When is a Diesel engine considered to be broken
08-12-2022, 02:55 PM
#1
Thread Starter
When is a Diesel engine considered to be broken
I am breaking in a MVVS 2.0 cc Diesel and would like to know when it is broken in enough to fly cl with it.
I have been running it at 11,000 rpm. On an 8-3 prop. This is a very wet four cycle. I alternate brief runs at 16,000 rpm. that are still very wet with more rpm available.
Hand starting is still being learned while being broken in so bench running is not all bad!
How may I determine when the engine is broken in?
Tia,
Franchi
I have been running it at 11,000 rpm. On an 8-3 prop. This is a very wet four cycle. I alternate brief runs at 16,000 rpm. that are still very wet with more rpm available.
Hand starting is still being learned while being broken in so bench running is not all bad!
How may I determine when the engine is broken in?
Tia,
Franchi
08-12-2022, 11:12 PM
#2
Running-in the model diesel engine in 1 hour with rich fuel mix in 10 000 rpm and right propeller size is sufficient until the engine is run-in. "4-stroke" break-in is not necessary, and it is enough that much oil comes out of the exhaust port to remove metal particles that have worn away until the engine gets a perfect fit between the parts that are driven together. In your engine at 2 ccm need the propeller size 9/4 or 9/6.
08-13-2022, 03:14 AM
#3
Read here: https://www.adriansmodelaeroengines.....php?cat_id=10
ferrous engines should be heat cycled and only run short runs with a lean-out and heat up, and pulling fuel to kill it and cool it off completely. Proper ferrous break-in takes 1-2 hours and will consist of 10-15 separate runs. Read the above link.
ferrous engines should be heat cycled and only run short runs with a lean-out and heat up, and pulling fuel to kill it and cool it off completely. Proper ferrous break-in takes 1-2 hours and will consist of 10-15 separate runs. Read the above link.
08-13-2022, 06:28 AM
#4
Thread Starter
Hi:
Thanks for the replies.
One to two hours appears to be a long time to bench run an engine. Can I break in this engine in the air if run quite rich?
The method that I use to break in engines is perhaps unique. I have my test stand mounted on a school desk with a lift up top. I run the engine at a very rich speed for awhile, and then I lift the top to 90 degrees. This causes the engine to break into a very fast 2 cycle. I then repeat this many times until the fuel is depleted or until I shut down the engine. I hope that this is heat cycling the engine. The range of rpm is 11000-16000rpm on a MAS 8-3 prop. This going from a very wet four cycle to a wet two cycle.
Comments/Suggestions
Franchi
Thanks for the replies.
One to two hours appears to be a long time to bench run an engine. Can I break in this engine in the air if run quite rich?
The method that I use to break in engines is perhaps unique. I have my test stand mounted on a school desk with a lift up top. I run the engine at a very rich speed for awhile, and then I lift the top to 90 degrees. This causes the engine to break into a very fast 2 cycle. I then repeat this many times until the fuel is depleted or until I shut down the engine. I hope that this is heat cycling the engine. The range of rpm is 11000-16000rpm on a MAS 8-3 prop. This going from a very wet four cycle to a wet two cycle.
Comments/Suggestions
Franchi
08-13-2022, 12:21 PM
#6
Thread Starter
Hi Quick Sport:
I read the page that you suggested prior to and since running my engine. What am I doing wrong? What form of damage may happen to my engine?
I run the engine at a fast four cycle and then at a fast two cycle to get the engine hot. Then back to a cool four cycle. I do this until the two once tank is empty. The engine is then permitted to completely cool and the process is repeated for an additional tank of fuel.
Perhaps this is not providing enough cooling for the parts to grow. If heating and cooling cycles cause the p&c to grow to a great fit, perhaps this heat/ cooling cycle could be done with a torch or heat gun and the final fit could be done by running the engine. Or, an oven may be employed to heat treat the p&c and leave the the final fit to actually take place after the parts have normalized.
An hour or two of bench running seems so very inefficient and wasteful.
Franchi
I read the page that you suggested prior to and since running my engine. What am I doing wrong? What form of damage may happen to my engine?
I run the engine at a fast four cycle and then at a fast two cycle to get the engine hot. Then back to a cool four cycle. I do this until the two once tank is empty. The engine is then permitted to completely cool and the process is repeated for an additional tank of fuel.
Perhaps this is not providing enough cooling for the parts to grow. If heating and cooling cycles cause the p&c to grow to a great fit, perhaps this heat/ cooling cycle could be done with a torch or heat gun and the final fit could be done by running the engine. Or, an oven may be employed to heat treat the p&c and leave the the final fit to actually take place after the parts have normalized.
An hour or two of bench running seems so very inefficient and wasteful.
Franchi
08-14-2022, 03:18 AM
#7
The way it should be done is first using a stopwatch for consistency. Run rich and undercompressed for a period of time - about 7-10 minutes. Lean out a d increase compression to clean up and build heat 1-2 minutes, remove fuel and allow engine to stop and completely cool to ambient temperature. Start procedure again.
The piston is wearing and particles shedding during the 4-cycle/rich mode. The piston is cold and not expanded. Excessive wear will damage the piston seal by wearing the piston too much. What you are trying to do is work harden the piston and liner bore and create a glass smooth surface. The return to 4-cycle rich mode and going back and forth never allows the piston and liner to completely cool which doesn’t allow the best cycle to complete. You start cold, work up to warm, then hot, then completely cool. Do this 7-10 times and then check to see if it will hold a lean flight setting without sagging. If it sags, do a few more heat cycles. The important thing here is the cycle of being cold, warm, hot, and back cold. This process is relieving the stresses in the piston and allowing it to expand and harden to its final surface which will then not wear much at all due to the surface of the piston and bore being so perfectly smooth.
That article does mention this and the reason for it.
The piston is wearing and particles shedding during the 4-cycle/rich mode. The piston is cold and not expanded. Excessive wear will damage the piston seal by wearing the piston too much. What you are trying to do is work harden the piston and liner bore and create a glass smooth surface. The return to 4-cycle rich mode and going back and forth never allows the piston and liner to completely cool which doesn’t allow the best cycle to complete. You start cold, work up to warm, then hot, then completely cool. Do this 7-10 times and then check to see if it will hold a lean flight setting without sagging. If it sags, do a few more heat cycles. The important thing here is the cycle of being cold, warm, hot, and back cold. This process is relieving the stresses in the piston and allowing it to expand and harden to its final surface which will then not wear much at all due to the surface of the piston and bore being so perfectly smooth.
That article does mention this and the reason for it.
03-25-2023, 12:47 PM
#8
Thread Starter
Hello:
Would not a 9-4 or A 9-6 prop place an excessive load on a 2cc Diesel? I can see the crank pin, con rod, and the wrist pin not being able to withstand that load.
Remember, this is not one of those long stroke side port engines from yesteryear.
Stay well,
Franchi
Would not a 9-4 or A 9-6 prop place an excessive load on a 2cc Diesel? I can see the crank pin, con rod, and the wrist pin not being able to withstand that load.
Remember, this is not one of those long stroke side port engines from yesteryear.
Stay well,
Franchi
03-27-2023, 03:36 AM
#9
Diesels are a little different animal compared to glow engines. Glow engines need a smaller prop and more rpm for lighter load to break in. Diesels are the opposite. The bigger the prop, the lower the compression setting needed, which equates to lighter mechanical load to break in. A 9” prop is too big for a 2cc glow, but I wouldn’t be worried about a low pitch 9” prop on a 2cc diesel. Technically, it probably is too big, but it should be fine.
