Nas19320

I have a Thunder Tiger .46 that I have a Pitts muffler on. I've had the engine on another plane and it runs beautifully with the stock muffler. The problem is that with both exhaust outlets open the engine struggles to pull fuel, as soon as I put a finger over one of the exhaust outlets it comes back to life. So I complelty blocked off one outlet and it has no trouble getting fuel but it is sluggish and loses about 2,000 rpm which makes the plane horrible to fly. So I plan on blocking the outlets with JB weld and then drilling the outlets and then increasing it's size until it runs correctly. My question is should I block both outlets and then slowly drill them out or should I block one outlet and leave the other open then drill the closed outlet until it runs right or does it not matter either way? Thank you.

blvdbuzzard

All I did was to cut a piece of 1/4-20 threaded rod about 3/8 inch long, drill a 1/8" hole in it and put one in each outlet. That gave me enough back pressure to get fuel from the tank to the carb. I was told I had the tank to far, to low, to small of fuel line and almost everything under the sun. Yet when I plugged the muffler, it came to life. I am not sure if JB weld will handle the temps, but won't hurt to try. I have also heard about stuffing brass wool into the pipes to generate more back pressure.




Dru.

ICE_MAN

JB weld wont handle the fuel. It gets soggy

txaggie08

get some steel putty. its designed for high temp, and when it hardens it drilabe(and tapable)

bubbagates

My Feedback: (32)

On some of the OS160FX's using the bison pitts muffler it's common to have to block a tube.

You can crimp one exhaust tube but it looks ugly

You can also go to the hardware store and buy a brass water pipe cap that fits over an exhaust tube, drill through both the cap and the tube and run a small bolt through them to hold the cap on.

As others mentioned, steel wool placed in the tube(s) will also work but it will become clooged after time with oil from the fuel

Nas19320

Thanks guys. I'm going to give the steel wool a try and I'll just change it out every once and a while.

radcon56

If the engine ran "Beautifully" with the stock muffler,why did you change it?

Nas19320

Because the engine moved from an Avistar to a Cap 232.

HillHopper

Hey txaggie08 - where can u find the steel putty. I know there are several brands but I've never been able to locate a local outlet for any of it. I have a pitts muffler that needs some repair/

Pilot Chad

My Feedback: (4)

Hillhopper,
Sounds like lowes and home depot would have it. Did you try there?

RCKen

My Feedback: (9)

HillHopper,
Most any auto parts store should have it. Just ask for it at the parts counter. Lowe's and Home Depot don't carry it that I know of.

Hope this helps

Ken

HillHopper

Yea I tried lowes and HD and they didnt know what I was talking about. I will try auto parts store. Thanks
OBTW - Most brands says it resistant to chemicals. Has anyone actually used it on a muffler. The tubes came out of my pitts on a crash. They are not bent and the flange is still on them. No damage to the rest of the muffler either. I want to see if I can stick them back in and use this to hold them in

RCKen

My Feedback: (9)

HillHopper,
Another option in your case would be to find a machine shop that can weld aluminum, they should be able to weld on the exhaust tubes. But in all honesty, unless it's a very high dollar exhaust unit it might be cheaper to just buy a new one instead of getting welded. But ask the machine shop anyway, it usually doesn't cost anything for an estimate.

Let me know what happens.

Ken

HillHopper

I will see what a machine shop thinks - if not them then I'll try something like the steel putty and see what happen - muffler no good as it is I assume so nothing to lose.
I'll post the results either way. Thanks guys

bhole74

The best fix for this problem would be to install a perry pump. If you restrict your muffler, it can rob you of the power benefits of the muffler. A perry pump will deliver the same amount of fuel to the carb reguardless of the plane attitude, no more leaning out when going verticle. It may also help lower fuel consumption. I have a 160fx with a Bisson pitts muffler and wasn't about to ruin the muffler by crimping one tube closed. I installed a perry pump and it has fuel on demand with no change in mixture from level flight or hanging it on the prop. I also went from consuming a 20 oz. tank of fuel in 11 min to over 20 min. My average flight (10 min. on my timer) uses less than 1/2 tank. Heck of a trade off for a $30 pump, glow fuel is much more expensive.

bhole74

Here is a link for a pump. [link]http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXDG59&P=ML[/link]

blvdbuzzard

There is a benifit to plugging one of the muffler pipes, it will reduce the noise. I have a Global Ulitmate with a Mag .46 in the nose. It runs great with the stock muffler yet with a Magnum Pitts muffler it would not run worth beans. I plugged one hole then most of the other and could not get enough back pressure to draw the fuel. I tried the brass wool, too and it just did not have enough volume to keep good fuel feed. I ended up re-plumbing the whole thing and putting on an old Perry OSC. fuel pump. It took another two hours of fiddling with carb setting and pump setting to get it just right. Now it idles like a dream, does not sage or load up in the mid-range and has a screaming top end.

Some plane are just pain to get things right. Then there are the ones that just don't care about anything and run for ever.

Dru.

mikeboyd

I have been using JB Weld and fiberglass cloth to plug the end of one tube of all my bisson pitts mufflers. I drill a small hole big enough for oil to drain out. I have had to do this on OS 1.6FX, ST2300/3250, MDS 2.18, etc. Always the same result, readjust the needle and they fly fine. No problem with the JB Weld plug loosening or failing for over two years. Good Luck.

Nas19320

I used JB Weld since I had it and ran 3 or 4 tanks through it on the ground and 2 in the air and it's holding together great. I too put a hole in it to allow the oil out. Thanks everyone.

HillHopper

Ok so other post here says JB weld will soften up in the muffler, fuel and heat I assume. I have looked for the "steel putty" mentioned above and have not found any at the automotive stores. My pipes came loose in a minor crash. Not bent and the flange is intact that goes up into the muffler. From others experience will the JB Weld be ok to use to stick the pipes back into the muffler. Welding them back is just to expensive.