understanding pipes

To know how to set up my bike I need to understand how things work.

I usually run a 51 tooth and a fatty.
I am now set up for endurance, I run a 50 tooth and a gnarly.  
I am going to run a 48 in the next desert scrambles.

My fatty was replaced by a gnarly.
They seem to have the same outside diameter.
The gnarly is thicker so there is less space inside.
Therefore the pressure would build up quicker at a lower RPM.
Therefore pressurizing the next upstroke sooner causing it to hit the power sooner.
Therefore you would get power at a lower RPM.

Am I even in the ballpark with my thinking?
Will the top speed, in the top of 5th gear,  be higher with the gnarly of lower because the hit comes on so soon.  
__________
"Every time I start thinking the world is all bad, then I start seeing some people out there having fun on motorcycles. It makes me take another look." -Steve McQueen

UM......hahha U need to give Don Emler a call. LOL    

yup he might know with MIGHT being the key word

i heard hes pretty dumb when it comes to pipes especially fmf pipes  
RIP old dirtrider

My understanding is that it has to do with where the expansion of the pipe starts more so than the thickness dag. If you notice, the pipes vary where the expansion cahmber starts and the diameter of the expansion chamber  
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____________________
MIKE
Phoenix, az
(07 yz250)
(99 yz125)


Every bush has its day (sanders, 2009)
Lack of enthusiasm is for the weak and timid. (alex, a.k.a. yz250 forever)

"I know much about nothing at all"(Maple, 2009)

Inless the gearing is super-high, in which case you need torque to pull the hear spacing, top speed is about horsepower. Either pipe has enough power to pull that gearing just fine. The Gnarly pipe will make the bike easier to ride on other parts of the course.  

daggit:
To know how to set up my bike I need to understand how things work.

I usually run a 51 tooth and a fatty.
I am now set up for endurance, I run a 50 tooth and a gnarly.  
I am going to run a 48 in the next desert scrambles.

My fatty was replaced by a gnarly.
They seem to have the same outside diameter.
The gnarly is thicker so there is less space inside.
Therefore the pressure would build up quicker at a lower RPM.
Therefore pressurizing the next upstroke sooner causing it to hit the power sooner.
Therefore you would get power at a lower RPM.

Am I even in the ballpark with my thinking?
Will the top speed, in the top of 5th gear,  be higher with the gnarly of lower because the hit comes on so soon.

I think you are overthinking things.

not sure what the gearing was at GH  but if its a faster track (remember the asphalt section?) drop a tooth or 2 (it will pull it with some clutch in the tight stuff)

do you still have the service honda engine?  

Autismspeaks.org
Gilbert AZ
06yz144,05yz85,02yz85

Yes, and I am going to run the gnarly and the 48.
I need to know how things work.lol
It looks as if the pipes are identical on the outside.  the expansion seems to be at the same point , but i will look again tomorrow.  
__________
"Every time I start thinking the world is all bad, then I start seeing some people out there having fun on motorcycles. It makes me take another look." -Steve McQueen

daggit:
Yes, and I am going to run the gnarly and the 48.
I need to know how things work.lol
It looks as if the pipes are identical on the outside.  the expansion seems to be at the same point , but i will look again tomorrow.

dagg you logic to me makes perfect sence how you are explaining things !!! i justam not sure about pipes ether   but i want to learn from this thread  
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Autismspeaks.org   check it out
--------------------
life in the fast rut!!!!
--------------------
my rides- 2008 yz250f fully modified, use to be j-laws bike
        &
IT400 1979 yamaha!!!
--------------------
Home: SO CAL

daggit:
Yes, and I am going to run the gnarly and the 48.
I need to know how things work.lol
It looks as if the pipes are identical on the outside.  the expansion seems to be at the same point , but i will look again tomorrow.

dagg you logic to me makes perfect sence how you are explaining things !!! i justam not sure about pipes ether   but i want to learn from this thread  
--------------------
Autismspeaks.org   check it out
--------------------
life in the fast rut!!!!
--------------------
my rides- 2008 yz250f fully modified, use to be j-laws bike
        &
IT400 1979 yamaha!!!
--------------------
Home: SO CAL

Ok, what I have found is that it is all about timing.

The old 2 strokes had straight pipes, a cone was placed on the end to lengthen the sound waves coming out, to create a suction, to draw the spent fuel out of the cylinder.

A reverse cone was placed onto that one to turn the negative wave back at the exhaust port as positive wave. forming an expansion chamber.  

The result was, the first cone drew fresh gas mix into the expansion chamber and the reverse cone forced it back in, supercharging cylinder.

The combination of header, expansion chamber, and stinger,(the section after the chamber), all play a role in the timing and force of the returning waves.

And since the force is sound waves, the thickness of the metal can help fine tune the engine.

The timing of the waves return has to be right to return while the exhaust port is open.

The shorter the belly of the chamber the sooner the return of the waves, which is good for high speeds.  
__________
"Every time I start thinking the world is all bad, then I start seeing some people out there having fun on motorcycles. It makes me take another look." -Steve McQueen

An added note.

The sound will be the same frequency as the engine is turning, that is, an engine turning at 8000 rpms generates an exhaust sound at 8000 rpms or 133 cycles a second--hence, an expansion chamber's total length is decided by the rpm the engine will reach, not displacement.  
__________
"Every time I start thinking the world is all bad, then I start seeing some people out there having fun on motorcycles. It makes me take another look." -Steve McQueen

Wow lol kinda makes sense dag! i think im also understanding whats going on in there at the expansion chamber  
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2006 YZ250

- FMF Gold Series Fatty
- Yamaha Racing Graphics Kit
- Twin Air Filter
- Vforce 2 Reed Valves
- Clarke long range tank
- Cycra Handguards
- Longhorn Triple Clamps
- Pro Grip-Grips
- Pro Taper Handlebar
- Renthal o-ring chain and sprockets

I imagine it is just alot of trial and error to find what works.  Lots of R and D.  
__________
"Every time I start thinking the world is all bad, then I start seeing some people out there having fun on motorcycles. It makes me take another look." -Steve McQueen

daggit:
Ok, what I have found is that it is all about timing.

The old 2 strokes had straight pipes, a cone was placed on the end to lengthen the sound waves coming out, to create a suction, to draw the spent fuel out of the cylinder.

A reverse cone was placed onto that one to turn the negative wave back at the exhaust port as positive wave. forming an expansion chamber.  

The result was, the first cone drew fresh gas mix into the expansion chamber and the reverse cone forced it back in, supercharging cylinder.

The combination of header, expansion chamber, and stinger,(the section after the chamber), all play a role in the timing and force of the returning waves.

And since the force is sound waves, the thickness of the metal can help fine tune the engine.

The timing of the waves return has to be right to return while the exhaust port is open.

The shorter the belly of the chamber the sooner the return of the waves, which is good for high speeds.

so theoretically that means I was very close to being right?  
--------------------
____________________
MIKE
Phoenix, az
(07 yz250)
(99 yz125)


Every bush has its day (sanders, 2009)
Lack of enthusiasm is for the weak and timid. (alex, a.k.a. yz250 forever)

"I know much about nothing at all"(Maple, 2009)

Yeah the length of the header and the size of the chamber work with the bleed of the stinger .
So a fat pipe would give you power at a later stage and higher rpm for busting out of corners.  
__________
"Every time I start thinking the world is all bad, then I start seeing some people out there having fun on motorcycles. It makes me take another look." -Steve McQueen