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MVVS 8 inconsistant runs

Old 11-27-2009, 11:34 PM
  #1  
slim56
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Default MVVS 8 inconsistant runs

I have an MVVS 8 that has had about a gallon of fuel run through it. It idles very consistantly with no increase or decrease in speed for 2-3 minutes and will throttle up to full throttle with no hesitation. I am running it with an APC 10 x 7 and I haven't leaned it out to a consistant 2-cycle run on the ground. I don't know what rpm this engine should be turning to be at its optimum power. When in the air at a constant throttle setting the engine has obvious rpm changes in the air. As I said before it is not leaned out to a full 2-cycle run. Dar, any suggestions that you can offer would be greatly appreciated. I would like to use this engine on a race plane in a timed break-out format.

Thanks,

Ken
Old 11-28-2009, 01:02 AM
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Default RE: MVVS 8 inconsistant runs

Ken,


You did not write much on the way the break-in was done...

But you wrote the engine has already gone through a gallon and "I haven't leaned it out to a consistent 2-cycle run on the ground..."


I can suppose you did not do it, as described in [link=http://www.rcuniverse.com/forum/m_1850473/tm.htm]this RCU thread[/link]; and not even as specified in the abbreviated, two line way, described in the manual...

...Since they both end in the 'break-in completion test', which entails fully leaning the engine to peak full-throttle RPM and observing it run, making sure it does not sag (no RPM loss) for 60 seconds straight...


Also, I cannot know from your description...

1. Is your MVVS 8.0 GFS/R a newer CNC model (blue anodized prop-driver and head, trapezoid ports in the sleeve), or an older hand-fitted one (neutral, or green anodized parts)?

2. Does it have the newer carburettor (no idle-stop screw on top, elaborate intake), or an older one?

3. Is it set up in the normal side-exhaust configuration, or is it a converted to rear-exhaust?

4. What exhaust system are you running on it (it does not come with one and the buyer has several choices from the manufacturer)?

5. What type of installation are you planing this engine for in the model?

6. What fuel you are using (you need 20% oil, more than half of it castor; and no to low nitro) and how is the compression ratio set up?


Please reply to all the above and we can continue from there.
Old 11-28-2009, 07:56 PM
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Default RE: MVVS 8 inconsistant runs


ORIGINAL: DarZeelon

Ken,


You did not write much on the way the break-in was done...

But you wrote the engine has already gone through a gallon and ''I haven't leaned it out to a consistent 2-cycle run on the ground...''


I can suppose you did not do it, as described in [link=http://I haven't leaned it out to a consistent 2-cycle run on the ground]this RCU thread[/link]; and not even as specified in the abbreviated, two line way, described in the manual...

...Since they both end in the 'break-in completion test', which entails fully leaning the engine to peak full-throttle RPM and observing it run, making sure it does not sag (no RPM loss) for 60 seconds straight...


Also, I cannot know from your description...

1. Is your MVVS 8.0 GFS/R a newer CNC model (blue anodized prop-driver and head, trapezoid ports in the sleeve), or an older hand-fitted one (neutral, or green anodized parts)?

2. Does it have the newer carburettor (no idle-stop screw on top, elaborate intake), or an older one?

3. Is it set up in the normal side-exhaust configuration, or is it a converted to rear-exhaust?

4. What exhaust system are you running on it (it does not come with one and the buyer has several choices from the manufacturer)?

5. What type of installation are you planing this engine for in the model?

6. What fuel you are using (you need 20% oil, more than half of it castor; and no to low nitro) and how is the compression ratio set up?


Please reply to all the above and we can continue from there.
I will try to upload a couple of images to help with the questions.

1. It is the MVVS 8.0 GFS/R (has blue anodized head only).

2. I believe it is newer carb. alot of curves on the intake, the only thing on the carb body is a hex set screw with a locknut on the back of the carb body.

3. It has a normal side-exhaust.

4. It came with a standard type muffler.

5. Currently it is in an upright position with a standard fuel tank. If I can get it running satisfactory I may add a bladder tank and turn the engine a little over 90 degrees.

6. Currently I am using Magnum 15% (synthetic/castor blend).
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Old 11-28-2009, 08:12 PM
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Default RE: MVVS 8 inconsistant runs

Lets Continue......

At the present time I cannot find the owners manual for this engine. I do recall following what instructions there where when breaking in the engine. Could you list the link to the RCU thread that has the breakin procedure. You probably don't recall but during the early running of this engine that it wouldn't hold a low-needle setting and you sent me some extra springs to put under the low needle.

Thanks,

Ken
Old 11-29-2009, 12:57 AM
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Default RE: MVVS 8 inconsistant runs

It has been a while, Ken Vaughn.


