like neoprene, at the UK Nationals a few years ago. It was labelled as diesel fuel tubing but had no identification on the pack other than that. It hasn't hardened and stays tight on tank and needle fixings. It is very flexible and takes a tight bend without the walls kinking. The trouble is I haven't seen any more of it. I don't remember who I bought it from either. Time's running out for replacing it, as there's only about 15 inches left.

Isn't that always the case?
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Old Jul 03, 2004, 02:44 PM
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I found some black neoprene at the LHS. The last T6 I used an OS .15 with an 8x3, it didn't clear the cowling much in diameter but it performd well. I guess I need to know about what RPM to expect out of the diesel compared to the glow engine to attempt a simular speed or better.
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Old Jul 04, 2004, 03:01 AM
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Tony I'd guess the clear yellow fuel tubing was from the PAW tent cus that's where I got mine. They still sell it and I wouldn't be surprised if Eric Clutton sells it in the US.

Steve
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Old Jul 04, 2004, 03:40 AM
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I think you're right Steve! I remember - now - getting a couple of spare needles, a spraybar and the tubing.

I'll get more at this year's Nats. where I'll fly my Clutton 'Kwod' as usual.

Thanks
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Old Jul 04, 2004, 05:20 AM
It flies? I like it!
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With the right prop, Team Race diesels regularly deliver 0.6 to 0.8 HP at 22,000 to 25,000 RPM. I suspect, though that the weight/drag of the T6 will make a prop that allows that kind of RPM unsuitable (team race models are usually under 13 ounces of weight ready to fly and about 24" span compared to 38-42 ounces and 44" span on that AT-6). Wild guess is about 14-17K RPM on an 8x4. Do post your results, if you will, so that we can all learn from the experience.

Good luck!
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Old Jul 04, 2004, 06:06 PM
Rocky Mountain High and Higher
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I can do that, but no pics if it goes into the ground

Are there any tricks to the fuel that would be favorable to this engine? Like with boosting the nitro in glow fuel.
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