Why Do My Exhaust Headers Have Crossover Tubes?

Motofool · May 26th, 2016, 02:27 PM

Copied from
http://www.cycleworld.com/2015/06/26...rossover-tubes

"Lots of motorcycle makers do this. The first time I saw such crossover tubes was on the Yoshimura 750 Superbikes.

The torque-boosting effect of exhaust pipes arises as follows:

As the exhaust valve(s) of a cylinder open, a positive wave of pressure travels down the pipe. When it comes to any point of expansion (such as when it joins a collectors pipe, or when it reaches atmosphere), that wave of expansion also expands back up the pipe. If it arrives in the cylinder during valve overlap (exhaust not yet quite closed, intakes just beginning to open), it draws out residual exhaust gas in the combustion space and can even propagate into the intake system, causing intake flow to begin even before the piston has moved downward on its intake stroke.

Because positive and negative waves alternate in the pipe, at some lower rpm it is a positive wave that arrives at the cylinder during overlap. This reduces torque at this rpm by stuffing more exhaust gas back into the cylinder and into the intake ducts, thereby delaying the intake process. In motorcycles with carburetors, the positive wave also causes an over-rich condition, as the carburetor adds fuel to flowing air no matter which way it moves.

By providing another point of expansion, crossover tubes—which are often quite small—can broaden the rpm range over which the negative wave arrives during overlap, thereby improving cylinder filling and power."

- Kevin Cameron

crazymadbastard · May 26th, 2016, 05:27 PM

To get to the other side?

cadd · May 26th, 2016, 08:54 PM

Quote:

Originally Posted by crazymadbastard

To get to the other side?

Why did the chicken cross the road?

jkv45 · May 27th, 2016, 06:51 AM

I'm guessing that in a race situation where you are looking for peak power only, you would not want to have crossovers tubes.

Anyone know for sure?

DEFY · May 27th, 2016, 06:59 AM

@cadd @crazymadbastard

I believe it's called mating, a rare event that occurs in nature when one header and another decide to get passionate. How else do you think headers are made? They aren't A sexual.

sharky nrk · May 27th, 2016, 08:40 AM

Quote:

Originally Posted by jkv45

I'm guessing that in a race situation where you are looking for peak power only, you would not want to have crossovers tubes.

Anyone know for sure?

In general from what I have been exposed to, that is correct.

Ghostt · May 27th, 2016, 10:45 AM

I know on cars, I've done the crossover pipe to help make I'd quieter, as far as flow goes it could help to reduce back pressure. Going thru two mufflers is better than one.

I think.....

RacinNinja · May 27th, 2016, 11:18 AM

Short answer: Torque.

Alex · June 21st, 2016, 07:09 AM

Also the answer to "what was one of the worst motorcycling movies made"

May 26th, 2016, 02:27 PM	#1
Motofool Daily Ninjette rider Name: Hernan Location: Florida Join Date: Mar 2011 Motorcycle(s): 2007 Ninja 250 Posts: A lot. MOTY - 2016, MOTM - Dec '12, Jan '14, Jan '15, May '16	Why Do My Exhaust Headers Have Crossover Tubes? Copied from http://www.cycleworld.com/2015/06/26...rossover-tubes "Lots of motorcycle makers do this. The first time I saw such crossover tubes was on the Yoshimura 750 Superbikes. The torque-boosting effect of exhaust pipes arises as follows: As the exhaust valve(s) of a cylinder open, a positive wave of pressure travels down the pipe. When it comes to any point of expansion (such as when it joins a collectors pipe, or when it reaches atmosphere), that wave of expansion also expands back up the pipe. If it arrives in the cylinder during valve overlap (exhaust not yet quite closed, intakes just beginning to open), it draws out residual exhaust gas in the combustion space and can even propagate into the intake system, causing intake flow to begin even before the piston has moved downward on its intake stroke. Because positive and negative waves alternate in the pipe, at some lower rpm it is a positive wave that arrives at the cylinder during overlap. This reduces torque at this rpm by stuffing more exhaust gas back into the cylinder and into the intake ducts, thereby delaying the intake process. In motorcycles with carburetors, the positive wave also causes an over-rich condition, as the carburetor adds fuel to flowing air no matter which way it moves. By providing another point of expansion, crossover tubes—which are often quite small—can broaden the rpm range over which the negative wave arrives during overlap, thereby improving cylinder filling and power." - Kevin Cameron __________________________________________________ *Motofool* *.................................Never ride faster than your guardian angel can fly* "Mankind is composed of two sorts of men — those who love and create, and those who hate and destroy. Love is the bond between men, the way to teach and the center of the world." - José Martí
	1 out of 1 members found this post helpful.

