snorkel head direction

Submitted: Thursday, Oct 03, 2002 at 00:00
ThreadID: 2087 Views:8610 Replies:19 FollowUps:8
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After reading a thread on the overlander site regarding snorkel head direction, comments were made about the different levels of fuel consumption relating to the direction of snorkel. It was said that at low speeds forwards is best, however at highway speeds they reckon that reversing the head is better???? It sure confused me as i was always under the impression the more air that was avalable the better, i.e the ram air effect. The bit that stumped me was when they said that too much air confuses the air flow meter and pumps in to much fuel, resulting in rich black exhausts. Does anyone have any ideas?? Andrew....
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Reply By: Beddo - Thursday, Oct 03, 2002 at 00:00

Thursday, Oct 03, 2002 at 00:00
I have just fitted a snorkel to my vehicle which is a 97 Toyota Surf diesel turbo intercooled (same motor as Prado) and I have just returned from a trip to Cape York and saw vehicles with the head turned around which puzzled me. Anyway my fuel economy was up compared to previous highway use and also there was no large amounts of black smoke. Would like to hear more about this because it sounds like @#$# to me. Cheers Jeff
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Follow Up By: Andrew - Thursday, Oct 03, 2002 at 00:00

Thursday, Oct 03, 2002 at 00:00
A lot of people in dusty dirty environs turn the head of the inlet to the rear to reduce the entrainment of crap into the air cleaner.. doesn't necessarily help the efficiency of the engine, but reduces the frequency of cleaning the element..
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Reply By: Greg Harewood - Thursday, Oct 03, 2002 at 00:00

Thursday, Oct 03, 2002 at 00:00
Correct me if Im wrong by I would have thought that driving technique, tyre pressures, load weight, vehicle aerodynamics and ground conditions combined will mask any advantage/disadvantage created by air flow through a snorkel (except in rather deep water!) - point it where it looks best and go for it!
Regards
Greg
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Reply By: Gorasn - Thursday, Oct 03, 2002 at 00:00

Thursday, Oct 03, 2002 at 00:00
I would leave it as designed - forward. Are they available for the Prado? And how to people rank mid sized 4wds? My feeling is Prado clearly leader, Pathfinder, Pajero, RAV4, Challenger, Ford, Suzuki, Subaru and clearly last the Land Rover Discovery.
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Follow Up By: Sambo - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
Yes snorkels are available for Prado, just had mine fitted to TD. I would have to agree as to your comments that the Prado is clear leader in Mid size 4wd. Cheers
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Follow Up By: Pathfinder - Wednesday, Oct 09, 2002 at 00:00

Wednesday, Oct 09, 2002 at 00:00
mmm, yes, Prado is the clear leader if you don't mind complex, unfixable breakdowns (particularly of the electronic variety) in remote locations... I'll keep my relatively old-fashioned mechanically-controlled turbo diesel thanks...
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Reply By: Grant - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
Hiya Andrew,
Not 100% certain mate but think that may be the other way around- they face them forward for hway use and whilst running slow through scrub and stuff turn them backwards to reduce the risk of getting them hooked up (at a guess). Facing them rearwards on hway apparantly creates a vacuum at the snorkel opening and reduces intake thus increasing fuel consumption.
Grant
AnswerID: 7148

Reply By: Member - Nigel - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
Seems to me that some people have their head screwed on the wrong way :)
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Reply By: ExplorOz Team - David - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
Andrew,The snorkel should always be pointing forward as designed. I have heard and seen people in convoy situtations turning the head around to reduce the intake of dust which may be of some merit, however at highway speeds turning the snorkel backwards would create a vacuum and starve the enigine of air. Seems a bit dumb to me and contary to manufacturer information.....David
AnswerID: 7152

Follow Up By: Troy - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
David,

what about a situation where a 4x4 has no snorkel - the air gets drawn from either inside the engine bay, or air travelling up via a wheel arch....

surely this "factory" setting limits air flow more that a backward snorkel ???? What about a donaldson ? snorkel manufacturers recommend them, and they also may be seen to limit airflow.

has anyone seen the amount of build up - water, dust, bugs - a donaldson pre-cleaner catches ? id prefer this crap (including water when it rains) not to go into my air intake.

It appears us backward snorkel travellers (most of the field in the outback challenge included) are part of the "dumb" brigade as you so eloquently put it.

Who moderates the moderator ?




