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What's the attraction of diesel plane engines?

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Old 01-22-2018, 01:20 PM
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H5487
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Default What's the attraction of diesel plane engines?

Please don't shoot me for asking but I don't understand the attraction of diesel engines in model airplanes. What am I missing?

Thanks,

Harvey
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Old 01-22-2018, 01:31 PM
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A filthy slimy mess and stinky exhaust
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Old 01-22-2018, 01:48 PM
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Originally Posted by BarracudaHockey View Post
A filthy slimy mess and stinky exhaust
Which pretty much describes many of my friends but that doesn't make me want to fly them.
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Old 01-22-2018, 02:41 PM
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Originally Posted by H5487 View Post
Please don't shoot me for asking but I don't understand the attraction of diesel engines in model airplanes. What am I missing?

Thanks,

Harvey
Nothing in MY opinion.
Diesel conversions are touted as producing more torque with 50% reduction in fuel consumption. I own at least 15 of them ranging from .40 to 2.76 Cu.In. and flew many of them extensively. The fact that I discovered is that in less than 10 flights, there is so much carbon build up in the cylinder head and between the ring and piston - that if you don't remove the engine and thoroughly clean it, you will experience severe loss of power and the engine will run erratically or not at all. Don't ask me how I know! I had two airplane crash twice each when the engines died on takeoff. I am now converting all my engine back to glow.
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Old 01-22-2018, 03:29 PM
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Thumbs down

I like the smell, the burp-burp noise and the fact that the abundant castor oil deposits in the exhaust rapidly heals the bloody cuts and bruises.

Last edited by qazimoto; 01-22-2018 at 07:21 PM.
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Old 01-22-2018, 06:05 PM
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No glow plugs, much less support equipment, slower tickover, rarely a flameout, less noise, the smell...

I feel the only engines suitable for long term diesel use are ringless designs. I had a couple conversion engines that had ringed pistons and they were a bear to get started by hand. The ringless designs with good piston seal start much much easier and there’s no worry of a piston ring getting hung up by carbon.
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Old 01-22-2018, 09:11 PM
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Pro
Gets you into the air if you live in a country where you can't get nitro and can't afford glow plugs.
Con
Makes your clothes smell bad.
Makes your skin smell bad.
Gets black oil on your airplane.
Requires expensive fuel.
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Old 01-22-2018, 09:25 PM
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Simplicity
Fun
Controllable ignition point without batteries/points/sensors
Fuel that is not aggressively poisonous if splashed on skin
Pleasant exhaust note
Cooler exhaust gas
No plug fouling / glow plug burn out / or circuit issues
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Old 01-23-2018, 05:30 AM
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Okey, here is my list of pros and cons:

Pro:
- no batteries or spare glow plugs needed, just bring some fuel and go fly.
- easy to start, just prime and flip
- loves to pull large props
- very pleasant sound due to the low revs
- no dead-sticks, it can hit and miss but the engine never quits (unless the fuel has run out of course)
- fuel economy is good (makes for long flights even with small tanks)
- a crowd pleaser, there is something very special about the whole experience and performance with a diesel engine that you will never get with a glow engine

Cons.
- the exhaust residues can stink (clean as much as possible of teh plane at the field and leave the rags there, then throw your clothes in the washing machine as soon as you get home, preferable run the washing machine before the mrs comes home)
- fuel is hard to find these days, you will have to keep a small stock that is stored properly.
- people will gather around you when you are about to start the engine for the first time of the day...

Last edited by Mr Cox; 01-23-2018 at 05:34 AM.
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Old 01-23-2018, 06:38 AM
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I think Diesels are so neat, I bought a cheap marine diesel off eBay and plan to put it in one of my
boats. It should rev hard and turn a big prop and likely move the boat as well or better than the junky OS .21 marine engine that’s in it now.

