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Hi guys,

I've read the threads for some time now and following with interest the mods made to various GU 3.0l models by your guys.

One of the key things mentioned for the diesel - is the fitting of a snorkel - I've had a Nissan fitted one since new.

Curious though as to what science determines the size of the intake head on the top of the snorkel?

Would the vehicle perform any different with say a bigger opening - which presumably would feed a greater volume of air into the intake?

Have tried search of pervious treads to see whether this has been discussed before

Cheers
Guido
 

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nissan patrol
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Even with a bigger snorkel opening, all that extra air would only be bottle necking at the air box connection.

My V8 had 2 holes in the air box that sucked in "cold" air. Even then the notice was barely noticeable. Spend the extra money on a fan to sit on top of your intercooler:)
 

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The Googlest, Apparently!
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Even with a bigger snorkel opening, all that extra air would only be bottle necking at the air box connection.
I would have thought even with the "bottle necking" you are still adding pressure, and therefore "squeezing" more air through to the filter and into the turbo / intake manifold, rather than just sucking the air in. I was thinking of putting a larger safari air ram (they do call it an "air ram" after all) onto my nissan snorkle for the same reasons. Further investigation needed for me I think, got a pretty handy fluids program, will have to see if I can run air on it to see the effect.
 

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Curious though as to what science determines the size of the intake head on the top of the snorkel?


Would the vehicle perform any different with say a bigger opening - which presumably would feed a greater volume of air into the intake?
The science is called fluid dynamics.


There are other greater restrictions, airbox, airfilter, besides isn't the turbo doing a good enough job. Diesels run excess air anyway, if you want more power you need to add more fuel not air.

Fitting a larger snorkle head would create more drag, so you would use more fuel.
 

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the size shape of the head of the snorkel is more about removing water from the air stream rather than ramming more air in. its very hard to ram air in at the low speeds you can drive at, there is nothing to keep the pressure in.
main thing with a snorkel is that its big enough and doesn't add to the intake restriction. pre turbo restriction causes a fair drop in turbo efficiency. you would get more improvements by changing the air filter box than the snorkel hat.
 

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The Googlest, Apparently!
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08KINGCAB

Quoting your;

""There are other greater restrictions, airbox, airfilter, besides isn't the turbo doing a good enough job. Diesels run excess air anyway, if you want more power you need to add more fuel not air. Fitting a larger snorkle head would create more drag, so you would use more fuel"".

So, if that is the case and a diesel motor runs an excess of air anyway, then why bother with an intercooler, or turbo in fact???? The idea for me of fitting a bigger air ram is not to feed more air to the engine to get more bang (I can increase the boost pressure for that), but to increase the efficiency of the turbo (or pistons in an NA motor) to deliver the air.

The thing here to learn is does the extra pressure from ramming more air into the air ram provide sufficient pressure to overcome the escalating pressure drop (back pressure) across the air filter, as more air is forced into it, to the benefit of the turbo by it requiring less energy to spin up. Mmmm, gonna need a rocket scientist here me thinks.

The 100kph forward motion of the vehicle would provide enough pressure to “keep” the air in, and at pressure, to a certain point where the rammed air “pressure” in is exceeded by the pressure drop (back pressure) of the airbox / air filter, as Tweak’e has pointed out. You will also lose some of the “rammed air” from the weep holes (or whatever they are called) that let the dust / water out after separation via the venturi effect inside the air ram.
 

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The Googlest, Apparently!
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Continued;

But I still think that having a larger “catch area” would increase the pressure against the filter and force more air into the system and thereby increase the “ease” of air delivery that feeds the turbo, or intake manifold. Look at it as a pre-charger, at present the air volume fed to the motor is increased only by the ability of the turbo suck (drag) the air through the filter / air box / elbows etc as it spins up from the exhaust gasses; this requires energy and could have a lag effect on the turbo.

