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[North Star]

Took my bike in for some engine mod work today- first time out of storage this year.

My builder/tuner likes the catless 2009 headpipes, and says they are good performers.

He took a look at my B x-pipe and commented on how small the collector was as compared to the OEM header.

How is the smaller collector beneficial? More/less tq down low?

I know way back Steve posted dyno charts when he first came out with the pipes, but I'd like to know about the theory behind why the Fullsac header design, specifically this smaller collector, is better than the OEM one.

[Doc 1]

What collector? The x pipe doesn't have a collector....it has the ''X''. As the gasses escape the front cylinder and enter the ''X'' it causes a vacuum in the rear cylinder pipe which clears it out for it's blow down then vice versa.
Doc

[North Star]

Guess thats what I meant- the chamber where the 2 goes to 1 before it goes back to 2.

[HOGMIKE]

Guess thats what I meant- the chamber where the 2 goes to 1 before it goes back to 2.

Would this help?
 

[North Star]

Yeah, I know what it looks like- apparently I don't know what it's called....in any case, it's much smaller than the OEM headpipe. Is this supposed to be better? Why?

Actually, I'm guessing the x configuration as Doc says creates better flow due to it's design as opposed to stock, which just has a chamber that the front/rear pipes pipes dump into before exiting back out through the 2 exhaust pipes- maybe?

[North Georgia Hawg]

Yeah, I know what it looks like- apparently I don't know what it's called....in any case, it's much smaller than the OEM headpipe. Is this supposed to be better? Why?

Actually, I'm guessing the x configuration as Doc says creates better flow due to it's design as opposed to stock, which just has a chamber that the front/rear pipes pipes dump into before exiting back out through the 2 exhaust pipes- maybe?

That's why it's called the X-Pipe! It's designed to produce the best flow and scavenging of exhaust gases between the two cylinders. It doesn't need to have a big collector like the stock header, because it doesn't need to accommodate a big catalytic converter inside of it.

Ken

[North Star]

Thanks guys. The proof will be in the pudding once the engine work is done on my bike and the final dyno charts are in. Builder hasn't seen any bikes with Fullsac pipes on, so he's not sure if it will do better or worse then the gutted stock headers, which is what he usually uses.

Should have it back in 7-10 days...can't wait. I anticipate 105 hp/130 tq with well over 100 tq from 2200-5000 rpms- I have a copy of a dyno sheet on another 110 that he built that shows this. I'll probably start a new topic on this build.

[Dead_Reckoning]

What collector? The x pipe doesn't have a collector....it has the ''X''. As the gasses escape the front cylinder and enter the ''X'' it causes a vacuum in the rear cylinder pipe which clears it out for it's blow down then vice versa.
Doc

Precisely!
It is and Eductor/Extractor just as you have mentioned.
The Exhaust Pressure from A Cylinder Header turns to Velocity when it passes through the  Larger Open "X" Chamber thus creating a partial vacuum on the other cylinder exhaust header ,

The less Backpressure on the after side of that "X" Chamber, the greater the velocity across the "X".

[willyB]

Hmmm, pressure turns to velocity.

I've got to re-read my physics books.

[North Star]

I'd like to hear from the horses mouth (Steve).....

[HOGMIKE]

I'd like to hear from the horses mouth (Steve).....

http://www.fullsac.com/

Give Steve a call.
He has a lot of experience with air-cooled engines, 4 and 2 cyl. Stock to full race.
 

[Fullsac Performance]

Thanks guys. The proof will be in the pudding once the engine work is done on my bike and the final dyno charts are in. Builder hasn't seen any bikes with Fullsac pipes on, so he's not sure if it will do better or worse then the gutted stock headers, which is what he usually uses.

Should have it back in 7-10 days...can't wait. I anticipate 105 hp/130 tq with well over 100 tq from 2200-5000 rpms- I have a copy of a dyno sheet on another 110 that he built that shows this. I'll probably start a new topic on this build.

I can promise you the X Pipe is substantially better than a gutted stock header. 130 peak TQ? That's a very high expectation from a 110" HD V Twin on pump gas.
I hope your combination of parts work well together and you get what your after.

Steve

[Midnight Rider]

What are you doing to the engine?  130 TQ is a lot to expect unless you're doing some really serious engine mods.

Big TQ = Big $$

[North Star]

See "My Engine Build" thread in the Twin Cam section for details of the work being done. I agree it sounds like high expectations, but Ive seen the dyno charts and the tq curve.

Having said that, does he have a happy dyno? Dont think so cuz I had my bike dyno'd elsewhere and later with him, and the numbers were within 2 hp/2 tq of each other.

I think due to his experience specifically tweaking the 110, and building  a bunch of them, he may have figured out some things about this particlar powerplant.