Has anyone done any experimenting with drilling the exhaust hole on a macs muffler?

Reason im asking is The macs muffler is for the 40-46 size engine and im running it on an OS50sx and was just wondering if the larger motor would benefit from a larger exhaust opening.

KennyRoy,

The Mac's one-piece costs $34 at Tower and adds no power.
If you de-baffle and drill the stock 783 silencer, you will get just as much power gain as drilling the Mac's, without wasting a dime.

The only advantages of the Mac's one piece are its size and weight.

Using even a rudimentary tuned system, like the Tower/Hobbico .46 muffler ($15) will give you much more power than you will save, with the light Mac's; about 400-1,000 RPM.

If you want a lot more power, the very expensive Jettstream and Ultrathrust are only $20-$25 more than the no-gain Mac's.

I run a Mac's on my OS.46 and I can tell a noticable difference in power. The verticle performance of my plane was greatly improved.

Shawn,

If your standard silencer was in standard form, i.e. with the baffle in place, you would notice a 300-400 RPM change, as you would if you removed the baffle from the standard silencer. In addition, the Mac's one piece weighs less then the standard silencer. If you fly a light 3-D model, you would notice, but it is in my first post.

Even Mac's themselves don't claim any power gain. They have full length tuned pipes that can realize real gains in power.

The original un-baffled silencer and the Mac's one piece are within about 100 RPM on most props.
This difference will be maintained if you drilled the exit hole larger on both.

Real power is made with products that are intended to make it and not in all case. It is not made with products not claimed to make more power.

See Jett, Nelson and other Performance products manufacturers' advertisements.

The main reason i got the macs pipe was the weight savings and its small size. Changing the muffler brought my plane down to 4lbs 1oz. plus was cosmetically more appealing.

I was already running the factory muffler with the baffle removed (OS46 on this plane) i know macs doesnt advertise any power gian but i got a 400 rpm increase (not much but a little) might possible say it was because needle valve tuning, but i dont think so. Could instantly tell a difference in power when i stood the model vertical, im sure the difference in weight helped here, but i think it has alittle more power too.

On a 3d model a "tuned pipe" doesnt give the effect i want. Makes the pwer band "peaky" for lack of a better way to describe it. Plus a big tuned pipe is heavy.

Thanks for all comments so far.

Know back to the 50sx and the original question. Has anyone done any experimenting with drilling the exhaust hole on a macs muffler?

Reason im asking is The macs muffler is for the 40-46 size engine and im running it on an OS50sx and was just wondering if the larger motor would benefit from a larger exhaust opening.

Kenny,

Increasing the exit hole diameter will increase the power, as well as noise.
At its high price and low power gain, I would not say the Mac's is a worthy investment.

But if it is good for you, who am I to doubt it.

A tuned pipe (full length) is not suitable for a 3-D model, unless it is tuned to aid the engine at mid-RPM.

A wide range tuned silencer, like the MVVS #3248 is much more suited for this purpose, but you will have to supply the header.
I believe Mac's makes one that is suitable for the .50SX, or you can make your own.

I won't get into the question of performance, but to answer your question, I have modified several mufflers to fit engines with holes that didn't quite match up. The only question is if there is enough edge distance. Simply drill and tap the existing holes for the next larger size screw, Then screw in aluminum screws of the size you tapped using loctite. Cut the alumimum screws flush on both sides of the flange. You have now plugged the existing holes. If the muffler uses through bolts, layout and drill new holes to fit the engine. If it is tapped to recieve screws through the engine flange, layout, drill and tap new holes to fit. The job is simple if you have a drill press to assure the accuracy of the machine work but can be done freehand if you take care. I don't have a MACS in the shop now, but the picture shows an in-cowl muffler modified to fit an engine with a closer screw pattern. You can see where the original holes have been plugged.

I had one on my TT .42GP and got maybe 100 r.p.m. more after I drilled out the opening. The performance was about equal to the mod. stock (drilled tailpipe,radioused the inside of the tailpipe opening, and streamlined the baffle) muffler, but I think it looks a lot cooler[8D], and as mentioned, it's lighter. Both gave about 200-300 r.p.m. increase over the stock un-modified muffler...

I'm running the macs one piece muffler for super tigre 40-45 on my 51 tigre and had no problems with it.

Roei,


Nobody here said anything about problems.
There is absolutely no reason you should be having any.

The question was about the power boost resulting from the 150~ NIS that you wasted for the unit.

The information provided here says that you may get about 100 RPM, in identical conditions, over the baffle equipped, standard OS muffler (not your Super-Tigre).

On the price/performance issue, this item is a failure. It may be light, comfortable, convenient and even attractive, but no cigar in the high performance field.

A model engine is not the most streamlined and beautiful part of the average model. It is the "business end" of the plane.
Anything that does not add a significant, positive functionality to the engine (more power, less noise, better fuel consumption, better idle, better transition), is all but useless.

The weight advantage is about 50 grams; significant, but too small to be paying so dearly for.

HI Dar,

You right about the price to value issue.
The only reason i got one is because the awful and stupid design of the super tigre muffler.
I'm didn't bought from any power reasons and now that i'm running it i can that there is no difference and no power boost.

But, now i can fly normally and i don't need to worry to lose my muffler and my model.
The Macs muffler really light compare to the ST, now i got a better performance because the nose of my model is light.
It don't break apart like the ST and quick to assemble it.

I need to take a look on it again and to see the issue about the drilling.

Hi Roei,

The fact that the Mac's one-piece solves your Super-Tigre's "break-apart" issue, is definitely an added functionality.
So you are with what I just wrote.

But if you want to add some real power too, your similar price options are quite limited.

The Jettstream and the Ultrathrust tuned silencers are much more expensive.
I am not sure if the Tower/Hobbico .46 muffler will fit the Super-tigre, although Adrian says it will.

This can be checked. The MVVS will require you to fabricate (or buy) an appropriate header.
The one that comes with the MVVS tuned silencer, only fits the much narrower MVVS exhaust stack.