Are Engines Being Starved of Air Intake?

[The Hulk]

So ive done some research on some people with boats no HP they take into a dealer and checks out ok, go back out on the lake and it seems sluggish etc.. open Engine hatch and wham lots of power again....

in looking at my bu i'm wondering if my engine is being starved of air ?

it seems we have side locker walls and covers/hatches and towel trays, its pretty sealed up if you ask me, yes ther eis a 3-4" intake tube as well as your two 3-4" intake tubes linked to the side of your boat.

in theory if you moving forward air should come in via windshield or the front through tube, as well air pulled in from the back side vents, however i wonder if 3-4" tubes are enough? does the engine have the power to SUCK that air into the boat or is it preventing proper air-flow

reading online starving the engine of air results in extra exhaust/smoke/CO2 and loss of Horse Power, sluggish performance etc..etc..etc..

if you consider drinking from a straw the longer the straw the harder it is to get the air or drink etc..

i'm wondering about adding two 4" blower fans to the intakes in the rear "backwards" wired when engine is on that they SUCK air into the engine area and doing a test before and after

i have a 2013 23LSV with SC LSA 555hp so my "air" requirements might be more than others with the Super charger..... although the smaller the engine perhaps the more important this might be.

to me it just seems like the engine area is way too sealed up for the amount of air the engine might need. yea i know there are gaps under seats, compartments, hatches etc.. but if the engine is having to SUCK the air rather than having it "there" then it cant be nearly as efficient IMO.

anyone with experience or thoughts?

Edited March 6, 2015 by The Hulk

[Pistol Pete]

I agree but, have no answers.

A 555 hp super charged motor is gonna need 02 up the ying-yang.

[SmoothWaterMan]

In round numbers your engine should draw 900-1000 cfm at wide open. How to convert that into air vents under vacuum I've no idea.

But, if it doesn't increase rpm with the engine hatch open, it's getting enough air.

pb

Edited March 6, 2015 by SmoothWaterMan

[MLA]

in looking at my bu i'm wondering if my engine is being starved of air ?

no

[Brian Young]

no

This should fix it.

http://m.summitracing.com/parts/sse-950-72102

[The Hulk]

Based on your 1000 cfm rate the two ducts in the rear (if the only area to pull air) would be roughly 32mph or 2,865 LFM linear ft/min possibly less with the other "holes" or front hose

the tubes are roughly 4ft from edge of boat down to engine area which means that is restricting further. trying to find some calculations of 4" pipes

as far as i know you have 2 from side Plus one longer one from front.

from the looks of things it does look like they may not be getting enough air if your hatches and sides and sealed up well, based on the above the side vents in the back should have some SERIOUS suction like a shop vac, have not put my hand over it to test when surfing etc..

with only going 9-12mph for surfing you can probably scratch out much air-pressuring being brought in from the front intake, especially with the bow rise blocking it further. moving forward would mean air going around the sides of the boat creates a somewhat "wing" airfoil effect, and naturally trying SUCK air out of the vents, making it at least somewhat harder for the engine to SUCK air through the vents when the natural air-pressure around a forward moving boat is trying to pull it out of the vents.

i seriously start to wonder if this has had some issues with various owners and smoke/exhaust extra CO2 when surfing at low speeds and not getting enough 02 into the boat. A weighted boat is working very hard and not getting a lot of air-pressure which at those RPM's in the "olden days" means fast and good air-flow/pressure being forced into the engine area.... surfing downwind and engine could seriously be starving if rough calculations are correct.

surely i will be adding some high speed blower fans to bring air in from both side to see what happens. For about $50 for 2 blowers its worth a test at least

Edited March 6, 2015 by The Hulk

[alpensurf23]

ever thought of an engineering job? I like the thinking and question, keep us posted.

[The Hulk]

I am an engineer =)

[Falko]

So in standard ducting, 4" duct will move 130 CFM at 1" loss per equivalent 100'. Using two four inch lines, say 10' each, and that spiral wound duct, you are probably getting .3-.4" of loss coming in through those lines. But that is only moving 260 CFM.

Now, your boat isn't nearly as air tight as you think it is, no where near.

Want to test it? Get a piece of tygon tubing about 6' long. Stick one end into the engine compartment through a hole that doesn't crimp it too much, some is ok, you aren't going to move air through it really, but it just can't be crushed.

put a little water in the tube, (that's right, u-tube manometer) and make a bend so the water sits in the bottom of the tube. Go for a run and watch the water. Is it pulled to the engine compartment side? I would expect not, but that will tell you if you are pulling a vacuum in the engine area. Lot less work and headache than adding fans and such. Oh, and one thing to consider about those fans, those are rated at 0" of static. Once you start adding some static pressure to overcome, their flow rates drop quickly.

