[BFlyer]

Is there a difference between front and rear exhaust canisters of a given size in terms of noise reduction and engine power?

I am looking to use a pair of MTW75 front or rear exhaust canisters for a DA 100. These canisters are quite long (355 mm). The rear exhaust version is less convenient to install because of the added length of the exhaust pipe. However it appears to be closer to a tuned pipe than a front exhaust canister, so I am naively guessing that it allows the engine to develop more power than the front exhaust version would allow. Is my naive conjecture true or false?

I would appreciate any guidance on resolving this question.

[rpm]

In my opinion your conjecture is true but I don't have any numbers to prove it. I think it makes sense that rear exit cans will have freer flow. I have had both front and rear exhaust canisters and have been happy with both. Currently using MTW75 rear exhaust with a DA120 and it runs great. Have had DA100 with front exhaust cans and it ran great. I doubt you would notice very much difference, so it the front exhaust better suits the install I would do that.

[RAMJET]

On a 2 cycle they require an expansion chamber to optimize performance , all cans used on R/C models are way to small to have any real power affect . yes it may or may not cause the engine to produce power in a different place then a standard muffler but they are not even close to having a large enough volume to optimize performance to any real degree . as far as the exit port ,it is used more as a pressure relief valve to keep pressure constant in the pipe, This combination of a expansion chamber that should be equal to the expanding gasses (not possible in a R/C aircraft) and the size of the exit port need to be in balance to keep the incoming fuel charge from going straight out the exhaust port . The size of the can and the diameter of the exit port will have more effect then the location of the exit port . Pressure will drop at the same rate inside a tire no matter where you puncture it. LOL. cheers

[grizak]

You won't notice much (if any) difference in performance between an MTW front or rear dump canister.

If you really want to maximize performance, you may want to consider the MTW TD80 instead of the TD75 - the TD75 is essentially discontinued now. The 75s work very well - but the 80 is an improvement - it is slightly longer (just a few mms).

[BFlyer]

Thank you for all the advice. My next question is probably the subject of an ongoing debate. Do canisters improve or reduce the engine power output compared to standard mufflers?

John and Jase Dussia’s YouTube videos on Extreme Flight airplane assembly and setup show their preference for standard mufflers. Is it because of power, weight or engine spool-up time?

Interestingly the new Extreme Flight airplanes that use carbon fiber for fuselage structure don’t have canister wells. Is this because most customers install standard mufflers, or because modern canisters plus header pipes isolate the exhaust flow to the exhaust pipe really well?

[BFlyer]

I got MTW 80 canisters, which are probably too big for the two 50 cc cylinders in the DA100L. However I got a noticeable improvement in power over the standard mufflers.

[scaleguy]

And the added benefit that everyone in your club will appreciate.... quieter running then the standard mufflers

[RAMJET]

Originally Posted by BFlyer

Thank you for all the advice. My next question is probably the subject of an ongoing debate. Do canisters improve or reduce the engine power output compared to standard mufflers?

John and Jase Dussia’s YouTube videos on Extreme Flight airplane assembly and setup show their preference for standard mufflers. Is it because of power, weight or engine spool-up time?

Interestingly the new Extreme Flight airplanes that use carbon fiber for fuselage structure don’t have canister wells. Is this because most customers install standard mufflers, or because modern canisters plus header pipes isolate the exhaust flow to the exhaust pipe really well?

Tune pipes done correctly can increase power dramatically . but that power is focused at the specific RPM the pipes are tuned for . That's why the power curve on 2 cycles with true tune pipes feels very peaky (not the pipes used on R/C planes, they are more like mufflers ). The power on true tune pipes will feel very low until it get's onto the pipe then the engine jumps to life because volumetric efficiency can be as high as 200% on a proper pipe . With standard mufflers the engine will be much more lineal and quicker to respond at lower RPM but will generate less overall power then it could with a pipe . Pipes used in R/C are more noise reducing devices then true tune pipes , may gain you a bit of rpm at the top but at the expense of throttle response , fine if you fly at WOT all day or need your plane to sound like a moped but I prefer performance of plain old mufflers , good ones are not very loud ...

[Cougar429]

Ramjet, have to disagree regarding the comment RC tuned pipes are more like mufflers. Back in the 80's used to run a few, (had the only Eagle 63 with a tuned pipe!).

Performance was very peaky, sort of like the racing bikes back in the 70s where we taped up the bottom of the tach. If the needle disappeared you were off the power band.

Yes, that performance was enhanced, but from memory anything you gained at the top end was lost through the rest of the range so engine would be a dog until topped out.

[RAMJET]

Gary I have a ton of information on making tune pipes for given displacements and have made quite a few . For a 100 cc engine the pipe would have to be at least 6" in diameter and 3 ' long to have enough volume to be of any real benefit . For a tiny little .63 (10CC)engine it was possible to make a pipe with enough volume to be a benefit , but those pipes were huge in displacement compared to what they use on big R/C gas engines . With 100cc sized engines it's just not possible to house a pipe that big in a R/C plane . There is so much more to tune pipe design then this simple straight header pipe cut to a given length going into a can of a given displacement . Just because a pipe gives you a slight benefit at some point in the RPM range does not mean it's designed or working correctly . For example , All expansion chambers need to have a cone header pipe to work correctly . I have never seen this used on any R/C plane engine ever because they are not proper expansion chambers . Take a look at a Yamaha YZ 125 expansion chamber , it's massive . Can you imagine how badly the same bike wound be choked out using a straight header pipe going into a rectangle chamber from one side of a 200cc R/C engine, it would be a total joke , you would loose 10 HP , hell I have put a bad dent in My YZ 125 expansion chamber and the power went to hell . A 125cc 2 cycle set up correctly like the Rotax Kart engine produces 20-34 hp and rev's to 14,000 RPM . Like I said before what we are using are equal to moped pipes and have about the same effect , The sad output of R/C gas engines compared to what is possible is proof of just how restrictive these pipes really are . Saying that most R/C gas engines are plenty powerful for what they need to do . You just have to chose the pipe that suits your needs , if you fly mostly under 1/2 throttle and work the throttle lots ,standard mufflers would work best for you. If you take off and fly almost the whole flight at full throttle like IMAC pilots do you will need something to keep that noise down, and would also benefit from the slight power increase at the top end. . cheers ..