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Rotax 912 Muffler?


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Is there such a thing as a ‘stealth’ muffler for the 912? If not, has anyone modified one for less noise, bearing in mind any power loss or drastic weight increase?

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Is there such a thing as a ‘stealth’ muffler for the 912? If not, has anyone modified one for less noise, bearing in mind any power loss or drastic weight increase?

CKT make a quite muffler. I have one and always get told how quite it is. Same comment when I over flew and landed at a forum members airstrip last Saturday.

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Wow ! you want quieter than a standard Rotax muffler ?

 

My muffler is an off the shelf Rotax 912 ULS job. My aircraft is so quiet I have fitted a siren to get the attention of those on the ground, particularly when contemplating a landing - my "problem ?" is the opposite of yours.

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Talking of this (and sorry, don't want to hijack the thread) - when I bought the second hand 912 he threw in the new muffler, donuts and pipes to make up a new system. (The motor was from a training aircraft with existing muffler in good condition - it made sense for him to keep the old one in place with the new engine).

 

I'm planning the pipes at the moment - as the entry points in the muffler are closer together than the exhaust ports on the engine, the pipes have to angle inwards as they meet the muffler (see picture attached).

 

I know there's a ball-end on the pipes that allows some rotation from straight into the muffler, but am I better off putting a bend in the downward leg of the pipe so the ball end seats straight into the muffler?

 

If you know what I mean!

 

2098198174_Mufflerdrawingincomplete.thumb.jpg.f9ac755700eeb061bbc6881dfa5e9de6.jpg

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Suggest you check out a number of Rotax 912 installations to get the best "feel" for this.

 

You may find that other factors will influence where and how much you "bend" eg oil filter clearance to facilitate installation /removal without having to loosed/remove the corresponding "pipe"

 

In the end having a good "ball & socket" alignment into the muffler is more important than how much you have had to bend the pipe to achieve clearance (probably a bit of a compromise will be required)

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Talking of this (and sorry, don't want to hijack the thread) - when I bought the second hand 912 he threw in the new muffler, donuts and pipes to make up a new system. (The motor was from a training aircraft with existing muffler in good condition - it made sense for him to keep the old one in place with the new engine).

 

I'm planning the pipes at the moment - as the entry points in the muffler are closer together than the exhaust ports on the engine, the pipes have to angle inwards as they meet the muffler (see picture attached).

 

I know there's a ball-end on the pipes that allows some rotation from straight into the muffler, but am I better off putting a bend in the downward leg of the pipe so the ball end seats straight into the muffler?

 

If you know what I mean!

 

[ATTACH=full]53179[/ATTACH]

Don’t forget to make you can still get your oil filter off and on again with regard to the front left pipe.

Mine has a bend that seemS to be for no reason until you pull the oil filter.

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Wow ! you want quieter than a standard Rotax muffler ?

 

My muffler is an off the shelf Rotax 912 ULS job. My aircraft is so quiet I have fitted a siren to get the attention of those on the ground, particularly when contemplating a landing - my "problem ?" is the opposite of yours.

 

My idea is not to piss the local residents off when using my private airstrip, I like minimal noise, even with my cars:-)

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My idea is not to piss the local residents off when using my private airstrip, I like minimal noise, even with my cars:-)

 

With my standard Rotax muffler my neighbours never seem to know when I am taking off (the noisiest time), dont even look up when I fly overhead.

 

If I want native/domestic animals or people off my paddock/strip, I have to do a very low level pass and/or use my siren or phone family to remove offending objects

 

One additional point : Propeller noise can be/is a big contributor to aircraft noise pollution- I use a Fiti two blade ground adjustable - subjectively sooooper quiet.

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Your prop noise is mainly due to some part of the blades going supersonic. Prop RPM's, forward speed and blade dia and to a lesser extent prop section and material. Not an issue with most U/L's. On higher horsepower stuff it's a significant part of the noise envelope on take off particularly. Nev

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Your prop noise is mainly due to some part of the blades going supersonic. Prop RPM's, forward speed and blade dia and to a lesser extent prop section and material. Not an issue with most U/L's. On higher horsepower stuff it's a significant part of the noise envelope on take off particularly. Nev

 

Cant explain why Jackc's aircraft seems noisy (to him) when mine, with same engine & standard muffler, is so quiet - so have started down alternative explanation track (propeller ?). Other factor could be related to prop wash/pulses against fuselage, bit unlikely but there you go,running out of possibilities.

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Talking of this (and sorry, don't want to hijack the thread) - when I bought the second hand 912 he threw in the new muffler, donuts and pipes to make up a new system. (The motor was from a training aircraft with existing muffler in good condition - it made sense for him to keep the old one in place with the new engine).

