Snorkels?

[LostInThought]

One of the replies above suggested a little research, so I started looking around, and thought I'd share what can be found and a few personal musing based on what's out there. Unfortunately, this one got long again... summary at the bottom.

DUST

ASPW of 4xOverland did a short 3min VIDEO HERE on the merits of a snorkel for dusty conditions that are similar to what I see near the Jemez Mountains of Northern New Mexico. The screenshots (below) from his video (which I recommend watching) show the dust issue. Note the dust flooding from the front wheel wells in both photos, also note the absence of dust at the top of the windshield where the snorkel intake would be mounted. The video also shows the result of knocking the dust out of the air filters on two vehicles driven in these conditions, one without a snorkel and one with a snorkel. The difference between with and without snorkel is very apparent. It seems to me that depending on where you drive, a snorkel can make a significant difference in the amount of dust/debris drawn into the air filter and this might be a real justification for a snorkel.




PERFORMANCE

I also ran across videos from Safari 4x4, showing dyno testing results with and without their 4" snorkel for:

a Ford Ranger which picked up ~+10% power and torque
and
a Toyota Landcruiser 200 Series which picked up ~30% power and torque

The videos aren't clear, but I believe the Ford Ranger is a 3.2 liter I5 Duratorq turbo diesel and the Toyota Landcruiser is a 4.5 liter V8 twin-turbo diesel based on the shape of the power/torque curves produced by the dyno testing. This makes sense - anything that helps a turbodiesel breathe generally improves performance. Notably, the Safari 4x4 videos don't make a similar claim regarding their 3" snorkels, which are about the same diameter as the stock intake plumbing. But this is their channel and their product. I think if they thought they could claim improvement for the 3" snorkel, or for non-turbodiesels, they'd have posted a video or five.

Because they've only posted videos of dyno testing on turbodiesels, I'm going to pull out a Oujia Board and a crystal ball and dust off some old thermodynamics skills - be warned, several semi-scientific wild-assed guesses ahead. So, with that said, I would expect the larger diameter intake to produce more improvement in a forced induction induction engine than a naturally aspirated engine and I would expect a diesel to respond better than a gasoline engine - so the turbodiesel results represent a best case (and of course, on the corporate channel, you put your best numbers out).

• Guessing based on some axial-flow fan testing I did 30+ years ago - the temperature difference over ~40ft of duct wasn't measureable and the flow was basically adiabatic/incompressible even at flow speeds resembling highway speed limits.
• With almost 2x (16/9) the cross-sectional area, a 4" will flow ~2x better than a 3", i.e. probably closer to half the velocity at the same volume than twice the volume at the same velocity, and thus a thinner boundary layer, so generally lower viscosity losses through the intake system upstream of the filter for the 4" diameter snorkel vs the 3" diameter snorkel.
• I'll have to think through how this might impact harmonic resonance issues, but my guess is that the longer path will push the 1st and 2nd harmonics of the snorkel to well below the operating RPM of the engine, leaving only the lower energy higher harmonics to worry about?
• As for the longer curved path of a snorkel of the same diameter as the stock intake plumbing, I would expect that the flow restriction this presents would be much smaller than the difference in restrictions presented by a clean vs dirty air filter - maybe less than 1/2"H2O on a manometer?

My next question is *where* might you see "gains"? The turbodiesels (above) picked up pretty consistently across the entire RPM range (often best at the low end) and I might expect similar consistency across the range for forced induction gasoline engines (though with less gain than the turbodiesels got). For a naturally aspirated gasoline engine, well, no one seems to be putting these on a dyno with and without a snorkel - BUT based on what is dyno'd with other intake mods, I would guess that for an NA-gasoline engine, you'd see next to nothing below 2000 RPM, with the best gains over 3000 RPM where the engine struggles most for air? (see the Underdog Racing Development site for an example, but beware: there was a 12F temperature difference during the tests which, surprise, FAVORED their product.) So it seems that adding a larger snorkel to a turbodiesel would be justified in terms of potential performance gain, but not for an NA-gasoline engine until someone produces dyno results to the contrary. (NA-diesel and FI-gasoline engines would fall somewhere between)

SUMMARY

• Snorkels are a WIN for dust
• Snorkels can gain performance for a turbodiesel if they are larger diameter than the stock intake plumbing
• I can't find dyno data for naturally aspirated gasoline engines, and from the absence I infer that snorkels aren't a performance win for these applications

Does this sound right?

 

[John21powerwagon]

For me personally, I’ll just change my filter as needed, be careful crossing water and avoid spending money adding a wart to my taco. We will see how the Power Wagon holds up when it eventually shows up.

