Hi Everybody!

Two years ago I bought in France an MVVS .49 with mini pipe part number 3248, then engine comes with a number "6" glow plug, I'm using a Master Airscrew 11x6 propeller. Well, the problem is that the engine is blowing (burning) the glow plugs and I feel that the engine is overheated. The elbow is attached to the side of the engine then, the rubber hose is connected to the tip of the elbow then connected to tuned silencer as far as I could. Some people told me that the the problem is that the silencer is too close to the elbow, that I have to enlarge the elbow about twice in long of the rubber hose, then attach the rubber hose and try to tune the silencer with a tach.

The engine is attached to the airplane in inverted position, my airplane is an Tower Voyayer ARF from tower hobbies, so I can't change the fuel tank position or something else, I was using an OS .46FX engine in this airplane and it was working fine, but the airplane was not fast as I wanted, so I decided to use my MVVS in this model. Attached to this, you'll find a picture of it where you can see how is it installed.

I think this is an incredible engine so powerfull and I don't want to damage it. In my country is not common to use MVVS engines, all the people use OS or Thunder Tiger, so nobody knows what's happening.

I appreciate any clue that you could give me in order to avoid overheat of the engine and and blowing glow plugs (on sunday I blew 5!)

Thanks in advanced,

Ricardo

Ricardo,


What fuel are you using???

When you use fuel with 0-5% nitromethane and 20% oil half or more Castor, as I do... Well, I have never had to change a burnt glow plug.
I have two such engines, both still with the original glow plug (Novarossi C6).

Too short a tuned exhaust system will burn out glow plugs, so even though this system is set-and-forget (it seems this engine was produced over 3 years ago, still having the old style carburettor and the neutral head - see photo of new model), you may want to use a 1" (2.5 cm) longer silicone coupling.

Then you can see how your glow plugs hold up.

But the main suspects are too much nitro, or too lean a mixture.

Hi Dar,

thanks for your fast answer, I'm using 20% castor oil I don't use nitromethane. About te engine, I bought it in France on March 2002 and I could have a good broke in in this year, after that I didn't use the engine.

The actual length of the silicone tube is 2.5", this is the original that came with the engine, so you mean that I have to change the rubber hose and increase the length to 3.5" and attach it as far as I can? a friend told me somthing similar, but he said that I have to increase the length of the elbow instead of the rubber hose because with the time if you increase the lenght of the rubber hose it will burns, is it true?

Which is the glow plug which fits best to this engine?

When the engine was working well I realized that the transition was not so smooth I mean when I push rapidly the throtle it takes a while to increase the speed about 1 or 2 seconds, but if I push it gently I got a perfect response, can I improve it or it is normal?

Which is the best propeller for this engine, can I use a 10x8, is that better than 11x6?

Thanks indeed again,

Ricardo

I was looking at the picture and it made me think that the engine has been so hot that it has been discolored. Does it overheat similarly with the cowl on and off? When the cowl is on, do you have good air exits?

Ricardo,


Besides the Novarossi C6 plug the engine comes with, the OS #8, the Enya #3 and the K&B-1L are the correct heat range to be good replacements.

I am aware Fox and other manufacturers also have similar glow plugs.


There is a very remote possibilities that your specific engine has all the production tolerances added up, to make the compression excessive, but I don't think so.

Is your engine cowled in, so as to impair its cooling (the cowl must have an exit twice as large as the enterance and it should have baffles to direct the airflow around the head and the cylinder cooling fins.

The added length of the tuned exhaust should manifest itself, in the distance between the header's rear end and the muffler's front' within the longer silicone coupling. You can buy such a silicone tube and it should not be too expensive.

The 10x8 prop should provide faster airflow, for improved cooling, but even with a low-pitch 12x4, cooling problems should not be evident.

The older carburettor has some behavior problems, from the low to high speed transition being too rich. And also a long term part-throttle condition make the engine load-up.
The only good solution is a new style #3216/3219 carburettor.

Hi Dar,

I bought the silicone hose, original length 2.5", the new one 4.5", the original distance between the elbow and the silencer was 1.25", the new distance is 3", I increased the distance 1.5" between the header and the silencer, do you think is it correct? I haven't started the engine I'll do on sunday, so I don't know if with this new length do I have to tune again the engine I mean, would I see any change in the behavior of the engine? or this cahnge just avoid the burnt of the glow plug, does the transition will continue working properly? I know, there are a lot of questions, so I'm so sorry if I bother you.

Finally, if everything goes well, If I change the propeller 11x6 to 12x4 as you said before, could I hang the airplane from the engine, I mean can I do a hover?

A friend told me that I could fix the transition problem if I increase the diameter of the carburator hole in 3mm, the actual diameter is 7mm that is 10mm after the change, is it true?

Finally, thank you very much for your help and information, it has been very useful to me.

Regards,

Ricardo

Hi Ricardo,


My name is Dar.

1. Your friend is incorrect. Current MVVS .49 engines do come with the new 8 mm choke, #3219 carburettor that simply works much better. But it is not a reason to modify you current carburettor and this suggestion will not change anything for the better...

2. The silicone coupling now seems too long. You should see about 1-1.5" of air, between the rear of the header and the front of the black, tuned silencer section (it seems to be 3.5" now). But it will not hurt to try.

3. The blackened header suggests that you may be running the engine too lean... This will cause overheating.

4. A 12x4 will provide more thrust and has about the same load as an 11x6 prop, but the cooling air-flow is slower and thus, it is more likely to cause overheating. When everything is adjusted properly, it should not be a problem, but find the cause first.

