I would like to shorten the 3" long single stack on my G20's Brillelli side dump muffler by approx. 1" but would like to know if doing so would reduce it's performance in any way.

Karol

If you are shortening it so the cowl slips on better, you can cut the stack inside the cowl short then use silicone heater hose or the silicone exhaust stack hose Tower sells to re-connect it once the cowl is on. http://www3.towerhobbies.com/cgi-bin...?&I=LXRVB9&P=0
Lots of choices...http://www3.towerhobbies.com/cgi-bin...7&C=GMCTRA&P=0

Better ask Scott, he would know.

My guess would be yes, it would reduce performance.

It won't change a thing, only make it easier to work with the cowl. The engine is not tuned to the muffler.

Thanks guys.

Karol

And the muffler is not tuned to the engine ......................

Do you think that shortening the stack might make it noticeably louder ??

Karol

I would hate to think I'm buying mufflers at these prices that don't take into consideration the motor they are going on.

Do you really think they design mufflers for looks rather than performance?

I don't know, I'm just asking.

Put 5 different side dump or wrap around mufflers on an engine and get 5 different rpm readings. And no, the side dump muffler is not tuned to the engine. It is a bare minumun device designed to reduce sound levels and does a crappy job in the process. If an engine is marketed with a side dump muffler it's to make it easier for the customers and for the seller to make more money. Take the muffler off and power will increase. An engine would have to have an incredibly short wave length port timing to benefit from having an expansion chamber placed so close to the exhaust port.

Both a standard side dump and wrap around Pitts mufflers are little more than exhaust deflectors with a spark arrestor. There's nothing inside them to help anything. Want to put that to the test? Tach the engine with and without a muffler. Spend a few bucks and to that test with mufflers from a few different manufacturers. Get back to us with the revelation.

Can you improve on them? Sometimes, but the outlet pipe length isn't going to make a difference. Diameters might, but not much. Punching out the spark arrestor usually helps a little. None of this applies to the old B&B mufflers. Those always reduced performance.

There are divisions in go cart racing where all you can run is a can.

There has been a lot of R&D on a tuned can. In lew of an expantion chamber.

I just assumed ..........

The bad news is I have an old B&B muffler on a US 35. [&o]

I did just enlarge the exhaust tubes 3/16th of an inch.
I should get it back from the welder tomorrow.

Thanks Guys

Most everyone would jump at a relatively free power increase so here comes the 64 million dollar question, is there any way that I can increase engine performance while sticking with the side dump muffler.

Karol

In it's stock form, not really. You need to make significant changes to the muffler for that to happen. Exhaust flow needs to be better directed, header length between the cylinder and the muffler needs to change. outlet diameter generally needs to increase. Performance increases occur with $$ investment increases. That has never changed. However, some mufflers work better than others and finding the one muffler takes time and money unless someone has already done the leg work. I know that a J&A wrap around Pitts provides more power at a somewhat lower noise level than a Bisson of the same type on a 50-52cc engine, while an Abell muffler has a noise level similar to having no muffler while equalling Bisson Pitts performance. Other engines have different quirks. The right side dump mufflers do slightly better than wrap arounds.

The B&B requires more than a pipe size change. It also requires that the outside of the muffler be moved quite a distance farther away from the cylinder exhaust port and the muffler volume increase. The old B&B have the outside of the muffler where the exhaust is forced to make a 90 degree change of directions much too close to the exhaust port. Throw a rubber ball at a wall at a 90 degree angle and see where the ball goes. Directly back at the point of original release. So what you have is a reflector consisting of super heated gases. Think about what that's doing to your engine. Most general use mufflers have a similar problem but to a lesser extent.

The typical muffler was designed and created to re-direct exhaust gasses and to slightly lower noise levels. They weren't designed for performance enhancements. They do the job they were intended for but to obtain more from them is unrealistic. It's better to obtain an engine in a size that will provide the required power by itself than to buy an undersized engine and hoping additional power to meet the need be found in tricking the exhaust. It can often be done but at a weight and money penalty. The D 85 has changed that to some extent since it was designed around different parameters from the basic "industrial use" cylinder.

With only a few exceptions most of the engines on the market use cylinders with port designs originally intended for industrial use applications. DA, 3w, MVVS, RCS, and a couple others have been designed or modified around model use, the rest were not. To obtain additional performance from them takes some time and money.

Well said Pat, and that says it all...............

Yes I do agree..... thanks Pat.

Karol

I would love a muffler that has some baffling in it to actually "muffle" the sound. It is a muffler after all! Some of the gassers are just ear splitting loud. I'm building a large sea plane for up at our lake cabin and I'm pretty sure the cops and DNR would be at my door in a matter of hours if I was buzzing around at the current DB levels some of these run at.

My experiences have shown the J&A to be one of the best if they alreay have one available for your engine type. I have not yet tried a J-tec so it's definately worth looking into. For quiet with a performance benefit you need to step up to a short cannister type. From there you end up at tuned systems.

I'm going to do a search and see if I come up with information that might assist me in making a home made can type muffler. Just the tinkering spirit in me that is awake and looking around for something constructive to do.

Karol

I currently have a Cap with a DL-50 with stock "muffler" on it. My friend flies a Yak witha DL on it as well, but has the new Jtec wrap around on it. While it is slightly quieter, it is stil quite loud.

Check out the thread Altavillan started about the Bud can mufflers. I've flown with him and his creations and they work out quite well after some pipe length experimentation.