MVVS diesel stuff
06-17-2011, 01:31 PM
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MVVS diesel stuff
On and off I have been running the MVVS line of diesels. tried out different fuels and setups.
I found out:
The standard cast iron piston diesel is a very decent engine up to 13,000 rpm. Above that vibration is worse than an ABC engine. ( I guess glow engines at 20,000+ rpm have spoiled me over the years)
A modified ABC engine ran exceptionally well, albeit not at very high rpm. Best rpm stil being about 12500 for smooth diesel power.
The standard engine contrapiston was a devil to adjust after the engine heats up. It just stays put at the highest compression setting. This was also the case in my ABC mod with brass CP and aluminum head.
Fuels tested : 40/40/20 ether/kero/oil prooved best with no need to adjust CP settings. Cetane boosters? I found no difference to speak highly of.
Experimented with dome or flat shaped CP / squish zones. Not much difference, at least nothing "Eureka!"
In order to solve the stuck contrapiston syndrome I made up a push/pull head. Head is aluminum, the 10mm dia flat top CP is steel with M4 thread. Adjusting screw is M6 with 9mm width across flats. No testing done yet. The diesel looks funny without tommy bar. It seems that there is room to add it, so I probably will braze one on. Less tools = more fun.
In the picture: (look into the exhaust ports)
left = modified ABC glow engine, aluminum head, brass CP
Middle = original MVVS diesel (steel cylinder, Cast iron piston)
right = Glow ABC liner with new push-pull head, cylinder lowered 0.5mm (shorter cyl. jacket) to create slight sub-induction and shorter port durations. Not yet run.
Any comments and/or discussions are welcome.
I found out:
The standard cast iron piston diesel is a very decent engine up to 13,000 rpm. Above that vibration is worse than an ABC engine. ( I guess glow engines at 20,000+ rpm have spoiled me over the years)
A modified ABC engine ran exceptionally well, albeit not at very high rpm. Best rpm stil being about 12500 for smooth diesel power.
The standard engine contrapiston was a devil to adjust after the engine heats up. It just stays put at the highest compression setting. This was also the case in my ABC mod with brass CP and aluminum head.
Fuels tested : 40/40/20 ether/kero/oil prooved best with no need to adjust CP settings. Cetane boosters? I found no difference to speak highly of.
Experimented with dome or flat shaped CP / squish zones. Not much difference, at least nothing "Eureka!"
In order to solve the stuck contrapiston syndrome I made up a push/pull head. Head is aluminum, the 10mm dia flat top CP is steel with M4 thread. Adjusting screw is M6 with 9mm width across flats. No testing done yet. The diesel looks funny without tommy bar. It seems that there is room to add it, so I probably will braze one on. Less tools = more fun.
In the picture: (look into the exhaust ports)
left = modified ABC glow engine, aluminum head, brass CP
Middle = original MVVS diesel (steel cylinder, Cast iron piston)
right = Glow ABC liner with new push-pull head, cylinder lowered 0.5mm (shorter cyl. jacket) to create slight sub-induction and shorter port durations. Not yet run.
Any comments and/or discussions are welcome.
06-17-2011, 01:48 PM
#2
RE: MVVS diesel stuff
Interesting. Thanks for sharing.
Is sub piston induction even useful if you are using a muffler? I would think that with a muffler then sub-piston induction would actually loose power over a regular piston setup.
Is sub piston induction even useful if you are using a muffler? I would think that with a muffler then sub-piston induction would actually loose power over a regular piston setup.
06-17-2011, 04:30 PM
#3
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RE: MVVS diesel stuff
ORIGINAL: pe reivers
On and off I have been running the MVVS line of diesels. tried out different fuels and setups.
I found out:
The standard cast iron piston diesel is a very decent engine up to 13,000 rpm. Above that vibration is worse than an ABC engine. ( I guess glow engines at 20,000+ rpm have spoiled me over the years)
A modified ABC engine ran exceptionally well, albeit not at very high rpm. Best rpm stil being about 12500 for smooth diesel power.
The standard engine contrapiston was a devil to adjust after the engine heats up. It just stays put at the highest compression setting. This was also the case in my ABC mod with brass CP and aluminum head.