The smell is a bit formidable, but I can deal with it. The fuel can be made cheaply enough (around $24/gallon) if using John Deere Ether. Diesel fuel costs me about double what my glow fuel costs mixing it myself. The lower fuel consumption makes up for the offset in cost.
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Old 01-23-2018, 12:11 PM
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Use white spirit (US mineral spirit) as the paraffinic component of your fuel and the smell is much reduced. Exhaust is cleaner as well.
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Old 01-23-2018, 01:02 PM
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Originally Posted by fiery View Post
Use white spirit (US mineral spirit) as the paraffinic component of your fuel and the smell is much reduced. Exhaust is cleaner as well.
There are two different types of ‘mineral spirits’ - the lower odor variety which is naphtha and the other is the more typical “paint thinner” which is a different spirit than naphtha. I was going to test both compounds for a friend that is sensitive to the exhaust smell that contains kerosene. I’d be curious to see the operation differences between these compounds.
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Old 01-23-2018, 01:10 PM
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I believe that F2C flyers may be using Recosol D60 in their fuel to replace the Kero component in their diesel fuel. Should be available in the USA.

http://www.recochem.com.au/index.php/products/industrial_products/degreasers/item/recosol_d601
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Old 01-25-2018, 05:21 AM
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I’ll have to keep looking around - I haven’t found a source for that solvent in the USA yet.
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Old 01-25-2018, 07:10 AM
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Default Diesel model aircraft engine

reliability
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Old 01-25-2018, 11:24 AM
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Originally Posted by qazimoto View Post
I believe that F2C flyers may be using Recosol D60 in their fuel to replace the Kero component in their diesel fuel. Should be available in the USA.

Products | Recosol D60 | Recochem - Australia
qaz, It has a high flash point, do you think it will require a higher compression setting and more ether?
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Old 01-25-2018, 04:41 PM
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To make the smell of diesel fuel more attractive to the missus use a little candle scent in the fuel and at least you will smell like a fruit or a flower or a spice. Anything other than ether and kerosene which are not your favorite antiperspirant.. Really small quantity of scent, think 10/12 drops to a gallon.
Black residue is usually a sign of over compression, the exhaust should be a honey.amber color. As to wearing an engine out it will if it is not handled right. I ran diesels in favorite aircraft. for 5 years or more without turning the head or needle valve. An electric starter will get it going and as it warms up it smooth's out. stop fiddling with the tommy bar
As to ringed engines I ran Super Tigers and K&B and other ringed engine without much difficulty although the K&B 4050 was really a powerhouse and it was lapped and ABC.. Also modern engines can use a little less oil then the old iron steel stuff from the 50s and Synthetic oil is the way to go with a modern engine. For that fact use it in your old iron stuff and clean out the carbon build up. your engine will thank you for it
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Old 01-25-2018, 10:09 PM
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Originally Posted by controlliner View Post
qaz, It has a high flash point, do you think it will require a higher compression setting and more ether?
I don't know about that but I understood that it was de-odourised and very carefully controlled regarding it's specification. Where as normal Kerocene especially Jet-A1 varies considerably. I just heard the suggestion that one cure for an overly sooty exhaust was to add more DII to the fuel mix.
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Old 04-01-2018, 07:27 AM
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Lightbulb White Spirit

Originally Posted by fiery View Post
Use white spirit (US mineral spirit) as the paraffinic component of your fuel and the smell is much reduced. Exhaust is cleaner as well.
Do you mean the " TURPS SUBSTITUTE" type used for thinning household gloss paints ?
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Old 04-01-2018, 03:22 PM
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Originally Posted by erik58 View Post
reliability
If that's what you call having to de-carbonize the cylinder head and piston every 10 or less flights.
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Old 04-27-2018, 08:58 AM
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Model diesels (compression ignition) are fun to play with. It never ceases to fascinate me that an engine can run without a spark or glow plug. Unlike many, I actually like the smell of the exhaust, although I agree that it permeates EVERYTHING and you will want to wear clothes you do not care about and rags you intend to throw away. That said, my flying experience with model diesels, both made for diesel (PAW and MVVS) and Davis conversions, is that other than fuel economy they do absolutely nothing better than a glow engine. And the improved fuel economy has far more to do with lower RPMs than it does the theory that Kerosene possesses greater BTU potential than Methanol. I too like being able to "adjust the timing" with compression, which allows ridiculously large propellers at lower RPMs, but have enjoyed my model diesels FAR more on the bench, than in the air.

