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New exhaust


Madhatter

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I have been requested to ask for comments by the CEO of an aircraft exhaust manufacturer I have been working with for some time on prototype exhausts for the CT. While the system we have been working is radically different, he has proposed manufacturing exact high quality replicas of the current exhaust system at a FRACTION of the cost. The risers that he makes are 321 stainless with smooth bends to provide smooth flow unlike the hollow donut sections for all the bends that Rotax uses. FD charges $800-$1200 per riser which is absurd. The components you can buy at Lockwood and Leading Edge need to be welded. These require a very experienced welder with jigs, not an average welder. I have all the expensive equipment required to do this and I would not even consider trying it.

While I understand that this ELSA territory he would like any comments on this. The CT's are getting more total time on them and you can only reweld to the point that it is no longer practical to salvage. A new exhaust system for a CT costs around $6000. Converting to ELSA costs $400-$800.

All I am asking for are comments as to whether there would be any interest

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5 minutes ago, Madhatter said:

I have been requested to ask for comments by the CEO of an aircraft exhaust manufacturer I have been working with for some time on prototype exhausts for the CT. While the system we have been working is radically different, he has proposed manufacturing exact high quality replicas of the current exhaust system at a FRACTION of the cost. The risers that he makes are 321 stainless with smooth bends to provide smooth flow unlike the hollow donut sections for all the bends that Rotax uses. FD charges $800-$1200 per riser which is absurd. The components you can buy at Lockwood and Leading Edge need to be welded. These require a very experienced welder with jigs, not an average welder. I have all the expensive equipment required to do this and I would not even consider trying it.

While I understand that this ELSA territory he would like any comments on this. The CT's are getting more total time on them and you can only reweld to the point that it is no longer practical to salvage. A new exhaust system for a CT costs around $6000. Converting to ELSA costs $400-$800.

All I am asking for are comments as to whether there would be any interest

As somebody who had an exhaust failure and owns an E-LSA, I would absolutely be interested!  I'm curious, can you project what the cost of the new system would be?  Would it just be the pipes from the cylinders, or the muffler and exit stack as well?  If it's really going to be mandrel-bent and one piece pipes, there is probably a minor power advantage to this as well...

 

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Longer term - I'd have interest in both replacement style and whatever is the new "different style", my bird is south of 600 hours and still decent shape.  An offering with performance benefits might drive me to move sooner, and I would not overlook the opportunity to increase heater performance as that is often a shortcoming on the current set up.

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I was shocked when I saw how terrible the exhaust system was as far as flow. As I remember my left front stack is the worst, it's mis-aligned and the curves do not transition smoothly either. I would think you could easily get 15/20% power increase with a smooth flow "header" system. But, then you have to think about heat build up and changing the prop to take advantage of the increased power. I am currently SLSA and don't really have extra cash to invest in this. But I totally agree that there is great potential for improvement there.

ET

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55 minutes ago, ibjet said:

I was shocked when I saw how terrible the exhaust system was as far as flow. As I remember my left front stack is the worst, it's mis-aligned and the curves do not transition smoothly either. I would think you could easily get 15/20% power increase with a smooth flow "header" system. But, then you have to think about heat build up and changing the prop to take advantage of the increased power. I am currently SLSA and don't really have extra cash to invest in this. But I totally agree that there is great potential for improvement there.

ET

PFFT!   15 to 20% That is 914 HP levels. Seams like if that was the case, rotax would know about it.

 

Sign me up because a new 914 is $30k.. 

 

 

 

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Two different exhaust experiments for a totally new exhaust. Good flight tests however now trying to reduce the noise level. Original rotax exhaust is aprox 100 dba. We are at 107 dba, difficult problem to solve without creating back pressure. These are strictly R&D to prove the design at this point.

20190803_200256.jpg

20190218_165429.jpg

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19 minutes ago, Madhatter said:

Two different exhaust experiments for a totally new exhaust. Good flight tests however now trying to reduce the noise level. Original rotax exhaust is aprox 100 dba. We are at 107 dba, difficult problem to solve without creating back pressure. These are strictly R&D to prove the design at this point.

Having quite a bit of experience designing exhaust systems for otto cyle engines, there are many programs out there(some free) that utilize CFD (Computational fluid dynamics) to tune the runner lengths to target a desired pressure wave. This can also be helpful if to tune the resonance to cancel out unwanted sound pressure levels while increase scavenging. 