Fuels tested : 40/40/20 ether/kero/oil prooved best with no need to adjust CP settings. Cetane boosters? I found no difference to speak highly of.
Experimented with dome or flat shaped CP / squish zones. Not much difference, at least nothing ''Eureka!''
In order to solve the stuck contrapiston syndrome I made up a push/pull head. Head is aluminum, the 10mm dia flat top CP is steel with M4 thread. Adjusting screw is M6 with 9mm width across flats. No testing done yet. The diesel looks funny without tommy bar. It seems that there is room to add it, so I probably will braze one on. Less tools = more fun.
In the picture: (look into the exhaust ports)
left = modified ABC glow engine, aluminum head, brass CP
Middle = original MVVS diesel (steel cylinder, Cast iron piston)
right = Glow ABC liner with new push-pull head, cylinder lowered 0.5mm (shorter cyl. jacket) to create slight sub-induction and shorter port durations. Not yet run.
Any comments and/or discussions are welcome.
On and off I have been running the MVVS line of diesels. tried out different fuels and setups.
I found out:
The standard cast iron piston diesel is a very decent engine up to 13,000 rpm. Above that vibration is worse than an ABC engine. ( I guess glow engines at 20,000+ rpm have spoiled me over the years)
A modified ABC engine ran exceptionally well, albeit not at very high rpm. Best rpm stil being about 12500 for smooth diesel power.
The standard engine contrapiston was a devil to adjust after the engine heats up. It just stays put at the highest compression setting. This was also the case in my ABC mod with brass CP and aluminum head.
Fuels tested : 40/40/20 ether/kero/oil prooved best with no need to adjust CP settings. Cetane boosters? I found no difference to speak highly of.
Experimented with dome or flat shaped CP / squish zones. Not much difference, at least nothing ''Eureka!''
In order to solve the stuck contrapiston syndrome I made up a push/pull head. Head is aluminum, the 10mm dia flat top CP is steel with M4 thread. Adjusting screw is M6 with 9mm width across flats. No testing done yet. The diesel looks funny without tommy bar. It seems that there is room to add it, so I probably will braze one on. Less tools = more fun.
In the picture: (look into the exhaust ports)
left = modified ABC glow engine, aluminum head, brass CP
Middle = original MVVS diesel (steel cylinder, Cast iron piston)
right = Glow ABC liner with new push-pull head, cylinder lowered 0.5mm (shorter cyl. jacket) to create slight sub-induction and shorter port durations. Not yet run.
Any comments and/or discussions are welcome.
This engine is popular in local c/l clubs for speed limited Diesel Goodyear racing. The best feature I've observed is it's absolute reliability. Starts very well hot or cold. I have one and use the pretty much standard c/l diesel "Oliver Tiger" brew of 20% Castrol M Castor, 32% Ether and 48% good quality Kero. On top of this we add Cetane booster about 15 ml/ Litre Iso Propyl Nitrate (IPN). Some use about 18 ml/Litre DII instead. These quantities are varied according to temperatures. More in the winter less in the summer.
Props are usually APC 7 x 6. Airborne RPM would be approaching 17K. The venturies are usually opened to about 4.5mm.
Vibration isn't really a problem that I've noticed. Some people retime them for a total exhaust duration of about 145 degrees. and take metal out of the piston to lighten it. It is particularly heavy as pistons go.
Many iron/steel piston/linered diesels are set up with tight contrapistons. You can look at it as a feature rather than a problem.
Do you really need to change the compression setting while the engine is running?
Probably not!
If you constantly change the comp setting the contra piston is going to wear much more rapidly.
One of the best features of the MVVS is it's hot or cold starting. It will start cold at the last running setting. If not, the cetane booster component in the fuel is wrong.
It's a pity that they're now out of production but the Parra 15D and the Fora Junior mk2 are good replacements.
Ray
06-17-2011, 04:47 PM
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RE: MVVS diesel stuff
Pe Reivers, I have two of the 2.5 cc diesels from the late 1990's I think. I have run one flying in old time model at lower RPM and have had no problems. Also I have three of the MVVS 10 cc diesels also from the late 1990's, maybe. One purchased new and the other two I got used at a great price. One was set up for glow and I installed the diesel head. I have run one on the test stand but have not flown it yet. I will use it for a large old time Texaco model of the late 1930's vintage. A big prop at low RPM for fuel economy. Do you stock the head gaskets/shims/spacers or whatever you call them? I would like to obtain some of these for the MVVS 10 cc diesel. Jack Hiner in the United States.
