Engine Air Supply

[849tigerbotkv1]

Definitely saw hood vents too.say what you want but you absolutely need hood.vents to get ultimate power. First hull I ever built had a bone stock sxr engine in it has.the hood had no vents only.vented through rrp.the seal on hood was so tight with hull it would flex took me a few runs to figure out the issue when the bilge fittin started whistlin I knew it needed more air. Night and day difference after I installed 2 hood vents

Same happened to nuklear on his aquabot

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Did nuklear ever drill holes on his hood to make a hood vents?

 

[superjet104]

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

 

[DAG]

The hull inlet does not need to be as large as the carbs because intake pulses get averaged. .

Kev, can you dumb this down alittle, not sure I understand what you are trying to say.

 

[restosud]

kawi 550's had that issue when racing with stock hood.suction held the hood down and boats ran like poop.a freestyle boat may not show the same symptoms as we rarely go wot for extended periods so air has some time to go back in but on bigger engine you can see the hoods get sucked in on stock yamy hull .
next time in the water i'll run a manometer to check vacuum.

 

[restosud]

frogskinz do not work is pressure differential is too great.water gets sucked right in.

 

[zyxwvu44]

Good thread, I was just searching for this about the xmetal pole. I have felt engine suffocating in my old sn, but not in my RN with the xmetal pole. Running a 780 with twin 38's. I am wondering if maybe i t is also sucking in air through the bilges as unless there's a ton of water only one is working at a time.


Any flow bench tests of OEM flame arrestor vs aftermarket, also aftermarket with the water sock thing on it?

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[River Rat]

Who has a picture of trickys hood lol? @tricky1

@DAG Isn't this one of his monsters?

 

[Byeai]

That's the dvx 1400

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[Christian_83]

Funny thing is, that i noticed (not because of this thread) that Xscream has made 2 types of hoods/hull for the KDX, i don't know why not just only go "big"
but i saw 2 different size intakes on the hoods, might be for 900 and 1200cc. But again i don't see why not only make the big intake?

 

[Marcgraham27]

Great Thread...I'm trying to decide if my hurricane needs hood vents with just a 701, dual carbs, pfp, xmetal pole.. Correct me if I'm wrong but would taking the hood off and going for a short rip to see if there is any substantial gains give us the answer to this question

 

[zyxwvu44]

Good thread, I was just searching for this about the xmetal pole. I have felt engine suffocating in my old sn, but not in my RN with the xmetal pole. Running a 780 with twin 38's. I am wondering if maybe i t is also sucking in air through the bilges as unless there's a ton of water only one is working at a time.


Any flow bench tests of OEM flame arrestor vs aftermarket, also aftermarket with the water sock thing on it?

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So I went out today and uncovered a small blocked hole in my hoodliner(about 3/4 and inch) and wow a lot more power. I was definitely suffocating my engine with just the xmetal pole breathers.

Definitely going to put a proper breather tube in and make it a bigger diameter.

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[fx1dan]

I run a 1100 in a xfs and haven't had a problem with breathing through my atp twin pole but you guys have got me thinking I might need more air.
I know rrp make a hood scoop but how comes you never see them being used, I just browsed facebook at a few top rides pics and they are all running 1000+ motors in rickter hulls with just the pole for air. surley if these guys would be the first to add vents if needed?

 

[kev.t]

Quick test dan, try running the ski around with the hood off. That will tell you if it's being strangled with it on. Just don't fall off ;-)

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[Sanoman]

l will be trying out my new SF without hood vents running an xs865 and xs pole.My foot rocket ran fine without hood breathers.But the low circus hood on this new ski may prove differently.

l don't think you can definitively say that all skis have to have hood breathers.

 

[just joe]

frogskinz do not work is pressure differential is too great.water gets sucked right in.

I completely agree. I tried them out and experienced no significant difference in water intake.

 

[Superjetjim]

Great thread, fx1Dan any update, did you try it with the hood off?

 

[kev.t]

I did jim. Quite a significant improvement so we are now trying to work out a decent way of putting some extra breathing into the skis.

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[sportfish258]

Sanoman took a cool vid of his hood getting sucked down on his freak . I think he was only breathing thru a x metal . Scott s showed me this a few years ago.

Seems like Art told me a long time ago you need a MINIMUM of 1.5 times the carb size. Ie 44's need 66 mm of breather tubes and so on.

The hulls are getting smaller and the availability of space is limited to run the tubes to the bottom of our hulls. My experience is that if you run tubes in shallow you ingest a ton of water.


Question:

What if you made a ball type valve that closed when the ski was up side down ...." my ski is in that position that a lot". It would have to be custom have not seen any thing off the shelf. The ball might have to be to heavy in order to work properly.

 

[McDog]

Water pressure would overcome any ball valve. I don't think it will work.

 

[849tigerbotkv1]

I think you just need to have the breather higher than the hood liner and place it on the intake side so when you flip your ski (of course clockwise) the water drains to the left of the hood then out