To keep the exhaust screws tight, use only metal-to-metal contact faces, and take care that all powder coat that might be present on the exhaust adapter flange is removed. I use no flange compound or anything else between the joint, and have not experienced leaks and/or loose connections.
10% oil is not recommended. You may get away with it for some time, and it is proof of the sturdy material combinations that MVVS uses. but I would recommend at least 15%, and even then, the engine must be run in well before using such a low oil content.
Feel free to call me old-fashioned :-).
Just plain automatic transmission fluid, (this is not transmission oil!), will do the after run job just as well. Some injector cleaning fluids will mix with methanol, and when blended to the fuel, will keep the engine clean inside.

I just came back from the field after puting an ultra-quiet muffler on my MVVS45. It hardly does 10K RPM with 5%, 10300 @ 10%, both with a 12X4. It also lacks a lot of power. I previously had the black tuned pipe on this engine, and it was much, but much stronger.
I moved to the quiet one due to noise restrictions in the field I am flying from.
I suspect the muffler limits the RPM to about 10K.
Any similar experience?


Ilan Barak

ISRAEL

Ilan,

Look earlier in the thread. It was on the .49, but the effect is similar. Also look at the messages from Jaka and Preivers.

It seems the #3245A quiet muffler robs the engine.
It causes a sharp fall in power.
Try using the #3248 tuned silencer that you have and add an expansion chamber after it. MVVS recommends adding a length of silicone hose to reduce noise.

Say what? A field in Israel with real, enforced noise restrictions???

Sincerely,

Some more rpms

Mvvs .45 with 3245A muffler 11*5 apc @ 11000 rpm

Mvvs .40 with 3245 muffler 11*5 apc @ 12500 rpm

Mvvs .49 with 3245 muffler 10*7 apc @ 14000 rpm


the A type mufflers really robs the engine of 10-15% power. But it sounds very pleasant to the ears !!

these are very usable data.
Some tests of my own to regain a few hundred rpm.

The A-type muffler can be dismantled into parts by removing the three screws, filing off the crimp,and slowly heating, until the epoxy gets soft.
Carefully wiggle the added damper off.
Ream the exhaust outlet out one millimeter. This compensates for the higher back pressure in the added chamber.
Using a 30 degee cone punch, form a bell mouth on the inner side of the stinger pipe.
With a suitable rat-tail file, ream the stinger pipe about 0.5mm.
Using liquid metal (market dependant), glue back the added damper, well lined up, and screw tight while the glue is still uncured.

After these mod's the exhaust note still is very agreable, and power loss is very much reduced.

Field data:
Engine .21 mvvs, MA 8x5 (1/12 combat, 85/15 fuel, no nitro) 16400 -16.600 rpm with standard 3235 muffler
This is ~500 rpm in excess of ACES regulations.
The modified 3235A-type muffler turns just around the limit of 16000 rpm (pinch-peaked, cold, 16.200, very hot 15.890) A silicone deflector will take care of the extra 100 rpm.
Noise is very much reduced by some 5 dB(A); it was 84 dB with the 3235, now it is 79 dB at 7 metres (77dB with non-modified 3235A-muffler)

Bobi,

Since horsepower realized on a given prop is to the RPM in the third power, if your engine turned 12,500 RPM and with the new muffler it turns only 11,000 RPM, It has lost roughly 32% of its previous power.

This is a much more acute loss than it sounds at first, not 10-15%.

Sincerely,

Preivers

if you have a picture of the modified A type ( before sealing the added chamber )......... it would be great.

i was thinking of removing a part of the inner exhaust and sealing the added chamber back.??