Snorkel flow rates

[sierrajim]

I'm in the process of making some changes to my GQ Patrol, namely the fixing of the booty fab intercooler piping the previous owner installed.

As part of this process I've been looking at my Airtec snorkel that was designed for a GQ non-turbo diesel. Since there's now a turbo running up to 17lb of boost the air requirements are far greater.

There's plenty of people on here that know stuff about stuff so I thought I'd ask the question./ Is it worth while pulling the Airtec Snorkel off and fitting a 3" stainless/alloy or whatever tube snorkel in its place?

[Struth]

Yes it is definately worth it, I would personally recommend a 4" snorkel for your setup, you will find much greater throttle response and power from this one simple mod.

The off the shelf snorkels are so much longer and turn so many more corners than are required for the job, therfore they slow down and restrict your airflow heaps.

Cheers

[dank]

Jim I know a guy that can do a really sweet 4" intake system for your GQ. All in Alloy, TIG, very pretty and fully waterproof.

[Struth]

Or you can have one of these if you like,





I know a guy who does them

[sierrajim]

How do they get on with water being sucked through? The Airtec/Safari units have a vent behind the scoop/head.

I'm running an enclosed pod filter housing (3")

[Struth]

It has vents where it joins to the snorkel tube that allow water to flow down the outside of the tube rather than into the tube.

Cheers

[beefy125]

Is that snorkel in the photo a 3 inch or 4 inch

[Struth]

4"

[KiwiBacon]

Cut the guesswork, put a restriction gauge on the airfilter housing.
Go for a run and see what it reads, then decide if it's worth changing.

[RED60]

Cut the guesswork, put a restriction gauge on the airfilter housing.
Go for a run and see what it reads, then decide if it's worth changing.

Gut feeling from me is that this "restriction" between say 3" to 4" is close to imaginery... there may technically be some minor difference... but I think it will/would be very small.... bring data...

[Struth]

Gut feeling from me is that turfing the aftermarket snorkel and fitting a custom 4" with a straight run to the inlet point will make a big performance difference.

But that's just a seat of the pants feeling from fitting a fair few 4" units and actually feeling the difference

[Clanky]

all things being equal (length and bends) and according to my calcs 3" mandrel bend tube will flow 15psi for a TD42 at 4000rpm
4" will do it also with the only difference being the air velocity is lower.
In reality a 3" on a tourer running say 15psi at 2500rpm will suffice all day long
Bigger HP engines will benefit from being able to flow more air through a 4"

My experience with the plastic snorkels is that they are very restrictive with stupid flow dynamics

Another factor to consider, if you want to run an air ram type Donaldson head or top spin pre cleaner on the snorkle, they only list on their catalogue sizes 3" & 6", No 4" stuff, so you end up having a huge one or an undersized one for the tube if you run 4".

[sierrajim]

Cheers for the responses guys. Next question is snorkel head forward (much the same as Struth's) or bent facing backward over the roof?

Being turbo there shouldn't be much of a difference??

What are yours worth Struth? Can you build one to go into the same hole as the Airtec/Safari Snorkel?

[Struth]

$550 without head, $650 with, both fitted and ready to suck air

They can be built to fit anywhere, just wether or not they look good is what changes. The whole purpose IMO is to remove air restrictions, being length and bends, and get into the engines air cannister ASAP.


Facing forward or backward is a big can of worms, backward doesn't let mud in when offroad, but the one on the picture can have the head swivelled to face backward or anywhere in 360 degrees really.

I run mine backward and 5 litres NA never struggles to get air, even at 5000 rpm.

[B.D.R]

You join the darkside Jim

I know with my Snorkle, you can't feel ANY differance when it's connected, or not, the top facing forward, Backwards and off, and that did'nt matter really which way it's been routed either

That's on the Mav with a RB30et and a GU snorkle, my old 4.2d 75 series was the same as well, i could'nt tell the differance when the Snorkle was on, or after a Tree took it completly off

There is either something wrong with the seat of my pants, or people might be imagining things

Chris

[KiwiBacon]

Cheers for the responses guys. Next question is snorkel head forward (much the same as Struth's) or bent facing backward over the roof?

Being turbo there shouldn't be much of a difference??

You won't notice any difference at all at legal speeds. If you can do 300 km/h then it's worth pointing it forwards.

[PJ.zook]

Another thing to think about is legality. I have heard that the new rules coming in ban metal snorkels due to further injuring dumbass pedestrians who wander onto the road. Although with all the indecision you can probably take that with a grain of salt.

[Struth]

You join the darkside Jim



There is either something wrong with the seat of my pants, or people might be imagining things

Chris

Don't really want to go down this shitfight path on snorkels again but mine was dynoed with a 3" and then dynoed with a 4".

Peak power with 3" was at 4800 rpm
Peak power with 4" was at 4200 rpm (same power just lower in the rpms)

Which also meant 20% more power at 2500 rpm.

Worthwhile gains I reckon.

[KiwiBacon]

You join the darkside Jim



There is either something wrong with the seat of my pants, or people might be imagining things

Chris

Don't really want to go down this shitfight path on snorkels again but mine was dynoed with a 3" and then dynoed with a 4".

Peak power with 3" was at 4800 rpm
Peak power with 4" was at 4200 rpm (same power just lower in the rpms)

Which also meant 20% more power at 2500 rpm.

Worthwhile gains I reckon.

Imagine how good it would be with no snorkel.

