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Modified muffler

Engine...Enya 19 with original CO2 bottle muffler.

Intention.. to make it quieter.

Muffler was unscrewed and a piece of aluminium tubing was fastened between the two halves. This just about doubled the exhaust chamber size and the exhaust note was lower pitched and a bit more pleasant on the ear. The engine has been used a few times and there were no problems.

Next stage.... I have inserted an aluninium tube, drilled with a number of small holes, into the muffler (the inside end is sealed off so the gas has to go through the holes in the tube to exit).

Run the engine on a test stand and it is much, much quieter. There is more back pressure from muffler to tank and the engine starts easily by hand. Just had to lean the mix and then had good transition.

I expect to lose some power as a consequence of better silencing, however, having very little experience with model engines is there something I may be overlooking. Any observations before I go try it ?

Will the increased back pressure cause overheating ? Fuel will be 20% castor and 5% nitro.

Reg

Reply to
reg
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It may or may not make a difference in power. If you check the RPMs before and after, you will get a better picture. Most likely, you will get a fairly big drop in performance and overheating with too much backpressure. If you want it real quiet and real powerful, build a Mousse Can Pipe for it.

Reply to
Paul McIntosh

Thanks Paul. I may have to play around with the number of holes in order to try and find an optimum trade off between sound level and backpressure.

At least I appear to be making some headway at quietening it down >:-)

I have been looking at the Mousse can designs and will probably have a go at one later, easier to modify this current silencer as I have all the bits to hand to play about altering it. Some power loss will not be a problem as long as I don't lose too much !

Reg

Reply to
reg

One thing yo have to think about is ANY power loss has a cause. Too much backpressure is one of those causes. This also causes incomplete scavenging which results in overheating and inconsistent running. There are good ways to reduce noise. Increasing backpressure by overly restricting the exhaust isn't one of them.

Reply to
Paul McIntosh

After trying it again today I formed the impression that although quiet it may well have lost some "sparkle"

Removed the tube from inside the muffler and enlarged the size of the holes in it.

Trying it again it needed richening by 3 clicks and then seemed to be more easily accelerating throughout the range. This has made it a little bit noisier and has also dropped the back pressure somewhat.

It is much quieter than the original muffler, starts and runs well, seems to be O.K on power.

I think it is ready to go fly when I get the opportunity.

Reg

Reply to
reg

The only way to know about the overheating is to try it and see what happens. Unfortunately.

Reply to
John R. Agnew

You are onto some interesting work. You can monitor the engine temp as you run the engine with a non-contact temperature gun. About $100. Andy

We can make a box of wood.....FLY!!

Reply to
RCPILOT48

Thank you for the replies.

I enlarged the original baffle holes I made as the engine seemed too restricted.

Running it on a stand showed it is slightly noisier than my first attempt, but the engine seems more responsive now. It is a great improvement on the original,basic muffler as supplied with the engine.

Only thing to do now is go fly it and see how it goes. It is performing O.K on the stand.... so hopefully...

If nothing else I have learned a bit on the way the carb settings and different back pressure from the muffler interact.

Reg

Reply to
reg

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