However, if the air supply had a higher pre-charge pressure to it than supplied by the standard smaller air ram, then the turbo should spin up faster as it does not have to expend as much energy “dragging” the air in. Therefore, at speed your throttle response should increase.

To me this would be handy just in overtaking some lumbering grey nomad, in a Honda CRV, pulling his caravan around Oz at 70kph while he watches the scenery go by. If a new bigger air ram, which is at 90deg to the forward motion of the vehicle when fitted to my Nissan snorkel, can be had for a hundred bucks then I will buy one and call it a science experiment. I will also post the results on the forum.

Agreed, at low speed it will make bugger all difference, and the added drag from such a small increase of surface area would make no difference from a fuel use perspective, and certainly a lot less than those 7 inch spotties mounted on the roof rack, or the roof rack and it’s cargo in general, or the extra “caravan mirror” hanging off each side of the doors, or the rest of the fruit people seem to hang off their vehicles, or even having your own elbow sticking out the window…..:confused:
 

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Your probably better off putting a billet airbox lid on to make it easier for the turbo to suck at all speeds.

http://www.patrol4x4.com/forum/gene...y-15/hi-flow-billet-gu-airbox-lid-kits-50428/

After all that dust evacuator valve is going to bleed off any pressure increase you get so rather than wasting money it makes more sense to just make it easier for the turbo to breathe.

After all even at 1500rpm the motors pulling around 150 cfm ( http://www.centriprecleaner.com/engineguide.html ) so I don't think you will get any ram effect even with quite a large increase in head size.
 

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The Googlest, Apparently!
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Your probably better off putting a billet airbox lid on to make it easier for the turbo to suck at all speeds.

After all that dust evacuator valve is going to bleed off any pressure increase you get so rather than wasting money it makes more sense to just make it easier for the turbo to breathe.

After all even at 1500rpm the motors pulling around 150 cfm so I don't think you will get any ram effect even with quite a large increase in head size.
Maybe so for a rock stock standard GU, but I am trying to pull the air into a 6.5lt engine through a standard nissan snorkel built for the max 4.2TD. So the air flow figures you quote are not my air flow figures. Along with this motor comes a lack of space in the engine bay, so much so that Brunswick build their own airbox so it will all fit in, so bang goes your billet box thingy as it's not standard GU, and I dont have a dust evacuator valve either.

And Doc Brown would have a heart attack if he heard you say that a science experiment is a waste of money....
 

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Continued;

But I still think that having a larger “catch area” would increase the pressure against the filter and force more air into the system and thereby increase the “ease” of air delivery that feeds the turbo, or intake manifold. Look at it as a pre-charger, at present the air volume fed to the motor is increased only by the ability of the turbo suck (drag) the air through the filter / air box / elbows etc as it spins up from the exhaust gasses; this requires energy and could have a lag effect on the turbo.

However, if the air supply had a higher pre-charge pressure to it than supplied by the standard smaller air ram, then the turbo should spin up faster as it does not have to expend as much energy “dragging” the air in. Therefore, at speed your throttle response should increase.

To me this would be handy just in overtaking some lumbering grey nomad, in a Honda CRV, pulling his caravan around Oz at 70kph while he watches the scenery go by. If a new bigger air ram, which is at 90deg to the forward motion of the vehicle when fitted to my Nissan snorkel, can be had for a hundred bucks then I will buy one and call it a science experiment. I will also post the results on the forum.

Agreed, at low speed it will make bugger all difference, and the added drag from such a small increase of surface area would make no difference from a fuel use perspective, and certainly a lot less than those 7 inch spotties mounted on the roof rack, or the roof rack and it’s cargo in general, or the extra “caravan mirror” hanging off each side of the doors, or the rest of the fruit people seem to hang off their vehicles, or even having your own elbow sticking out the window…..:confused:

Mate if you think putting on a bigger snorkle head is going to help overtake grey nomads then go for it, maybe you can get a job at Safari as there chief design engineer.:grinroll:
 

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The best thing about a snorkel apart from the water crossings is that the intake air is up out of the dust if you do dirt road/track driving. Also it's further away from your engine and the air is cooler.
 