 

I'm planning the pipes at the moment - as the entry points in the muffler are closer together than the exhaust ports on the engine, the pipes have to angle inwards as they meet the muffler (see picture attached).

 

I know there's a ball-end on the pipes that allows some rotation from straight into the muffler, but am I better off putting a bend in the downward leg of the pipe so the ball end seats straight into the muffler?

 

If you know what I mean!

 

[ATTACH type=full" alt="Muffler drawing incomplete.jpg]53179[/ATTACH]

Hi Marty you will need to lube the ball ends every 100 hours so each second oil change, so not a big issue even if you had to do every oil change.

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H

My idea is not to piss the local residents off when using my private airstrip, I like minimal noise, even with my cars:-)

Hi Jack Re exhausts I’m prepared to bet a carton of beer that my standard CKT exhaust noise is quieter than any standard Rotax exhaust setup. So for quietness they are worth the money and top shelf quality made.

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H

 

Hi Jack Re exhausts I’m prepared to bet a carton of beer that my standard CKT exhaust noise is quieter than any standard Rotax exhaust setup. So for quietness they are worth the money and top shelf quality made.

 

I take they have to be imported? Or available locally?

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To make your Rotax quieter just add a turbo. My CTLSt 914 with constant speed Neuform prop is very quiet to the extent that my next door neighbor even commented on how little he can hear it.

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Wow ! you want quieter than a standard Rotax muffler ?

 

My muffler is an off the shelf Rotax 912 ULS job. My aircraft is so quiet I have fitted a siren to get the attention of those on the ground, particularly when contemplating a landing - my "problem ?" is the opposite of yours.

 

Hi skippydiesel,

 

I have trouble getting sheep off my strip sometimes and have thought of a siren also, can I PM you for details.

 

Cheers,

 

Dean

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I also had to fit a siren to get the wildlife off the runway. I used a burglar alarm siren from the local Jacar electronics aviation supply company. it is surface mount 12v piezo and uses very little current. I screwed it to the firewall. Use a mini toggle switch with supply from the landing light circuit.

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Hi skippydiesel,

 

I have trouble getting sheep off my strip sometimes and have thought of a siren also, can I PM you for details.

 

Cheers,

 

Dean

I also had to fit a siren to get the wildlife off the runway. I used a burglar alarm siren from the local Jacar electronics aviation supply company. it is surface mount 12v piezo and uses very little current. I screwed it to the firewall. Use a mini toggle switch with supply from the landing light circuit.

 

Hi Farmpilot/Dean - Just like Dean I am using a car (12v) burglar alarm siren, mounted on the firewall/undercarriage frame, as close to my cowling air exit as feasible. I use a press switch from JayCar (press on/release off), In my case came out of an old Mercedes wreck, I purchased for parts. So origin unknown but definitely an after market, not an MB original. I started with a motor bike horn but it wasn't quite laud enough. There are heaps on the web, unfortunate you have to take their word and give them the dough, befor you find out how laud they are.

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Hi Farmpilot/Dean - Just like Dean I am using a car (12v) burglar alarm siren, mounted on the firewall/undercarriage frame, as close to my cowling air exit as feasible. I use a press switch from JayCar (press on/release off), In my case came out of an old Mercedes wreck, I purchased for parts. So origin unknown but definitely an after market, not an MB original. I started with a motor bike horn but it wasn't quite laud enough. There are heaps on the web, unfortunate you have to take their word and give them the dough, befor you find out how laud they are.

 

CT9000, skippydiesel.

Thanks for your reply’s. I’ll do a bit of horn hunting online.

Cheers.

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That's pure fun to read for a Swiss: Chase the sheep from the landing site. We are only allowed to land on aerodromes and airports (except if the fan stops). And on a defined set of glaciers, if you have got the endorsement for that.

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That's pure fun to read for a Swiss: Chase the sheep from the landing site. We are only allowed to land on aerodromes and airports (except if the fan stops). And on a defined set of glaciers, if you have got the endorsement for that.

It's not uncommon here to have kangaroo hazards and such on aerodromes.

 

https://www.crc.id.au/xplane/charts/ERSA-2020-FEB-27/Moree%20(YMOR)%20FAC.pdf

https://www.crc.id.au/xplane/charts/ERSA-2020-FEB-27/Caboolture%20(YCAB)%20FAC.pdf

https://www.crc.id.au/xplane/charts/ERSA-2020-FEB-27/Dalby%20(YDAY)%20FAC.pdf

https://www.crc.id.au/xplane/charts/ERSA-2020-FEB-27/Millmerran%20(YMMN)%20FAC.pdf

https://www.crc.id.au/xplane/charts/ERSA-2020-FEB-27/Pittsworth%20(YPWH)%20FAC.pdf

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