professor
Active Member
This style muff will go on my weedwacker engine so I decided to adapt it- temporary for this test- to the featherlight weedeater that is going to power my gas-electric bike.
The muffler has only 2 little gills to get the exhaust out of the stock muff. The actual muffler is inside a heat baffle (pretty cleaver, cooling air from the fan is blown thru this baffle around the muff.
I had to seal up a pipe around where the gills go to be able to attach it to an added on muffler.
Here is a pic of the amazingly small outlets:
The inlet is about an inch by a half.
I pryed open the gills some and added (maybe shouldn't have) a hole next to them. Covering these is a section of weeedeater shaft (super thin 3/4 outside dia.) that I split for a bit and braized onto the muffler. I had not realized the silver color is aluminization. The alum. does not like to burn off. I thought the stuff was zinc (don't breathe the fumes for that either), after seeing the miserable time I was having, I ground some of it down - finished brazing and sealed the rest with hi temp ultra silicone Like so-
To the right is the other half of the baffle which I needed to cut-out a place for the pipe to fit and have go back together.
The muffler would not connect to the smaller tube so I wrapped a cotton rag around it for this short test:
Wacker with just my pipe added to the stock muff:
idle-80 ( dead stock was 78.5)
3/4 throttle- 90.6 (about the same as stock)
Wacker with my muffer added:
idle-73
3/4 throttle- 85
This is a very informal test, checking the with the exhaust aiming right at the meter about 39 inches away. A worst case deal.
Decibels are not like temperature graidents. I don't remember the details except that something like a 3 or 4 difference in Db is a difference of 1/2 sound pressure.
This muffler may have been quieter with smaller driller holes - something about the size of the waves that are able to go thru.
All in all, I am pleased.
I do wonder if those tiny gills were a factory idea to control the rpm of the engine?
The muffler has only 2 little gills to get the exhaust out of the stock muff. The actual muffler is inside a heat baffle (pretty cleaver, cooling air from the fan is blown thru this baffle around the muff.
I had to seal up a pipe around where the gills go to be able to attach it to an added on muffler.
Here is a pic of the amazingly small outlets:
The inlet is about an inch by a half.
I pryed open the gills some and added (maybe shouldn't have) a hole next to them. Covering these is a section of weeedeater shaft (super thin 3/4 outside dia.) that I split for a bit and braized onto the muffler. I had not realized the silver color is aluminization. The alum. does not like to burn off. I thought the stuff was zinc (don't breathe the fumes for that either), after seeing the miserable time I was having, I ground some of it down - finished brazing and sealed the rest with hi temp ultra silicone Like so-
To the right is the other half of the baffle which I needed to cut-out a place for the pipe to fit and have go back together.
The muffler would not connect to the smaller tube so I wrapped a cotton rag around it for this short test:
Wacker with just my pipe added to the stock muff:
idle-80 ( dead stock was 78.5)
3/4 throttle- 90.6 (about the same as stock)
Wacker with my muffer added:
idle-73
3/4 throttle- 85
This is a very informal test, checking the with the exhaust aiming right at the meter about 39 inches away. A worst case deal.
Decibels are not like temperature graidents. I don't remember the details except that something like a 3 or 4 difference in Db is a difference of 1/2 sound pressure.
This muffler may have been quieter with smaller driller holes - something about the size of the waves that are able to go thru.
All in all, I am pleased.
I do wonder if those tiny gills were a factory idea to control the rpm of the engine?
