I'm planning a new project and will be needing a Pitts style muffler.

I see that I can get a Slimline and a Bisson in the Pitts style, but I'm wondering which one is quieter? or, are they both very quiet, or both very noisy?

I'm looking at a Bisson 2175 (LX8673), or a Slimline 6002 (TH LXFH36)? There's about a $20 difference in price. I don't want to get something that I don't need, but I also want to make sure that I can meet our club's very strict sound rules...

The engine is Supertigre .75. Alternate suggestions would be appreciated as well.

Comments anyone?

Thanks,

Bob

The Bisson (BCM) will be quieter due to the greater volume. Bisson also makes a strap on muffler that isn't bad. Davis Diesel offers very nice strap on German made steel mufflers that are very effective - picture attached. I managed to get one plane down to 88 Db using one of their strap on mufflers (not Pitts style). If you're really serious about noise control you can experiment with mufflers. Here are a few pix of the Dubro Arise muffler used in conjunction with a home made mousse can muffler - not a tuned pipe, it's baffled too. Very effective, and minimal power loss. Volume and baffling are the key to effective muffling. Use of a prop with more load to drop the RPM is necessary as well (less diameter - more pitch). Prop tip noise is the enemy. The slower you can run the prop (keeping the tips from approaching Mach) the better - APC props are quiter than most, those thin tips are very efficient.

the bisson will be quieter for the .75. but i would lean toward the st g90 instead of the .75. both are good engines, the 90 is a bit better. plus you can get a baffled slimline for the 90 which may be fairly quiet - i just noticed this baffled slimline of the tower site.

ed

These are the current Davis In Cowl mufflers, they are of high quality, very quiet and do not effect rpm. The engines are an MDS 2.18, Irvine 1.50 and a Dieselized Irvine .25, the extra muffler goes on a Super Tigre .90 also Dieselized. You'll just have to excuse the clutter on my work bench, I'm suffering from a real bad case of projectitis and have been going through engines checking bearings, re-building an engine for a friend, you know how it goes.

Thanks for the info so far. As for the engine, I had already had the .75 in my inventory, and the budget just won't let me get a .90 at this time. BUt I'll bear what you say in mind for future projects.

Any other comments or ideas? I hadn't thought about the Davis or Dubro mufflers. I'll look them up!

Thanks,

Bob

I like and have had excellent luck with bisson mufflers, very quiet and I don't see much RPM drop, if any. I have a few ST-90's all in TF Warbirds, with Bisson Pitts, all very nice, love that combo. ST-75 is good too, Have fun!!!

I have a Slimline Pitts on my Irvine 53. It's out of hand loud. Not sure if a Bisson would be quiter but the Slimline is certainly not.

I have a Bisson on my Moki 1.80 and it's a very tolerable volume. Nobody has ever said it was loud and our field is one that manages db levels very closely.

Hobbsy - looks like you like doing it quietly too. Nice to see. Those Davis Diesel mufflers aren't cheap, but they sure do the trick. I've even got their biggest can on my G-62. I notice that usually threads on quietening things down die a quick death - no interest I guess... until flying fields are lost. Too bad as only a little effort can bring remarkeable improvement with little power loss. Personally, I find it less stressful and more enjoyable to fly quieter planes. I certainly can see the beauty of electrics, but I like engines! Nothing worse than some guy with a loud engine tuning his screaming beast in the pits.

Daryl, I also have the In Cowl fourstroke SoundMaster for 120 sized fourstrokes and it works great on my old high compression Saito 150, I'm going to try it on my new Enya 1.55, the 1.55 has an irritating bark in the exhaust that I don't like. Could you give us a pic. of the G 62 one. Thanks

i bought two of the davis diesel mufflers - the first was for an os61sf. this was the "new" version which does not have the strap- it has a flat plate brazed to the muffler - you drill through holes in this plate to mount the muffler. this muffler worked very well and was nice and quiet. so i ordered one for my next st g90 - but they sent the old design with the strap mount- and the strap mount is a real pain. it will not mount on the g90 and stay there. so i tried modifying it, but it still wouldn't stay. so i gave up on this muffler. if anyone wants it i will sell it for $30 inlcuding shipping. i have ground off the sides of the aluminum adaptor a bit but it still works fine.

ed

Hobbsy - here's a pix of the G-62 setup. This is the largest can they sell. It was about $110 and they want about $75 (ouch!) for the flex pipe. I managed to score the flex pipe for considerably less off the 'net. I'm running an APC 21 X 12 component 3 blade prop with it and most of the glow powered planes drown me out when I'm flying. Still have pretty decent power too, but of course it's restrictive and there has to be some power loss involved. It's the quietest gasser I've ever heard! Getting back to the topic though, N1EDM, if noise is an issue at your field you should take RC34074 up on his offer - that strap on muffler he's offering is exactly the one I used to tone my S.T. 90 down to 88 Db! It's probably the most effective off the shelf option available, and $30.00 is very reasonable - they are not cheap.