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.

What y'all think? Am I being a tight wad? Or is it reasonable to run the smaller muffler?

 

[Master ACiD]

why do you need a new muffler?

 

[TallPaul]

I pulled it because the mounting flange is warped and leaking. This was from the muffler hitting something (previous owner) and maybe worsened when I ran over an alligator (truck tire tread) the other day, which tore off the running board bracket, ripped in two the generator tailpipe hanger and bent the generatoer tailpipe. Anyway, the muffler is rusty and makes noise when you shake it (rust inside), and has a small (maybe 1" dia) hole from where a small bung on the muffler bent and tore it. Only thing that is an issue is the hole and I guess I can patch it with heavy sheet metal and an exhaust gasket.

Guess I'll do that for now.

 

[JTK]

Paul, if that one mounts up without issues, you are good to go. I bet a whole new exhaust from Generac would be super expensive, if you could even get one (depending on the age).

Joel

 

[TallPaul]

Yeah, I bought the shorter muffler 2 years ago with flange, gasket, and pipes for only $40. Was going to use on a portable generator, but never got around to it. Maybe use existing muffler for now as stated above and save the new one for later.

Ideally would like to reroute to make less vulnerable to road hazards.

 

[Bill Kapaun]

"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"

But aren't they also expanding as the pressure drops?

I'd try it and see what happens. Maybe it'll all be lost in the noise!

 

[Master ACiD]

i know that rv's need quiet mufflers since you guys like to park and run the genset to have a/c and power. (i have a honda inverter generator on my slide in camper).

try the muffler out, you got nothing to lose. if its too loud though then tey adding the old one after the new one so have 2 in series. noise is a big issue with rv's. dont forget to use some GOOD rubber exhaust hangers. if you cant find any for a decent price, a cut up tread of an old car tyre works GREAT. ive gone that for years with custom exhausts.
just remember to do a good clean looking job so youre rv neighbours dont laugh.

 

[TallPaul]

Guess I have to try it out because the flange for the new one won't fit the old one and the hole is bigger than I thought. I looked in the old one and the inlet dead ends and has 14 holes along the sides, maybe 1/4 inch each at most--pretty restrictive.

Thanks

 

[TallPaul]

It failed the blow test. There is hardly any resistance in the old muffler, but the new one has considerable. I found the 14 holes inside the old muffler's inlet are about total .5 - .7 sq inch, whereas the new muffler has one big hole that is about .3 sq inch. Not sure if there is any other passage.

Now maybe if I bore an extra hole (can plug outside part with a screw or bolt), it might free up the flow. Guess I have little to lose.

 

[TallPaul]

Whoops, forget last post. Forgot about hole in old muffler. Covered hole and blow test not signigicantly different. Can use new muffler.

 

[Papa Bear]

I'd go with straight pipes ... a la H.D.

 

[Propflux01]

Quote:

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I'd go with straight pipes ... a la H.D.

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He would have to disconnect one of the plug wires first!