Harley Davidson Forums

anjumkha · Apr 27th, 2011, 01:41 PM

eGlide 2007

What is the purpose of the cross over pipe?

RibEye · Apr 27th, 2011, 01:45 PM

As far as I can tell, it is to increase overall exhaust flow velocity, improving the scavenging (emptying) of the contents of each cylinder during its exhaust stroke, with the inertia of exhaust gasses from one cylinder being able to draw/suck on the other cyclinder's exhaust port, helping it empty more quickly and completely.

Enjoy,
Rich P

wilks3 · Apr 27th, 2011, 01:55 PM

Exactly RibEye, Helps balance system to pull more spent gases out of cylinders.
wilks3

Dr.Evil · Apr 27th, 2011, 03:11 PM

Quote: Originally Posted by RibEye View Post

As far as I can tell, it is to increase overall exhaust flow velocity, improving the scavenging (emptying) of the contents of each cylinder during its exhaust stroke, with the inertia of exhaust gasses from one cylinder being able to draw/suck on the other cyclinder's exhaust port, helping it empty more quickly and completely.

Enjoy,
Rich P

It sounds right, except that you can not draw exhaust from the other cylinder on it's compression stroke. It was my understanding that the crossover allowed pressure wave build up, a low pressure escape path to flow into, allowing for better flow over all and better cylinder scavenge. The MoCo may test the exhaust for the location of pressure points in determining where the co pipe should go.

slayer · Apr 28th, 2011, 12:51 AM

If you are really interested check out RB racing's website. They go into great detail to explain this. Sounds pretty intense the lengths they go through to figure it all out.

mike5511 · May 4th, 2011, 03:50 AM

Quote: Originally Posted by smitty901 View Post

It is called scavenging. For an HD it is as close to best of both worlds as you can get.
HD big Vtwin produces better low end torque with a 2 to 1 exhaust system. But a free flowing system produces more power on a flat out wide up top end run.
The HD system allows the exhaust to act a lot like a 2 to 1.
Start your ride up walk around back places hands near exhaust feel the difference. The system also allows of easier tuning.

I just went from tru-duals back to a stock header. I was looking for more torque. (went with Jack Pot Dyno Tuned mufflers) Seems to have helped.

Apr 27th, 2011, 01:45 PM	#2
RibEye Contributor$ Ride: 2003 Road King Classic (100th Anniversary FLHRCI-X) Join Date: Sep 20th, 2009 Location: Tucson AZ Posts: 799 My Mood:	Re: Cross over pipe As far as I can tell, it is to increase overall exhaust flow velocity, improving the scavenging (emptying) of the contents of each cylinder during its exhaust stroke, with the inertia of exhaust gasses from one cylinder being able to draw/suck on the other cyclinder's exhaust port, helping it empty more quickly and completely. Enjoy, Rich P

Apr 27th, 2011, 01:55 PM	#3
wilks3 Community Star Ride: 2010 FatBoy Join Date: Dec 12th, 2009 Location: Southern Illinois Posts: 627 My Mood:	Re: Cross over pipe Exactly RibEye, Helps balance system to pull more spent gases out of cylinders. wilks3 __________________ Member of the Illinois Patriot Guard "I see" said the blind man who could not hear...

Apr 27th, 2011, 03:11 PM	#4
Dr.Evil Community Star Ride: '05 FLSTC Join Date: Mar 11th, 2010 Location: S.W. Michigan Posts: 699 My Mood:	Re: Cross over pipe Quote: Originally Posted by RibEye View Post As far as I can tell, it is to increase overall exhaust flow velocity, improving the scavenging (emptying) of the contents of each cylinder during its exhaust stroke, with the inertia of exhaust gasses from one cylinder being able to draw/suck on the other cyclinder's exhaust port, helping it empty more quickly and completely. Enjoy, Rich P It sounds right, except that you can not draw exhaust from the other cylinder on it's compression stroke. It was my understanding that the crossover allowed pressure wave build up, a low pressure escape path to flow into, allowing for better flow over all and better cylinder scavenge. The MoCo may test the exhaust for the location of pressure points in determining where the co pipe should go. __________________ Member, Michigan Patriot Guard Riders - To Say, Thank's for Your Service

Apr 28th, 2011, 12:51 AM	#5
slayer Start The Engine Ride: 2007 FLHRS Join Date: Feb 21st, 2009 Location: B.C. Posts: 32	Re: Cross over pipe If you are really interested check out RB racing's website. They go into great detail to explain this. Sounds pretty intense the lengths they go through to figure it all out.

May 4th, 2011, 03:50 AM	#6
mike5511 Start The Engine Ride: 08 Ultra Classic Join Date: Sep 19th, 2010 Location: NW Arkansas Posts: 10	Re: Cross over pipe Quote: Originally Posted by smitty901 View Post It is called scavenging. For an HD it is as close to best of both worlds as you can get. HD big Vtwin produces better low end torque with a 2 to 1 exhaust system. But a free flowing system produces more power on a flat out wide up top end run. The HD system allows the exhaust to act a lot like a 2 to 1. Start your ride up walk around back places hands near exhaust feel the difference. The system also allows of easier tuning. I just went from tru-duals back to a stock header. I was looking for more torque. (went with Jack Pot Dyno Tuned mufflers) Seems to have helped.

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