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Follow Up By: Exploroz Team - David - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
I can write what ever I want just as you can this forum is not moderated except for illegal or indecent material.I may not be a huge expert on every aspect of 4WD mechanics though I have only travelled around the country a few times, fully service all my own vehicles and had many many debates with others on topics such as this. Additionally I speak to suppliers and manufactures all the time. If it seems dumb to me and it seems dumb to others then how about a technically correct answer.As I mentioned turned around is fine for dusty conditions where prolonged exposure to dust would be an issue (such as the outback challenge - this is an extreme event and not something that you everyday 4WD is worried about). In reference to the intake internal to the chassis correct no forced air effect however no vaccum effect either (which I think is worse). As for water entering the air system I have driven for days through major tropical downpours and not even had any water appear in the water trap of the air filter. When you are stopped the water will not enter, at speed the water hits the back of the intake and runs out of the head before it even gets near the downtake pipe. As for dust entry I would suspect that the swirl effect of having the filter backwards could actually be worse (awaiting a techincal answer). Bugs, crap and dirt, well of you are exposed to huge amounts then install a pre-cleaner bowl head and not a snorkel head, I have never had that much junk enter that I would be worried. I am also very confident of fuel economy improvements in my vehicles with the snorkel installed to manufactures specifications.David
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Follow Up By: Flappan - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
Andrew, geez if your going to quote people get the words right first.

The thread says it is WORSE to have it pointing backwards, better to have it fowards, and then explains what David has said above.
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Reply By: Grant - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
Bit harsh Troy, I believe David was being critical of the idea rather than any persons. I can quite clearly see your point re donaldsons etc, the air intake on both my vehicles is behind the grill and breathes pretty well (for all I can tell), I was under the impression that while a snorkel allows reduces the likelihood of water in the intake it also force feeds air (somewhat) but yeah I guess you're correct in that it also attracts a lot of unwanted into your filter as well. Have you experienced reduced economy at higher speeds with yours reversed?
Grant
AnswerID: 7156

Follow Up By: Troy - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
Hi Grant,

ummm - yeah - looks by the reactions to my last post - it did come across a little aggressively - so apologies for that.

Economy not effected adversely for me with snorkel reversed.

will lay off the angry pills too....





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Reply By: flappan - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
All this started because someone didn't read the thread properly. It is fairly obvious what is being said.

Go and have a read yourself.

http://forums.overlander.com.au/messageview.cfm?catid=3&threadid=1745
AnswerID: 7157

Reply By: Grant - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
Hey where is that fella Ralph with his Pedders complaint, he'd go well about now.ha
Grant
AnswerID: 7158

Reply By: winaje - Friday, Oct 04, 2002 at 00:00

Friday, Oct 04, 2002 at 00:00
Hi Andrew, fitted a snorkel to my TD5 Discovery about 30000 kms ago, and have not noticed any black smoke at all. The smoking may be in vehicles that are indirect injection, as they are charateristically a lot smokier than direct injection diesels. Bill Church
AnswerID: 7161

Reply By: Member - Nigel - Saturday, Oct 05, 2002 at 00:00

Saturday, Oct 05, 2002 at 00:00
From what I've read, most pre-cleaner manufacturers set a maximum recommended speed (less than 100 km/h) when a pre-cleaner is in use on a snorkel. I guess the same would apply to a reversed head. OK for slower travel, but not good at highway speeds.
AnswerID: 7177

Reply By: tim - Saturday, Oct 05, 2002 at 00:00

Saturday, Oct 05, 2002 at 00:00
andrew, you've created some 'debate' to say the least, i'd have to agree with the exploroz team as many years in the 'car game' all of the major manafactureres/suppliers describe the working effect of the snorkel head as forward facing, now how about you post a question relating to how good or bad landrovers are just to see if you could get more responses, regards tim
AnswerID: 7180

Reply By: Andrew - Saturday, Oct 05, 2002 at 00:00

Saturday, Oct 05, 2002 at 00:00
Thanks for all the responses, it's good to see a bit of interest generated. You've all pretty much summed up what I originally beleived, but as I said in my initial statement, reading overlander confused me a little. I had my snorkel fitted the week after i bought my patrol so I had no idea if it actually had any effect on fuel (diesel) consumption for better or worse. Cheers....
AnswerID: 7182

