Ram Head vs Rearward Facing Open

[gubigfish]

Hey all

Just wanted to get everyones thoughts on a Ram Head vs a Open Rear Facing snorkel in a Turbo Setup.

I would have thought that a RAM head would be better because the air is being forced into the snorkel? Whats everyones take on Pros and Cons?

[threedogs]

everyone says RAM but IMO it stops at the air cleaner doesn't it.
I have a forward facing "ram"head to draw in clean air in dusty convoy situations.
Also good for sourcing air up high for river crossings,
As for the rear facing stainless jobs ,not my cup of tea but they look good against some paint jobs

[the evil twin]

Only advantage I every noticed was less bugs in the airbox and filter if I faced the head backwards.

A proportional amount of ram air pressure will still appear on the downstream side of the air cleaner because they are designed to be a particulate filter with as minimal flow restriction as possible, but, yes there will be some differential pressure loss.

When I think it through IMHO the effect of Inlet ram pressure on a VNT turbo engine must be quite low overall.
The Turbo is governed by the ECU via the Boost Pressure Sensor to produce 'X' pressure, lets say 30 PSIA (absolute) seeingas we are talking ZD30.
If we ignore the differential pressure loss across the filter for ease of explanation then lets say hypothetically the atmospheric pressure of the day is say 14 PSI and there is no ram pressure then the Turbo boost control mechanism will adjust the vanes for another 16 PSI
If you introduce say 2 PSI of ram air pressure after the air filter then the turbo inlet pressure will be 16 PSI and the Turbo only needs to boost 14 PSI so the vanes will be positioned accordingly.

I have seen a lot of claims on Forums from no effect at all to better power and fuel economy but short of properly instrumented results on a wind tunnel and dyno it is very difficult to quantify the gains if any of snorkel head position.
A lot of the rear facing custom pipe snorks are much bigger cross section and better flow patterns than the moulded patterns as well.
That means one would be comparing apples and oranges unless you use identical snorks as it may be a raised airflow advantage being more than the ram pressure disadvantage that gives any improvement

Bottom line is unlike a belt driven supercharger an exhaust gas driven turbine supercharger is used to harness the otherwise unused energy in the gas stream so having to produce maybe a couple of PSI lower boost pressure would have only a very small improvement to engine performance.

[mudnut]

There was a thread about this last year. The OP reckoned he got better economy with the opening facing backwards.

http://www.nissanpatrol.com.au/forums/showthread.php?21312-Snorkle-intake-backwards-better-fuel-economy-GU8&highlight=snorkel+head

[threedogs]

one of the mags did a comparo after fitting snorkles and found the
air intake temps were cooler than if it was drawn from under the bonnet as in an OE situation.
Only one or two degrees though which gave a slight increase in power

[the evil twin]

There was a thread about this last year. The OP reckoned he got better economy with the opening facing backwards.

http://www.nissanpatrol.com.au/forums/showthread.php?21312-Snorkle-intake-backwards-better-fuel-economy-GU8&highlight=snorkel+head

Yeah, I remember that thread. Like a lot of people I was following it with a fair bit of interest.
He was the only one with a big difference, some had a small change and many others noticed any difference at all.

The OP said it dropped his fuel consumption to 10.2 LPH at 120 KPH which is pretty freakin' awesome esp with cruise control selected.
I don't know of anyone getting anything like that with a 2 inch lift albeit he was running 32's over the more common 33's

Not saying the OP was full of it as we all know what a weird bit of kit the CRD's can be as far as fuel economy etc, simply saying he seemed to be the only one that saw a big difference

[threedogs]

10.2lt/100k @ 120kph from a CRD seems hard to believe even with stock size tyres.
Revs would be around 2400/ 2500 I'd imagine, cant see it myself but all motors are different

[BigRAWesty]

Op also did the test on the open road.
So if you had even a 10/h wind change that would add or reduce a fair amount of efficiency.

There was a proper wind tunnel test done I believe and pressure increase in the airbox was nill.

Imo the "ram head" is a mimic but the supposedly separate water also??
At 100 km/h the rain still hits your window so I can't see how it separates...

Anyway. If you have a turbo I think it's personal choice..

[gubigfish]

Cheers all I would think if the water level is up around the top of your windscreen you have bigger problems anyway

[P4trol]

The ram head sits over the snorkel, ie the water hits the snorkel and dribbles down the outside and through the gap between ram head and snorkel.

[Hodge]

The ram head sits over the snorkel, ie the water hits the snorkel and dribbles down the outside and through the gap between ram head and snorkel.

That's right it is the water trap.

51098

As per the main topic. Correct me if I'm wrong, but you would get better fuel economy facing the head rearwards, simply due to less air being pushed in, therefore, the MAF sensor will lower the fuel mixture as well ? I dare say he may have also had a proportional power loss too (probably not noticeable).
There is also the "venturi" effect , which was talked about a few times, when it comes to facing the snorkel rearwards.

https://www.google.com.au/search?sourceid=chrome-psyapi2&ion=1&espv=2&es_th=1&ie=UTF-8&q=venturi%20effect%20snorkel

[ako89]

Cant fault my radius fab rear facing snorkel