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The Googlest, Apparently!
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So much "negativity" 08king, do you have any good days??.....

and I agree BradM, trouble is I only get into the wet (north part of Oz) once a year if I'm lucky. Most crossings here in the dry south west is ankle deep at best. Maybe with these changing weather patterns I will get more of a chance in future. But, as you say, a snorkel does help on all the dirt roads we have by moving the intake away from the turbulence under the vehicle and the heat in engine bay, and I was surprised how hot it get's running the 6.5lt, must be from lack of space reducing ventilation.
 

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The Googlest, Apparently!
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By the way BradM, love your quote

“Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic!”

Mine is usually;

Impossible is a word to be found only in the dictionary of fools. Napoleon Bonaparte.
 

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I was thinking of a mod/using a snorkel or part of the existing snorkel as a airflow for the intercooler. The idea is to drag the cooler air over the intercooler as a better alternative than the scoop. Progress so far - Umm writing the idea in a forum
 

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take your snorkel head off and go for a drive

if you expect masses of change in power, your not going to get it.
 

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I had to turn my snorkle head around the other way while driving back from Vic - too many locusts and dust. Didnt make any change to power so i dont see how making the size of the head bigger would do anything noticable.. my 2c +gst.
 

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Drillerboy; said:
Maybe so for a rock stock standard GU, but I am trying to pull the air into a 6.5lt engine through a standard nissan snorkel built for the max 4.2TD. So the air flow figures you quote are not my air flow figures. Along with this motor comes a lack of space in the engine bay, so much so that Brunswick build their own airbox so it will all fit in, so bang goes your billet box thingy as it's not standard GU, and I dont have a dust evacuator valve either.

And Doc Brown would have a heart attack if he heard you say that a science experiment is a waste of money....
I'm on the iPhone app so I can't see sigs but if your motor is N/A then yes it still pulls around 150cfm. If it's turbo intercooled then it's pulling 318 cfm.

So your better off putting on a 4" snorkel tube. And if your still worried about restriction then go twin snorkels. But you aren't going to get any performance increase from an increase in surface area of the snorkel head but you MAY get one from increasing the throat diameter all the way to the engine.

Cheers,
Nic
 

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The Googlest, Apparently!
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Mmm, must be something about my saying;

"fitting a bigger air ram is not to feed more air to the engine to get more bang (I can increase the boost pressure for that), but to increase the efficiency of the turbo (or pistons in an NA motor) to deliver the air"
and;
"However, if the air supply had a higher pre-charge pressure to it than supplied by the standard smaller air ram, then the turbo should spin up faster as it does not have to expend as much energy “dragging” the air in. Therefore, at speed your throttle response should increase."

that is a little hard to understand, I have at no time said I was after more power, I'm looking at it in an efficiency aspect, so I don't understand where all this is going.
 

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The Googlest, Apparently!
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Continued;
However, I have been doing a little research in to the question and from a Bushtracker moderator there is a thread that ends with;

“A bigger head unit to ram more air into the snorkel could work. However this would only work at higher speeds, and I suspect it could still be air starved when you romp on it at lower speeds…. I would opt for the immediate fix of #1, pending the Lone Rangers further experimentation on the AIS filtration system larger filter box and double air entry from the Snorkel… In summary, both ends positively ramming air into the filtration box, is a major improvement, 17.99% is HUGE.”

The +/-18% is not about a bigger head, but “positively ramming air into the filtration box” is a key to what I am looking at. So, I will do my little experiment anyway, if its good, then bonus for me, if not, well a $100 is one less night on the grog over my month off, after doing my month on….
 

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By the way BradM, love your quote

“Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic!”
Was thinking the same ;)
 
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