5. You will definitely have to re-tune the engine and the part-throttle behavior will not be improved.

6. Overcome your overheating problem first!

Hi Dar,

I'm so sorry about the mistyping about your your name, I apologize. As you sai, I have to overcome first the overheatingand that is what I'm going to do on sunday. about the distance between the edge of the header and the edge of the silencer it was originally 1.25" and if I understood well this distance was in the range that you mentioned but the engine was overheated, however, as you suggested I'll trim the silicone hose up to 2" then, I'll start to tune it and cut as much as I can without overheat the engine and get the best response from the engine.

On monday I'll let you know what happened and what was the final result.

Thanks you very much again for you answers, and sorry again abour your name []

Regards,

Ricardo

No need to apologise, Ricardo.

We are all human and so we err...


I also suggest that you check that your fuel is not old (could have absorbed humidity from the air).
Just to play it safe, get a NEW jug of fuel, with 20% oil, at least half must be Castor and 0-5% nitro.

Make sure you start with the mixture setting quite rich and then, lean it down very gradually.


This engine should not overheat and has excellent cooling in general.

Hi Dar,

I'm so sorry for the delay, I had a car accident so I couldn't check it on 22th Sunday. Yesterday I went to the field, I didn't cut off the silicone hose as you suggested me, I wanted to try it as long as I could and see what's going on. Some importan things to remember, the distance between the header and the silencer was extended up to 3" (originally it was 1.5"), fuel 20% castor oil and 10x8 propeller.

Now here we go...... I started the engine with a new OS MAX #8 glow plug (these glow plug are so expensive here about USD12), It was a little bit hard to start the engine but I could after a while. I wait for about 3 minutes to warm the engine up, then I started to increase the power.

At the beginning it was so "unstable" I mean the sound wasn't smooth (I don't know if this is the right way to explain I do hope you can understand me), but I guess the engine temperature was good and the glow plug was Ok, however I left it running for 3 minutes at full power (full throtle), and with the pass of the time the engine started to sound better, I checked the RPM it was about 10.800, however half minute after was 11.500 - 12.000 and increasing. I was always touching the cylinder head in order to check the temperature and at this momment it was a little bit hot.

After that, I decided to test the plane in vertical position, everithing was good, but when I returned to the horizontal position it stopped suddenly again. I switched off everything and wait for it to cool, it was after 4-5 minutes then I could removed the glow plug and as usual it was burnt!!! I couldn't believe it! and at this momment your words came to my mind "There is a very remote possibilities that your specific engine has all the production tolerances added up, to make the compression excessive".

I decided to disassemble the engine and check its condition. As soon as I removed the cylinder head I wonder that there were metal pieces over the top of the piston and the back of the cylinder head was in so bad condition, full of small "holes" due to the metal pieces that were in this chamber(have a look to the pics), also I could see that in the edge of the piston there was a missing piece I mean, in the border there was an small hole, I also found a big piece of metal, then continuing I removed the cylinder body just to have a look of the piston and the other parts.

As soon as I removed the piston I could see that the connecting rod (part number 0951) was broken at the top where the piston pin fix it to the piston. The connecting rod has two bronze parts one in the upper part connecting with the piston retainer and the other one which connects to the crankshaft. the upper bronze part was broken.

For me this was a huge surpise! this engine was such a mess!!!! I ran two OS engines during 5 years and I neved had this kind of problems and as you remember this engine has been used less than 10 times this mean 10 x 15 minutes maxium flight = 150 minutes that is about 2 hours of use and everithing inside onf the engine is a ****!

To be honest I can't believe that the MVVS quality is so bad, of course it's not your fault but I want to show you what had happend and what do you think about this issue.

Attach you'll find some pictures of the broken parts.

I wanted to replace everithin I'd have to buy the cylinder head, cylinder, piston and connecting rod but you could imagine that if I buy all these spare parts could be exactly the same price if I buy a new engine in my country. Do you know if I can use a different connecting rod from another engine, I don't know super tigre, webra, etc.? I tried one from an OS .46 FX it fits perfectly with the piston but the lower hole is too big so, I can't use it.

As you know I bought this engine on march 2002 do you think I could get some warranty from the manufacturer, this is a quality problem with this engine, if so, do you know what is the procedure?

I hope to see the light at the end of the tunnel.............

Regards,

Ricardo

I hope you are OK and that the damage will not cost you too much to repair, or is fully insured.


This is an ABC engine!
It must not be cold enough to touch, even during break-in, as illustrated in the thread I linked in a previous post.

Only cast iron piston, steel sleeve engines and ringed engines must be warm and touchable, only in the beginning of the break-in.

I cannot believe this either.

This damage is quite extensive.
I have never seen any such damage in any MVVS engine; not even in very old ones.

I may have more to say later about this.

As for parts cost, please E-mail me.
Parts are much less expensive than you may think.

American market prices and prices in your country, do not apply elsewhere in the world.

Ricardo,


I believe someone from MVVS has made, or shortly will make contact with you, regarding the condition of your engine.

Hi Dar,

Thanks for all your comments about my porblem. For me is hard to believe this situation. I'll write you an email to know what can I do with it.

Regards,

Ricardo

Novarossi 6 is a COLD glow plug, Enya 3 is HOT and will be NEVER USED WITH MVVS ENGINES! I tried Malina 1 (Czech) hot plugs with my 4,6 cm3 MVVS and they were burned after 2-3 flights!
My 2 cents
Witold