What are the differences between these two below. Both are Mac exhaust. One is just a muffler and the other a tuned pipe. But the black muffler looks very similar to a tuned pipe? So what's the differences?

The tuned looks to be heavier and more un-aerodynamic.

The black one is a muffler -- just that. It doesn't give notably better engine performance than a stock muffler, although it weighs considerably less and has slightly less frontal area.

The tuned pipe is a performance enhancing tool for particular applications. It can boost HP quite noticeably, but in a narrow RPM band. It ain't an everyday exhaust system.

Here's more than you probably ever wanted to know about tuned pipes:
http://www.findarticles.com/p/articl...4/ai_n13498021
This is written for boaters, but the principles are the same for any 2 stroke motor. The pipe acts as a sort of supercharger. Tuned properly, it packs air/fuel mixture into the cylinder of the engine, increasing HP. They were used a lot on older pattern airplanes until the .60 engine restriction was lifted. Larger engines in a lower state of tuning seem to be the ticket today.

I'm not sure but that the Mac's mufflers aren't designed as a kind of 1/4 wave pipe. In the applications where I've seen them used, they do seem to boost power over a stock muffler, just not as much as a pipe.

Pipes can also serve as a kind of regulator of power output in certain applications, and can be very effective as mufflers. The long Hatori pipes of the late 80's helped quiet the noisy pattern planes down a lot by allowing lower RPM operation with bigger props.

Okay, so the black Mac muffler is more aerodynamic and a little better power wise than a stock muffler. And the Mac tuned pipe is best for power output, but a little less aerodynamic and probably weighs more.

I plan on putting this on my TT .46 in a F-20 tigershark speed prop plane. I know that HP/RPM is important to speed, but so it weight and drag....not to mention wing loading the heavier the plane....

Anymore opinions?

Hi!
Get at (small) magic muffler from Dave shadel at Performance specialties in Nevada instead!
You will get around 15-20% more power with one of those (same as with the long tuned pipe in your picture) but in a much smaller package (more like the black silencer in your picture which is no good... and terribly loud). Or get a MVVS mini-pipe and make an adapter to make it suit your engine and get the same power increase as with the Dave Shadel pipe (15-20%)but a lot cheaper.


Regards!
Jan K
Sweden

Change out the stock engine bearings for some high-perf units

Has anyone recently tested the Mac's black muffler on a .46? I recall I did a single test several years ago on a Thunder Tiger .46 and either lost rpm or got nothing extra. I also remember I tested the .61 size on a TT .61GP and lost 500 rpm over the stock muffler. As a result of these, I ditched all my black Mac's. Maybe they have changed.

Lost power over a stock muffler?! Wow. I don't want that...

What about the Jett mufflers?

I want a muffler or pipe that will provide power, low mass, and fairly aerodynamic. I don't care how loud it is...