06-18-2011, 01:43 AM
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RE: MVVS diesel stuff
In the '70s I had a MMVS 2,5D similar to this but with a integral round exaust stack : I run it with pressure from the crankcase and a large venturi just like glow with 25% castor 25% ether 50% kerosene fuel plus 3% amyl nitrate ( a recommended MVVS blend ).
Propeller was 7x6 taipan and RPM well beyond 18000
The engine had a front needle bearing and a rear ball bearing, started very easily even if I was very scared because of pressure feed ...[X(]
It disappeared in a fly away due to a lines cut in a combat match: the plane fell in a corn field never to be found again[&o]
Propeller was 7x6 taipan and RPM well beyond 18000
The engine had a front needle bearing and a rear ball bearing, started very easily even if I was very scared because of pressure feed ...[X(]
It disappeared in a fly away due to a lines cut in a combat match: the plane fell in a corn field never to be found again[&o]
06-18-2011, 03:26 AM
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RE: MVVS diesel stuff
ORIGINAL: pe reivers
In order to solve the stuck contrapiston syndrome I made up a push/pull head. Head is aluminum, the 10mm dia flat top CP is steel with M4 thread. Adjusting screw is M6 with 9mm width across flats.
In order to solve the stuck contrapiston syndrome I made up a push/pull head. Head is aluminum, the 10mm dia flat top CP is steel with M4 thread. Adjusting screw is M6 with 9mm width across flats.
How does the it pull? Is the thread screwed into the the contra piston? I'm kind of lost on the M4 and M6 part.
06-18-2011, 03:59 AM
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RE: MVVS diesel stuff
First let it be said, that the MVVS 2.5 diesels are still available from MVVS. So are the diesel conversion heads for 10cc. I stock them. MVVS some time ago produced a batch of them by popular demand.
The diesel head I made is meant as an experiment. The head has M6 thread (pitch is 1.0mm)
Inside the M6 screw there is M4 thread (pitch is 0.7mm). The contrapiston has a M4 extension that engages with the M4 thread in the M6 compression adjusting screw. One full turn of this screw adjusts the 10mm dia CP by 0.3mm. (1.0 - 0.7). With this system you can both pull the CP and push it.
The advantage of using a ABC cylinder set is the extreme wear resistance and the very light piston.
I have made one conventional diesel head button for the ABC liner set. So far I like this better than the push-pull. Not done testing it though. I will probably replace the brass CP in the conventional setup with a steel one in order to balance heat expansion rates.
The diesel head I made is meant as an experiment. The head has M6 thread (pitch is 1.0mm)
Inside the M6 screw there is M4 thread (pitch is 0.7mm). The contrapiston has a M4 extension that engages with the M4 thread in the M6 compression adjusting screw. One full turn of this screw adjusts the 10mm dia CP by 0.3mm. (1.0 - 0.7). With this system you can both pull the CP and push it.
The advantage of using a ABC cylinder set is the extreme wear resistance and the very light piston.
I have made one conventional diesel head button for the ABC liner set. So far I like this better than the push-pull. Not done testing it though. I will probably replace the brass CP in the conventional setup with a steel one in order to balance heat expansion rates.
06-19-2011, 02:55 PM
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RE: MVVS diesel stuff
Pe´your glow conversion has a back plate mount and its beam mounts machined off, and I assume that the engine is entirely capable of being mounted this way.
Would you think that the entire sub 8cc MVVS range could be similarly mounted? Are the cases strong enough around the back plate area?
Thanks mate.
Would you think that the entire sub 8cc MVVS range could be similarly mounted? Are the cases strong enough around the back plate area?
Thanks mate.
06-19-2011, 07:17 PM
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RE: MVVS diesel stuff
Strong enough indeed. Mine have been treated very
badly and even augered in on asphalt and no sign of
failure. I use 1/16 inch aluminum and the stock bolts.
