tuned pipe question (SBP)

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mechanickid

mechanickid

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Aug 7, 2008
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nh
does the tuned exhaust pipe sold by sick bike parts improve performance more than taking all the baffling out of stock pipe would? (which is a straight shot out)
in my experience with these motors no back pressure is better than some.
 
Ghost0

Ghost0

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Mar 7, 2008
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Bellingham, WA
If back pressure meant nothing on a 2 stroke then all the tuned pipes would have the same diameter stinger pipe as the header pipe. I have yet to see a properly designed expansion chamber where this is the case.

mechanickid,
Read the reviews on our site about the pipe and it should let you know what you can expect as far as performance improvements.
 
foureasy

foureasy

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Jul 9, 2009
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tucson
got one right here. with as much porting as i did to this motor and a stinger that was .60 of the inlet pipe, you could not even get to the powerband unless you were going downhill, and when you did it felt like the motor was gonna zoom off the frame and down the road. i tried a few different combinations with the stinger and found that the outlet size being the same as the inlet gave this motor such a broad powerband and made the bike so rideable, that there is no other option for me. every inch of stinger that i cut off made it better and better. maybe it only works on high rpm motors, cause thats all i've tried it on. maybe you should try it before you bash it, cause 39-40mph with a 36t sprocket and a 24.5" tire seems pretty good to me.


 
Ghost0

Ghost0

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Mar 7, 2008
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Bellingham, WA
Not bashing anyone, simply stating the facts as backed up by 30 years of 2 stroke tuning experience as well as any tuned pipe design literature or design software you care to read or use. Header length and expansion chamber shape will effect the required stinger size and apparently your design to work correctly needs a larger stinger size. Nothing wrong with that but for an optimum design to provide improved power through a large rpm range typically requires a little back pressure. They are all a bit of a compromise. The trick, in my opinion, is to get one that provides increased power over a wide rpm range rather than peak power in one small rpm range.
 
foureasy

foureasy

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Jul 9, 2009
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tucson
The trick, in my opinion, is to get one that provides increased power over a wide rpm range rather than peak power in one small rpm range.
Click to expand...

that is exactly what i have done with the aforementioned pipe
 
mechanickid

mechanickid

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Aug 7, 2008
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nh
okay so back pressure DOES matter, otherwise these would be no better than just taking exhaust off all together.

ghost0, i only found one pipe review one the site, are there more?


also, does anyone know HOW an pipe changes the powerband? as in the term "up on the pipe"
 
Ghost0

Ghost0

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Mar 7, 2008
763
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Bellingham, WA
If you click on the little arrow above the review section on the right side of our home page it will take you to all the reviews.

All tuned pipes increase horse power over some rpm range, some do it over a small rpm range that can be at low, middle or high rpm. I think ours does a nice job of increasing the power band over a larger rpm range than most.
 
E

eisle89

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Jun 16, 2008
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El Paso, Texas
I have two of the SBP expansion pipes and they are great. If I can offer a suggestion, do all your porting and such before hand. Then use the blue silicon tubing between the header and the expansion chamber as long as you can get it at first. Then play with shortening up that length until you get the response you want. Mine was 11" from head to expansion chamber,then I welded it up.
 
X

xlite

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Jun 18, 2009
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ny,ny
eisle89 said:
I have two of the SBP expansion pipes and they are great. If I can offer a suggestion, do all your porting and such before hand. Then use the blue silicon tubing between the header and the expansion chamber as long as you can get it at first. Then play with shortening up that length until you get the response you want. Mine was 11" from head to expansion chamber,then I welded it up.
Click to expand...
I bought the SBP exhaust for one of my Zoom 80cc slant but haven't installed yet.

Exactly what engines did you have and what modifications?

Did you tune for low end or high end?

Is the 11" from flange to start of expansion bulge? Measured along inside or outside?
 
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