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how big does a snorkel need to be?


TOR4x4

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does the length of the snorkel mean it needs to be bigger diameter?

The longer your snorkel, the more air resistance your going to get.

I've got a Safari Snorkel fitted to my 300 TDi Defender, with it's large top but the outlet at the base of the snorkel is only about 2.5" dia.

Hope that helps.

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I would think for a 4.6 you really want 3" diameter if it is going to be that long?

Std tin pipe mushroom hat Mantec/Rebel type snorkels for Tdi engines are 2.5" I think. Ask Nige (Hybrid_from_Hell) what he used for his 4.5 Eales, I think it was 3" but there is a thread on here somewhere if you do a search...

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I would think for a 4.6 you really want 3" diameter if it is going to be that long?

Std tin pipe mushroom hat Mantec/Rebel type snorkels for Tdi engines are 2.5" I think. Ask Nige (Hybrid_from_Hell) what he used for his 4.5 Eales, I think it was 3" but there is a thread on here somewhere if you do a search...

Try this one, http://forums.lr4x4.com/index.php?showtopic=2741&hl=

There are three or four threads to go along with this one to cove H-F-H build.

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Guest diesel_jim

This thread came courtesy of Dave Gomes on the D-90 Source (hi Dave if you're still reading! how's the hybrid build-up going?)

I've been poking around the Machinery's Handbook (INDISPENSABLE reference

source) a little and found a few interesting things (see p.2319 and 2324 of

22nd edition, if you're interested for info on flow of air and water)

1- if you use 3" diameter smooth-wall pipe and keep the right angle bend

radius to at least 3x the pipe diameter, a right angle bend has the same

restriction as 4 feet of pipe (this is listed for water, not for air).

2- if you consider that a 3" pipe has an area of 3.14*1.5^2 or 7 sq.

inches, or 0.05 sq ft, and the engine is drawing 140 CFM, then the air is

moving through that pipe at a speed of 140/0.05 or 2800 feet per minute,

47 ft per second, or about 32 MPH! It's easy to believe that anything

getting in the way of air moving that fast can cause a restriction in a

hurry.

If we assume 50 fps air velocity, and a VERY clean instalation using 6 ft of

straight, smooth pipe, and 3 90 degree bends of 9" radius, then the equation

for pressure loss looks like:

P= 18 * 50^2/(25,000 * 3)= 0.6 ounces per square inch, or 0.07 inches of

mercury (vacuum)

That's just for the (probably over-optimistically clean) piping. I'd

imagine the pre-cleaner itself has more restriction on it's own. We'll see

what Centri says. I wonder what restriction is offered by a paper element

air cleaner? I hear that an oil bath cleaner like the old Series ones is

one of the most effective, lowest restriction, filters for ultra-fine dust

that there is, when it's kept reasonably clean, and that the ideal combo for

engine cleanliness is a pre-cleaner for bigger particles, with an oil bath

for the little stuff......

Oh well, enough musing for today...Time to think about Double Cardon joints

a bit.... :^)

-Dave G.

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i need to fabricate a snorkel for my 4.6, it needs to be about 2.5 meters long, what diameter does it need to be, ideas please.

Fitted a 3 metre 88mm tube to my 5.0l TVR engine .

Mark Adams said when i asked him that he has never found any differnce on a rolling road no matter how long it as long as its the same size as the air box :D

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Fitted a 3 metre 88mm tube to my 5.0l TVR engine .

Mark Adams said when i asked him that he has never found any differnce on a rolling road no matter how long it as long as its the same size as the air box :D

interesting, as the JAP engined V twins required a 19" from valve centre line to bell mouth inlet tract to develop optimum power irrespective of carb bore, 19" every time, which pretty much reflected that which theory suggested on most long stroke motorcycle engines, but which was ignored due to size restrictions on what could be squeezed in the chassis rails on other marquee's.

There's a lot of theory, and what actually works on a rolling road pressurised inlet test, depends how much time or money you have spare

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interesting, as the JAP engined V twins required a 19" from valve centre line to bell mouth inlet tract to develop optimum power irrespective of carb bore, 19" every time, which pretty much reflected that which theory suggested on most long stroke motorcycle engines,

Perhaps because each cylinder draws in it's air in pulses so the length may be critical for that reason - rather like the volume/length of a performance 2-stroke exhaust being critical for back pressure? On a V8 the flow is smoothed out because there are 8 cylinders drawing air. There are different length trumpets in the plenum chamber though so that the inlet tracts are the same length for each cyclinder.

Chris

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Perhaps because each cylinder draws in it's air in pulses so the length may be critical for that reason - rather like the volume/length of a performance 2-stroke exhaust being critical for back pressure? On a V8 the flow is smoothed out because there are 8 cylinders drawing air. There are different length trumpets in the plenum chamber though so that the inlet tracts are the same length for each cyclinder.

Chris

yes, so the issues of inlet length are solved in the inlet manifold or plenum chamber depending on carb or EFi, so additional lengh on the snorkel becomes no issue, as long as the bore is not restricting what can get to the airbox and then inlet ducts for the manifold or plenum. Sorry, sorta thinking while typing and coming to the same conclussion above, think a ram air style snorkle top will be going on mine now rather than a mushroom top ;)

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Minivin - I don't think you'll see any performance improvement if that's what you're after... :(

This has all been covered in previous threads.

Al.

aiy, but as they say bull(poo) baffles when people who are not in the know ask ;)

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Pod, I'm going 3" throughout with including twin intakes into the rear mounted airbox. That on a 2.8 TGV

i might be daft but surely the snorkell has to be matched to the exhaust. after all everthing you suck in has to be expelled. so if the performance exhaust has a diameter of 2" the snorkell only needs to be 2"?

P

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Hmm, that's like saying the engines ability to breathe doesn't affect it's performance, which is obviously not the case, for example, as I understand it a Rover V8's heads/air intake are the single biggest hurdle in generating better performance.

A 2" pipe will DEFINITELY limit flow considerably compared to a 3" pipe - especially since circle area is proportional to the square of the radius.

Your point on the surface of it makes complete sense, however, it is more complicated than just pure diameter on the exhaust - you've got cylinder purging, presuure waves and all that stuff going on. Tube diameter affects performance - the relationship between rpm and power/torque. It's FAR more complex than just 'bigger tube equals better'.

Even if the exhaust was seriously limiting output, I see no reason not to minimise losses on one side, just because they aren't minimised on the other.

Al. :)

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i might be daft but surely the snorkell has to be matched to the exhaust. after all everthing you suck in has to be expelled. so if the performance exhaust has a diameter of 2" the snorkell only needs to be 2"?

P

No because when you are blowing something you can pile as much pressure as you like to make it go faster through a small hole, but when you are sucking something you only get 1 bar to vacuum and then you run out of air because there's none left...

At least I think that would be correct :)

Edited so I can mutter that bluddy turbot-charger beat me to it :angry::P

Edited by BogMonster
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also one factor that has not been mentioned yet is the scavaging effect of the exhaust which tends to draw-out the exhaust gases by what could be termed a vacuum during the last stages of the exhaust valve closing due to the pressure pulse reaching the end of the exhaust and sending a return pulse back up the system.

However lets not go into that as we can start talking about resonance, megaphone affects et cetera and there is enough books out there on the subject ;)

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