Madhatter Posted February 6 Report Share Posted February 6 On 1/30/2024 at 6:14 PM, Anticept said: I don't know why 316 is being used in exhausts as filler for 321. It goes against all the material I have. The one single thing it has going for it is its ease of weldability, but 347 is superior for exhaust because of the heat resistance and the prevention of precipitating chromium carbides at intergranular boundaries at elevated temperatures leading to corrosion and cracking with cycles. 316 is quite vulnerable to this problem and is worsened by welding especially if it's not annealed. Maybe 347 is newer than 316 and everyone's stuck with 316 out of tradition. I'm not sure. The industry has problems with being stuck with long outdated methods too, be it because of the relatively niche application, or that it's geriatrics are working on 50 year old knowledge and haven't learned anything new, or the wheels of regulation turn at the same rate. Maybe you are misremembering. Maybe there is something I'm missing. Maybe 316 is that much CHEAPER to work with and nobody expects it to be a problem within the lifetime of the part. Maybe 316 is much happier to work with leaded fuels. But I am missing something if 316 is the standard and nobody's asked about moving to 347. It's like how material recommends copper antisieze on stainless parts. Mountains and mountains of evidence and research that say it will corrode the stainless and NICKEL should be used and other industries and standards have caught up with that, but AVIATION material still says copper. As for the exhausts, I've lost count of the amount of repairs we have done. We had the one crack on the side, but the rest of the time, it's replacing the cups from wear. These exhausts last quite a long, long time. I imagine the lead creates a lot more problems in a standard aircraft exhausts with the lead, but I don't know if the lead oxide can react with the stainless like elemental lead can. Elemental lead corrodes stainless badly. Your experiences are just not matching up to mine, despite tens of thousands of hours of service combined in the fleet. I had a long talk with the company that manufactures the new CT exhaust system that I now use. While they still use 316 filler rod in some cases they prefer 347 for my application. So YOU ARE CORRECT, my error. Oddly enough the filler I practice with is 347. However they commented on those rewelding cracked exhaust components, as not smart. In my experience most mufflers need replacement around 1000 hrs, even a new cirrus only makes it to 700 to 1000hrs. We never weld cracks in certified, ever, and for good reason. Quote Link to comment Share on other sites More sharing options...
Anticept Posted February 6 Report Share Posted February 6 I also did a little more research. 316 is indeed the OLD stainless steel for high temp applications. Which also uses 316 filler. But as said, at extremely high temps like exhausts... it doesn't last as long. 321 does. Right around 950 F is where this is an issue. 321 can't be used as filler either because the titanium in it is an issue, it doesn't stay where it's supposed to. It cannot be used as a filler if you need the stabilization. 347's other stabilizers like nobium make up for it and continues to do its job even when it was used in welding, and is compatible with 321 without compromising its integrity. If 316 is used on 321, basically you have nothing better than a 316 joint. the 321 base metal stabilizers don't cross into the 316 filler. Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted February 20 Report Share Posted February 20 On 1/31/2024 at 9:45 AM, Madhatter said: This exhaust is a copy of the original but much higher quality however it can only be used on ELSA and is available. This is the problem with SLSA as the manufacturer controls all parts and can charge whatever they want. I have an ELSA...post or PM me the price of this, I might be interested. Quote Link to comment Share on other sites More sharing options...
Madhatter Posted February 20 Report Share Posted February 20 The complete exhaust for the SW is $3200. That's 1/2 the FD price 3 years ago. Much better quality. The lead time however is 12 weeks as they are very busy this time of year Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted February 21 Report Share Posted February 21 18 hours ago, Madhatter said: The complete exhaust for the SW is $3200. That's 1/2 the FD price 3 years ago. Much better quality. The lead time however is 12 weeks as they are very busy this time of year Thanks. I've always hated the quality of the CT exhaust, I'll start planning for this upgrade. Does it include a muffler, and if so is it the same dimensions as the original? Does it include its own heater shroud or use the factory shroud? Quote Link to comment Share on other sites More sharing options...
Madhatter Posted February 21 Report Share Posted February 21 Includes the muffler but not the shroud. The entire exhaust is identical to the original but with smooth bends. The shroud muffler stand off rings are welded much better which is where my cracks formed in the original exhaust. Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted February 21 Report Share Posted February 21 46 minutes ago, Madhatter said: Includes the muffler but not the shroud. The entire exhaust is identical to the original but with smooth bends. The shroud muffler stand off rings are welded much better which is where my cracks formed in the original exhaust. Awesome, thanks. Quote Link to comment Share on other sites More sharing options...
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