Have the AWI 4 n 1 exhaust on the RV-8, was wondering if anyone else is having problems with the collecter cracking? Have 230 hrs on the plane and it has cracked 3 times so far. AWI has made us a new collector , it also has cracked. We have the exhaust supported ahead of the collector, but have no real solution for supporting the 4 n 1 collector itself. Any ideas would be appreciated. Thanks.
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AWI 4 in 1 exhaust
- Thread starter N53LW
- Start date
Bubblehead
Well Known Member
I have about 200 hrs on this system with no problems. I supported the collector off the rear two bolts that connect the collector to the 4 pipes. I used a system similar to the Vetterman system. I will post pictures over the weekend.
I did cut the collector a little at the rear to get a more rearward opening. I also cut the two top pipes from the cylinders so that the collector would move up a little closer to the fuselage. Perhaps you are trying to pull it up toward the fuse and putting some stress on the system.
I did cut the collector a little at the rear to get a more rearward opening. I also cut the two top pipes from the cylinders so that the collector would move up a little closer to the fuselage. Perhaps you are trying to pull it up toward the fuse and putting some stress on the system.
Hmmm.....mine is supported aft of the pipe join, in the middle of the collector section, using cable loop hardware supplied by AWI. I really like the design. However, no flight time yet.
Follow-up report...cracked collector here, 144 hours in service. One socket was splitting away from the collector body. The cracks seem to originate at the interior welding (the "cone" area). Don't think it has anything to do with the support method. AWI has made weld repairs; we'll see how it holds up.
Phil, had any further problems?
Phil, had any further problems?
Jerry Cochran
Well Known Member
The single pipe setup...
begs the question. What is the advantage? Faster speed/lower drag, cost, esthetics?
begs the question. What is the advantage? Faster speed/lower drag, cost, esthetics?
gnuse
Well Known Member
Wicked Stick
Well Known Member
Cracked pipe between collector and heat muff area.
Today while performing my condition inspection, I found the following:
My RV-8 has 123 hours tach time on it.
Seems to me that since the other 3 pipes are fine, that this one might have been defective or mis-aligned when welded at the factory causing stress in that area. I have read others having collector issues, but thought I'd post this to see if anyone else has experienced an issue with theirs in this area.
Today while performing my condition inspection, I found the following:
My RV-8 has 123 hours tach time on it.
Seems to me that since the other 3 pipes are fine, that this one might have been defective or mis-aligned when welded at the factory causing stress in that area. I have read others having collector issues, but thought I'd post this to see if anyone else has experienced an issue with theirs in this area.
Wicked Stick
Well Known Member
Hi Dan,
Where are you going with this ? Even if there's room for it to go deeper, it's locked into that position from the welded bracket attach point. The other pipes have some reasonably straight sections near that area where the welded bracket is located, but this pipe is very close to the bend. I'm taking an educated guess here, but I think the combination of the bend and weld may have left that area a little thin and pre-maturely caused it to start cracking there. It's not cracked all the way around (yet), so it must have started in the area near the welded bracket.
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Toobuilder
Well Known Member
Just as a data point, I made my own 4-1 with 30 inch primaries and a slip fit collector. I have one of the primarily tubes welded solidly to the collector and the other three are retained to the collector by the often seen tabs, bolts and compression springs. I have one solid link hangar at the aft side of the sump bolted to a tab welded on a primary in front of the collector. It should also be noted that I have ZERO ball joints anywhere in the system and the flanges are welded to the primaries (no slip fit at the head) and the whole system is mild steel. In other words, its built just like drag race headers have been done for the last 50+ years, and I have not had a single crack in 400+ hours of service.
...and I also have about $200 worth of materials and a weekend of fabrication wrapped up in the whole thing.
...and I also have about $200 worth of materials and a weekend of fabrication wrapped up in the whole thing.
