I have always already had this question-

2c OS glow engines always came with a baffle in the exhaust. Presumably, this is to reduce the sound output of the engine. But I was always told it reduces power output as well and since our field doesnt really have noise issues, I was always asked to remove it. Dont know whether it really makes a difference though.

Thing is, whichever engine I removed the baffle from, didnt last too long or was eratic in operation, whether due to the baffle or some other reason I am not sure. But some on the field insisted on leaving the baffle on for the 46 and 55 due to the next reasoning

Another point of thought is the location of the baffle- on smaller engines like the 46ax and the 55ax, the pressure nipple that pressurizes the fuel tank (vent line that goes back to the tank and also serves to push fuel to the carb) is located before the baffle whereas on the 75ax, the nipple is located after the baffle. Since the baffle definitely increases upstream pressure, this would mean the 46 and 55 require the higher vent pressure to work properly whereas the 75 isn't as dependent on vent pressure.

Just wanted to know everyone's thoughts on this issue

Ameyam

If there are no noise issues I would remove the baffle. In my experience the engine would then run a little cooler.

I never noticed a difference in the needle sensitivity due to the muffler pressure being reduced.

I experimented with this a while back on a Thunder Tiger .46 PRO (close enough to an OS .46). What my very limited work showed what that it depends on the RPM you're turning as to whether or not it will help. More flow is not necessarily a good thing since flow through an engine is all about pressure pulses. Changing the flow changes the timing of the pulses, so a more open passageway can actually restrict flow. What I found was that with a prop that gave me 13300 rpm peaked on the ground removing the baffle actually cost me 300 rpm. Given the greater noise it was a lose/lose. I didn't notice any difference in needle valve sensitivity although the settings did change. When I went down to less prop I got 14200 with the baffle in and 15000 even with it out. It makes sense that the manufacturers put the baffles in given that, since most sport pilots run their engines around 13k-14k rpm. It actually improves the power there, and it leaves the option to remove it for the pattern pilots and racers who want to let their engines unwind more.

I don't know about Pylon, but Pattern has specific noise limits and they do measure that at Pattern events.

As noted above, "noise issues" come up at some clubs. Ours has a noise limit established, even thouth we are not in any sort of n urban area. The neighbors, even though they are not very close by,l have complained about the full scale planes that come in - we fly at a New Jersey Forestry field where they bring in water tankers to help battle fires in the pine-barrens and the Wharton State Forest. And they attribute that noise with our models. We realie that all it would take is one politician to get on the side of the neighbors, we would be looking for a different place to fly.

As far as power differences, well, since I've never removed the baffle, I can't tell you if you would get any increase in power so I would have to let the RCU experts answer that question.

CGr.

Normally, removing the baffle increases the top end power at the expense of noise, idle smoothness and transition/mid-range (possible dead sticks). I do NOT recommend you trying this as a beginner or if you are not confident of a safe landing in the event of a random engine quit.
Advantages/disadvantages of exhaust alterations are all dependent on any given combination variables of engine model, prop load, fuel, glow plug, set-up and flying style. Change one thing and you could have an entirely different beast....good or bad. That's what half the fun is in this hobby, experimentation, but be sure you are up to that step first.

You can sometimes find a shortcuts by asking what's working on a specific engine. Give lots of details, plane, prop, glow plug, fuel brand-nitro-oil , current rpm, muffler(baffled?) desired results, flying style.

I've been hearing a lot of good stuff about Mac's new "high volume" one piece black muffler#6720 for the 55AX.

I had an OS 46 with that Macs muffler. It was excellent. It was on a plane bought as a "club trainer". It really wasn't a plane that needed a muffler like that, but it worked out just fine. The engine ran well and had lots of power.

CGr.

I have never noticed a nickles worth of difference but I only tested with the OS .46La engines. I used several of them during my fun fly days, the LAs. I did remove them from all my engines though but just because of vibration and the gray slime that comes out of the muffler when the baffle gets loose. Other then that there is no reason to remove them. I think this would be a good question for Bill Baxter from OS factory support? I know I never did any serious testing and no longer have any of the small engines with that type of muffler.

Who told you to take out the baffles?

