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Exhaust for ULS

  • Eugene
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2 weeks 4 hours ago #21022 by Eugene
Exhaust for ULS was created by Eugene
Working on relocating muffler from top to behind the engine.

Found some cracks, hope you can see them on pictures below.

Trying to do better job at new location.

Looking for good installation practices - how many spring joins we need to have minimum 4 or 8?

Muffler needs to have Lord mounts or not.

Can I install flex joins right next to engine heads 2-3 inches away from outlets?

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  • Bill Hertzel
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1 week 6 days ago #21025 by Bill Hertzel
Replied by Bill Hertzel on topic Exhaust for ULS
The final photo looks like someone already welded over a previous crack.
The more flex you can build into the installation the better.
It looks like the current mounting had no give at all.

Keep in mind that if you ever want to install Exhaust Gas Temp Sensors you will need a few inches of solid pipe right near the head.
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1 week 6 days ago #21026 by garrett
Replied by garrett on topic Exhaust for ULS
Here is a picture of Evectors exhaust pipe upgrade that allows flex.
midwestsportplanes.com/wp-content/upload...t-Tubes-With-EGT.jpg
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1 week 6 days ago #21031 by Eugene
Replied by Eugene on topic Exhaust for ULS
Thank you!

I didn't know that flex piping is available.

Learned something important today. I was told that muffler needs to be installed on engine as rigid as possible. No rubber mounts or springs! We want engine and muffler to vibrate as one unit together.

I was told Rotax 914 is done this way. Hope this is correct.

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1 week 6 days ago #21034 by garrett
Replied by garrett on topic Exhaust for ULS
The 914 is a low compression engine, a UL with a a turbo charger. Like Roger said part of the vibration problem is due to the ULS's high compression. Some have installed a spacer between the block and cylinders to drop compression a bit to help with the vibration. I had tried a stronger springs and ended up with a cracked up exhaust up system like yours. While helping a friend with a Evector airplane I noticed the flex on the down pipes, his whole system had fallen off in flight and they offered the upgrade pipe flex kit to deal with the vibration as shown in my last post.
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1 week 6 days ago #21035 by Bill Hertzel
Replied by Bill Hertzel on topic Exhaust for ULS
I am surprised that you have fractures directly next to a flex joint.
That joint requires that it have Anti-Seize compound reapplied occasionally/as needed.
The Copper Based Lubes are for higher temperatures than the Aluminum Based products.

See LMM Section 05-20-00, Page 5.
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1 week 5 days ago - 1 week 5 days ago #21055 by Eugene
Replied by Eugene on topic Exhaust for ULS
So far for every question about my airplane I usually get 3 different answers. And I need with my Russian brain to decide which one is best. So question about exhaust system was not any different.

I talked to Lockwood this morning and looks like they don't support their mufflers at all. Muffler is hanging down on 4 pipes only. They think it's the best way and they have very good results with it.

So, I have three different options: support muffler with rubber lord mounts, make it rigid, or don't support at all!

Maybe I should go ask my wife which option to choose. Maybe she knows....
Ok, she thinks that install muffler on top of the engine was mistake on Interplane part. Very big vertical distance from engine mounts make big movements side-to-side on engine start/stop.

Mistake #2 was to mount oil cooler on to this muffler. So, this relatively heavy combination is sitting on rubber mounts on very top and trying to brake loose!

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1 week 4 days ago #21067 by garrett
Replied by garrett on topic Exhaust for ULS
You are on the right track, Eugene, with your attention on the vibration and perfecting the exhaust system. A friend of mine has a similar aircraft and has struggled with parts and pieces coming off the motor due to vibration which caused a lot of expensive propellor damage and down time. I also had a tail pipe come off my Remos GX which uses CKT's exhaust. The tail pipe fell off at a weld and burned the fire wall and side of fuselage that led to a year of down time. Due to Remos having financial problems I had to try and find exhaust muffler springs and went with a slightly stronger springs (which were continually breaking) immediately led to muffler cracks and probably led to the tail pipe falling off. After getting the exact replacement springs from Remos including a new muffler the exhaust problems are gone for now. I was was amazed at how even springs and tension is so critical to the performance of the exhaust.
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1 week 2 days ago #21099 by Eugene
Replied by Eugene on topic Exhaust for ULS
In order to fabricate engine cowling I need to relocate muffler and oil cooler. I listen to different people and made the conclusion that muffler position behind the engine, just like on this picture, is the best compromise.

I was told this:

#1 - muffler on top of the engine with oil cooler present a lot of drag. It is sitting in clean the air stream and disturbing airflow into propeller.

#2 - muffler with oil cooler on top is relatively heavy combination and sitting on 4 long pipes above the engine = creates a lot of stress on joints and overtime lead to some cracks.

#3 - I talked to propeller manufacturer and they don't see any issues with hot exhaust to be even 2 inches away from propeller. I was told that over time I will see maybe some discoloration on propeller blades, but it will not effect Life expectancy at all.

#4 - muffler behind the engine Will be sitting inside of aerodynamic shade. It will not create additional drag and it will not reduce propeller efficiency, because air behind engine Is very much disturbed already, very much like airflow behind fuselage of this airplane.

#5 - with a lot of effort muffler can be possibly installed in front of engine and right behind the oil tank. Muffler will need to be insulated in that case and that will cut dramatically life expectancy of this unit. If you choose not to insulate muffler, then diverter needs to be made to redirect hot airflow away from engine. On pushers where engine is seating much higher - there is possibility to divert air right down below. But on this airplane I have a baggage compartment below.

#6 - I agree that BRS box is big and bulky. But it is already installed directly on to airframe and cannot get any lower. Maybe I can convert this unit in to soft pack and this way it will get much more compact. I have to do my homework about that.

#7 - oil cooler will be installed right behind water cooler and I was told that this is best location for it.

So, this is what I know so far

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1 week 1 day ago #21105 by Eugene
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1 week 1 day ago #21106 by garrett
Replied by garrett on topic Exhaust for ULS
Eugene, have you thought about just using straight pipes into a collector? Watch this.
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