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Diesel 4 strokes

Old 12-15-2010, 08:10 PM
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ZachB10
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Default RE: Diesel 4 strokes

Excellent.  I like the idea of no ignitor, always a pain in my opinion.  I'm OK with one prop size...  I run a 14x8 on my Saito 80 currently, do you just adjust the mixture until it's running properly, or how do you know which size to use?  Since no ignitor is needed to start it, how do you prevent the engine from firing if you flip the prop?  Or does it have to be turned over at higher speeds to fire?

I'm a complete diesel newbie, sorry if I'm asking dumb questions.

Old 12-15-2010, 08:27 PM
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Default RE: Diesel 4 strokes

You do not want to flip the prop on a Diesel casually, they will start right in your hand on occasion. As to the mixture, you run them at peak/lean. The disadvantage to no compression adjustment is if trying to run a smaller prop the engine turns higher rpm for a given throttle opening reducing cylinder filling time and in turn reducing the compression pressure. That .80 above will barely run with a 13x6 on it but runs spot on perfect with the Bolly 13.5x8.
Old 12-15-2010, 08:38 PM
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Default RE: Diesel 4 strokes

How is prop size accounted for on full conversions?

Do you get much better fuel economy by using diesel in the .80?
Old 12-16-2010, 11:38 AM
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Default RE: Diesel 4 strokes

Mr. Davis recommends a 50% load increase. The .80 uses less fuel on Diesel by running with the carb not fully open and at a leaner needle setting. I will try an even larger prop when I have some extra time. I tried to run an Enya .53 four stroke on Diesel but it would only run at full throttle
Old 12-16-2010, 01:16 PM
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Default RE: Diesel 4 strokes


ORIGINAL: Evgeny-arm


ORIGINAL: ZachB10

How is prop size accounted for on full conversions?
Do you get much better fuel economy by using diesel in the .80?
Optimum adjusted diesel motor is capable not only to give good capacity, but also to show super profitability.
My motor of 4 ounces ate 18 minutes.
And if to compare to these motors - they give so much capacity and an operating time having very small tank.
http://technohobby.com.ua/online-sho...5sm3-dlya-f2-c
http://technohobby.com.ua/online-sho...ya-f2-c-yunior
http://technohobby.com.ua/online-sho...5sm3-dlya-f2-c
Thus do not concede on capacity Glow Engine.
Agreed, F2C motors are freakish when it comes to power and range but they are very specialised.

But Isuppose with thousands of man hours in development behind them its no wonder they are good at what they do!

By the way, I believe that a glow F2C team race engine would be more powerful (but only just) but lose out greatly on range and the ability to hot restart.

Old 12-26-2010, 02:07 PM
  #206  
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Default RE: Diesel 4 strokes

ORIGINAL: Evgeny-arm

At me it is now very cold (temperature-30 degrees Celsius), therefore I cannot continue work on the motor even in that premise in which removed work of my motor.

I not использывал still additives in fuel - amyle nitrite and so forth additives with which help can increase capacity to 15-20 %.
Привет, так очень холодно для компрессионные двигатель.. Лучше в лето..

I not used still additives in fuel - amyle nitrite and so forth additives with which help can increase capacity to 15-20 %.
Ответ: не добавыть большее чем 3%, если большее чем 3% двигатель будеть трудно регулировает из-за проблемы с задержки воспламенения.

Как проверить сгорания завершения: он оставит сажи на поршня о том, что работы Lanova камеры. Нет сажи средства полностью горения нет.

English:

Hello, so very cold for the model diesel engine .. Better in
summer ..

I not used still additives in fuel - amyle nitrite and so forth
additives with which help can increase capacity to 15-20%.
Answer: do not add more than 3%, if more than 3% of the engine will
difficult to regulate because of problems with the ignition lagg.

How to check the complete combustion: it will leave soot on the piston means the
Lanova cell works. No soot means no burning completely.
Old 04-14-2021, 06:55 PM
  #207  
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There are definitely a lot more variables with a 4 stroke diesel, but they do run.

