2-Stroke Exhaust Question

[Beeweldmut]

it sounds like you don't understand the concept of an expansion chamber at all ???

I will gladly listen to your explanation of how that husky exhaust functions

 

[xb33bsa]

it lets the exhaust out :
but it is not a tuned exhaust the power output is way down from stock

 

[Beeweldmut]

it lets the exhaust out :
but it is not a tuned exhaust the power output is way down from stock

that part is pretty obvious. But it is still capable to some degree of returning sound waves. Just not in a tuned manor.

 

[xb33bsa]

no that thing is not returning any sound waves : backpressure yes, sound waves no
educate yourself on the concept

 

[Beeweldmut]

no that thing is not returning any sound waves : backpressure yes, sound waves no
educate yourself on the concept

i have enough education to know that I buy an expansion chamber already tuned and not attempt to build one myself.

 

[Scooter trash]

Back pressure, sound wave it's a pressure wave. Potato, pototao, It keeps the intake charge from exiting out the exhaust port on the up stroke. To get a good result involves a lot of stinger exchanges. It's not easy, the expansion chamber is like a pneumatic accumulator. There needs to be stored up resistance to properly work. Not to much or to little. I put expansion chambers on my H-2 after several mods, larger carbs, recut ports and it was a nightmare to get the stingers adjusted just right. The more power you put out the bigger capacity you need in the chamber. It's been over thirty years since I played with smokers, so maybe there is something new, just don't know.

 

[Beeweldmut]

That's is a straight diameter pipe, but it is bigger than the exhaust port. So it's still a place for air to be stored and pulled back into the motor on the down stroke. I wouldn't say it's tuned at all, but capable of running .

re-read my post. I wasn't trying to imply scavenging in the exhaust was a good thing, but it came out that way.

 

[xb33bsa]

ok but it cant suck back air because the exhaust energy and transfer cycle is pushing out and what happens when a motor that was designed to have tuned exhaust does'nt have it is some of the fresh transfer charge is lost because there is no reverse pressure wave to stuff it back in at excactly the right few milli's in time before the exhaust port closes on its way back up resulting in a low volume charge,with zero boost
when all this happens in a tuned exhaust motor it actually slightly compresses the charge as it stuffs it back into the chamber
the transfer charge is thusly allowed to pretty fully sweep the bad gasses out of the combustion chamber
but the part of the transfer charge that goes down the header pipe is lost without a tuned reverse sound pressure wave
there is never really any sucking back in at the exhaust port

 

[mydlyfkryzis]

The reverse pressure wave also acts lie a turbocharger, raising the pressure in the cylinder before it closes the port and compresses the fuel. It essentially creates a higher compression ratio.

When timed right, it helps scavenge the exhaust, by creating lower pressure at the exhaust port as the pott is opened, then the returning pressure wave stops the intake charge from escaping, while increasing the pressure in the cylinder.

Hard for some to grasp that the expansion chamber is part of the exhaust system and part of the intake system...

 

[xb33bsa]

that is what you feel when a 2 stroke "comes on the pipe" it is boost pressure on the scavenging transfer acting to efficien-tate the power ;D
love it time to get my RD350 preperated and running i guess

 

[mydlyfkryzis]

My cousin had a Ace Hodaka super Rat....Peaky as all hell....Amazing, scary power when on pipe, nearly nothing off pipe. 2 Strokes are amazing on their power to weight ratio....

My favorite 2 stroke was the Suzuki Titan 500, like Bradj's....It had a broad power band, unusual for 2 strokes...was the most 4 stroke like bike... but still had lot's of power for what it was.....

 

[Beeweldmut]

there is never really any sucking back in at the exhaust port

Are you talking about on this bike or on any 2stroke? Either way I'm not sure I agree with that.

But looking at other 400 husky's, I'm not sure that exhaust is to far from stock.

