Fording Depth vs. Snorkel Height

[rayra]

 

[Hillbilly Heaven]

New found problem with snorkels. Squirrels hiding acorns in the airbox. I guess a wire mesh screen is in order.

 

[onemanarmy]

At the risk of being branded a heretic...

Do you really need a snorkel intake at the roof level?

I mean, unless you're trying to assault a beach from a landing craft, how often are you intentionally crossing water that washes over the windshield of your vehicle?

And, to be fair, I suppose having the intake that high would keep water out if you stalled mid stream, but then your exhaust would flood back to the heads, anyway...

Or, the only other option my be just over the hood...which may be too low, so the next logical location is at the roof.

And, we're just talking water issues here. Dust is an entirely different issue, which pretty much justifies putting the intake as high as possible.

And lastly, there's the cool factor. And if that were the ONLY factor, just glue / velcro a non-functioning snorkel to the fender and A-pillar, and voila!! You're cool!!

for 99.99%....BLING

 

[onemanarmy]

Those desert racers have the intakes in the cab.

not sure what your point is?

 

[Retired Tanker]

Those desert racers have the intakes in the cab.

not sure what your point is?

I was kinda wondering about that, too. Only saw 1 snorkel.

And if you're following someone in a dust cloud (as you would be in racing) I would think that the tallest snorkel possible wouldn't be much help.

 

[Pilat]

(images removed for brevity]

All of those are breathing dustless air.

Following those cars, though.

 

[rossvtaylor]

If you're following someone in a dust cloud, having a snorkel is the least of your concerns. One of the first fatal crashes I had to investigate was a "ride-in-the-dust-cloud, oops-he-stopped" kind of crash. Okay, back to your regularly-scheduled snorkel discussion!

 

[1stDeuce]

Just an FYI on the exhaust side of this discussion... I've started plenty of carbureted and FI vehicles with the exhaust underwater. It's only a problem if the water level is higher than the cylinder head, and you leave the engine off for a while. Due to valve overlap, and rings not sealing perfectly, water can eventually push the air backward past the rings and valves and get into the engine. But ONLY if the engine is underwater.

Stalling and restarting immediately will not be a problem. If the exhaust is deep enough, there can be some back pressure that may make a carbureted engine a little more difficult to start, but adding just a bit of throttle overcomes the back pressure, and once it's running it should be fine. FI seems to handle it better, as it automatically maintains idle speed.

For any armchair explorers who disagree, please consider an I/O boat... Mine had a Chevy 4.3L in it, same as an S-10. The exhaust exit is 2-3' below the water line, but the engine is above. Zero problems starting. You're welcome.

 

[eggman918]

At the risk of being branded a heretic...

Do you really need a snorkel intake at the roof level?

I mean, unless you're trying to assault a beach from a landing craft, how often are you intentionally crossing water that washes over the windshield of your vehicle?

And, to be fair, I suppose having the intake that high would keep water out if you stalled mid stream, but then your exhaust would flood back to the heads, anyway...

Or, the only other option my be just over the hood...which may be too low, so the next logical location is at the roof.

And, we're just talking water issues here. Dust is an entirely different issue, which pretty much justifies putting the intake as high as possible.

And lastly, there's the cool factor. And if that were the ONLY factor, just glue / velcro a non-functioning snorkel to the fender and A-pillar, and voila!! You're cool!!

OR commuting in Phoenix.. :snorkel:

 

[Dake21]

OR commuting in Phoenix.. :snorkel:

Been there, done that and I was amazed to see how many people do not care and drive into the water anyway. Same for 6 feet high snow bank, of course that ''4x4'' fiat 500 will make it! :ugh:

 

[Rando]

I am not convinced of snorkels as a dust reduction strategy either. There are two factors that to me would suggest that a snorkel may actually be worse for reducing dust:

1. "Fugitive Dust", which is the technical term for mechanically produced dust from a road source, doesn't actually decrease significantly between say 1m and 3m above the road surface. In fact there is even some evidence to suggest that at ~30 - 40m from the source there would be a greater mass of dust at 3m compared to 1m. Here is a figure from some actual measurements of dust as a function of height above surface:

From: Cuscino, Thomas A., Robert Jennings Heinsohn, and Jr Clotworthy Jr. "Fugitive dust from vehicles traveling on unpaved roads." (1977).

Based on these measurements, raising your inlet from 1 - 3 meters is not going to get you above the maximum dust mass loading, however gravitational settling may increase the fraction of finer dust which is harder to filter.

2. A forward facing snorkel will actually increase the amount of dust your intake is ingesting relative to the ambient dust concentrations. This effect is called 'anisokinetic sampling' and is something we commonly use when sampling cloud particles (very similar to dust) from aircraft. The principle is that if you are driving fairy quickly, your car is moving faster than the air going into your inlet (as an aside I have heard it claimed that this 'ram air' effect actually increases HP!). In this scenario, much of the air that is hitting your snorkel actually has to go around the snorkel as velocity of air entering your snorkel is lower than the velocity of the vehicle (the middle figure below). The dust particles have far more momentum than the air, so the dust that was contained the air that went around your snorkel ends up going into your snorkel. Depending on the relative velocities, you can easily get a factor of 2 or more in dust enhancement.

From a dust perspective you would do mush better to have your intake a meter or so above the road, and protected from the air stream - like inside a fender :ylsmoke:

Of course none of this applies to using a snorkel for water crossings, or to look awesome.

 

[Hillbilly Heaven]

Am I correct in that the first graph was measured 36.6 m from the road as being from the side.

 

[Rando]

Am I correct in that the first graph was measured 36.6 m from the road as being from the side.

Correct.

 

[Hillbilly Heaven]

It would seem to me that dust would follow in a column. At 36.6 meters there would be a significant time period before the dust cloud reaches that far. The column of dust starts expanding soon after the vehicle passes. The density of the cloud decreases over time. So it really depends on how close you are following the lead vehicle. It gets worse and complicated the more vehicle involved.

I can't disagree with the 2nd part. What you are saying makes logical sense but I don't know enough science to agree or disagree.

 

[Rando]

You make a good point. There is some data from this same study closer to the road (18M) that shows essentially the same pattern, with a more pronounced increase in dust at 3m relative to 1m. But the specifics of this are not really that relevant as I am sure this is a function of the type of road surface, type of vehicle, speed of vehicle, wind speed and alignment of the zodiac. My point was just to show that it is not necessarily true that there is significantly less dust at 3m than at 1m.

I personally think snorkels look cool, and it is none of my business if anyone wants to put one on their car. If you are worried about dust though, there are probably better but less cool looking options.

It would seem to me that dust would follow in a column. At 36.6 meters there would be a significant time period before the dust cloud reaches that far. The column of dust starts expanding soon after the vehicle passes. The density of the cloud decreases over time. So it really depends on how close you are following the lead vehicle. It gets worse and complicated the more vehicle involved.

I can't disagree with the 2nd part. What you are saying makes logical sense but I don't know enough science to agree or disagree.