Good luck, let us know what you find.

[Andrew63]

could just remove the hatch for a before & after test run

[Ndawg12]

could just remove the hatch for a before & after test run

take the whole sunpad off, engine dividers out, run it hard and see if there's an increase in RPM's, if so you'll know you're on to something.

[Kalamazoo]

or block one of the two intakes and see if it 'chokes'...

[Dare2goBare]

Ok, so I have a question / thought? I would think Malibu has taken all this into account in there boat designs for

maximizing HP? These are high performance tugs, and squeezing out every once of performance would be a key concern.

[pook77]

could just be one of those things Indmar thought Malibu thought of, and vise-versa. Not to mention they do all of their testing with these boats at sea level. So the air is nice and dense.

[05hammerhead]

Ok, so I have a question / thought? I would think Malibu has taken all this into account in there boat designs for

maximizing HP? These are high performance tugs, and squeezing out every once of performance would be a key concern.

I wouldnt put as much faith in engineers as youre doing. Same intake design for all motors sizes seems weird and I would guess they arent testing it with the kind of weight some guys here are throwing in the boat. Not to mention the variation of bow rise associated with different props/speeds/weighting etc.

[robbennett]

Maybe we should run a big tube from our intakes out under the seat over the v drive. Or maybe make a cold air intake system that completely moves the air filter to the interior of the boat where it can breathe. I can only imagine how loud it would be then.

[nyryan2001]

I doubt they are being starved... or struggling for air. especially the 555... with a pulley driven air crammer and air sucker forcing in thru the K&N filter and into the cylinders...it absolutely gets in there.

Between the rear vents on your boat, the standard blowers where they pull their fresh air and all the cracks and compartments... plenty of air instake into the engine compartment for engine use.

As an engineer also myself, in my undergrad... I was looking into how regular ambient air is 28% O2. Ever see what happens when you increase O2% to an open flame? Started tooling around with how would engine efficiency/hp/tq be affected if we could increase O2% as it's fed into the engine...even just a little to say 35%, would be similiar to nitrous. We know on the exhaust output side we can strip CO2 apart and convert with that exhaust running across certain materials at high temps... concept was an exhaust heated? pre-catalytic converter intake to increase O2 % as its fed into the engine to increase performance.

I need Malibu's patent lawyers.

[formulaben]

If there's a lack of air in the engine hatch area, then it there would be a low pressure around the engine and it should be very hard to open the hatch while running at high RPM. I doubt that is the case.

[Falko]

Lifting the hatch/seats whatever isn't going to give you accurate representation. It gets hot in the engine compartment. Simply opening the hatch can give cooler air and bring the hp up slightly. Really, $3 of clear tubing and 2oz of relatively free lake water will tell you pretty quick if your engine compartment is pulling a vacuum.

[shawndoggy]

I like the Hulk. His ideas are wacky, but they are frequent and make just enough sense to get people thinking. Keep up the out-of-the box thinkin' Hulk!

[D-GOOSE]

What if you cut a hole in front of the trans below the rear center seat? Or In the side rear seat area (just before the locker) put a blower to push air in the trans area.

[Bill_AirJunky]

Seems like an easy test would be to just remove the engine cover for a few laps at various speeds. Does the engine perform any differently?

[WakeGirl]

I doubt they are being starved... or struggling for air. especially the 555... with a pulley driven air crammer and air sucker forcing in thru the K&N filter and into the cylinders...it absolutely gets in there.

Between the rear vents on your boat, the standard blowers where they pull their fresh air and all the cracks and compartments... plenty of air instake into the engine compartment for engine use.

....

Exactly. The engine compartment is hardly sealed. Start looking at all of the ways that it isn't & you'll quickly see that the engine is very likely not starving for air. Now whether or not that air is cool enough is a whole 'nother discussion.

What if you cut a hole in front of the trans below the rear center seat? ....

That was my first thought.

Seems like an easy test would be to just remove the engine cover for a few laps at various speeds. Does the engine perform any differently?

Easier would be to just remove the rear center cushion & tray.

[Andrew63]

Ok, so I have a question / thought? I would think Malibu has taken all this into account in there boat designs for

maximizing HP? These are high performance tugs, and squeezing out every once of performance would be a key concern.

One would expect this is the case.

Some of us are just born tinkerers & with the extended winter in the US, have time on our hands to ask ....what if.

The Hulk being an Engineer looks like he fits this bill.

I often though about removing one or all of the drink holders on the rear of the CM hatch just to see if there is any difference.

But, the water was too good & kept skiing

[DocPhil]

. I was looking into how regular ambient air is 28% O2.

20 % but who's counting