 

[Scooter trash]

You can increase the low and midrange to be almost like a four stroke. You have to have a lot of different needle jets and jet needles along with different carb slide angles to get there. It takes patience along with trial and error. Two strokes have got to be the most difficult to tune engines there is. The two stroke is more a super charger than a turbo charger since it is positive displacement. As the piston travels down it is compressing the crankcase with fuel/air charge, then as it passes the transfer ports, the charge is forced into the combustion chamber. Hopefully not out the exhaust port to much, it is never perfect. Most two strokes have that turbo lag effect, but a fined tuned one will just be go like hell then Oh sh"t! I can maintain positive boost with my engine as low as 3k RPM. When it hits 7K to 8k the power doubles instantly and feels like a two stroke from hell.

 

[xb33bsa]

Are you talking about on this bike or on any 2stroke? Either way I'm not sure I agree with that.

But looking at other 400 husky's, I'm not sure that exhaust is to far from stock.

no sucking back through the exhaust is happening on any 2 stroke it is always blowing out
at least when running when cranking it over without any fire i guess it could be possible that just before the transfers open because there is no hot expanding stuff in there
way before the piston reaches bdc and pretty shortly after the exhaust port opens,the transfers open and the pressurised charge is looped up through them and the exhaust port continues to foo out hot expanding exhaust gasses through bdc and as the piston goes back up the transfer continues helps the scavenge,no sucky at the exhaust
and the stock pipe on that husky 400 is far from being a straight tube it is a tuned expansion chamber i have had one in my hands so i know this
they have come a long ways since those old huskies tho

 

[xb33bsa]

You can increase the low and midrange to be almost like a four stroke. You have to have a lot of different needle jets and jet needles along with different carb slide angles to get there. It takes patience along with trial and error. Two strokes have got to be the most difficult to tune engines there is. The two stroke is more a super charger than a turbo charger since it is positive displacement. As the piston travels down it is compressing the crankcase with fuel/air charge, then as it passes the transfer ports, the charge is forced into the combustion chamber. Hopefully not out the exhaust port to much, it is never perfect. Most two strokes have that turbo lag effect, but a fined tuned one will just be go like hell then Oh sh"t! I can maintain positive boost with my engine as low as 3k RPM. When it hits 7K to 8k the power doubles instantly and feels like a two stroke from hell.

the pressure in the crankcase and transfers is not what boosts a 2 stroke,it is only what fills the combustion chamber and scavenges/removes the bad air(exhaust gas)
the exhaust port on all 2 strokes is always open while the transfers are open this is why the transfers cannot really boost cumbustion chamber pressure
the transfers close before the exhaust port on all 2 strokes
these facts are written in stone for any NA 2 stroke
in GP racing they banned supercharged 2 strokes after only a season or 2, now there was a monster of an engine !!
it is the tuning of the pipe and the reverse sound pressure wave
that raises combustion chamber pressure

 

[redroptop]

and the stock pipe on that husky 400 is far from being a straight tube it is a tuned expansion chamber i have had one in my hands so i know this
they have come a long ways since those old huskies tho

Would you be able to explain how they work then? And how we can build one?
Like Shane said, is there a cone inside that we don't know about, or is that pipe size increase so subtle that the pipe looks strait?


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[VonYinzer]

Read the book I linked on page one.

 

[xb33bsa]

Would you be able to explain how they work then? And how we can build one?
Like Shane said, is there a cone inside that we don't know about, or is that pipe size increase so subtle that the pipe looks strait?


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the oem 400 husky pipe goes from 2" or so up to a diameter 5" aprx center section..
like von sed read up on it it is fasinating stuff
that count dude that built that pawn stars bike was an idiot to have put straight pipe on a 2 stroke

 

[redroptop]

the oem 400 husky pipe goes from 2" or so up to a diameter 5" aprx center section..
like von sed read up on it it is fasinating stuff
that count dude that built that pawn stars bike was an idiot to have put straight pipe on a 2 stroke

That's what I want to hear.

Thanks man.

Now, you're interrupting my reading.


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[xb33bsa]

you can use computer software to plug in all your specs in order to design your own expansion chamber
quite a few careful measurements must be made, involves some basic skills and using a degree wheel ,but it will be fun 'cause the outcome you could really take pride in