 |

11-02-2009, 02:11 AM
|
 |
Senior Member
|
|
Join Date: Oct 2006
Location: Golden Valley, MN
Posts: 3,017
|
|
Questions for those designing exhaust systems
Has anyone ever run a system using a rear system tube that does not go down first? Why not go straight back and up to ta left exist high mount position?
I haven't seen my bike complete for a year now so I don't know if this would even be possible. After looking at some WSBK pics from Simone's recent scans I realized this may be possible. Is there performance gains that would be lost from a "straight shot" off the rear cylinder?
|

11-02-2009, 02:46 AM
|
|
Senior Member
|
|
Join Date: Jul 2006
Posts: 1,958
|
|
the point of the rear cylinder pipe going down and linking is to allow for pulse tuning... as the pulse from the front cylinder passes the point where the rear exhaust tube joins it sucks the pulse from the rear cylinder out... it aids in exhaust scavenging... it's the same idea as x pipes you see in cars.
|

11-02-2009, 02:54 AM
|
 |
Senior Member
|
|
Join Date: Aug 2007
Location: maryland
Posts: 1,250
|
|
you would lose the effects of scavenging. which does improve hp and torque. think of the pipes as dueling syphon guns. one helps the other draw spent gasses out and fresh mixture in. it also helps to balance out flow between cylinders since packaging constraints often dictate two completely different pipes. It would be a cool setup though and would probably have a nice top end hit, but it would sacrifice linearity somewhat.
__________________
06 rc51 banzais, pcIII... the usual
94 vfr 750 40k miles
94 yamaha full carbon track whore
|

11-02-2009, 02:55 AM
|
 |
Senior Member
|
|
Join Date: Aug 2007
Location: maryland
Posts: 1,250
|
|
see what happens when you get up to leave a piss. wibbly comes in and beats you to it.
__________________
06 rc51 banzais, pcIII... the usual
94 vfr 750 40k miles
94 yamaha full carbon track whore
|

11-02-2009, 03:17 AM
|
 |
Senior Member
|
|
Join Date: Oct 2006
Location: Golden Valley, MN
Posts: 3,017
|
|
Thanks guys for your serious input. DOn't get me wrong, I will not be the one trying to do this but it just seemed logical to do this in light of weight savings. I have seen some interesting Ducati exhaust layouts that essentially do what I was propsing.
|

11-02-2009, 03:19 AM
|
|
Senior Member
|
|
Join Date: Jul 2006
Posts: 1,958
|
|
as far as weight savings goes it's best to take it from the top of the bike.. not from the bottom. i'd leave the exhaust and focus more on something like an aluminum tank, battery relocation, monocoque tail etc...
|

11-02-2009, 03:28 AM
|
 |
Senior Member
|
|
Join Date: Oct 2006
Location: Golden Valley, MN
Posts: 3,017
|
|
WAY ahead of you there wiblly, on my own bike that is!
Now I am just trying to balance my free time with the rc getting a decent split with the NC this winter.
|

11-02-2009, 03:32 AM
|
 |
Senior Member
|
|
Join Date: Oct 2006
Location: Golden Valley, MN
Posts: 3,017
|
|
update!
What if you met the two pipes together before splitting them of to either side after the front cylinder comes up through the swingarm where the rear cylinder normally would have?
Does that make sense?
|

11-02-2009, 03:37 AM
|
 |
Senior Member
|
|
Join Date: Aug 2007
Location: maryland
Posts: 1,250
|
|
so you wanna put the merge in the tail section? it would help, but wouldn't be ideal
__________________
06 rc51 banzais, pcIII... the usual
94 vfr 750 40k miles
94 yamaha full carbon track whore
|

11-02-2009, 03:42 AM
|
 |
Senior Member
|
|
Join Date: Aug 2007
Location: maryland
Posts: 1,250
|
|
the front and rear head pipes should(in theory) be equal length and join at a place that inhibits reversion of exhaust pulses back into the cylinder. I would think the front head pipe would end up way to long, and the rear you would have to do some serious snaking to get enough pipe in there. kinda like the one version of the rc211v setup where the two rear cylinders joined in the tail, but there was a full 360* donut in there. I'll see if I can find a pic.
__________________
06 rc51 banzais, pcIII... the usual
94 vfr 750 40k miles
94 yamaha full carbon track whore
|