 

[USStrongman]

So many haters with nothing more than watching someone drive down the road with a snorkel and it triggered them. Get over yourselves.

The AEV snorkel I run is waterproof, but utilizes the OEM airbox that they walk you through how to waterproof it during install. Nothing to it and added maybe an additional 20 mins. In addition it retains the drain tubes in the bottom of the airbox as water can enter the snorkel through the intake with RAM style intakes. I run the Donaldson style intake filter with a K&N in the box.

The reason I have one? Dusty roads in Tx and NM where I mostly wheel combined with a 2021 trip to Alaska. We plan on not taking all highways there but to get some FS roads, etc and am certain we will run into fordable water.

 

[LostWoods]

One of the replies above suggested a little research, so I started looking around, and thought I'd share what can be found and a few personal musing based on what's out there. Unfortunately, this one got long again... summary at the bottom.

DUST

ASPW of 4xOverland did a short 3min VIDEO HERE on the merits of a snorkel for dusty conditions that are similar to what I see near the Jemez Mountains of Northern New Mexico. The screenshots (below) from his video (which I recommend watching) show the dust issue. Note the dust flooding from the front wheel wells in both photos, also note the absence of dust at the top of the windshield where the snorkel intake would be mounted. The video also shows the result of knocking the dust out of the air filters on two vehicles driven in these conditions, one without a snorkel and one with a snorkel. The difference between with and without snorkel is very apparent. It seems to me that depending on where you drive, a snorkel can make a significant difference in the amount of dust/debris drawn into the air filter and this might be a real justification for a snorkel.

View attachment 181746View attachment 181747


PERFORMANCE

I also ran across videos from Safari 4x4, showing dyno testing results with and without their 4" snorkel for:

a Ford Ranger which picked up ~+10% power and torque
and
a Toyota Landcruiser 200 Series which picked up ~30% power and torque

The videos aren't clear, but I believe the Ford Ranger is a 3.2 liter I5 Duratorq turbo diesel and the Toyota Landcruiser is a 4.5 liter V8 twin-turbo diesel based on the shape of the power/torque curves produced by the dyno testing. This makes sense - anything that helps a turbodiesel breathe generally improves performance. Notably, the Safari 4x4 videos don't make a similar claim regarding their 3" snorkels, which are about the same diameter as the stock intake plumbing. But this is their channel and their product. I think if they thought they could claim improvement for the 3" snorkel, or for non-turbodiesels, they'd have posted a video or five.

Because they've only posted videos of dyno testing on turbodiesels, I'm going to pull out a Oujia Board and a crystal ball and dust off some old thermodynamics skills - be warned, several semi-scientific wild-assed guesses ahead. So, with that said, I would expect the larger diameter intake to produce more improvement in a forced induction induction engine than a naturally aspirated engine and I would expect a diesel to respond better than a gasoline engine - so the turbodiesel results represent a best case (and of course, on the corporate channel, you put your best numbers out).

• Guessing based on some axial-flow fan testing I did 30+ years ago - the temperature difference over ~40ft of duct wasn't measureable and the flow was basically adiabatic/incompressible even at flow speeds resembling highway speed limits.
• With almost 2x (16/9) the cross-sectional area, a 4" will flow ~2x better than a 3", i.e. probably closer to half the velocity at the same volume than twice the volume at the same velocity, and thus a thinner boundary layer, so generally lower viscosity losses through the intake system upstream of the filter for the 4" diameter snorkel vs the 3" diameter snorkel.
• I'll have to think through how this might impact harmonic resonance issues, but my guess is that the longer path will push the 1st and 2nd harmonics of the snorkel to well below the operating RPM of the engine, leaving only the lower energy higher harmonics to worry about?
• As for the longer curved path of a snorkel of the same diameter as the stock intake plumbing, I would expect that the flow restriction this presents would be much smaller than the difference in restrictions presented by a clean vs dirty air filter - maybe less than 1/2"H2O on a manometer?

My next question is *where* might you see "gains"? The turbodiesels (above) picked up pretty consistently across the entire RPM range (often best at the low end) and I might expect similar consistency across the range for forced induction gasoline engines (though with less gain than the turbodiesels got). For a naturally aspirated gasoline engine, well, no one seems to be putting these on a dyno with and without a snorkel - BUT based on what is dyno'd with other intake mods, I would guess that for an NA-gasoline engine, you'd see next to nothing below 2000 RPM, with the best gains over 3000 RPM where the engine struggles most for air? (see the Underdog Racing Development site for an example, but beware: there was a 12F temperature difference during the tests which, surprise, FAVORED their product.) So it seems that adding a larger snorkel to a turbodiesel would be justified in terms of potential performance gain, but not for an NA-gasoline engine until someone produces dyno results to the contrary. (NA-diesel and FI-gasoline engines would fall somewhere between)

SUMMARY

• Snorkels are a WIN for dust
• Snorkels can gain performance for a turbodiesel if they are larger diameter than the stock intake plumbing
• I can't find dyno data for naturally aspirated gasoline engines, and from the absence I infer that snorkels aren't a performance win for these applications

Does this sound right?