Trimming the pipe so the pipe could not bottom in the socket was an experiment suggested by AWI after a crack repair on my collector. The idea was to add a little flexibility, and some room for thermal expansion. In this case thermal expansion would create a high tension stress in the link (runs cooler, extends less than the pipe itself), which would load the tabs right at the crack location. Any truth to the explanation? I dunno. Mine hasn't given any more trouble.
Pipes
I made a set of 4 straight pies for my Skybolt out of swimming pool hand rails. 304 stainless , .049 wall . Cut out the bends you need and tig them together . I had a slip joint with springs about half way up the system . 200hrs no problems .
I considered making the one for my 8 but the cost of the collector and flanges added up to close to $500. I purchased the AWI system for about $1200 .
I will check the clearance of the pipes to the collector before the first startup .
Tom
I made a set of 4 straight pies for my Skybolt out of swimming pool hand rails. 304 stainless , .049 wall . Cut out the bends you need and tig them together . I had a slip joint with springs about half way up the system . 200hrs no problems .
I considered making the one for my 8 but the cost of the collector and flanges added up to close to $500. I purchased the AWI system for about $1200 .
I will check the clearance of the pipes to the collector before the first startup .
Tom
Bubblehead
Well Known Member
I now have 400 hours on my AWI 4 into 1 without any cracking. I will do an extra good inspection at the next oil change.
I trimmed the two upper pipes about 1/2" so that the collector would ride up a little higher in the tunnel. Without doing that they were bottomed out in the collector and the collector was closer to the lower cowling than I wanted.
Wicked Stick
Well Known Member
Dan,
I see now what you were getting at, and it does make sense, the other 3 pipes going into the collector did have a little wiggle room depth wise, but I remember the #3 pipe having to be shoved all the way in to line up.
Last week I sent my collector and the #3 pipe back to AWI so they could inspect it. They told me that they no longer put those attach brackets on the upper two pipes any more and that my #3 pipe did seem to be a little tight in the end of the collector, so it very well may have been caused by the weld, near the bend and no room for flexing.
To AWI's credit, they promptly replaced my #3 pipe with a brand new one free of charge. (I only had to pay for the shipping) The new one didn't have to go so deep into the collector this time either. It was also suggested by my local A&P IA to apply a high temp Anti-Seize compound (the silver colored stuff) to the ends before inserting them into the collector.
Though it seems there's been some issues, I would still recommend AWI as a great company who provides great service and support's their product.
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grayforge
Well Known Member
gnuse mentioned that if one had heard a 4 into 1 exhaust, they wouldn't ask about the advantages over a 4 pipe system. What is the audio difference?
I'm about to pull the trigger on an exhaust and am deciding between Vetterman 4 pipe or AWI 4 into 1. I have an ECI IOX-370. Their cold air sump only allows the use of the Vetterman 4 pipe system. AWI 4 into 1 is supposed to work too.
I'm a bit concerned about the cracking issues in AWI systems, though those were older posts and maybe they have those bugs worked out.
Thanks!
I'm about to pull the trigger on an exhaust and am deciding between Vetterman 4 pipe or AWI 4 into 1. I have an ECI IOX-370. Their cold air sump only allows the use of the Vetterman 4 pipe system. AWI 4 into 1 is supposed to work too.
I'm a bit concerned about the cracking issues in AWI systems, though those were older posts and maybe they have those bugs worked out.
Thanks!
Russ McCutcheon
Well Known Member
Any chance of some photos, sounds like a fun project!
BillL
Well Known Member
Probably, I have a TG and AWI 4-1. I don't know about the clearance needed for the nose gear. I can take a picture when I get mine reassembled. Right now , the engine is off and being used (self imposed) as a "prize" to get the cabin wiring completed. I have of focus on my peas before eating the carrots.
If you really, really need it, I will hang up the engine and add the pipes. Just let me know.
Aerosporty
Active Member
My B?cker has a Skydynamics 4 into one collector. It is supported by the 4 pipes (obviously) AND a bolt at the firewall. Two flanges are welded on top of the collector, just behind the merge of the 4 pipes. Hard aerobatics for 15 years, and no cracks!