The Building Board: O.S. .52 Surpass DIESEL
Old 09-20-2021, 07:23 AM
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Has anyone tried the high ether (55% +) fuel used in the old fixed compression diesels? They trimmed the compression by adding a few % increase in oil. With the ether/oil mix you need to use 25% SAE30 weight motor oil to calm down the ether and prevent detonation, castor does not calm the ether but could add 5% to the total oil. Seems this should work as ether has a very wide fuel/air ratio like methanol. The old Drones ran very reliably on this fuel and won lots of stunt contests in its day. Also need to load the motor with the correct prop. A good source in the US for ether is John Deer starting fluid. Just mix this with the motor oil and go fly, other starter fluids will work if they have at least 50% ether (they should have ether listed as the first ingredient on the list). Again just mix with 25% motor oil and go.

Best, DennisT
Old 09-20-2021, 03:15 PM
  #209  
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Back to the BS about calming the ether. My lord.... lets get real here.
Old 09-20-2021, 05:55 PM
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Originally Posted by 1QwkSport2.5r View Post
Back to the BS about “calming the ether”. My lord.... let’s get real here.
You might have different views but I don't know how many fixed compression diesels you have used but they used very high ether content and because ether has a very wide air/fuel ratio it made for very reliable starts and runs (the Drone Diesel won a lot of control line stunt contests in it day before the very light Fox 35 glow rose to dominance). Here is an article that explains how it works (.AdriansModelAeroEngines.com :: Fixed-compression Diesel Operation). Adrian is an engine guy and knows a lot about all types of diesels and how to get performance from them. When running high ether with it can detonate. Both kero and mineral oil have a calming effect on the ether getting it to burn smoothly. Some high powered chemist may be able to explain the reactions but this was found way back in the 1930's by the Brits and French. One of the things that fixed compression needs is the wide ignition range that ether has, it also cools the engine a lot, kero needs the variable compression design as it adds heat and needs the ignition point to be adjusted to control the engine temperature. If you research the heat value of ether and kero you will find that there is not that much additional Heat Value with Kero, so you don't lose that much power with the high ether fuel as some would suggest.

It is true that guys have run the Drone on standard fuel but it depends a lot on the day, They try to run them like it was an Oliver Tiger that was designed for the kero fuels. This type of fuel can damage a fixed compression engine because you can't back off the ignition timing and it overheats (like running a Fox 35 in 95F day on a wide blade 10x6 with a muffler, it just over heats and sags, reduce the prop to a 9x6 and BAM it works).

First time I ran my Drone I didn't know how they ran or what diesel fuel they used. I thought diesel fuel is diesel fuel, I had OK Cub diesel fuel so that is what I used. Fueled it up in the back yard, a little exhaust prime. One very hard flip of the Drone 11x10 factory prop and BAM it started and ran great. Next day we went to the field to fly it and the day was a little cooler. I primed just like the day before and flipped as hard as I could (for a 14 year old boy), well I flipped and flipped and flipped, got a pop and flipped and flipped got another couple pops and finally it got enough heat to start and run. Very poorly, I played with the needle but didn't know I needed to open it a lot to smooth it out (later once I got the factory instruction manual I learned that trick). I got it in the air, it missed and just barely pulled the ship. I think I horsed it through one loop. Some 60 years later I put that in a Guided Whistle OTS ship, now I got the correct fuel. Drone stated on first or second flip, opened the needle to smooth out the run at around 5900 rpm. Flew the ship just fine, but it need the correct fuel to be reliable.

Best, DennisT

Last edited by Stuntguy13; 09-20-2021 at 06:12 PM.
Old 09-20-2021, 10:15 PM
  #211  
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Diethyl ether detonates easily. That’s why it was and is used. Back when the fixed compression jobbies came to be, they used ether and heavy weight mineral oil because thats what they had. Nothing more or less besides some minor details. 4-stroke diesel conversions are finicky because of the fixed compression - they tend to knock and rattle unless you change to a higher ether content fuel. The consequence to high ether fuel is it lacks power. Ether/mineral oil has very little energy density to it. Kerosene is packed with thermal energy, which the fixed compression 2-strokes can’t handle. Think slag engines. Modern engines need to be in good mechanical condition and have stout conrods. If not, uncle Rodney comes to town. Run them hard or overcompressed and they break. Run them lean and they just quit.

Model diesels are not true diesels. They are however an Otto cycle hybrid. They run in a controlled detonation. No calming effects needed. Model diesel combustion is rather violent by nature and the more ether there is the more violent it is.

