I bought a used MVVS 49 on RC Universe, and put on a 3245 A (quiet) muffler instead of the tuned pipe that came with it (we have noise issues at our field). This engine replaced an OS 46 FX (ringed) that was getting old. I was expecting the MVVS to outperform the 46 FX, in terms of vertical performance, but it doesn't.

I love the throttle response of the MVVS, but it won't pull my 40 Ultra Stick with unlimited vertical like the OS used to.

I have a compression tester and the MVVS tested between 115 and 120 psi. I have a new Irvine .53 and it tested 155 to 160 PSI. I love the throttle response on the MVVS much more than the OS, but I'm wondering about vertical performance.

Is my used MVVS worn out (starts with a hand flip on 5% nitro), or are these results to be expected with the quiet muffler?

I should mention that I'm using an 11x6 APC, and the OS was using a 10.5x6 APC.

Thanks,

Ken

KrazyKen,

There was another thread about two months ago, dealing with the MVVS .45, with the same #3245A muffler.
Similar observations.

This muffler is VERY quiet, I am told it is 4 db lower than the OS.46FX with the standard, baffle included muffler.
But it is also excessively restrictive.

On the other hand, the MVVS with the #3248 tuned silencer, may not be as audibly offensive as you think.
MVVS recommend adding a length of 1cm i/d silicone hose at the end of this tuned silencer, to reduce noise considerably.

Try to measure this engine with it. It is quieter than with the standard #3245 muffler.

Buying a used engine has its pitfalls. You can never be completely sure what you are getting. Try removing the glow plug and turning the engine over. You should feel a slight "pinch", as the piston goes over TDC.

If you feel nothing at all, you may have bought an engine that was either;
1. Broken in very rich, four-cycling (it should be done only two-cycle rich, as a tapered bore engine).
or,
2. Has accumulated over 150 running hours, or a large number of lean runs.

It does sound to me, more like a "constrictive" silencer problem.

This, although your compression tests make me think otherwise.

Hi!
The first MVVS .49 made were delivered with the 7mm intake carb but later MVVS decided to replace that carb with the bigger 8mm (3219) carb
If you don't have the bigger carb ...order it and see the
difference. Also check that you don't have two head shims installed ...the MVVS .49 were at first delivered with an extra headshim as they knew americans were fond of high nitro contents (above 10%)...the previous owner might have put it in....

Regards!
Jan Karlsson
http://hem.passagen.se/airracing
.

Jan,

MVVS 8.0 engines are still being delivered, as standard equipment, with the new #3216 7mm carburettor.
You can, however, order them with the new #3219 8mm carburettor. No additional cost.

If you say nothing, the #3216 is what you will get.

Thanks for the thoughtful replies guys...much appreciated.

My engine does not have a shim. It does have the 7mm carb.
It does not squeak when turning the prop with the glow plug out, and it does not have much resistance when doing that. However, with the head off and turning the prop, the liner will grab at the top of the stroke and move up about 3mm.

Any ideas on where to get parts (piston/liner/rod)?

Thanks,

[email protected]

krazyken
i m using a.49 with 3245A quiet silencer with a 11*6 APC prop.
n i get about 11300 rpms .

if you want more out of this engine then use the 3245 muffler or the 3248 pipe. a friend has one with minipipe running a 10*7 apc taching at 14000 rpm on the ground. (the OS does not beat this) n fuel is fai.

Call Robert or Debbie over at Morris Hobbies, 800-599-6887.

Your engine seems OK to me. Try the "grab condition" with a dry liner, so the oil film will not obscure fit issues.
You are comparing the tamest MVVS version, heavily muffled with probably a more competetive Rossi setup. This A-type muffler is a real power robber, though quite silent.
Your compression measurement indicates, that you may want to go up in nitro a bit.
Like Dar said, using the mini tuned mvvs pipe will bring the engine up to par, best combined with a smaller prop. (pitch)
The lower pitch will allow the engine to go up in revs, which is not restricted by the A-muffler.
I never tried to get the most of a .47 with this muffler, so maybe Dar can shed more light on this, because my experience with the A-type is mainly restricted to the combat series engines. These engines rev up quite a lot once airborne. Since a hover condition is something else, you must allow for that with pitch.

There are many sources for MVVS parts. If you do some searching, you will find good service and pricing.