Fullsac MX Header pipe
Seasoned HDF Member
Joined: Jan 2008
Posts: 13,676
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From: State of Confusion
The fact that is comes with a full size cross-over and mounts, helps in that balance flow your looking for and the nice curves to get the exhaust over to the leftside is a big improvement over the stock type "T" bone flat cross-over. Look at most other pipes you can clearly see the "T" joint doesnot promote the flow to the leftside. That is just why you may think one is cheaper than the other but you are getting less too.
HD EFI Guru
Joined: Jan 2008
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Let's start with the HD stock pipe to compare too. The stock head pipe has a "T" joint to direct the flow to the left side (cheaper cost). Then the cross over has a sharp 90 bend about an inch of straight then another sharp 90 bend! Then it runs under the bike and makes a few more bends to get it into the left side muffler. All of the pipe area under the bike is then squished down to about an inch in height on the outside so the flow area is even less. Anyone who believes this promotes flow is sadly mistaken! I am sure the factory has a height limit so that is why they squish the damn thing down so far. As long as you use the stock cross under your pretty much stuck with the "T" joint on the head pipe to make it work. That also saves the manufacture $$$ if they do not replace it but it has a cost on the performance side.
The Fullsac MX tosses the factory cross over pipe in the trash with the head pipe so you lose the "T" joint and lose the terrible cross over. They increased the primary length, installed a "X" collector then split out both sides nicely with gentle bends to get the supplied full diameter cross over onto the bike. A heavy duty billet AL bracket is supplied to mount the new cross over into place and support the pipes. It uses all the factory heat shields so it is pretty stealth looking once installed. The head pipe comes with provisions for both style O2 sensors with them properly placed. No cheesie adapters to put the small O2 into the large O2 bungs that others manufactures are using. It also cost more than others by price only, but once you look at what your getting/ gaining I feel it's more than fair as the quality is second to none. As I said before you can buy cheap or buy quality, your choice.
Seasoned HDF Member
Joined: Jan 2008
Posts: 13,676
Likes: 11,468
From: State of Confusion
very informative, thanks..I had no idea the OEM was compromising so much..sounds like the left side is truly all show and no go..kind of phony and feel duped..maybe one of these days I'll do it all right but for sake of learning more for now I have 2 questions regarding the SE Hi Flow exhaust (setting aside cost/value because clearly it's bad)
https://www.harley-davidson.com/stor...annon-mufflers
1. how much more flow goes to the left side with this design?..hypothetically speaking let's just say OEM is 80/20 and this system would be XX/XX? and if it's significant what would be the benefits?
2. how much exhaust heat reduction/relocation benefit would be recognized moving the cat from the head pipe to the mufflers?
thanks
https://www.harley-davidson.com/stor...annon-mufflers
1. how much more flow goes to the left side with this design?..hypothetically speaking let's just say OEM is 80/20 and this system would be XX/XX? and if it's significant what would be the benefits?
2. how much exhaust heat reduction/relocation benefit would be recognized moving the cat from the head pipe to the mufflers?
thanks
Last edited by mjwebb; Aug 19, 2017 at 08:07 AM.
Ultimate HDF Member
Joined: Oct 2016
Posts: 5,063
Likes: 2,582
From: On my bike!
very informative, thanks..I had no idea the OEM was compromising so much..sounds like the left side is truly all show and no go..kind of phony and feel duped..maybe one of these days I'll do it all right but for sake of learning more for now I have 2 questions regarding the SE Hi Flow exhaust (setting aside cost/value because clearly it's bad)
https://www.harley-davidson.com/stor...annon-mufflers
1. how much more flow goes to the left side with this design?..hypothetically speaking let's just say OEM is 80/20 and this system would be XX/XX? and if it's significant what would be the benefits?
2. how much exhaust heat reduction/relocation benefit would be recognized moving the cat from the head pipe to the mufflers?
thanks
https://www.harley-davidson.com/stor...annon-mufflers
1. how much more flow goes to the left side with this design?..hypothetically speaking let's just say OEM is 80/20 and this system would be XX/XX? and if it's significant what would be the benefits?