Last edited by RichardGee; 04-27-2018 at 01:49 PM.
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Old 04-27-2018, 01:34 PM
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Default White Spirit

The turps substitute is the correct product for use in model diesel fuel. Leave the stove naphtha for camp stoves.
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Old 04-27-2018, 02:00 PM
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Originally Posted by RichardGee View Post
Model diesels (compression ignition) are fun to play with. It never ceases to fascinate me that an engine can run without a spark or glow plug. Unlike many, I actually like the smell of the exhaust, although I agree that it permeates EVERYTHING and you will want to wear clothes you do not care about and rags you intend to throw away. That said, my flying experience with model diesels, both made for diesel (PAW and MVVS) and Davis conversions, is that other than fuel economy they do absolutely nothing better than a glow engine. And the improved fuel economy has far more to do with lower RPMs than it does the theory that Kerosene possesses greater BTU potential than Methanol. I too like being able to "adjust the timing" with compression, which allows ridiculously large propellers at lower RPMs, but have enjoyed my model diesels FAR more on the bench, than in the air.
I suspect that had you flown them more in the air (as i did extensively), you would have lost your enthusiasm in no time. Crashing an airplane every 8-10 flights due to carbon build-up rendering the ring useless, resulting in considerable loss of power, would have clearly showed you how impractical, and, useless the whole concept is. I have about 15 useless "Paper Weights" and some 12 gallons of diesel fuel left in my shop to prove my point.
Just my 2C.
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Old 04-27-2018, 02:21 PM
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Wink

Originally Posted by N99JH View Post
I suspect that had you flown them more in the air (as i did extensively), you would have lost your enthusiasm in no time. Crashing an airplane every 8-10 flights due to carbon build-up rendering the ring useless, resulting in considerable loss of power, would have clearly showed you how impractical, and, useless the whole concept is. I have about 15 useless "Paper Weights" and some 12 gallons of diesel fuel left in my shop to prove my point.
Just my 2C.
I flew a Super Tiger .45 Davis Diesel conversion. After fewer than 6 flights, it ate a wrist pin retainer clip, which essentially destroyed the engine. Until that time it had always performed superbly as a glow. I sent it to Hobbico and they actually repaired it under the 2-year Warranty. I never ran it as a diesel again. I flew a P.A.W. .35 TBR RC on a Buzzard Bombshell old timer. I approached full throttle just to get the airplane into the air and then never ever went past 1/3 throttle for many flights. It was happy running like that and I never had an ounce to trouble with it. Flew an MVVS .61 diesel on a sport plane. On the extremely rare occasion I could get it to start and run, I flew the plane, but could never throttle down as the engine would never recover from an idle. This engine was sold by MVVS with both glow and diesel heads, and a smaller carburetor, but it was by far the worst performing diesel I have ever had the misfortune of running. I had always assumed U/C would be ideal for a diesel, but that isn't the case. They are as rare in U/C use as RC. I like diesels anyway....
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Old 04-28-2018, 09:01 AM
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Ringed engines should NEVER EVER be used as Diesel conversions in the air. IMVHAIO. Ringless pistons are the proper way to go as is the proper fuel. Synthetic oils have NO place in model diesel fuels. Set the engine right and you shouldn’t have to do much to it for a long time. Carbon buildup in a short period of time causing the engine to not run properly leads me to believe either improper engine settings or incorrect fuels being used. IMO.
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