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  • Re: Are exhaust systems interchangeable UL/ULS/IS?

    by » 6 months ago


    Thanks for the history lesson. I stared at the RV-12 pictures as much as I could today, and pretty much had concluded exactly what you confirmed.  I can see the Rotax part number in some pictures, so that part was easy, and I can also see that they appear to have bent the tubes some to tuck the muffler up closer to the bottom of the engine.  That would be helpful for me, since I don't have much room below.  I have a potential lead on someone who is willing to sell one of the Van's systems with about 70 hrs. 

    Since I only have the 80 HP engine, I'm still considering the dual muffler Toucan system.  I think it would fit the limited space I have a little better.  The Onex is a single seat of course, so even less cowling space than the other models.  

    I'm not completely against fabricating my own tubing.  You can get mandrel bends pretty easily, and it wouldn't be the first stainless aircraft exhaust I TIG welded.  It would be the second, but who's counting :-) 

    Thanks,

    Rusty

     


  • Re: Are exhaust systems interchangeable UL/ULS/IS?

    by » 6 months ago


    Great, hope whatever you pick works for you.  My only problem with 2 into 1 systems is they tend not to last a long time before cracking.  There is very little in the way of heat expansion and contraction absorption with that design type.  I know that it is tricky to get enough movement and not so much as to leak.  I note that some people wrap mufflers also, not a fan of that myself as it tends to retain the heat on the pipes and promote cracking.  It will help reduce temperature under your cowl but at an expense of early muffler failure. (my opinion) 

    Whatever you do be sure that you have a way to allow the heat to dissipate when on the ground after flight (turn around heating)  As in most Rotax installations there is no real technical need for a lot of baffles like an air cooled.  the drawback here is the heat will collect at the top of your cowl on a hot engine shutdown.  if you mount your oil tank inspection door on the top of your cowl get in the habit of opening it after flight when on the ground, let that hot air out....gives you an excuse to have one of them red flags (remove before flight!) on it while on the ground.  

    Cheers


  • Re: Are exhaust systems interchangeable UL/ULS/IS?

    by » 6 months ago


    I'm really leaning toward the Toucan system, just because it offers so much flexibility in mounting angles.  From the pics I've seen, they seem to use slip joints on at least one end of the muffler, with no clamp in the pictures I saw.  I figured that was for expansion. 

    For undercowl temps, I could always swing them to the outside, and just route them outside of the cowl.  Problem solved :-)   Heck, the cowl is so narrow that they have to cut holes to let the VW cylinders stick out, but I'll find a way to keep everything inside.   

    Cheers,

    Rusty


  • Re: Are exhaust systems interchangeable UL/ULS/IS?

    by » 6 months ago


    Rusty

    If you look at the ICON A5 they use a 2 into 1 exhaust (very expensive) They do have a blister on their nacelle with airflow to cool them.  Just a thought if you were looking for ideas on how to deal with your cowl.  

    The 2 into 1 is always going to be somewhat louder than the 4 into one chamber.  the key to keep your back pressure in control is to be sure that the canisters volume, combined volume, is at least 5 liters 1.32086 US gallons.  ½ of that is .66 US gals.  This is important.  check them out, it appears like from the pictures they might be just fine.  The 100 HP engine is 1352 CC and I believe that system was designed for the 80 HP is 1211 cc.  (84 mm bore vs 79.5 mm bore, same stroke) 

    Cheers


  • Re: Are exhaust systems interchangeable UL/ULS/IS?

    by » 6 months ago


    The cowl is going to be a nightmare for sure.  I've given some thought to cheeks on the cowl, similar to the RV-3/4.  That would allow the mufflers to be straight out to the side if needed.  I do think I can sneak them in below the cylinders though. 

    The guy who owns the Toucan company now bought it a couple years ago, but the story he got from the developer was that they worked with a Rotax engineer to verify that the backpressure was within recommendations.  I have to believe that was with the 80 HP engine, but don't know for sure.  100 HP would be nice, but prop clearance is a huge issue already, and 80 HP is what they had (in theory) with the VW engine, so I should be happy enough. 

    Rusty

     


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