Back pressure is different than muffler pressure. Muffler pressure goes into the tank and is not allowed in profile. Back pressure is a restriction to the exiting exhaust gasses. It could be created by a muffler, or by a variable rotary or butterfly exhaust restrictor. Back in the dark ages when mufflers weren't used and carburetors were primitive, exhaust throttles were used alone or in conjunction with carburetors. Both devices limited the airflow through the engine; carburetors on the inlet side of things, exhaust throttles on the outlet side.
All that being said, if you are running a good quality modern carburetor (translation: OS) on suction, typically you can make your engine work with open exhaust. I ran a Webra rear intake 61 for many years on straight suction using an OS 4E carb. This carb has a 10 mm bore, and perked up the engine quite a bit compared to the stock Webra carb, which also ran very nicely. I believe I had to drill the needle seat out very slightly to get it to run rich, but I was also running 50%. On low nitro it may not be necessary to drill it out.
As an aside, I really love the sound of an engine with an exhaust throttle. Someday I may have to build something for nostalgia just so I can use an old Supertigre with the "bow tie" on the exhaust.
Topic: Mufflers for Carrier engines (Read 547 times)