May 26th, 2016, 05:27 PM	#2
crazymadbastard I'm crazy,your excuse is? Name: Winston Location: Connecticut Join Date: May 2013 Motorcycle(s): 250 2007 ninja Posts: A lot.	To get to the other side? __________________________________________________ My Cafe Racer Build My intro post
	2 out of 2 members found this post helpful.

May 27th, 2016, 06:59 AM	#5
DEFY ᗧ•••ᗣ•ᗣᗣ•••ᗣ Name: Nick Location: NY Join Date: Nov 2013 Motorcycle(s): 2009 Ninja 250R and 2014 Triumph 675R Posts: A lot.	@cadd @crazymadbastard I believe it's called mating, a rare event that occurs in nature when one header and another decide to get passionate. How else do you think headers are made? They aren't A sexual. __________________________________________________ Spoiler for topic: It might just be the [you] tag

May 27th, 2016, 10:45 AM	#7
Ghostt in your machine Name: Scott Location: Summer Shade, Ky. Join Date: Oct 2014 Motorcycle(s): 98 Ninja 250/F12 aka ZX-2R "SERENITY", 91 Ninja 500/A5 aka ZX-5R "Phoenix", 84 Honda GL1200A "SIREN" Posts: A lot. Blog Entries: 25 MOTM - Jun '17, May '16, Mar '15	I know on cars, I've done the crossover pipe to help make I'd quieter, as far as flow goes it could help to reduce back pressure. Going thru two mufflers is better than one. I think..... __________________________________________________ *violente et ignorantia* ZX-2R BLOG *Twitter and Instagram = Ghostt_Scott* *I'm not here to change your mind, just to inform.*

May 27th, 2016, 11:18 AM	#8
RacinNinja Vintage Screwball Name: B Location: Washington Join Date: Feb 2016 Motorcycle(s): 2011 Ninja 250, 2008 Ninja 250, 2019 KTM 1290SDR, 2017 FZ10 Posts: A lot. MOTM - Mar '16	Short answer: Torque. __________________________________________________ Goin' fast on slow bikes!

May 27th, 2016, 06:51 AM	#4
jkv45 Rev Limiter Name: Jay Location: WI Join Date: Jul 2013 Motorcycle(s): '06 SV650n, '00 Derbi GPR, '64 CA77 Dream 305, '70 CL450 Scrambler, numerous dirt bikes Posts: A lot. MOTM - Jun '18, Oct '16	I'm guessing that in a race situation where you are looking for peak power only, you would not want to have crossovers tubes. Anyone know for sure?

June 21st, 2016, 07:09 AM	#9
Alex ninjette.org dude Name: 1 guess :-) Location: SF Bay Area Join Date: Jun 2008 Motorcycle(s): '13 Ninja 300 (white, the fastest color!), '13 R1200RT, '14 CRF250L, '12 TT-R125LE Posts: Too much. Blog Entries: 7	Also the answer to "what was one of the worst motorcycling movies made" __________________________________________________ Montgomery Street Motorcycle Club / cal24.com / crf250l.org / ninjette.org ninjette.org Terms of Service Shopping for motorcycle parts or equipment? Come here first. The friendliest Ninja 250R/300/400 forum on the internet! (especially Unregistered)

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