11-02-2009, 03:48 AM
|
|
Senior Member
|
|
Join Date: Jul 2006
Posts: 1,958
|
|
Quote:
Originally Posted by johnyisthedevil
the front and rear head pipes should(in theory) be equal length and join at a place that inhibits reversion of exhaust pulses back into the cylinder. I would think the front head pipe would end up way to long, and the rear you would have to do some serious snaking to get enough pipe in there. kinda like the one version of the rc211v setup where the two rear cylinders joined in the tail, but there was a full 360* donut in there. I'll see if I can find a pic.
|
i always wondered about this... should the pipes be of equal length with a v-twin firing pattern? i can understand on an i4 but with a v-twin you wouldn't expect identical length pipes to create the same pulse tune... no?
maybe i'm just picturing it wrong...
|

11-02-2009, 03:49 AM
|
 |
Senior Member
|
|
Join Date: Aug 2007
Location: maryland
Posts: 1,250
|
|
__________________
06 rc51 banzais, pcIII... the usual
94 vfr 750 40k miles
94 yamaha full carbon track whore
|

11-02-2009, 03:51 AM
|
 |
Senior Member
|
|
Join Date: Oct 2006
Location: Golden Valley, MN
Posts: 3,017
|
|
|

11-02-2009, 03:54 AM
|
 |
Senior Member
|
|
Join Date: Oct 2006
Location: Golden Valley, MN
Posts: 3,017
|
|
Ah what do those idiots at HRC know!

|

11-02-2009, 04:07 AM
|
 |
Senior Member
|
|
Join Date: Aug 2007
Location: maryland
Posts: 1,250
|
|
Quote:
Originally Posted by wibbly
i always wondered about this... should the pipes be of equal length with a v-twin firing pattern? i can understand on an i4 but with a v-twin you wouldn't expect identical length pipes to create the same pulse tune... no?
maybe i'm just picturing it wrong...
|
true some extent as I understand it. a twin will inherently not scavenge as well or as evenly as a four, but I belive that is why your premium kits like Sato and Akrapovic use different sized pipe on one side. in order to increase the velocity a tad and make the rear cylinder "suck" for a slightly longer period of time. I digress though my twin tuning is pretty limited.
__________________
06 rc51 banzais, pcIII... the usual
94 vfr 750 40k miles
94 yamaha full carbon track whore
|

11-02-2009, 02:31 PM
|
|
Member
|
|
Join Date: Jun 2009
Posts: 69
|
|
Read A Grahm Bell's "Performance Tuning in Theory and Practice"
There is a wealth of information about exhaust theory.
|

11-03-2009, 03:03 AM
|
 |
Gold Sponsor
|
|
Join Date: May 2003
Location: Live free or Die
Posts: 13,861
|
|
the rear tube is too short and you will lose serious power and that is part of the reason for the dup in the 2-1's, they all have too short a rear header tube by several inches
__________________

www.carbonpartz.net
1990 RC30 going for 125hp
1995 RC45 New baby needs the dough
2001 RC51 done to the 9's
2004 CBR 1000rr done past the 9's and stolen!
2006 Yamaha R1 Black Dragon GP cans
2008 New Baby Caleb 0 miles
2009 Possible V4/S1KRR
Black Dragon Exhaust & Moto GP cans
www.blackdragonexhaust.net
This message is hidden because Jami6989 is on your ignore list.
This message is hidden because robfromsc is on your ignore list.
|

11-03-2009, 03:41 PM
|
 |
Si vis pacem, para bellum
|
|
Join Date: Jul 2009
Posts: 76
|
|
Amazing balance on the CBR... 
__________________
Cool ain't perfect. Perfect ain't cool.
|
| Thread Tools |
|
|
| Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT. The time now is 12:08 PM.
|