 

Do these designs have a heat exchanger for the heater?

 

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Heater is easy but not necessary at this time.

As far as a tuned system the calculations are massive with a lot of very expensive test equipment including a dynamometer. Also it requires some engine mechanical data that I don't think Rotax would release. We are just trying to build a different system that works. There has been talk of dyno testing but that is in the future. It must be profitable first

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Skunkworks85 I was just remembering claims of HP increase when you replace a stock exhaust in a car with a header system. But, in those systems, you have room to put a muffler downstream from the free flow plumbing. This is a very complex issue! I love that kit that Warmi shared (http://www.rotax912exhaust.com/en/). If I needed an exhaust system, I'd buy that, cut everything to the size I needed, make a jig to hold it in place, and take it to my local welder. 

ET

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Talked to several people involved with the Flight Design as a business,  all seem to be open to better, cheaper parts but there will never be an MRA for these items. While SLSA is a good thing the unintended consequence is that the parts and prices are 100% controlled by the manufacturer. They can charge anything they want and there will never be any other option. Even items that have a patent eventually become open for anyone. So ELSA will will be the only legal way to use these parts unless the FAA changes the rules and that is not going to happen in anyone's lifetime.

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On 4/3/2020 at 6:22 PM, WmInce said:

They USED TO build good stuff at affordable prices. And their tech support is outstanding.

I fixed that for you.  Their stuff is still top-notch, but it's no longer a "more affordable" option.  They are right up there with Garmin pricing now.  The change seemed to happen when they went from "all in one" devices like the D-180 to the Skyview system, where they separated out the AHARS and other devices as individual (and pricey) components.  On the face the panel prices look the same, but once you add all the same capability the newer stuff is  2-3x more expensive.  Of course it includes capability like synthetic vision that the older panels never had, so I'm not saying there is no added value.  But Dynon went from an obvious option pricewise to a premium priced option, seeming overnight when Skyview came out. 

Just an observation, not a knock on Dynon.  As I said, their hardware is top notch, and I'm probably just jealous I don't have a newer panel in my airplane...  :D

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7 hours ago, ibjet said:

There was a new experimental amphibious airplane tied down in a shaded tie down when I went out to my hangar today. This is the kind of tuned exhaust that could give 15/20% more power to an engine. 

Screenshot_20200405-230341_Gallery.jpg

Interesting.  I don''t think I'd want my hot exhaust blowing on the back of my prop though!

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7 hours ago, ibjet said:

. This is the kind of tuned exhaust that could give 15/20% more power to an engine. 

Screenshot_20200405-230341_Gallery.jpg

 

you have to see it the other way,,,  you have the 100hp  WITH the tuned exhaust ( and airbox) ,  and loosing some power with an untuned exhaust

and THIS particular installation ( Titan Tornado, Searay ) is VERY Noisy....as there is no muffler. 

For practical reasons (fitting the cowling) , many  plane manufacturers  put the muffler in the back ( tractor configuration) .

Flight Design did very well with this as the 4 exhaust pipes length are very similar

 

The picture below shows a Sling 2 aircraft, they managed to have the rear pipes as long as the front ones.

Africa trip_13.JPG

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15 hours ago, ibjet said:

There was a new experimental amphibious airplane tied down in a shaded tie down when I went out to my hangar today. This is the kind of tuned exhaust that could give 15/20% more power to an engine. 

Screenshot_20200405-230341_Gallery.jpg

Exhaust (flow) is not the item that will increase the BSHP of an engine, A properly tuned exhaust will utilize the resonance of the exhaust pulses to improve the volumetric efficiency, (cylinder filling). meaning that the volume of 1 cylinder is 338 cc's, and 338 cc's of air/fuel mixture make it into the cylinder on the intake stroke then the volumetric efficiency is 100%,  this is almost next to impossible on a naturally aspirated(4 stroke) engine, most are running in the low %90's a perfectly tuned 4 stroke exhaust can improve that to maybe 96% but you are talking pre-turbo F1 cars. 

A 2 stroke can make above 100% due to the transfer ports being overlapped and the inertia of the air moving into the cylinder. but that is only at one specific range (power band) 

A turbo engine can increase the VE to whatever, until the ring lands decide to blow off.

 

My point is, there is no exhaust that will improve the 912 hp levels by 10-15%. maybe at best 2% with a highly designed system

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