Exhaust Expansion pipe?

[Snow Camo 237]

Hey guys I am trying to gain an understanding of what this style pipe has on a 4-stroke. I hear the 2-stroke guys talk about them all the time. 

 

I found this one on ebay listed for an 83-84 250r. I thought that engine was a 4-stroke? I am getting ahead of the curve and sorting through exhaust options for the future. 

 

Can anyone explain what purpose and  Benefits these would provide on the 200sx engine if any?

 

Here is the link to the pipe.

[Fishfiles 19,705]

ATC250R  or TRX250R are  2 stroke engines , that exhaust you pictured is  called an expansion chamber , I consider it like a header  for a 2 stroke ----

[SlammedRanger 1,504]

The other reason you will see them on alot of race quads mainly the pro's is it helps with scavanging of exhaust gasses and can also change the tone to abide by the decible limits required for racing in a particular class. But yeah the 250r is a 2 stroke and there would be no benefit from putting that big of an expansion chamber on a 4 stroke at all.

[Derf40 132]

Snow, throw that thing in the trash..it will only fit the bike it was made for (reason for it's shape)..There is a lots of books written on 2-stroke exhaust systems. most of the 2-strokers talk about the power band, that's where they get the most of their power/ per RPM. When the motor reaches this rpm it feels like a turbo comes on. The design of the pipe determines when this power comes on..This is as simple as I can explain it... Read lots of books. Have a good day...Derf

[_Wilson_™ 6,430]

I read it's been called or described as a part time supercharger at certain rpms..... 

[Fishfiles 19,705]

I had the Kawasaki 500 Triple two-stroke , I had a " Hooker " three into one pipe on it , if you like two strokes , it had a sweet sound , I will never forget that sound , Ka' Wa'''''Sa'''''''''Keeeeee''''''''''''''' 

[Harleydavidson 222]

1 hour ago, Fishfiles said:

I had the Kawasaki 500 Triple two-stroke , I had a " Hooker " three into one pipe on it , if you like two strokes , it had a sweet sound , I will never forget that sound , Ka' Wa'''''Sa'''''''''Keeeeee''''''''''''''' 

Mmmm H1s with a 3 into one is ear candy and H2 is even better 

[_Wilson_™ 6,430]

I'm not trying to control the thread or step on anyone's toes...... But i fond this rather interesting .....also not sure it's right on the money pure description .... 

 

https://www.motorcycle.com/how-to/how-twostroke-expansion-chambers-work-and-why-you-should-care-3423.html

[retro 3,871]

2 strokes get expansion chamber pipes to assist in cylinder scavenging. 4 strokes get header pipes to assist in cylinder scavenging. Big difference in design between the two and they won't interchange.

[Snow Camo 237]

1 hour ago, Fishfiles said:

ATC250R  or TRX250R are  2 stroke engines , that exhaust you pictured is  called an expansion chamber , I consider it like a header  for a 2 stroke ----

Well I was wrong when I assumed they were a 4 stroke. Lol.

39 minutes ago, SlammedRanger said:

The other reason you will see them on alot of race quads mainly the pro's is it helps with scavanging of exhaust gasses and can also change the tone to abide by the decible limits required for racing in a particular class. But yeah the 250r is a 2 stroke and there would be no benefit from putting that big of an expansion chamber on a 4 stroke at all.

 

Ok good to know. When I get a cam I will need to upgrade the exhaust. Is tuning the exhuast pipe dimensions worth the work or should I just step up the next avaliable pipe size, supertapp muffler and call it good?

 

  I ask because I saw somewhere a guy spoke about putting a 9" tapper starting at the head leading to larger pipe. He used a program to determine the exhaust length and pipe diameter.

 

I read good reviews on this supertrapp muffler. The one thing that stands out in reviews is users say the muffler builds hp and torque lower and keeps steady throughout the rpm band. 

 

Here is a good exhuast design article.

[SlammedRanger 1,504]

If your planning on building your own exhaust header you will need to be pretty skilled at welding very very thin tube. Best option is stainless. There are alot of things that can be done but the way to perfect it requires alot of calculations and a flow bench. Are there any aftermarket places that make a pipe for the 200sx? The aftermarket places would have already done all those calculations and save you alot of leg work. If not this process gets alot harder. Its not a simple bigger is better situation. Pipe length and diameter all play a roll. But there is a point where its too much and a point where its too little. And this is where trial and error with a flow bench are necessary. With alot cheaper material at first obveously lol.

[_Wilson_™ 6,430]

@Wheeler Also can give some insight on this to..... Performance ... He mods just about everything he gets..... Lol!..... I think even a weed eater or it might have been a leaf blower... Lol!.... Why anyone would want more power from ether one of those machines is something i try not to think about... Lol!! 

[SlammedRanger 1,504]

1 minute ago, _Wilson_™ said:

@Wheeler Also can give some insight on this to..... Performance ... He mods just about everything he gets..... Lol!..... I think even a weed eater or it might have been a leaf blower... Lol!.... Why anyone would want more power from ether one of those machines is something i try not to think about... Lol!! 

Some people have alot of leaves to blow. And performance is a must! LoL😉

[Snow Camo 237]

1 hour ago, SlammedRanger said:

If your planning on building your own exhaust header you will need to be pretty skilled at welding very very thin tube. Best option is stainless. There are alot of things that can be done but the way to perfect it requires alot of calculations and a flow bench. Are there any aftermarket places that make a pipe for the 200sx? The aftermarket places would have already done all those calculations and save you alot of leg work. If not this process gets alot harder. Its not a simple bigger is better situation. Pipe length and diameter all play a roll. But there is a point where its too much and a point where its too little. And this is where trial and error with a flow bench are necessary. With alot cheaper material at first obveously lol.