The link to the RCU break-in thread is: [link=http://www.rcuniverse.com/forum/m_1850473/tm.htm]http://www.rcuniverse.com/forum/m_1850473/tm.htm[/link]

The link was wrong in the original reply - corrected now.


Your engine is the new design, but might still have the older sleeve design.
It does take a slightly longer break-in, but performance is virtually the same.

I understand Magnum fuels have become popular lately, due mainly to lower cost... But I could not find the lubricant package formulation in their web site.
So, I have no idea how much castor oil is in the fuel... I suggest that you obtain a gallon of fresh PowerMaster GMA 5%, Sig Champion 5%, or even Morgan's Omega 5% fuel (add 3-4% castor oil).

I suggest that you repeat the break-in. It will only take an hour of your time and two tanks of fuel.

Also, since your engine is not 'decompressed', 15% nitro is simply out of the question; unless you are flying in far northern climates...

The glow-plug in the photo appears to resemble an OS A3/#6, which is way too hot for this engine.
It needs a medium-cold glow-plug, such as the Novarossi C-6S (original), the Rossi R4, the K&B-1L and the like. Even an OS #8 will work.

The problem is compounded by 15% nitro... It manifests itself as 'misbehavior'...


Since this engine is biased toward tuned exhaust systems, like the #3248 tuned silencer, the #3245 muffler that it now has will give you average performance for its displacement; around 13K with the APC 10x7 and 5% nitro.


Let us start from there.
Old 10-27-2010, 01:14 PM
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Default RE: MVVS 8 inconsistant runs

Hi!
First of all mount the engine correctly! That means mounting the engine so that the tank sits correctly in comparence to the carb!
That's vital!!!!
Most of the time that means having the engine mounted on it's side!

Second it seems that there is a vide spread roumor that modern ABC, and ABN engines need special running in procedures.The simple fact is that you just run them a couple of tanks at a slightly rich setting with the throttle fully open and adjust the rpm with the high speed needle...slightly rich...then go fly!!! Simple as that! Don't complicate things that don't have to be complicated...

It's only ringed or lapped engines that need prolonged running in!!!!

Use a 240cc-300cc tank (8-10oz)Not bigger! And do use two clunks (Uni-flow set up) for more even pressure flow of fuel to the carb.
Best of course is a Tettra"Bubblelesstank".But that's an overkill for most sport fliers.

10x7,11x6 or 12x4 are good prop sizes for most airplanes and RAM,Graupner Cam-pro and APC are the props of choice.

Suitable glow plugs are Enya 3 or 4 or OS 8 ..or that MVVS uses the Nova Rossi 5 or 6.

As for MVVS carbs, I see that you have the "new" carb MVVS came out with appr ten years ago. Most of the time MVVS supplied their 6,5, 7,5 and 8,0cc engines with the 7mm intake carb. But from personal tests I know that the 8mm carb is better to use on all those engines as it gives better performance and still throttle as well as with the smaller carb.
Old 12-18-2010, 11:08 AM
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Default RE: MVVS 8 inconsistant runs

Karl,

I have tried all suggestions, except mounting engine on its side or even perhaps turned a little more. But, what is a Uni-Flow System????

Thanks,

Ken
Old 12-20-2010, 03:55 PM
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Default RE: MVVS 8 inconsistant runs


ORIGINAL: slim56

Karl,

I have tried all suggestions, except mounting engine on its side or even perhaps turned a little more. But, what is a Uni-Flow System????

Thanks,

Ken
A Uniflow system is where the air from the inlet pipe is forced to always exit into the tanks space submerged under the fuel head instead of simply exiting inside of the tanks air space.

This system provides a constant and even resistance to the fuel draw as the incoming air must ALWAYS fight against the pressure of being under the fluid and is achieved by placing the air outlet very close to that other submerged pipe, the fuel inlet - but not too close as air bubbles can be attracted into the intake.

Research the 'Mariottes Bottle' principle to find out more!

http://en.wikipedia.org/wiki/Mariotte%27s_bottle

Old 12-27-2010, 09:43 AM
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Default RE: MVVS 8 inconsistant runs

This is a fantastic engine, I have two of them. Lean it out to just a tad on the rich side and let it scream, tune the low end needle correctly and enjoy. Oh, and 15% nitro might be be too much like Dar says.
Old 12-31-2010, 12:33 AM
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Default RE: MVVS 8 inconsistant runs


ORIGINAL: asmund

This is a fantastic engine, I have two of them. Lean it out to just a tad on the rich side and let it scream, tune the low end needle correctly and enjoy. Oh, and 15% nitro might be be too much like Dar says.
I also have two MVVS 8's, one a diesel conversion from Dar and now another in its original glow form.

They are a bit heavy for their size but very strongly built and take to being a diesel very well!



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