Follow Up By: Ken D - Sunday, Oct 06, 2002 at 00:00

Sunday, Oct 06, 2002 at 00:00
Maybe its a little late to enter into this debate, buts here's some other spanners in the works to think about.- Can a rear facing snorkel reduce dust pickup, look at the back of your car after a dusty trip, low preasure areas appear to trap dust.- Further to this what if you pointed the intake sideways. Sound silly? Mercedes off road trucks have a sideways facing intake on top of the cab. I'm sure they were thoroughly tested. Other off road trucks have a raised air intake that turns and faces downwards at the top, effectively the same. - Heavier debris such as insects can't fly directly in. - All this aside, considering the airflow of the average 4WD at 100kph, say 4litre engine @ 3000rpm = 6000litres per minute, does the pressure created either way mater significally?- I just thought I'd stir the pot.-- Anyway gotta go. I'm of to rotate my air intake.--Oh ##*t which way? Help please.-
Cheers
Ken
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Reply By: Member - Keith - Sunday, Oct 06, 2002 at 00:00

Sunday, Oct 06, 2002 at 00:00
An interesting discussion....thanks to contributors. But while on the subject of snorkels, what's the opinion of the oil+foam filters. One type fits over the snorkel head and another is suspended in the snorkel tube like a wind sox?
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Reply By: Welshmun - Tuesday, Oct 08, 2002 at 00:00

Tuesday, Oct 08, 2002 at 00:00
I can't resist joining in with this one :)

Lots of discussion in this thread about ways of preventing dust & debris entering the intake by pointing the snorkel head every which way, but I'd be pretty sure if there's debris around the intake it wouldn't matter too much which way it was pointing - in it would go.
Even at moderate revs there's quite a suction from the motor.
Isn't a major point of a snorkel that (apart from letting you run under water -well diesels anyway) it takes air from 2 metres off the ground which just has to be cleaner .. .

Doug (newbie)
PS just got back from Fraser and found bird feathers in mine -
It was probably a magpie doing a swoop from behind . . .
Joking aside, of course the snorkel head has to point forward !
AnswerID: 7263

Reply By: IAMGQ - Saturday, Oct 12, 2002 at 00:00

Saturday, Oct 12, 2002 at 00:00
Face forward, get everything inside the snorkel e.g insect.......no doubt it increase the air flow (assume clean air filter) it MAY improve eng combustion. (that's why most of trucks use snorkel face fowward)

Face backward/sideway, can prevent object,debris get into snorkel directly (e.g. insects). It may not get as much air flow into the intake port but I doubt if it really lower the performance. Since even travelling 100km, there are still plenty of air can get into the engine even it face backward. Simple experiment but may be dangerous, When driving 100km/h, open window, extend your head (ask your mate to do it ! ) outside the window and face backward, is it really that hard to breath ? I don't think so. Same principle, It may create a slighly higher vaccum area but the eng still can get enough air for max performance.

Ask you self :
(1) Would you prefer to get more air(face foward) including most of debris in air directly to get extra air which may not improve performance but you need to clean filter more often ...............OR
(2) Would you prefer to get less air (face backward) which may not worsen performance but you may not need to clean air filter so often ?

For me, City/Hwy face forward like truck. Dusty environment e.g. in convoy or there is potential getting mud into the intake (easily when driving trough mud hole), turn it backward.
THAT'S WHY THEY DESIGN TO ALLOW TO TURN IT FORWARD OR BACKWARD.
If still need to debate, I think we really need to have a "Wind Tunnel" test for it.

EVERYBODY IS RIGHT !
AnswerID: 7340

Reply By: Member - Mal - Tuesday, Oct 15, 2002 at 00:00

Tuesday, Oct 15, 2002 at 00:00
Dear all, I reckon I can make a quid out of this! I have just finished the design drawings for a constantly rotating snorkle inlet powered by the air pressure as you drive. The faster you drive the faster it rotates, but it has adjustable vanes so you can adjust the the speed to rotation ratio. The up market model will also have an infra-red detector which will momentarily lock it in the reverse direction if it detects any nasties about to enter. David, I promise to market it exclusively through ExplorOz. Can anyone tell me what the optimum RPM would be at 100kph? And what are your thoughts on a built in GPS? Appreciate any feedback. Mal T.
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Reply By: Member - Cruiser1 - Tuesday, Oct 15, 2002 at 00:00

Tuesday, Oct 15, 2002 at 00:00
Sounds wonderful Mal! Don't forget to add a spotlight so you can see those 'roos coming from the sides or the magpies swooping from behind........ :)
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Reply By: johnsy - Tuesday, Oct 15, 2002 at 00:00

Tuesday, Oct 15, 2002 at 00:00
If you are driving in convoy and driving in dust you are maybe a little to close
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