[rockcrawler31]

You join the darkside Jim



There is either something wrong with the seat of my pants, or people might be imagining things

Chris

Don't really want to go down this shitfight path on snorkels again but mine was dynoed with a 3" and then dynoed with a 4".

Peak power with 3" was at 4800 rpm
Peak power with 4" was at 4200 rpm (same power just lower in the rpms)

Which also meant 20% more power at 2500 rpm.

Worthwhile gains I reckon.

Imagine how good it would be with no snorkel.

I'd be curious to know how it would go actually. I wonder how a 1HZ with turbo would go without a snorkel or filter? i'm interested to see how it would go on mine for a short run, but i'm worried i'd pick up something out of the engine bay. curious though. Perhaps if i ever get it dynoe'd i'll check it out.

[Clanky]

Chris[/quote]

Don't really want to go down this shitfight path on snorkels again but mine was dynoed with a 3" and then dynoed with a 4".

Peak power with 3" was at 4800 rpm
Peak power with 4" was at 4200 rpm (same power just lower in the rpms)

Which also meant 20% more power at 2500 rpm.

[/quote]


I am not sure your quote of "20% power more at 2500rpm" would be quite correct, as I suspect that the 3" would more than likely be able to flow the required amount of air same as the 4", due to the fact it could flow enough for 4800rpm (albeit starting to lose power).
Does the dyno graph show this to be correct?
My other question if I may ask, was the 3" identical to the 4" in design. A variation in the internal length,number of bends, weld dags on the inside of the pipe, etc can have a marked effect on vacuum (negative) flow dynamics, of which I am no guru.

(P.S. Not arguing, if its working for you . Im just curious - sometimes real world testing is worth more than calcs on paper)

I currently have a 3" S/S mandrel bend snorkel, and now that I have a turbo running 15psi, I have been researching if there is a benefit of going 4" for a touring vehicle.
My thoughts are:
3" is easier to fit in an engine bay. (+ I already have it)
I can get a Donaldson 3" ram head and cyclonic pre cleaner for 3". Nothing for 4"
The air filtration ( media + housing) is probably the biggest restriction, moreso than the snorkel
Total length of the inlet tract

Q: Is it a benefit going to 4" when running 15psi on a TD42 which will hardly ever see 4000rpm????

[Struth]

Prior to a snorkel it ran a 6 cyl commodore airbox that received air from behind the headlight same as the 3VZE did, it did not go real well but also wasn't dynoed in this state.

With a pod filter directly on the throttle body tube it just sucked superheated air from the extractors and ali radiator, made 26 less rwkw, but when the engine was cool and the outside air cool and dense it flew this way.

The 3" snorkel had 1 more 90 degree bend than the 4" has and used rubber bends wherever it needed it, was the same unifilter oiled filter as the 4" uses.

Yes the dyno sheet shows 20% more power at 2500rpm with the 4" snorkel.

It now has a custom airbox with standard 5.0 panel filter and wont be dynoed until the new engine is fully run in.


But I guess it's not just seat of the pants that tells me a 4" has a noticeable improvement over a 3" and common sense dictates that a custom snorkel that enters the airbox with minimal length, bends and restrictions will outperform an aftermarket snorkel all the time. I can see why off the shelf units are made the way they are, they are easy to fit and connect to the factory air take up points.

A larger tube will also flow more air at lower velocities which equals less drag as well as providing a larger quantity of static air in the tube that flows easier into the lower pressure os the intake system.

[sambo]

Has anyone actually measured the restriction on a 3" vs a 4" and has some results that they can post up?

[Tazz]

I'm running an enclosed pod filter housing (3")

Do you want to keep this style of snorkel head?
I could be wrong but if you do i'm thinking this will be a major air flow restriction point so not sure how much gain you'd see in performance with either style of snorkel?

[zookimal]

Cut the guesswork, put a restriction gauge on the airfilter housing.
Go for a run and see what it reads, then decide if it's worth changing.

x2

[hokey]

i've made a couple of millweld style stainless snorkels. photo shows it unpolished with the heat marks still on it



Uploaded with ImageShack.us

pm me if you're interested

[sierrajim]

I'm running an enclosed pod filter housing (3")

Do you want to keep this style of snorkel head?
I could be wrong but if you do i'm thinking this will be a major air flow restriction point so not sure how much gain you'd see in performance with either style of snorkel?

Pod filter is going out at the same time as the snorkel.

Now that I have the dual battery bracket in I'm running out of room in the engine bay. What looks to be the solution is to fabricate an air box closer to the firewall. This will allow me to run a filter out of a Chevy Duramax (which i have a shelf full of here) and will also cut down the length of intake pipe by about two feet.

[sudso]

Worst restriction in an intake is a blocked filter!

[85lux]

As many have said above,
"gut feel" and "seat of pants" is rubbish.
Automotive Engineering is that exactly, ENGINEERING
"gut feel" and "seat of pants" belongs with astrology, not engineering.
By the way, the restriction is very easy to measure, very accurately.
All you need is some clear plastic tube, water and a ruler.
Google Manometer

[85lux]

I'll get the ball rolling.
Measure the vacuum before the filter, IE in the cavity in the airbox on the snorkel side of the filter.(so we're measuring airbox vacuum, before the filter, not having our results affected by clena/dirty/different brand filters)




^The setup



^omm hg at rest





notice the water in the tube has lifted 20mm on one side and lowered 20mm on the other side. this means we have a total of 40mm hg.

^40mm hg at 4200rmp WOT, full load, using brakes to load engine.



GQ 4.2 carby, on gas, no snorkel.

start measuring your airbox vacuums and post up to make this thread useful.