# HS/HSS 1332 (GX390) Muffler Upgrade



## tonysak (Dec 24, 2013)

Hi,

I'd like to put a SuperTrapp "Muffler" on my HSS's OEM muffler. I already spoke to Super Trap going on top of a muffler is absolutely fine assuming it's sized correctly. 

My question is, does anyone know if the OEM muffler exhaust output could be threaded? Is there enough material there to support the supertrap? Could I screw a pipe flange on there with some sort of gasket?


----------



## JnC (Feb 21, 2014)

Why not use one of these? 

https://www.ebay.com/itm/HONDA-GX39...d=352089272332&_trksid=p2060778.c100290.m3507


----------



## tonysak (Dec 24, 2013)

Because I would need to remove the stock muffler and toss it. If I leave the stock muffler on, and install the SupperTrapp on that, I will get a -7dB result from where it is now. I will gain +5dB simply by removing the stock muffler (I think that is what they are rated at), then get a -7dB reduction when the trap is installed which will only yield a -2dB net reduction, no beuno. 

I play music in my 3m sound reduction earmuffs. I know the honda's are much quieter than others of the same size, I'd like it to be even quieter.


----------



## nwcove (Mar 2, 2015)

i dont think i would be comfortable having the extra weight hanging off the manifold, but you could probably find someone who could tig weld a fitting to the existing muffler.


----------



## tabora (Mar 1, 2017)

If there's extra back pressure from stacking the mufflers, it might rob some power, too. The pressure waves in an exhaust system are a complex thing...


----------



## JnC (Feb 21, 2014)

How about this one?

https://www.northerntool.com/shop/tools/product_200674235_200674235

direct fit, you can put one of those exhaust flappers on it.


----------



## jonnied12 (Jan 14, 2017)

tabora said:


> If there's extra back pressure from stacking the mufflers, it might rob some power, too. The pressure waves in an exhaust system are a complex thing...


 Correct.


----------



## tonysak (Dec 24, 2013)

JnC said:


> How about this one?
> 
> https://www.northerntool.com/shop/tools/product_200674235_200674235
> 
> direct fit, you can put one of those exhaust flappers on it.


I saw that one. I'm not sure how that thing was going to fit, plus I didn't want to have the exhaust directly in front of my face. I guess I could get a hose and run it where i want but that isn't really a clean install. It also has no reviews, nor does it list any sound reduction specs. It's main purpose might just be to reduce emissions, the sound reduction might be a passive second.

I'm handy, but I don't fix things for a living, so I don't have half the gear some of you guys have to rig stuff up. Hoping for something simple. Anyway, I was just curious, I am sure one or two of you guys have held the actual muffler in your hands.


----------



## JnC (Feb 21, 2014)

tonysak said:


> I saw that one. I'm not sure how that thing was going to fit, plus I didn't want to have the exhaust directly in front of my face. I guess I could get a hose and run it where i want but that isn't really a clean install. It also has no reviews, nor does it list any sound reduction specs. It's main purpose might just be to reduce emissions, the sound reduction might be a passive second.
> 
> I'm handy, but I don't fix things for a living, so I don't have half the gear some of you guys have to rig stuff up. Hoping for something simple. Anyway, I was just curious, I am sure one or two of you guys have held the actual muffler in your hands.



Have you thought about upgrading the spark arrestor? 

The snowblower GX390 spark arrestor is just a screen, 










where as I have worked with some GX390s from powerwasher units etc where they use a much more aggressive baffle type spark arrestor. Its a cheap upgrade and wouldnt change the appearance of the muffler and might give you an extra few dbs off of the noise level. 

Honda part number for the bigger arrestor is 18355 ZE3 010

and it looks like this


----------



## tonysak (Dec 24, 2013)

Thanks an interesting thought... thank you.


----------



## RedOctobyr (Mar 2, 2014)

Just in case it's helpful, I found this, which talks about 2 different Honda muffler part numbers for the GX390, one quieter than the other: 

https://www.justanswer.com/small-engine/658jc-honda-gx390-generator-can-quieter.html

I'm not certain which muffler you have, of course, but if you have their louder version, perhaps the quieter generator version may be a useful option.


----------



## Marlow (Dec 17, 2016)

Just get better headphones.


----------



## tabora (Mar 1, 2017)

Or maybe Tony should be the guinea pig for the Truck Stack conversion...



tabora said:


> For anyone wanting to actually do the truck/tractor stack exhaust, here's what you would need to do it:
> 
> 1. GX390 Exhaust Flange 1" NPThttps://www.ebay.com/itm/HONDA-GX39...d=352089272332&_trksid=p2060778.c100290.m3507​2. 1" NPT SS Street Elbow (from flange to exhaust stack - use a clamp to attach muffler stack to 1-5/16" OD threads on elbow)https://www.ebay.com/itm/1-NPT-Fema...039124?hash=item41c28f3414:g:07IAAOSwVm5Y9Dii​3. 1-3/8" inlet to 1-1/2" outlet muffler assemblyhttps://www.ebay.com/itm/70210081-R...224087&hash=item5d4bb84d8e:g:jZkAAOSwJ7RYVFpE​4. 1-1/2" rain coverhttps://www.ebay.com/itm/1-1-2-Inch...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649 ​All available on eBay... Have fun!


----------



## tonysak (Dec 24, 2013)

tabora said:


> Or maybe Tony should be the guinea pig for the


I'm not much of a rolling coal guy. Plus i gave no doubt seeing the stack in my range of vision will drive me nuts. 

The other honda muffler looked interesting but, it looks almost twice the size which would make sense. 

I'll pop off the muffler and mess with it.


----------