 

I was actually thinking I could have an exhaust shop make the bends and I could figure welding the flange end at the head. I am no pro but I find stainless easy to weld. It will look like crap due to me not having gas, but I get it done with a stick or three lol🤣

 

In that link or vid there is mention of a site with an exhaust design calculator. I plan to use it and give things a shot. I am all about having fun so trial and error is just part of it session

 

I have not found any aftermarket exhaust for the 200sx

Edited December 25, 2022 by Snow Camo

[retro 3,871]

There are other online header design calculators too. The best one ever is Larry Meaux's Pipemax at $45. It runs on a computer and keys on tuning for max Volumetric Efficiency. But a single cylinder 200cc motor isn't gonna yield much power per dollar invested. 10% - 15% increases in torque in a motor that size costs a lot of money. But it's a lot of fun for sure!!!

[Snow Camo 237]

1 hour ago, retro said:

There are other online header design calculators too. The best one ever is Larry Meaux's Pipemax at $45. It runs on a computer and keys on tuning for max Volumetric Efficiency. But a single cylinder 200cc motor isn't gonna yield much power per dollar invested. 10% - 15% increases in torque in a motor that size costs a lot of money. But it's a lot of fun for sure!!!

 

 

Honestly I really do not expect to make a big difference in hp. I would just be building it for fun. Even if it makes 2hp after the piston,  cam, head work and exhaust I it would be worth saying I did it for fun. 

 

I would like to setup a small flow bench to see what kind of cfm numbers I can come up with.  Hopefully that will help figure what cam will be worth it.  I do plan to shoot for 8.2-8.5 dynamic compression.  I will have to see if a custom cam grind is an option.  Web says the cam core needs to be sent in for welding and grind,  so maybe it is an option. 

 

[Snow Camo 237]

Since i will be building this little motor what other then cam, piston and head port work could I do for fun?  Is milling the head and or jug worth the time?  

 

Maybe larger valves and a 250 engine carb in hopes to get more air flowing in?

[Wheeler 2,468]

@_Wilson_™ yes I have modified my leaf blower, weed eater, & like u said anything I can hahaha. 
 

yes those exhausts r for a 2 stroke. VERY different than an exhaust for a 4 stroke. They (4 stroke) will only make power when sized for the accommodating mods. If u toss a large exhaust in without a cam, or larger piston ect, u may loose power… so keep that in mind…   

[Snow Camo 237]

Gotcha. I only plan to install an exhaust header when I upgrade said items. However I do plan to pickup that supertrapp muffler somewhere in-between tires and plastics. 

 

The stock exhaust has a chamber and a turbulator looking fan (that does not spin) inside. No packing whatsoever, so I plan to do away with that. I found one review from the comments of a you tube video where the supertrapp was said to give more power throughout the rpm range. I am pretty sure it would benefit more then the stock exhaust. I have attached a picture of what the inside of the stock exhaust looks like when the spark arrestor is removed.

[Wheeler 2,468]

Unless Supertrapp has changed over the years without me knowing, they have always used baffle plates. U can add or subtract plates based on mods, & sound. White Brothers back in the day were the same. That fan looks like some crazy Amazon gimmick. I would NOT put that on my atv. Get yourself a good HMF, FMF, or similar. (Your gonna want packing!) Unless u can find a true Suoertrapp with plates.
 

just my 2c

 

 

Edited December 27, 2022 by Wheeler

[Snow Camo 237]

5 minutes ago, Wheeler said:

Unless Supertrapp has changed over the years without me knowing, they have always used baffle plates. U can add or subtract plates based on mods, & sound. White Brothers back in the day were the same. That fan looks like some crazy Amazon gimmick. I would NOT put that on my atv. Get yourself a good HMF, FMF, or similar. (Your gonna want packing!) Unless u can find a true Suoertrapp with plates.
 

just my 2c

 

 

Yep supertrapp is the same. I'll use the baffles to my benefit. That should workout nicely when tuning and crusing not trying to make a racket.

 

That fan is just to give an idea of what is inside the factory muffler. Whenever I get the time I will pull the spark arrestor so you all can see what's in the factory muffler. Honda designed the muffler with a non operational fan turbulator looking thing.

Edited December 27, 2022 by Snow Camo

[Snow Camo 237]

https://supertrapp.com/supertrapp-412-15000-4-inch-universal-aluminum-racing-series-muffler-1-5in-id-1-75in-core-8-disc

 

 

This^^^ is the supertrapp I plan to use. It's direct from

 Supertrapp. 

[Wheeler 2,468]

On my old 300bbk, I had the WB baffled muffler. I totally forget how many plates I ran. But it sounded “goooood”!!

[Snow Camo 237]

Just now, Wheeler said:

On my old 300bbk, I had the WB baffled muffler. I totally forget how many plates I ran. But it sounded “goooood”!!

 

Nice! That's one thing I am looking forward to is a good sound. I started looking at modding a fmf or something to fit, but quickly realized I would not be able to moderate the sound. Supertrapp it is lol

[Wheeler 2,468]

I run a full 300ex stainless FMF right now. The ole girl is loud but sounds good! The ability to tweak the exhaust for performance with a ST is awesome.