MVVS engine muffler tests.

Jan 22, 2008 ,
With the standard 58cc engine I did some muffler tests in order to define the best header length for the MTW RE2 tuned pipe, and to compare the power output with other muffler systems.

Mufflers tested so far:
MVVS 3204, THE standard MVVS muffler, optimized for operation below 6500 rpm. Low rpm are needed to keep the noise down.
Krumscheid  KS94-4, Their 4-chamber canister muffler
MTW RE2, The MTW tuned pipe for 40 - 60 cc engines. tested with 500mm, 400mm and 300mm header length.

The propellers in my test ranged from 21" to 24" two and three blades, for rpm between 5500 and 8000. These props are only used for testing. and have been extensively measured for pitch and power absorption to produce clean power curves.
Test props: (all 3W props are wood).
Mejzlik 24x10x3 carbon
Mejzlik 23x10x3 carbon
Mejzlik 23x10 carbon
Menz-S 24x12 wood
3W 24x10.2
3W 24x8
3W 21x12
3W 21x10

Interesting side note:
When testing the tuned pipe with different header lengths, props that did not allow rpm at above best torque values sagged in rpm when the pipe came up to operating temperature.
Probable explanation: When the pipe gets hot, it's tuned rpm range shifts towards higher rpm, taking the peak torque rpm with it and away from the prop power demand. In a hot pipe the prop therefore had lower available torque, and rpm sagged a typical 200 - 400 rpm.
The reverse was true for props that turned above the best torque rpm. They gained 100 - 300 rpm when the pipe got hot, because the torque peak moved to higher rpm, thus pushing prop rpm upward.
This way, very large props can be set up for totally non-sagging operation by just adding some extra header length. The same is true if the prop operates at rpm just above the 3/4 rpm power hump. (see curve for RE2 tuned pipe at 300mm header length)

Test data:
:
goto graph