Last edited by 1QwkSport2.5r; 09-20-2021 at 10:18 PM.
Old 09-21-2021, 09:12 AM
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Q,
The mineral oil and kero do clam the ether detonation, not perfect but enough. Both ether and kero 's heat values are close but kero burns at a higher temperature so you get a little more punch but the engine does run hotter and you need to be able to back off the compression to keep from going in sag range (this is one of the signs that your fuel has lost ether, the engine starts overheating). The fixed compression engines did fine if run where they were designed with the proper fuel and prop load. The Drone Diesel in its day (and for OTS today) did win a lot of control line stunt contests, the Miron won lots of free flight contests.. If you read Adrian's article you will get the complete picture on fixed compression engines. How this equates for a 4 stroke diesel is something the engine manufactures need to detail in the ops manual.

Best, DennisT
Old 09-22-2021, 04:47 PM
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Im glad I didnt obtain my diesel knowledge from you.
Old 09-24-2021, 10:58 AM
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Originally Posted by 1QwkSport2.5r View Post
Im glad I didnt obtain my diesel knowledge from you.
Q,
We are not that far apart on most diesel issues. We seem to have difference views on ether being calmed down by mineral oil or kero. Fact is it doesn't matter, both approaches work for there intended use, I don't have to understand how it works, it just does.

On the 4 stroke front I watched a number of YouTube videos ( Engines @ dieselrc.com) showing several 4 strokes running on diesel. Some were just glow versions where they hooked up diesel fuel and with the use of a starter off they when. Some got assistance with the ignitor momentarily connected to get it started. Most were very under compressed but they ran. Seems the simplest conversion would be one of the HP VT FC.25 or 21's since they use a belt to drive the rotary OHV train. Would put in very thin head gasket to increase the compression and it should work pretty good. There was an interesting review of the purpose built Enya 41 & 36 diesel 4 strokes. They have compression around 20:1 and are for the most part fixed compression. They use head gaskets and the dummy plug to trim the compression along with the oil % in the fuel (this is an old Drone diesel trick that Fox later used with the stunt 35 and Super Fuel). Both engines cost a fortune but the report said they started easy and ran solid at around 9K rpm swinging a big prop.

Another interesting thread is here: Model Diesel Engines - Page 1269 - RC Groups talks a bit about the Drone Diesel and Enya 4 stroke diesel.

Q, where are you getting your diesel fuel from? Do you mix your own and what do you use for ether source? This is probably one of the more active threads on the Everything Diesel forum, been fun.

Best, DennisT
Old 09-24-2021, 05:02 PM
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I mix my own fuel. K1 Kerosene, Jet A, or #1 diesel fuel, virgin first pressing castor oil, Amsoil Cetane Boost, and John Deere brand ether. My per gallon cost to make it is about $27.
Old 09-26-2021, 06:20 AM
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Q,
How do you get the ether from the JD can - spray into a container or degas, punch holes and pour out?

Here in FL the temps in the summer make keeping ether in the mix a bit of a challenge. I use a cold pack and foam cooler to keep it cool. Been working on a mix as you go approach to have oil and kero in container then spray in the JD starter fluid and quickly mix, let degas a minute or so. Fuel tank and fly.

Best, DennisT
Old 09-26-2021, 08:15 PM
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I drilled a spray tip that fits the Ether cans and can use a straw from a can of Brake Cleaner. The Ether tips don’t fit straws and Brake Cleaner tips don’t fit the Ether can. Careful work with a drill bit in a Brake Cleaner tip and I am off to the races. I have a 16oz canning jar with a wide mouth lid that I use as a decanting vessel from the ether can. I drilled a few holes in the lid of the jar to vent the propellant off and have marked graduations on the side of the jar. I put the Ether can in the freezer for an hour score I decant it. One 7oz (by weight I think) can of ether gives about 8 fluid ounces of liquid ether. I end up doing about 10oz of ether to a quart of fuel. (30% ether by volume). I keep my mixed fuel in a sealed steel can (formerly an Acetone can) with the threads wrapped in plumbers tape. That can is then kept in 2 ziplock bags and kept in my basement (about 64F most of the year) and it keeps just fine. I never have to top it up with ether.

I treat the liquid ether as pure ether after its decanted. John Deere is almost entirely ether with the other ingredient being the propellant.

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