What's with the design of ZNEN 4-stroke exhausts?

[mjsfoto1956]

I'm struck by the design of some of the ZNEN 4-stroke exhausts. To my eye they look just like 2-stroke exhausts. I doubt it is because of looks -- could it be that these exhausts extract a few more horsepower out of the GY6 motors?

Take a look here:

• ZNEN Interceptor exhaust
  

Would appreciate your thoughts.

M

[2stroked]

All snake oil and magic beans I WOULD THINK. Probably just made to look like that so people that don't know better believe it is what it looks like. "Gee....it has an expansion chamber! Those are like a turbo charger for a two stroke! It has I be twice as good for a four sroke!"

[benji]

I'm pretty sure it's just for looks.

[mjsfoto1956]

but this is not "aftermarket" -- this is "oem" from ZNEN/BMC and it is stock on a handful of their bikes. I get the possibility of an evil marketing angle (frankly I think it is ugly). But is there any possibility of some sort of benefit (even if minor)?

M

[eclark5483]

No, 2 strokes work on harmonics, 4 strokes rely on valves. The pipe is just a show pipe.

[gsx600racer]

Its for looks. Unfortunately the exhaust valve closing would put the kabash on "if" any performance gains.

It is funny when you see one of these on a 4 stroke. I chuckle every time.


Here is a 150cc with one of them fancy pipes.

longisland.craigslist.org/mcy/6106208974.html

[benji]

Here's a cute Lil baby one on a ruckus.

[eclark5483]

I think the only benefit, if any, that these mufflers MIGHT give, is a more free flowing exhaust. That benefit is quite nominal on a 4 stroke, but still there. If anything, you get this cool looking pipe that makes a mean sound. So only REAL benefit of buying one is to increase your penis size by 1/2". Not worth the money when better solutions are available at a lower price. Don't be fooled by the pretty contours and stated claims. 4 stroke and 2 stroke are different sciences all together. You need to think to yourself, what good is a pipe that sends a sound wave back up into the exhaust port gonna do when your output is controlled by a cam shaft and valves?

Take a look at this video on how a chamber pipe benefits a 2 stroke (starting at the 2 min 15 second mark), and ask yourself if that same thing can happen with a 4 stroke, cam driven engine:

[benji]

May 6, 2017 4:50:47 GMT -5 eclark5483 said:

I think the only REAL benefit of buying one is to increase your penis size by 1/2". Not worth the money when better solutions are available at a lower price.

Can you post a link?
A 1/2" is a lot haha

[eclark5483]

Yeah, that might have been over stated, should have said, will increase size by 1/2mm.

[benji]

Mmmmmmm. Still might be worth it.... I'll talk to the wife.

[eclark5483]

Being a bit serious about it.. One would think, and I guess I've never seen any tests done on this.. that if a chamber pipe is used on a cam driven 4 stroke engine, that charge of left over gas (which would of course be smaller then what a 2 stroke expells).. gets sonic-ly bumped back up to the cylinder, but then it has no where to go. If any bit at all is pushed back into the cylinder, it still will undergo 2 more strokes before being re-used in the combustion burst from the plug.. If you have that much leftover gas on a 4 stroke to be of any worth by being pumped back, then you have a downright shitty burning scooter that's way too rich!! But anyway, my thoughts are, if the back pulse has no where to go because of a closed valve, then it is collecting at the exhaust tip on the cylinder and creating a potential heat issue.. At least that's what one would hypothesize anyway. I do.

[benji]

I think they do something similar w diesels, but opposite. Almost like a venturi in the exhaust tip, but I don't know a lot about it. Something about it creating back pressure at the right resonance.

[eclark5483]

I think a chamber pipe on a 4 stroke would actually be more restrictive and counter productive. Think of the idea of a "FREE FLOWING" exhaust. The piston comes up and expells all that exhaust out the valve, the most efficient way for it to do that is have nothing pushing back at it (restricted muffler). Seems counter productive to stick a chamber pipe on it which is designed to send a pulse back. So in addition to being only just for looks, this very dumb idea of a pipe design, could actually be holding you back.

[2stroked]

That's if the belly of that " expansion chamber" is actually real. Has anyone cut out one open? That swelled part may just be a skin... Idk.