Ralph
badly and even augered in on asphalt and no sign of
failure. I use 1/16 inch aluminum and the stock bolts.
Ralph
06-20-2011, 02:27 AM
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RE: MVVS diesel stuff
I have never used beam mounts on my glow engines, or any other engine if I could avoid it. They are so clumsy!
It would be different in very narrow full length fuselages, with engine bearers integrated in the fuselage side.
The housing is strong enough on all sizes.
It would be different in very narrow full length fuselages, with engine bearers integrated in the fuselage side.
The housing is strong enough on all sizes.
06-20-2011, 01:16 PM
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RE: MVVS diesel stuff
Pe
May I ask what you are using for the "O" ring seal on the exhaust manifold?
The seal on your engines is a pink, red-ish colour, the stock item on my 2.5D is a pale straw colour.
May I ask what you are using for the "O" ring seal on the exhaust manifold?
The seal on your engines is a pink, red-ish colour, the stock item on my 2.5D is a pale straw colour.
06-20-2011, 02:14 PM
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RE: MVVS diesel stuff
I cut the "O-rings" from the silicone tube that comes with the MVVS tuned mufflers. The rings are cut about 5mm wide, and have more wall thickness than the original MVVS flat section rings. They are harder and a much better fit than the original MVVS part.
edit:
The mvvs silicone rings are nice as long as the muffler part is new. More wall thickness in the ring, and eventual some overlap to the rest of the engine caters for a quite tight muffler connection when in combination with the steel spring thingy. I like the system a lot. I can disconnect the muffler in a jiffy, and reconnect it again as needed. Perfect every time.
edit:
The mvvs silicone rings are nice as long as the muffler part is new. More wall thickness in the ring, and eventual some overlap to the rest of the engine caters for a quite tight muffler connection when in combination with the steel spring thingy. I like the system a lot. I can disconnect the muffler in a jiffy, and reconnect it again as needed. Perfect every time.
07-02-2011, 07:11 AM
#15
RE: MVVS diesel stuff
Some of my MVVS engines.
I thought that this little 1.5cc MVVS diesel engine was pretty neat. I still need to figure out something for a muffler for it, otherwise I can't fly it at the local flying field.
I had acquired this 2.5cc MVVS RC diesel engine from Pe Reivers recently.
This is my MVVS .61 diesel engine I acquired a while back. I have cleaned it up and have the glow head on it for the time being, so I can test run it and dial it it before I try the diesel head on it.
I thought that this little 1.5cc MVVS diesel engine was pretty neat. I still need to figure out something for a muffler for it, otherwise I can't fly it at the local flying field.
I had acquired this 2.5cc MVVS RC diesel engine from Pe Reivers recently.
This is my MVVS .61 diesel engine I acquired a while back. I have cleaned it up and have the glow head on it for the time being, so I can test run it and dial it it before I try the diesel head on it.
07-02-2011, 09:34 AM
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RE: MVVS diesel stuff
You would have to make a clamp-on muffler. file a half circle out of the flange to make a neat fit. Then a counter piece w th the two bolts to hold it tight.
BTW, If you run the .15 diesel with the muffler, remove it after the run or you will get corrosion of the steel liner and cast iron piston.
From what I have heard, the tommy bar can be left alone once set, if you use 35% ether, 40% kero, 25% oil with 1% IPN
I have tested the engine without IPN, and needed 40% ether before I was happy with the results.
BTW, If you run the .15 diesel with the muffler, remove it after the run or you will get corrosion of the steel liner and cast iron piston.
From what I have heard, the tommy bar can be left alone once set, if you use 35% ether, 40% kero, 25% oil with 1% IPN
I have tested the engine without IPN, and needed 40% ether before I was happy with the results.
07-02-2011, 01:40 PM
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RE: MVVS diesel stuff
Earl
Your MVVS .61 appears to have a "series I" R/C carb.
MVVS make a "nozzle kit" to update the idle needle to current spec. You then get much better transition.
Your MVVS .61 appears to have a "series I" R/C carb.
MVVS make a "nozzle kit" to update the idle needle to current spec. You then get much better transition.