Very simply, intakes only help performance where they are the obstruction and a snorkel is nothing more than a long intake.

To explain your point from a mechanical standpoint, turbo diesels (emphasis on turbo) nearly always benefit from improved airflow (from a stock config) prior to the turbo as there is nothing else to bottleneck. The reason diesel engines can run away is because there is no regulation of airflow whatsoever and they instead modulate fuel injection and injection timing to control power. There is nothing but tube ahead of the turbo so the intake tube and filter by default are the only available obstruction when the turbo pulls a vacuum in the tube under load (which differs from a gas-powered forced induction engine as those will always have a throttle body as the greatest restriction). Larger tube makes more air available in that system, less work for turbo, and therefore more power to the ground. There is a functional limit to this but I have yet to see a turbo diesel that doesn't gain from a larger intake whereas I have yet to see a gasoline powered vehicle in the past 10-20 years that did gain consistently beyond the margin of error in fuel quality and ambient conditions.

With a turbo diesel, other factors come into play like the density of cool air and the difference in ambient vs under-hood temps which can also add a fair bit of power. The important thing in the end is that the snorkel tube (1) doesn't cause unnecessary turbulence, and (2) doesn't add any unnecessary restrictions on airflow compared to stock.

As for the usefulness of a snorkel, I think its usefulness in dust has been beat to death at this point and its really the only reason to have one in a modern vehicle. With all the electronics, you have much greater concerns than sucking in water and a snorkel does nothing to save your alternator or some other module that is down low. Just look at any vehicle that offers an optional snorkel and the fording depth will almost always be the same due to the limitation with electronics.

 

[RonaldHoward1313]

I chose to run a snorkel mostly because I like the looks of them. But, when I put it on I found out it did improve my fuel mileage by about 1mpg. It also seems to run a little cooler. For those that say it restricts airflow, I suggest you do some research into it. While at a stop at idle, no it will not bring more air to the engine, but during highway speeds it acts like a ram and forces more air into the engine. This is well known proven fact. The air filter you use makes a difference in this also. I put a K&N filter in and it did improve the mileage again by .5-1 mpg. No, my snorkel is not waterproof....nor will it ever be. i do not run that deep in water, and there are many other things needing to worry about if you think about going that deep. With running 33" tires on stock gearing, heavy steel bumpers, winch, slider steps and 2" lift I am back up to almost 17mpg. I have actual real work experience that a snorkel does work and does improve air flow and mileage. And that goes right along with the studies and the facts.

 

[Lanlubber In Remembrance]

When I say “Pre-Filter” I’m not talking the little screen at the top... I’m talking a real pre-filter...
View attachment 181715

Will it work on my coffee pot too ?
Ok bad joke for serious talk. I do have a snorkel that is yet to be installed (like many other things). I dont live where there is a bunch of standing water I might drive through but I have plenty of dust that I would worry more about. We have sand storms all through out the southwest that will pull you over to the side of the road quickly for lack of visibility. One day I will have it installed but there are many other things that I will have done before I worry about the snorkel.

 

[smritte]

I'll have to think through how this might impact harmonic resonance issues, but my guess is that the longer path will push the 1st and 2nd harmonics of the snorkel to well below the operating RPM of the engine, leaving only the lower energy higher harmonics to worry about?

I would think this will only come into play at high throttle, low vehicle speed. At higher speed the air is going to compress slightly as it hits the air filter, take the filter out and the dynamic should change. Either way, as long as the resonance is minimal, the velocity will drop the air charge temperature some. Basic formula is 10 degrees =1% power change. The temp drop will probably negate any issue there.

I've done dyno testing on my 04 TJ comparing stock intake vs a cowl intake I made out of 3inch ABS with a ford mustang air cleaner assy. I have also done quite a bit of testing "cold air" intakes on Hondas.

Neither are snorkels but the science will be similar.

First the Hondas. K&N open element air cleaner and a "short ram" intake vs stock. The K&N had 2 problems over stock. First was the air temp increase. Pulling air from the engine compartment raised the intake air temp by around 70 degrees (10 degrees = 1%) Right off we had a 6-8 hp loss. Second was the harmonic as mentioned by @BCNP4runner, the harmonic flattened the torque curve in the center of the power band. Result was loss of power and torque over stock but was able to get a few more RPMs at the top end outside of the power band.

