tennesseect Posted April 27, 2014 Report Share Posted April 27, 2014 My 07 CTsw slowly got noisier over the past few months and then got real loud. When I opened the cowling I found a chunk of metal - about 2" X 6" - missing from the front right of the muffler. My wife and I flew it 40 miles home. There were no abnormal instrument readings other than a somewhat lower than normal left cylinder head temp. Is this normal wear and tear? Do I just replace the muffler or is there something else I should check? Link to comment Share on other sites More sharing options...
Anticept Posted April 27, 2014 Report Share Posted April 27, 2014 You need to fix that as soon as possible, it is a fire hazard. The muffler also drives a certain back pressure into the exhaust of the engine; without it you lose fuel economy and increase wear on the valves. * Also, have someone look at the muffler to make sure there's nothing else wrong with it. I don't know if CTs have internal baffles to help with the back pressure tuning; if they do, it can block the exhaust and exacerbate the problems. * Explaination: Engines are tuned to have a certain amount of "valve overlap," which is the time between the exhaust and intake strokes that both valves are open. The reason is as follows: the exhaust valve is open throughout the exhaust stroke, the intake valve opens right at the end of said stroke. This means there is inertia of the exhaust gasses leaving the exhaust port, and high pressure at the intake. Exhaust ports are also smaller than the intake port, and Bernoulli's principle takes effect. The intake port air is at a higher pressure, and the exhaust port air is at a higher velocity. Coupled with the fact there is already inertia carrying the exhaust gases out, this allows some of the intake air to further purge the combustion chamber of exhaust gasses, and help with cooling. With no back pressure, the cooling effect is amplified, and you lose a lot more intake air (which means more fuel goes out the exhaust too in carb engines). This is where the efficiency part comes from. Valves, without back pressure, can slam into their seat, increasing wear. That's why it's bad for valves to have no back pressure. Link to comment Share on other sites More sharing options...
FastEddieB Posted April 27, 2014 Report Share Posted April 27, 2014 I agree with Anticept - that plane should have been grounded. Not only a fire hazard, but carbon monoxide poisoning hazard as well. Must be fixed before further flight, via repair or replacement. Link to comment Share on other sites More sharing options...
Roger Lee Posted April 27, 2014 Report Share Posted April 27, 2014 Was the piece missing from the exhaust pipe, the stainless muffler on the outside edge or from the cabin heat shroud around the muffler? The whole piece is actually missing? No matter which one it needs replacement. Link to comment Share on other sites More sharing options...
Tom Baker Posted April 27, 2014 Report Share Posted April 27, 2014 Roger, I know there is a part number in the CTSW parts manual for the muffler and piping, but do you know if it is a Flight Design only part or a standard Rotax part? I have ask Ted to send me pictures to figure out what is going on. Link to comment Share on other sites More sharing options...
Roger Lee Posted April 27, 2014 Report Share Posted April 27, 2014 Hi Tom, The muffler itself is Rotax, but FD did the heater shroud. I would be interested in the pictures too when you get them. If you replace the muffler only then the female sockets for the pipes have to be welded on. If you have to get a complete muffler I bet it will be from FD and it probably won't be cheap for the entire piece. The muffler from Rotax alone is $1289. You might be able to rob the FD parts off the muffler and reuse them. Link to comment Share on other sites More sharing options...
Jacques Posted April 27, 2014 Report Share Posted April 27, 2014 the muffler alone [ # 973674 ] is MORE expensive than the 'kit' [ # 973676 ] which includ the muffler kit 973676 is ~$300 less Link to comment Share on other sites More sharing options...
mocfly Posted April 27, 2014 Report Share Posted April 27, 2014 It would be nice if the pictures could be posted so we can see the failure, Seems very odd. Link to comment Share on other sites More sharing options...
FastEddieB Posted April 27, 2014 Report Share Posted April 27, 2014 Agreed. If we're talking a chunk out of the muffler shroud, that's completely different. Link to comment Share on other sites More sharing options...
Anticept Posted April 27, 2014 Report Share Posted April 27, 2014 It makes no sense if it's the shroud. tennesseect said it was getting louder and louder, missing a piece of the shroud doesn't do that. Link to comment Share on other sites More sharing options...
FastEddieB Posted April 27, 2014 Report Share Posted April 27, 2014 True. I forgot that part. A hole in a muffler would ground me in a heartbeat. Link to comment Share on other sites More sharing options...
Tom Baker Posted April 27, 2014 Report Share Posted April 27, 2014 He sent me a picture in a text. The hole is in the muffler. It looks to originate at the tail pipe and go forward towards the heat shroud. Link to comment Share on other sites More sharing options...
tennesseect Posted April 28, 2014 Author Report Share Posted April 28, 2014 I have attempted to attach a picture I took today of my muffler. I hope it is visible. Link to comment Share on other sites More sharing options...
FastEddieB Posted April 28, 2014 Report Share Posted April 28, 2014 Again, this is important. You should not have flown the plane in that condition. Glad it worked out for you, but exhaust problems like this can and have killed lots of pilots. Link to comment Share on other sites More sharing options...
Anticept Posted April 28, 2014 Report Share Posted April 28, 2014 You might have baked your cowling. Have a mechanic look at it too. Can you take a few pictures of the inside of the bottom half? Link to comment Share on other sites More sharing options...
Roger Lee Posted April 28, 2014 Report Share Posted April 28, 2014 I haven't seen or even heard of something like this. My best guess is it started to crack around the weld at the pipe and with vibration and exhaust pressure and pulsation took its toll expanding the cracks. Why it broke out as it did is anyone's guess. Regarding the break towards the center, is there anything welded right where it seperated? These guys are right, it should be grounded until fixed. Sorry, but this won't be cheap. I'm going to send this to Rotax and get their take. Link to comment Share on other sites More sharing options...
mocfly Posted April 28, 2014 Report Share Posted April 28, 2014 WOW! I'm off to the hangar in the am to check that area. Link to comment Share on other sites More sharing options...
sandpiper Posted April 28, 2014 Report Share Posted April 28, 2014 The welds in the muffler need to be looked at every time the cowl is off and for sure at annual. I posted here a couple of years ago that I had a weld go bad. I had it welded immediately not wanting the crack to get worse. Link to comment Share on other sites More sharing options...
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