Engine Air Supply

[ChadGnarly]

Sportfish has the right idea, just need a 2" version. I run at least 4 2.5" breather tubes on all my skis. More air the better.

 

[sxipro02]

Do those frog skins even work? My hood doesn't have any vents

I put those on top of my breather tubes for a while, They didnt keep out any water and actually killed the performance when they got dirty. The dirt would get wet and choke off all the air intake to the point the ski would not rev up past idle. It took some time to figure out the issue but I know Ill never use them again.

 

[sxipro02]

I was having water ingestion issues with my old intake setup so Im going to run it like this this year, Looks like it will work better.

This was the old way, I had 3 2'' tubes on it. The new ones are 2.5'' shop vac tubes.

 

[Superjetjim]

Great thread, so how do I fit breathers to my new XFS?! I was thinking perhaps a couple of bilge fittings on the firewall piped up high then down do bottom of engine bay (to avoid run back)? Not sure this will give enough though?

 

[hink320]

Great thread, so how do I fit breathers to my new XFS?! I was thinking perhaps a couple of bilge fittings on the firewall piped up high then down do bottom of engine bay (to avoid run back)? Not sure this will give enough though?

This is actually exactly what I did to my Footrocket. I was running dual bilges, but I found I didn't need them for the riding I do so I removed the bilges and just ran the tubes down to the bottom of the hull. My 1200 seems to run fine with just pole breathers and the bilge breathers.

 

[XJCrawler]

Great thread, so how do I fit breathers to my new XFS?! I was thinking perhaps a couple of bilge fittings on the firewall piped up high then down do bottom of engine bay (to avoid run back)? Not sure this will give enough though?

You could order the ninja hood scoop and add some breather tubes

 

[fx1dan]

This is actually exactly what I did to my Footrocket. I was running dual bilges, but I found I didn't need them for the riding I do so I removed the bilges and just ran the tubes down to the bottom of the hull. My 1200 seems to run fine with just pole breathers and the bilge breathers.

would you notice a difference in performance if you block the bilge outlets up?

 

[DAG]

Thats what I want to know.
If a XMW only breaths 3 sq inches. I'm curious if people running tube poles (8 sq inchs) would notice a difference if they stuffed a rag down one tube (4 sq inches) Even with 1 tube blocked it would be more volume than a xmw pole.
Don't some of you have kids, get them started on a science fair project.

 

[hink320]

would you notice a difference in performance if you block the bilge outlets up?

I don't think so, I ran it last year with the bilges hooked up and it doesn't feel any different with them disconnected and using the outlets for air intake.

 

[Philip Clemmons]

Most of the skis out there don't get enough air. Big motors need big air. I've experimented with it on many skis, including freaks, the red brawler with TPE 1105, my KDX, and some others. Everyone showed noticeable gains with more air. You have to balance air in versus potential water in for your application. Flatwater boats with big engines get away with more because a skilled rider won't ever let go of the ski. Surf guys have tougher conditions and may WD tv to compromise between the two. The XS hoods are all large openings. The smaller was the early design. They were one of the first to figure it out.

I've never added air and not noticed a noticeable improvement.

 

[hink320]

Most of the skis out there don't get enough air. Big motors need big air. I've experimented with it on many skis, including freaks, the red brawler with TPE 1105, my KDX, and some others. Everyone showed noticeable gains with more air. You have to balance air in versus potential water in for your application. Flatwater boats with big engines get away with more because a skilled rider won't ever let go of the ski. Surf guys have tougher conditions and may WD tv to compromise between the two. The XS hoods are all large openings. The smaller was the early design. They were one of the first to figure it out.

I've never added air and not noticed a noticeable improvement.

Ya, I'm thinking my motor would benefit from more air, but my hood doesn't have a liner and i really don't want to cut into my beatiful carbon hood

 

[wanderer1]

I cant believe this thread is 4 pages long. So you think that running big ported motor, big carbs and pipe while giving it a more limited air supply than the oem's give a stock motor is gonna work? I also don't think XS was he first to figure it out, just something that has been forgotten. Anyone ever looked at a 250cc dirt bike air box all drilled out? Running a lot more air back in the day just on my old PJS 550 than most guys are giving their 900 today. Is a motor not an air pump? Ya get out what you are willing to put in. Just my 1 cent

 

[Philip Clemmons]

I also don't think XS was he first to figure it out, just something that has been forgotten.

Well I'll rephrase. They were the first to do something about it with their hull designs. Who else has air inlets like that on their hoods

I'm just stating the facts. I'm completely unbiased from a brand perspective. I was at the point on my Freak that I needed to open the inlets up, but didn't want to grind on my tro stage paint. Lo and behold, about the same times, XS increased their openings significantly.

It's their for a reason.

 

[wanderer1]

Like I said Phil, I think its just something that has been forgotten by a new generation of hull builders and then by the new generation of riders. Put your ski on a trailer in the water, 1/2 throttle you can't lift the hood off you got an issue.

 

[Philip Clemmons]

Ya, I'm thinking my motor would benefit from more air, but my hood doesn't have a liner and i really don't want to cut into my beatiful carbon hood

That can be a challenge. They work ok with less air, but maximum performance (and significant gains) can be found with the proper amount of air. Getting that right is different with every hull/hood/pole setup out there.

 

[Sanoman]

l didn't have a 1200 in my rocket like Chad.l ran an 865 with no breathing except the XS pole.Never had an issue with air volume,which l found strange.So l can agree with him running a 1200 in his rocket.

The new SF is a different story.Here is a short video of the same engine and pole set up w/o hood breathers.lt should explain precisely what Phil was explaining!

Ok,the vid will not load from my iPhone or pad!

Can someone help please

 

[KTM434]

@Sanoman there ya go buddy. Where's your build thread on this beauty?

 

[Freakrider]

XS advised me to run at least 3 hoses off my hood liner for the 900R. sj762 is running 4 on same but I figured more water would rush in when ski is upside down. Runs great on 3 hoses but Phil has me wondering about this now.

 

[LimitedSlip7]

Thats pretty nuts! Someone really needs to hook up a manometer. It's really difficult to compress a hood like that just by putting my body weight on it, so the force on that hood have to be pretty extreme. Assuming there is about 18"x25" of area on the inside of the hood seal, just a 1psi pressure difference would result in 450lbs of force pressing down on the hood...

 

[KTM434]

XM breather tubes aren't very big when you subtract the area used for steering cable, throttle cable, start/stop switch and the kink at the pivot. My Freak had two 2.5" breather tubes in the hood just for a 771 with dual 44s. Freakrider, what size carbs are you running?