TJ. Jeep chose to pick up the air inside the engine compartment as well as running a slightly restricted intake. One of my tests was installing a temp sensor just past the air cleaner and driving a slow canyon on a 100 degree day. 100 degree ambient and the intake temperature was almost 300 degrees. (10 degree=1%) 100-300=200 degree difference = 20% power loss. This is a calculation, not done on a dyno yet.
Cut a hole in my cowl, shorten a mustang air cleaner and run that to my throttle body using 3inch ABS pipe.
First the Ford air cleaner had more than twice the surface area of the Jeep. Both were delco air cleaners. On the dyno, I will not get any benefit from the high pressure at the base of the windshield like I would driving. I also installed a gas analyzer to monitor emissions.

My fear was causing a harmonic that would kill my mid range torque like the Hondas by modifying the intake. The dyno difference was slight. I gained only 2 HP and no real torque, then we closed the hood. The cowl air ran at ambient and the stock averaged around 100 over ambient with a fan blowing on the front. 8-10 hp increase with very little torque increase and no harmonic issue. Driving down the freeway my intake temp stayed at ambient and on highway I picked up a little over 1mpg.

The only reason I wont run a snorkel is, I don't want to cut a hole in my fender. I have no doubt there would be a slight increase.

 

[Boostpowered]

Best I can get scientifically, real time info.
At 14 mph.


At 0 mph.


At 35ish mph slowing down

 

[LostInThought]

I would think this will only come into play at high throttle, low vehicle speed. At higher speed the air is going to compress slightly as it hits the air filter, take the filter out and the dynamic should change. Either way, as long as the resonance is minimal, the velocity will drop the air charge temperature some. Basic formula is 10 degrees =1% power change. The temp drop will probably negate any issue there.

I've done dyno testing on my 04 TJ comparing stock intake vs a cowl intake I made out of 3inch ABS with a ford mustang air cleaner assy. I have also done quite a bit of testing "cold air" intakes on Hondas.

Neither are snorkels but the science will be similar.

First the Hondas. K&N open element air cleaner and a "short ram" intake vs stock. The K&N had 2 problems over stock. First was the air temp increase. Pulling air from the engine compartment raised the intake air temp by around 70 degrees (10 degrees = 1%) Right off we had a 6-8 hp loss. Second was the harmonic as mentioned by @BCNP4runner, the harmonic flattened the torque curve in the center of the power band. Result was loss of power and torque over stock but was able to get a few more RPMs at the top end outside of the power band.

TJ. Jeep chose to pick up the air inside the engine compartment as well as running a slightly restricted intake. One of my tests was installing a temp sensor just past the air cleaner and driving a slow canyon on a 100 degree day. 100 degree ambient and the intake temperature was almost 300 degrees. (10 degree=1%) 100-300=200 degree difference = 20% power loss. This is a calculation, not done on a dyno yet.
Cut a hole in my cowl, shorten a mustang air cleaner and run that to my throttle body using 3inch ABS pipe.
First the Ford air cleaner had more than twice the surface area of the Jeep. Both were delco air cleaners. On the dyno, I will not get any benefit from the high pressure at the base of the windshield like I would driving. I also installed a gas analyzer to monitor emissions.

My fear was causing a harmonic that would kill my mid range torque like the Hondas by modifying the intake. The dyno difference was slight. I gained only 2 HP and no real torque, then we closed the hood. The cowl air ran at ambient and the stock averaged around 100 over ambient with a fan blowing on the front. 8-10 hp increase with very little torque increase and no harmonic issue. Driving down the freeway my intake temp stayed at ambient and on highway I picked up a little over 1mpg.

The only reason I wont run a snorkel is, I don't want to cut a hole in my fender. I have no doubt there would be a slight increase.

Thank you! This is *very* useful info and clearly demonstrates the impact of pulling the intake charge from inside vs outside the engine bay with a so-called "cold-air-intake" via a fender or snorkel.

Based on this it seems I should amend my summary to say that if the stock intake you're replacing draws air from the engine bay, a snorkel (or other cold air intake) would produce 5-6% more power and that if you're already drawing air from outside the engine bay, we wouldn't expect much change in power?

Last question: Your TJ, does it have the 150hp I4 or the 190hp I6?

 

[LostInThought]

Best I can get scientifically, real time info.
At 14 mph.
View attachment 181860

At 0 mph.
View attachment 181861

At 35ish mph slowing down
View attachment 181862

This is for a Tacoma? Which app and ODBII reader are you using? Would you recommend it?

