Safari snorkel Top - which way?

In article , 'T' writes

Arguably you get less crud into the air filter with it facing backwards. I can see it causing a low intake pressure at speed, but heck...

My one is a mushroom, but I'm tempted to put a baffle in to achieve the same effect. I usually pick bits of straw out of the filter around harvest time, so muck does evidently get drawn in as it is now.

Regards,

Simonm.

The snorkel is primarily to get the air intake up above the dust when operating in very dusty conditions. Assuming you have a diesel engine, the airflow into it will be such that anything round it will get sucked in regardless of the direction it is facing, so you might as well have it facing forward where you will get a slight boost in manifold pressure at speed rather than a slight reduction - help to make up for the friction losses of the longer intake and increased aerodynamic drag. JD

I take your point, especially about boosting the input pressure (and the downtube isn't that wide - mine looks like a piece of rainwater downpipe), but if something punctures the filter I think you may have a bigger problem than low pressure.

Once a decent sized bit of rubbish gets into the pipe it'd be like doing the Cresta run, and it will hit the filter with some speed. I'd have thought the snorkel would be worse than an ordinary inlet for that, partly because the length of pipe would encourage laminar flow and partly because the smaller diameter would increase the velocity (for a given volume).

Having said that though, I don't recall dozens of failures through airborne rubbish getting into the turbo, so perhaps it's moot.

Regards,

Simonm.

Do some maths regarding the amount of air an engine gulps, and you'll soon see that it matters not a jot - you can't ram it in quicker... :-)

I recall the layout of the air filter and housing on my 110 was such that anything coming into the filter housing via the intake would hit the hard plastic before being drawn down through some fins and then through the metal gauze and filter paper before heading to the engine, seems unlikely to me that anything could realistically enter the filter housing fast enough to get through that plastic wossit, and after hitting that it'd be pretty inert energy-wise I would have thought.

-- Mark.

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On or around Mon, 12 Sep 2005 08:50:02 +0000 (UTC), "'T'" enlightened us thusly:

pointing forwards you get a minor ram-air effect, but you also collect a lot of dust, rain etc. as you go along. backwards makes that a bit less likely. Also too much ram-air can upset gas systems on LPG vehicles.

On Mon, 12 Sep 2005 08:50:02 +0000 (UTC), "'T'" scribbled the following nonsense:

I tend to point it forwards for road use, mainly because on a long run with the window open, SWMBO gets fed up of the intake noise which is more pronounced when pointing backwards and towards the window.

Off road I point it backwards, I have seen people hit water too hard and spalsh water up the windscreen and onto the roof. I figure that If I do this, pointing backwards it will be less likely to swallow water.

The aircleaner is designed so as not to be likely to be damaged by this sort of thing. Actually airflow through the snorkel is likely to be pretty turbulent, although the velocity will, as you say, be pretty high. The pressure loss due to the snorkel will, in fact be greater than any possible gain from facing forward, pointing out that unless you operate in a very dusty area, or engage in deep wading (and for this a snorkel is only one of the required items), there is no reason for using a snorkel. As a fashion accessory they are relatively harmless, but will result in a very minor loss of power. JD

so JD was, like...

ISTR a post from Pantelis a while back that said he had noticed a considerable improvement in performance with a snorkel fitted. Pantelis? You there?

What about a spinning stainless steel top as you see on the stacks of entral heating boilers. Should set up a nice cyclonic effect too for increased performance.

;0)

Lee D

Hi, as a long term user of the snorkel I leave the ram head facing forward to get as much cool air as possible.

When fitted correctly, there are small gaps (4 from memory) around the lower edge where the head fits the snorkel, and these allow any water that gets "blown" in to exit on the outside.

How many trucks do you see that make their swan going backwards? With fuel costs being what they are, they all face forward to get the maximum benefit from the ram head.

Some people also face the opening towards the windscreen and say this gives them the cool air but with less debris, flying insects etc

In convoy work, or extreme dusty work, then we decapitate the swan's head, and put on the mushroom (cyclonic precleaner). These are amazingly efficient but you do hear the turbo a lot more.

I guess if Peter, Safari designer and manufacturer, had wanted the ram head to face backwards then I'm sure he would have put the Safari name in a different location, and given his experience with turbos and snorkels I'm happy to trust his judgement on this one.

Cheers

Phillip >Just got a safari snorkel. Fitted wuth the top facing forward. But I see

You could rig up some kind of turbo driven by the airflow as you drove along :)

Rich Hi,

this is true and it has also been noticed by other owners of Camel Trophy evented vehicles fitted with Mantec snorkels and using 200 and 300 Tdi engines.

Take care Pantelis

On or around Mon, 12 Sep 2005 15:12:31 +0000 (UTC), "Neil Brownlee" enlightened us thusly:

I did that, once.[2] concluded that the size of blower you need is considerable, to make any useful contribution. Probably do better to arrange an oxygen feed... but then you need an awful lot of oxygen too.

however, ram-air does work - if you take a pipe with cross-section n sq.in. and attach a funnel 2n sq.in. in diameter to the front of it, then travel through the air, the pressure in the pipe increases, even though the engine is sucking air out of the other end of the pipe. Increased pressure "for free" [1] increases the O2 content, making it possible to burn more fuel.

's only relevant at significant forward speeds, though.

Too-small a blower doesn't have the same effect: it absorbs power in the first place, and then if the airflow exceeds what the blower is capable of generating, it actually creates a restriction in the inlet instead. A small-ish blower could be useful at low revs, provided you have a means of diverting inlet air around it at higher revs.

[1] TANSTAFFL - in this case, more drag from moving the vehicle through the air. [2] consider a 2.5 litre engine, of 4-stroke design. every revolution, the engine sweeps a volume of 1.25l, thus for every revolution, 1.25l of air is sucked into the engine. depending on conditions, this air may or may not be at normal pressure. If the engine is now running at 2500 rpm, then every minute, 2500*1.25 = 3125l/m of air goes through it. If you prefer cfm, well, 1 cu.ft. is about 28 litres (28.32 to 2dp) so that's 110-odd cfm.

which is a lot. now consider the average inlet tube, which is about 6cm diameter. CSA of that is 9*pi or a bit over 28, (conincdentally almost the same as the cfm above...), so 1l of air occupies about 35cm of such a tube, so if you're looking for 3125l/m than that's going to be 3125*35 cm/min =

111607. *60 for cm/hr, [6696428] but that's silly, so divide it by 100,000 you get 66.9 km/h.

On a similar vein I have a mantec snorkel with a cyclonic top but have been thinking about getting the Safari 'ram' type head instead. Does anyone know where I could get one of these that fits the mantec snorkel?

Thanks

Tony.

We have a 'top hat' or whatever its called top on our V8 90. The engine is mildly tuned and produces approx 200bhp. When we had on the rolling road with the snorkel connected it reduced engine output by approx 40bhp. So now what I do is for normal day use I stick with the K&N's and for off road I connect up the snorkel. Richard

so Austin Shackles was, like...

Wow. I'm off to bed after reading that.

On or around Tue, 13 Sep 2005 22:15:07 +0100, "Richard Brookman" enlightened us thusly:

hehe. 's not a problem to me, doing that sort of thing. I used to do it in me head while travlleing on slow roads.

one day I'll reprise the thing about why, in a queue of traffic separated by

1-second intervals, the 8th and 9th cars (IIRC) inevitably collide in the event of the one in front stopping... cue cross-thread...

Depends who's at the front! ;o)

Lee D