2. how much exhaust heat reduction/relocation benefit would be recognized moving the cat from the head pipe to the mufflers?
thanks
That head pipe at least has a "X" collector area which would have to be better than the "T" style but since the regular street cannons are so tame I bet these with the cat in them are super weak.
Seasoned HDF Member
Joined: Jan 2008
Posts: 13,676
Likes: 11,468
From: State of Confusion
yeah, Steve gave it really nice endorsement from a professional bike builder perspective that sold me on it..looks impressive..like I said earlier..maybe at some point I'll do the exhaust upgrade right..probably another year after warranty expires and my bike runs great now, albeit this Summer has confirmed it can be a HOT SOB
HD EFI Guru
Joined: Jan 2008
Posts: 4,492
Likes: 4,778
very informative, thanks..I had no idea the OEM was compromising so much..sounds like the left side is truly all show and no go..kind of phony and feel duped..maybe one of these days I'll do it all right but for sake of learning more for now I have 2 questions regarding the SE Hi Flow exhaust (setting aside cost/value because clearly it's bad)
https://www.harley-davidson.com/stor...annon-mufflers
1. how much more flow goes to the left side with this design?..hypothetically speaking let's just say OEM is 80/20 and this system would be XX/XX? and if it's significant what would be the benefits?
2. how much exhaust heat reduction/relocation benefit would be recognized moving the cat from the head pipe to the mufflers?
thanks
https://www.harley-davidson.com/stor...annon-mufflers
1. how much more flow goes to the left side with this design?..hypothetically speaking let's just say OEM is 80/20 and this system would be XX/XX? and if it's significant what would be the benefits?
2. how much exhaust heat reduction/relocation benefit would be recognized moving the cat from the head pipe to the mufflers?
thanks
I cannot say how the SE High Flow will work out as the cost was more than I was willing to spend. That said it is much closer to the Fullsac MX design with a nice full size cross over and an "X" pipe design with a smooth bend to direct exhaust to the left side. It still has shorter primary's which promoted higher RPM performance more so than longer primary's which promote the low to mid range. The passenger will most likely feel a heat reduction on there right foot area with the cat moved to the mufflers.
I've include a picture of the stock cross over and "T" joint and anyone who says this is a good setup for performance, needs to go learn how exhaust works as they clearly do not know anything about exhaust flow. As I said before once you start looking at what is included with the Fullsac MX kit it's not all that expensive for what you are getting.
Seasoned HDF Member
Joined: Jan 2008
Posts: 13,676
Likes: 11,468
From: State of Confusion
thanks..with no real working knowledge of exhaust flow characteristics, if you put the OEM next to either of the two we're talking about and asked folks to choose it'd be 100% NOT OEM obviously
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Ultimate HDF Member
Joined: Oct 2016
Posts: 5,063
Likes: 2,582
From: On my bike!
I cannot say how the SE High Flow will work out as the cost was more than I was willing to spend. That said it is much closer to the Fullsac MX design with a nice full size cross over and an "X" pipe design with a smooth bend to direct exhaust to the left side. It still has shorter primary's which promoted higher RPM performance more so than longer primary's which promote the low to mid range. The passenger will most likely feel a heat reduction on there right foot area with the cat moved to the mufflers.
I've include a picture of the stock cross over and "T" joint and anyone who says this is a good setup for performance, needs to go learn how exhaust works as they clearly do not know anything about exhaust flow. As I said before once you start looking at what is included with the Fullsac MX kit it's not all that expensive for what you are getting.
I've include a picture of the stock cross over and "T" joint and anyone who says this is a good setup for performance, needs to go learn how exhaust works as they clearly do not know anything about exhaust flow. As I said before once you start looking at what is included with the Fullsac MX kit it's not all that expensive for what you are getting.
Are you the same Steve that owns Fullsac? I see on the website the owners name is Steve.