 

[Boostpowered]

This is for a Tacoma? Which app and ODBII reader are you using? Would you recommend it?

Chevy colorado 2.8 diesel. Torque app, elm327 v1.5 reader.
Yeah I'd recommend it.

 

[Boostpowered]

Around 35mph under boost passing a slowpoke.

 

[LostInThought]

Around 35mph under boost passing a slowpoke.
View attachment 181865

This is helpful to put some numbers/ranges on the intake velocity.

With your 4" snorkel, the air velocity varies from roughly 16ft/s (like a 10mph breeze) at idle to 114ft/s (77mph) passing at 35mph.

A 3" snorkel would change these to 22ft/s (15mph) at idle to 202ft/s (137mph) passing at 35mph... about a 2x difference. Though I can imagine that trying to move air through a 3" dia. tube at ~130mpg might induce enough turbulence and viscous drag to present a significant restriction.

 

[JDGreens]

Since I am planning on modifying my rig extensively in the near future, adding the need to run a compressor for ARB lockers and I am looking forward to mounting my compressor where my air box used to be I'm going to be modifying my rig with a cold air intake/snorkel.

I'm not a fan of how a snorkel looks but with the space it will free up and it will be a more efficient intake system then the stock system. So for me it's a no brainer,

 

[Boostpowered]

What it looks like at highway speed cruising.

 

[smritte]

Based on this it seems I should amend my summary to say that if the stock intake you're replacing draws air from the engine bay, a snorkel (or other cold air intake) would produce 5-6% more power and that if you're already drawing air from outside the engine bay, we wouldn't expect much change in power?

In a nut shell, yes. Obviously there are a number of factors involved. In the case of my TJ, air was pulled from next to the radiator and at low speed the engine heat added to the mix. It also didn't help that the intake manifold is on top of the exhaust manifold. Any drop in air temp will help there more than a vehicle where this is not the case. I also install a restriction gauge inline on all my vehicles to monitor air cleaner restriction. Interesting how little the gauge moves when the air is slightly pushed against the filter instead of pulled.

Last question: Your TJ, does it have the 150hp I4 or the 190hp I6?

04 Rubicon I-6. I don't remember the numbers (I did this in 07) but they were fairly close to published numbers and the vehicle had 16k miles. At the time I had watched a multipage discussion just like this on Jeep Forum. I had access to everything needed so I ran my own testing on the air intake mod and the fuel injector mod. I just did it like I do everything like this, simple curiosity.

 

[MidOH]

Those numbers are meaningless, especially since turbocharged. Use a simple manometer. You got any clear Rubber tubing?

I promise you that it's very highly unlikely that you're going to see any power gains. That 30% number?........Lolz, really? I can completely remove my hood, intake, and air filter and not even get 2%.

 

[Boostpowered]

We probably would use a manometer if it were the 1960s and everyone was still using carburetors, but its 2021 now and most everyone these days has a electronic controlled fuel injection or electronic diesel diret injection that runs a mass air fuel meter along with multiple o2 sensors on the hot side. There is no need for such archaic instruments anymore, not too many folks are filling batteries with electrolyte or testing radiator fluid anymore, not much distributor points these days either.

 

[MidOH]

It's just so you guys can see the difference in air pressures in real time. So you can literally see the water level jump, as the engine pulls a vacuum through a straw. Been there done that. Although some of the those extra thick ones for the Tacoma's might be interesting and free flowing.

A simple pipe can restrict gas flow at low pressure more than most people understand. Check out some natural gas plumbing for example. Low pressures require massive diameter pipes, and hopefully short runs.

You just duct tape it to the windshield for an hour to see. I use one every week in engine rooms up to 12,000 hp.

 

[Crayoneater]

I would have to admit I at first thought they were solely for water crossings my self. I had seen a timmy the toolman video adding a snorkel, he and his helper explained the benefits of one. Naturally that lead to seen more videos out of Australia discussing their main reasons for the snorkels was to reduce the amount of dust and dirt going to the air filter.

I ended up getting one after finding chunks of mud and dirt in the bottom of my air box. How it got past the fender liner and in the small intake tube that was in the wheel well is beyond me. The part of the snorkel/rubber elbow that passes through the fender is about twice the size of the oem. As for any performance gains I would say it be negligible, off idle seems the same but the mid to upper RPM it doesn't seem to labour as much (feels smoother) but that is coming from the seat of my pants dyno. It dose help with the dust, I'm not having to clean the K&N filter as often. I am thinking of getting a dust pre-filter (looks like a salad bowl) to try out.