MVVS 35 IFS
 

Hi Guys

Which muffler will keep this gas engine at 85DB sound level, or below ?


Any recomendations DarZeelon?


Which one is most quiet of these two ?

RE: MVVS 35 IFS
 

Sonnich,


I don't think any silencer your plane can carry will be able to do that.

Those extreme sound criteria are even exceeded by electric motors (prop noise).


Maybe someone else has actualy seen a silencer that can?

RE: MVVS 35 IFS
 

well.. ill start with one of the stock silencers, and see how it performs....... But which one of the two above are best/least noisy ?
We dont messure the sound level at our club......but it says 85db in the rule book.

Just as long as the engine is "pleasant" to listen too, poeple dont mind. :)

RE: MVVS 35 IFS
 

Sonnich,


I guess it is a flip of a coin.

Dave Hobbs wrote the 'dustbin' #3298/35 muffler makes a mellow sound and is not too noisy (the .61-.91 version #3298/10).
It obviously costs less, but the Pitts style #3271 has more volume and more exit area. It should make better performance.

RE: MVVS 35 IFS
 

Thanks Dar.

Ill buy the pitts, and try a 22/8 for lowest Rpm.

Do you know if the pitts style wil mount inverted?
it looks symetrical...

RE: MVVS 35 IFS
 

Just recieved it....

Nice engine!

RE: MVVS 35 IFS
 

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RE: MVVS 35 IFS
 

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RE: MVVS 35 IFS
 

1935g or 4.26lbs with silencer, ignition, and batt.

RE: MVVS 35 IFS
 

its going to replace my saito 150...

RE: MVVS 35 IFS
 

It says to run in the engine in 30 minutes using a 4% oil mix......

At what power setting should this be done ?

RE: MVVS 35 IFS
 

Sonnich,


Start at part throttle and gradually advance to full, on the test stand.

The engine will not be fully broken in, before it has consumed about 10-12 litres of fuel.

You will be able to fly it reliably, after about 30-40 minutes.

Don't reduce the oil before 4 litres are used.

RE: MVVS 35 IFS
 

Thanks Dar [8D]

RE: MVVS 35 IFS
 

Fianly I took the engine/plane with me to work.... Cant fly it due to snow outside [&:]

I could not find the reccomeded 2 stroke oil, so I bougt some Shell ADVANCE Ultra.

Is is ok to use this oil for breaking in ?
It is full synthetic, so I guess break in will take longer time ?


2mb movie with it running, and the stock MVVS Pitts style muffler.
I like the sound of it. Not too loud. Also it sounds louder with the ecco in the hanger :)

http://bornholm.adsl.dk/modelfly/files/yak/Yak-MVVS.wmv



But I had a hard time priming the engine.
it would not draw fuel into the carb by turning the prop.
I primed it by by pumping fuel into the vent line of my tank, forceing it into the carb.
Also tipped the plane over and primed it directly into the venturi.

Its started fine after a few flips on the prop.
It also runs great at the moment with the 22/8 prop.
ofcourse the needles have to be set when the engine has been broken in.

RE: MVVS 35 IFS
 

Sonnich,


The Walbro carburettors sometimes get the diaphragm stuck, so it becomes an effort to start the fuel flow.

Most high quality two-stroke oils should do the job.

You are right with your assumption about the break-in.

I believe the 22x8 prop is a bit large. The largest recommended size is 20x10, which is about equal to 21x8.
22x8 is good for a 40-45 cc engine.

RE: MVVS 35 IFS
 

argg man....you think the prop is too big.

I read this review, and wanted the quietest setup.
http://morrishobbies.com/reviews/MVVS_215_3.jpg

he uses a 22x8 prop

mine is a mejslik prop...

Do you think the 22x8 prop will overheat my engine?

RE: MVVS 35 IFS
 

Sonnich,


I cannot be sure, but this is what I fear.

From the clip, the RPM sounds pretty good for a bigger engine, but in extended full throttle, at low speed, you could see the engine getting hotter.

Read the review. The guy wrote this himself.

RE: MVVS 35 IFS
 

Thank you Dar.

I have ordered the 2 wooden props for my engine 20/10 and 21/8 to tyr out too...


If the engine liks the smaller props, Can I cut down my nice and expensive 22/8 carbon prop to a smaller diameter and re-balance it ofcourse ?

RE: MVVS 35 IFS
 

Sonnich,


It is not that this engine likes smaller props.

This size (22x8) is simply too large for the engine to spin at optimum RPM.
This size is good for a 45 cc engine.

Unlike small glow engines, that are rated at 17,000 RPM by their manufacturer, but actually spun at 12,000-13,000 max, for most of the time, large and ignition engines are best propped close to their rated RPM.

This is because they can spin a big, efficient prop at these RPM levels.

Your 35 cc engine is rated at 9,000 RPM and the 22x8 prop is spun close to 6,000.

There is no way this could be good.


I would not suggest that you cut down your carbon prop, unless you know exactly what you are doing.

RE: MVVS 35 IFS
 

hehe...no, I do not know exactly what Im doing [8D]

I have just read alot about gas engine....but there are not many poeple running them at 9000rpm.

6000rpm on a 22/8 is quite good isn`t it ?


But don worry....I have ordered new props :-)


What can happen by cutting off an even amunt on my carbon prop, and sanding it smoothe again ?
Shouldn`t be any weaker ?

RE: MVVS 35 IFS
 

Sonnich,


Most carbon-fiber props are made with hand laid fiber cloth and uni-directional fibers.

The fibers at the tip are sometimes arranged to give the tip its best strength.

Contact the manufacturer of your prop, to verify the structural integrity of the prop will not be compromised, by cutting down the tips.

The prop's efficiency will be effected for sure, unless you sand the tips to resemble their original contour.

The wood props that you ordered will spin at a more effective RPM level.

A 22x8 at 6,000 is equivalent to 2.51 HP.
A 20x8 at 8,000 RPM; 4.07 HP.

I guess you can understand the difference.

RE: MVVS 35 IFS
 

Sonnich,

Maybe the props that you did order are also a bit on the big side...
From my example it comes out this way.

RE: MVVS 35 IFS
 

Thanks for your time and help Dar.

When the snow melts here, I will try some real world trials with different props to suite my plane. :D

Im not too keen on having the prop go faster because of noise restrictions. But I dont want to overheat the engine either.
My 1,8meter plane weighs 6,5kg`s so I can sacrifice some power for less noise [8D]

RE: MVVS 35 IFS
 

Dar, is the piston liner supposed to be dead center both up/down and side to side directions ?

RE: MVVS 35 IFS
 

Sonnich,


I don't exactly understand what you are trying to ask, with that photo.
It is possible for the cores to shift slightly in a cast part (the cylinder casing is cast and then machined).

The head seems to sit squarely on the top of the sleeve.

Can you please elaborated your inquiry?