07-02-2011, 02:08 PM
#18
RE: MVVS diesel stuff
Fiery good info Just checked mine I am ok have the newer carby maybe thats whay I never noticed an issue, it also wears a Davis head he made them for the 21/40/61
Do have the 40 Davis head and of course the smaller ones 09 and 15s stock MVVS diesel heads cheers- martin
Do have the 40 Davis head and of course the smaller ones 09 and 15s stock MVVS diesel heads cheers- martin
07-02-2011, 03:32 PM
#19
RE: MVVS diesel stuff
Thanks for the info fiery, I appreciate it.
Yeah if the .61's carb is acting funky I'll know what to look for then.
Pe Reivers, that is interesting about the corrosion. I haven't really noticed any corrosion with model diesel engines yet. So I'll keep that in mind for sure. I always assumed that the diesels didn't have corrosion issues like the glow engines did, especially with higher nitromethane percentages and synthetic oils. But lower quality kerosenes do have a higher sulphur content and that would convert into sulphuric acid with moisture around. I suppose the nitrogen compounds in the exhaust might make some corrosive substances too. But usually castor oil would do wonders at preventing corrosion.
Thanks for the tip.
Yeah if the .61's carb is acting funky I'll know what to look for then.
Pe Reivers, that is interesting about the corrosion. I haven't really noticed any corrosion with model diesel engines yet. So I'll keep that in mind for sure. I always assumed that the diesels didn't have corrosion issues like the glow engines did, especially with higher nitromethane percentages and synthetic oils. But lower quality kerosenes do have a higher sulphur content and that would convert into sulphuric acid with moisture around. I suppose the nitrogen compounds in the exhaust might make some corrosive substances too. But usually castor oil would do wonders at preventing corrosion.
Thanks for the tip.
07-03-2011, 01:24 AM
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RE: MVVS diesel stuff
ORIGINAL: earlwb
Thanks for the info fiery, I appreciate it.
Yeah if the .61's carb is acting funky I'll know what to look for then.
Pe Reivers, that is interesting about the corrosion. I haven't really noticed any corrosion with model diesel engines yet. So I'll keep that in mind for sure. I always assumed that the diesels didn't have corrosion issues like the glow engines did, especially with higher nitromethane percentages and synthetic oils. But lower quality kerosenes do have a higher sulphur content and that would convert into sulphuric acid with moisture around. I suppose the nitrogen compounds in the exhaust might make some corrosive substances too. But usually castor oil would do wonders at preventing corrosion.
Thanks for the tip.
Thanks for the info fiery, I appreciate it.
Yeah if the .61's carb is acting funky I'll know what to look for then.
Pe Reivers, that is interesting about the corrosion. I haven't really noticed any corrosion with model diesel engines yet. So I'll keep that in mind for sure. I always assumed that the diesels didn't have corrosion issues like the glow engines did, especially with higher nitromethane percentages and synthetic oils. But lower quality kerosenes do have a higher sulphur content and that would convert into sulphuric acid with moisture around. I suppose the nitrogen compounds in the exhaust might make some corrosive substances too. But usually castor oil would do wonders at preventing corrosion.
Thanks for the tip.
I ran the MVVS 2.5 on several fuels with different types of "kero" The oldfassioned lamp oil we call petroleum, odorless lamp oil, party lamp oil, engine diesel fuel, heating fuel. All showed cylinder/piston corrosion if I left the muffler on. It made itself noticed as a slight gritty feeling when turned over the first few times.
I also used several oils. Castor, synthetic two stroke oil, regular engine oil. No difference. It must be something in the alloys and muffler exhaust gas that causes it.
When running a small prime after removing the muffler, all is well, in my stored engines as well.
07-03-2011, 05:22 AM
#22
RE: MVVS diesel stuff
cub mvvs 15 said pix loaded did not even with photo bucket added off to the repair place martin
thx earl for the help with issue but still no go on pix
thx earl for the help with issue but still no go on pix
07-04-2011, 02:53 AM
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RE: MVVS diesel stuff
MVVS did stop producing 2.5cc diesels some time ago, but by popular demand made one more production run. They now have stock, but I suppose under these circumstances asking them to put in extra design effort in the engine is one step farther than they planned to go.
The same holds true for the small glow engines. They are available as long as parts last.
The same holds true for the small glow engines. They are available as long as parts last.