T

TIPSYNIPPER

Active Member
Hi Guys,
I am interested in buying an RV4 here in the UK but live and operate out of a very noise sensitive area. The a/c is fitted with a CS prop' (Hartzell blended) and a AEIO320 B1B 180hp engine. Can anyone offer advice on silencing the beast! I have looked at the Vetterman w'site, but would like someones experience in the real world please!
Thanks
Neil
 
Neil,
here in Germany we have strict noise limits and they usually only can be achieved with mufflers and/or RPM restrictions. There is the Liese company producing effective bolt-on mufflers (see pic below). There are others making good mufflers for a better price. May be some Swiss builders will post, they too have strict noise limits.


 
The Aeroturbine muffler
http://www.aeroexhaust.com/mufflers.html
has gained some acceptance with the Mazda Rotary Engine powered aircraft group. Rotary engines have an exceptionally harsh exhaust blast, and these are one of the few mufflers that do not fail in service. I have a turbocharged Mazda Rotary, and it is still loud with the muffling effect of the turbo. I took a sound pressure reading (near my face) in my RV-8 of 116.7 DBa @ 142 MPH @ 4500 MSL.
I've been wearing a David Clark passive head set, and my ears are ringing. I have tried a Headsets Inc. DRE-6001 ANR (active noise reduction) headset which is very helpful.
I have made a 'piccolo pipe' tip, which I will try on the next flight, but if it's unsatisfactory I plan to install an under slung muffler. The Aeroturbine is polished stainless and has a pleasing round shape that I hope won't look out of place.

I'm interested in muffler mounts and exhaust pipe flex joints to keep aerodynamic drag and stress under control. Any helpful comments are welcome.
 
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Can anyone comment on the Vetterman's mufflers?

The other option is replace your CS prop with a FP prop. The reason is the FP will not spin as fas on takeoff, thus producing less noise. Of course you could fly your CS prop like a FP and not push the blue knob all the way in on takeoff.
 
I have no real experience to share, but am in a similar situation. We have a cross-over exhaust on our RV-4. Therefore we are looking for two Liese 76x150-L mufflers as shown on the Liese website. It looks as the technically simplest solution to us.
http://www.hliese.de/Experimental/experimental.html
The Gomolzig muffler would be an alternative, but it will need supension from the fuselage an we would have to join the two tubes first. You can see an example on a Swiss RV-6 HB-YLL in the link below:
http://www.flightforum.ch/forum/showthread.php?t=83766
I think Supertrap mufflers were used as well on one or two aircraft in Switzerland, but they seem to degrade rather fast. The dampening material inside will not withstand the temperature and pressure pulses very long.
 
If you open the link under my signature, you can see my two most recent efforts. The Piccolo Pipe reduced the cabin sound level by 2 Decibels, the underslung muffler reduced it by 4. The muffler & pipe added 12 pounds and did cause a loss of speed.
I don't have any readings taken outside the plane, I plan to do that soon.
I'm planning to position the Db meter 50 ft to the side of the runway center line, 100 ft ahead of the start line. Then perform a takeoff with someone taking note of the readings along the way.
Just a reminder, my plane is an RV-8 with a Non-Lycoming engine, so comparisons are limited, but the tip and muffler pictured would fit any application. 2 or 4 pipe exhaust systems would need a collector.
 
SuperCubDriver said:
Neil,
here in Germany we have strict noise limits and they usually only can be achieved with mufflers and/or RPM restrictions. There is the Liese company producing effective bolt-on mufflers (see pic below). There are others making good mufflers for a better price. May be some Swiss builders will post, they too have strict noise limits.


Click to expand...

I think I would rather deal with noise than that muffler falling out of the sky in my yard !
Tom
 
N941WR said:
Can anyone comment on the Vetterman's mufflers?
Click to expand...

I have them on my -7 with a parallel valve IO-360. About 170 hours now. I've never run anything else, so I can't personally make a comparison, but plenty of locals have commented on how quiet my plane is. Both heard from the ground and as passengers with me. They are somewhat bulky; getting the left side muffler to clear the cowl and everything else took some doing. I had to mold a blister in the cowl. I had to suspend them from the engine mount. There was simply no way to tie them to the engine only, which would have been my preference. So far so good, the spring-loaded ball and socket joints seem to absorb the wet dog shaking on start/shutdown. I did toss the stainless hanger tubes supplied by Vetterman, making some out of 4130 instead.

I'm happy with them overall and would purchase them again.
 
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