Generator Muffler Question

[TallPaul]

I have a V-twin Generac engine on my motorhome generator. The engin is a GN-480. Anyway, I need a new muffler. Now I happen to have a brand new muffler similar to the one that is on it. The new one is smaller. Here are the dimensions: (Old, New)


Width: 4", 4"
Length: 16", 11"
Inside diameter of pipe entering muffler: 1", 1"
Inside diameter of pipe exiting muffler: 1.375", 1"

So, my reasoning is

1) A smaller muffler is not necessarily more restrictive (I can do a blow test through each muffler).

2) The smaller outlet on the new muffler is not a problem since both mufflers already are restricted to that size at the inlet and as the gasses flow away from the engine they cool and thus take up less space.

Does this make sense? What could go wrong using the shorter length muffler?

[TallPaul]

I have a V-twin Generac engine on my motorhome generator. The engin is a GN-480. Anyway, I need a new muffler. Now I happen to have a brand new muffler similar to the one that is on it. The new one is smaller. Here are the dimensions: (Old, New)


Width: 4", 4"
Length: 16", 11"
Inside diameter of pipe entering muffler: 1", 1"
Inside diameter of pipe exiting muffler: 1.375", 1"

So, my reasoning is

1) A smaller muffler is not necessarily more restrictive (I can do a blow test through each muffler).

2) The smaller outlet on the new muffler is not a problem since both mufflers already are restricted to that size at the inlet and as the gasses flow away from the engine they cool and thus take up less space.

Does this make sense? What could go wrong using the shorter length muffler?

[Tom N]

Is a spark arrestor incorporated in the original muffler?? If so does your replacement muffler have a spark arrestor??

-Tom

[TallPaul]

No spark arrestor on original muffler, at least not anywhere visible (could it be inside?). New one has a screen in outlet pipe, which I would remove as it would make too much restriction.

But now I am thinking I will patch the old muffler and keep running it for now. Can use new one later. Potential for higher back pressure if more restrictive. That could be bad for engine, depending on how much. A smaller increase, no problem but lowers power and increases heat in engine.

[TallPaul]

EDIT: I did a blow test and the new muffler was much more restrictive, but when I covered the hole in the old muffler they were about the same, so new muffler should work.

Also book says muffler does not have a screen type arrestor, but has a special construction that acheives that function. Will have to use screen type in new muffler.