Muffler upgrades

[hlondono111]

Hello, I have a Tiger 2 with an EVO .46 and it flies like a bat out of hell, I am still a begineer and I don't do to much acrobatics, but I was wondering what the difference is with upgrading to a different muffler pipe, I see people flying arround with this huge pipes and I was wondering if these make the plane fly faster or just louder?

[ivanc]

Depends what you mean by "huge pipes". If you mean long pipes - these are called tuned pipes which improve the engine performance mainly by increasing the rpms - that's why they scream. They are good for fast planes. For pattern and 3D you do not need a lot of speed (for 3D you do not need speed at all) so you wouldn't see them on such planes. Some engines are not designed for use with tuned pipes - they usually break conrods, crankrods, crankshafts. The tuned pipe also increases the wear on the engine. Of course there are engines specifically designed for use with tuned pipes - they simply cannot work reliably without one.
Other than that there are also tuned mufflers (shorter that the tuned pipes), mousee (not sure if I spelled it right) can mufflers, etc. They have a similar to the tuned pipe function but in much less degree. For example current Tower engines are equipped with tuned mufflers so they scream a bit. You can even mount a Tower tuned muffler on a OS46FX/AX and it starts screaming too.

[DaveSawers]

The idea of tuned pipes is to produce more power. Their effect is similar to turbocharging in that they increase cylinder pressure and hence how much fuel/air mixture is burnt on each cycle. More power doesn't necessarily mean more speed or more noise.

Adding a tuned pipe doesn't necessarily improve performance. They have to be carefully setup for the engine and prop combination you are using. On some engines, they won't make any noticeable difference no matter how carefully they're setup.

[PureEvil]

The idea of tuned pipes is to produce more power. Their effect is similar to turbocharging in that they increase cylinder pressure and hence how much fuel/air mixture is burnt on each cycle. More power doesn't necessarily mean more speed or more noise.

Adding a tuned pipe doesn't necessarily improve performance. They have to be carefully setup for the engine and prop combination you are using. On some engines, they won't make any noticeable difference no matter how carefully they're setup.
I believe a tuned pipe is more like a car header. A turbocharger puts positive pressure into the cylinder. A tuned pipe is no more than a pipe. It cannot put positive pressure into the cylinder. A tuned pipe is used to increase the scavaging effect, which will pull in a cleaner charge of air/fuel into the cylinder, not force air into the engine. Without a tuned pipe, more of the exhaust gases stay within the cylinder limiting the amout of fresh air and unburnt fuel in.

[ivanc]

PureEvil, don't be so harsh on Dave - I think he is figuratively speaking. Yes the tuned pipe improves (greatly when properly tuned) the scavenging of a 2-stroker but this is the beginners forum, so I suggest we keep our explanations simple.

[DaveSawers]

I believe a tuned pipe is more like a car header. A turbocharger puts positive pressure into the cylinder. A tuned pipe is no more than a pipe. It cannot put positive pressure into the cylinder. A tuned pipe is used to increase the scavaging effect, which will pull in a cleaner charge of air/fuel into the cylinder, not force air into the engine. Without a tuned pipe, more of the exhaust gases stay within the cylinder limiting the amout of fresh air and unburnt fuel in.

I'm afraid that's not correct.

A tuned pipe works because when the exhaust port opens, a shock wave (a pressure wave) travels the length of the pipe, bounces off the end wall of the pipe and travels back towards the cylinder. As the shock wave travels away from the exhaust port, it creates a negative pressure behind it that sucks out all the burnt exhaust gases and some of the next cycles fuel/air mixture. As the shock wave travels back towards the exhaust port, it pushes some of the fuel/air mixture back into the cylinder creating more presure in the cylinder than you would get from normal aspiration. JUST LIKE A TURBOCHARGER.

The trick in getting tuned pipes to work is to get the length of the pipe exactly right so that the shock wave arrives back at the exhaust port just as the exhaust port is closing.

Most of the theoretical work on tuned pipes was done on motorcycles. Do a search on the Internet to read more.

[ivanc]

This is the best explanation I've ever read on tuned pipes! Thanks Dave!

[DaveSawers]

Thanks :D

I wrote an article on this several years ago. I think I might put the gist of it in a topic in the Engines forum for general information.

[hlondono111]

Can I put a tuned pipe on my Tiger 2 with a Evo .46?

[PureEvil]

PureEvil, don't be so harsh on Dave - I think he is figuratively speaking. Yes the tuned pipe improves (greatly when properly tuned) the scavenging of a 2-stroker but this is the beginners forum, so I suggest we keep our explanations simple.

I didn't mean to come over harsh. I apologize for that.

[PureEvil]

I'm afraid that's not correct.

A tuned pipe works because when the exhaust port opens, a shock wave (a pressure wave) travels the length of the pipe, bounces off the end wall of the pipe and travels back towards the cylinder. As the shock wave travels away from the exhaust port, it creates a negative pressure behind it that sucks out all the burnt exhaust gases and some of the next cycles fuel/air mixture. As the shock wave travels back towards the exhaust port, it pushes some of the fuel/air mixture back into the cylinder creating more presure in the cylinder than you would get from normal aspiration. JUST LIKE A TURBOCHARGER.

The trick in getting tuned pipes to work is to get the length of the pipe exactly right so that the shock wave arrives back at the exhaust port just as the exhaust port is closing.

Most of the theoretical work on tuned pipes was done on motorcycles. Do a search on the Internet to read more.

Thats very interesting. Learn something new each day. :) I am an auto tech by trade, graduated from wyotech in 94' and have never heard of this theory before. Post up your article for me to read! lol i wanna know more. i just might have to fab a pipe up for myself.

[DaveSawers]

Can I put a tuned pipe on my Tiger 2 with a Evo .46?

You can try it if you need more power. It may not give you much improvement though.

[Joe Ford]

Dave I run tuned pipes on my pylon planes. However, at partial throttle they dont work well...the motor isnt "running on all cylinders" so to speak. If this is a 3D, trainer or aerobatic aircraft wouldnt it be better to put something on it like a Mac pipe...the little black ones? (Sorry dont know their official name as I've never owned one) I believe they give a better "all-around" performance increase without sacrificing low end power etc. Yes? Many of my club members use them on their ultra sticks and can blow me away with my stock muffler.

[DaveSawers]

The main thing that makes a tuned pipe "peaky" (i.e. not work well at all throttle levels) is the exhaust timing. This is ignoring for the moment the design of the actual pipe. High performance motors have a longer exhaust timing than sport motors which means the exhaust port stays open longer so the pipe can get more fuel/air mixture in there. Since the piston is well on its way up when the exhaust port closes, if you don't get that pressure wave exactly right, it won't run right. At partial throttle, the timing is all wrong so it runs roughly or not at all.

The small pipes such as the Macs and the ones you get on Jett and Nelson motors are half wave pipes which means the pressure wave makes two trips to the end of the ppe and back while the exhaust port is open. They are often designed for a specific engine/prop/model combination which is why they work so well. On a sport motor, the whole setup is anyway less critical and you often get a performance boost simply by installing one.

Would I recommend tuned pipes for anyone who doesn't understand why they're adding one? No.
Would I recommend one of the add on half wave pipes for beginners? No. Usually the last thing they need is more power.