Are you racing in competition when any and every micron in performance could mean the difference of a win or lose. Or are you just a sport flier out having fun?

If the engine is running fine and your happy with the power then why change things.

This plane the engine is on. Will it show a 10% change in engine power?

A high wing trainer with it's draggy flat bottom airfoil will not notice if you added a .10 displacement bigger engine.

If you want to get rid of the baffles then get rid of them. In fact get rid of that entire expansion muffler and get a tuned pipe if you want to see a real increase in power.

I had used the same original black muffler on both the 46FX and 55AX. The performance was ho-hum on the FX and lacking on the AX. I figured it was a good replacement for stock that wouldn't vibrate apart, also the plane for some reason or another seemed to have less smut on it (air stream more laminar?) , but no real perceptible power gain. Several guys now tell me the new larger volume black muffler works a lot better (55AX), but I have yet to try it myself.


The next level up are called "tuned" mufflers, such as Ultrathrust (discontinued) and the Jett-stream mufflers.
Be warned, some "tuned" mufflers can really add power and speed to the point that you exceed the plane's (trainer?) designed operating envelope and the plane's control surfaces can go into "flutter". This can quickly destroy the plane. Example: Kadet L-T40, whole horizontal stabilizer flutter or World Models Skyraider I and II strip aileron flutter using an OS 55AX ,Ultrathust muffler and Master Airscrew 11X7 S-2 series prop. With stock muffler/baffle these planes were fine. Some "tuned" mufflers can also have poor mid-range and transition characteristics.


I had a Evolution 46 NT on a Quickie. It ran best with the baffle in, but the baffle gets loose and beats itself to a pulp, I recall the gray silver slime.

Anyway watch out for these hot rodders at the field.

As Gray Beard will attest there are guys on here that will tell you
that a Sig 4-Star 40 "Designed for a .40 4-stroke engine" will only fly
well once you put a .90 sized two stroke in it.


"No way! Putting a Saito 40 in a 4-Star 40 is like putting a V6 in a Corvette"!

"You can always throttle back"!

"Why yes, I do have a 1,500 HP engine in my Ford Pinto".

Guilty,as charged. The slowest plane I own, but the fastest of it's kind. (anti-flutter mods!)

LOL! NO WAY! I thought you were just sayin! "Why yes, I do have a 1,500 HP engine in my Ford Pinto".

One, I am not a trainee- I have been flying since 2007 and though engine problems flattened my progression graph, I am a decent pilot. Dont worry about deadsticks. I have had so many of them on my 75ax and two 55ax I probably have more deadstick landings than normal ones. Things only began to improve once I got my current FS91SII and Dle20 (though I have had a deadstick on the dle as well but that was due to debris in the carb fuel filter)

Two, I am more a 3d pilot when it stays running, so midrange would be more important. But most of all, they must keep running. Mine tend to lose compression or quit (No, I havent tested the refurbrished 75ax yet)

Three, even my trainer is semi-symmetrical wing 65" span. In fact it can do everything in the book other than 3D and I have done lots of pattern flying with

This post was simply to find out what others do.

I still wonder, why does the 46/55 have the nipple before and the 75 after the baffle. Oh, by the way, we use mostly the power box silencers that come with the OS engines

Ameyam

I can't recall the last time I had a dead stick but I do know what plane it is, it only happened during the set up of the plane during all the trim flights, that was over a year ago. It was a plane problem and not an engine problem from the start so it doesn't really count anyway. I had to install the fuel tank way too far from the engine due to the planes design, a scratch build.
It is my only two stroke in use too, the SK .91. The SK muffler is a copy of the Ultrathrust and has no baffle.
If you are having dead sticks then you are having other problems that have nothing to do with the muffler. You should never have a dead stick with the DLE unless you have something like an ignition or spark plug problem.
Dead sticks happen because of a reason and it isn't the muffler.
AMISH, I'll bet you big money you don't have the original door handles inside the Pinto!!! I drove them when they were new and have a lot of memories about them!!

1500 HP???

Might want to have your dyno calibrated.
Looks like fun though.

Scott Mooney]
Scott Mooney Racing Engines