Snorkel = Snake Oil ?
- Thread starter mauricio_28
- Start date
mauricio_28
Adventurer
Despite a previous similar discussion and the discussion at hand, it seems that there is not overwhelming consensus for or against. I probably will end up installing one for the Nissan Navara TDI that will be arriving in my garage in two weeks. Water and flooding are always nearby here in tropical Indonesia.
Any issues related to the the waterproofing of electricals particular to the Navara?
Any issues related to the the waterproofing of electricals particular to the Navara?
hochung said:
Only your 12th post and already trying to cause trouble!
I love it! :snorkel: :jump:
eepwall:ntsqd said:
I have never seen a snorkel manufacturer post CFM ratings for their product. I can offer two experiences:
Using a stock Ford 5.0 HO from a '91 Mustang as the power plant in the CJ-7, engine rated to draw 550 CFM, a Safari Snorkel designed for the TJ, which uses a 4.0 with a quite similar CFM rating (The TJ airbox is rated to supply 550 CFM), would not provide sufficient air flow for the stock 5.0 V-8. We drove one leg of a transport stage in 2002 with a group of insane Aussies, doing 80+mph in the middle of the night about 100 feet apart on a one lane dirt road for just about 60 miles. At the end of that trip, aside from changing underwear, we found we had consumed about 18 gallons of fuel. The guys behind us wanted to know if we had a problem because our tailpipe smoke was blacker than a diesel. The snorkel, which should have been good for around 500 CFM, snuffed the V-8 like a potato in the intake. We disconnected it, and later that week had to run through a lake in 3 feet of water with no snorkel. Not a fun adventure, that one. Should have put the snorkel back together and just kept my foot out of it.
So, because the plastic snorkels on the market didn't get the job done, I built one out of 3.5 inch stainless tubing. Mandrel bends and the whole bit. You would think that if the engine uses a 52mm throttle body, that a 3.5 inch intake tube (about 89mm) would pass all the air you might need. It doesn't. With the new snorkel attached, the engine works fine until you approach WOT, at which point it flattens out (I can now do most any speed up to 95 and still get 12mpg instead of 3 so there is an improvement, but I can feel that pillow when I get up there around 80 so I know there is restriction). I haven't bothered to dyno the system and probably won't, but there is a definite problem with tubing diameter and lengths found in common snorkels, all of which needs to be taken into account.
Air is a fluid. Boundary layer resistance is an attribute of fluid dynamics. The effective free flow diameter of a tube is less than its literal inner diameter, and the longer the tube and the faster the fluid travels, the worse the problem. Try breathing through a 2 inch length of garden hose. Then try breathing through a 100 foot garden hose -- if you can. That is the effect of having a long intake tract. The longer it is, the larger it has to be to work at all.
So I don't see a snorkel as a performance upgrade. Instead it is a compromise. Hopefully a snorkel made to fit your vehicle will work as advertised, but keep in mind that most of them have no better than a 2.5 inch diameter at their narrowest point, which is fairly small for the job. We get away with it because we are not building NASCAR machines and don't usually drive at WOT.
Even though I face the intake forward and slightly toward the windshield to pick up the pressure pulse off the front of the car, I don't see a significant gain from any sort of "ram air" because the benefit, if there is one, is lost before it gets to the engine.
If I were going to build another system for mine, I would likely use 5 inch tube.
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IronSmiles
Observer
mauricio_28 said:
Actually, there are a lot of people who support getting one, IF it's installed properly and you at LEAST waterproof your electronics as best you can. But like it's been said around here a 100 times, it's all about what makes YOU more comfortable trailing in YOUR rig. :victory:
the dude
Adventurer
Like others have stated, it also depends on what vehicle you are driving and what other modifications for fording water you have done.
For myself, I am lucky that my Land Cruiser has no electronics controlling it once it gets running. No distributor or computer to worry about. The only issues I have encountered are slipping belts when wet. You also need to be concerned about starters and alternators for corrosion after the water crossing.
I also have all my vents (axles/t-case etc.) ran to the back side of my snorkel.
As for the loss of air, I am not sure on that one. I think with my turbo you might see a bit more of lag... It sure does whistle sucking that air in, and I can hear the turbo spool up a lot louder now.
And as others have said, I suck a lot less dust and grime into the air filter. A huge bonus that makes the snorkel worth it for that alone.
Oh, and the picture, this just got deeper and went over the hood. Unfortunately no pics. Both rigs had 38+ tires:
For myself, I am lucky that my Land Cruiser has no electronics controlling it once it gets running. No distributor or computer to worry about. The only issues I have encountered are slipping belts when wet. You also need to be concerned about starters and alternators for corrosion after the water crossing.
I also have all my vents (axles/t-case etc.) ran to the back side of my snorkel.
As for the loss of air, I am not sure on that one. I think with my turbo you might see a bit more of lag... It sure does whistle sucking that air in, and I can hear the turbo spool up a lot louder now.
And as others have said, I suck a lot less dust and grime into the air filter. A huge bonus that makes the snorkel worth it for that alone.
Oh, and the picture, this just got deeper and went over the hood. Unfortunately no pics. Both rigs had 38+ tires:
pete.wilson
Adventurer
Hey
For all those that thought I was picking on them; I have a couple of questions.
What king of filter do you use with your snorkel and where is it physically located?
I read in another post about a 7 inch and a 10 inch prefilter used in conjunction with a snorkel? Wouldn't it be better to use this setup?
How did you re-route all of the other vent lines, so you don't ingest water into the other locations. How tight is things like firewall grommets, door seals vents, heater/AC components and the like?
Thanks
Pete Wilson
For all those that thought I was picking on them; I have a couple of questions.
What king of filter do you use with your snorkel and where is it physically located?
I read in another post about a 7 inch and a 10 inch prefilter used in conjunction with a snorkel? Wouldn't it be better to use this setup?
How did you re-route all of the other vent lines, so you don't ingest water into the other locations. How tight is things like firewall grommets, door seals vents, heater/AC components and the like?
Thanks
Pete Wilson
TeriAnn
Explorer
madizell said:
Interesting thing about engines, the volume of air they pump depends upon the RPM the engine is turning when the measurement is taken. A 550 CFM engine draws 550 CFM at a given RPM and less below that RPM. I run a 1970 302 with 1991 Mustang EFI so in my usual anal retentive way did my homework before choosing an air cleaner.
Of interest is a formula commonly used to calculate the CFM an engine draws at different RPMs.
Using this formula, a Ford 302, Chevy 302 or Ford 5.0 draws:
131 CFM @ 2000 RPM
197 CFM @ 3000 RPM
328 CFM @ 5000 RPM
Of course the engine may draw more under acceleration.
My engine normally runs between 700 RPM and 3000 RPM so cruise air flow is below 200 CFM.
I used this information to figure the minimum flow spec for my air filter.
This is what I ended up with:
Prefilters have a maximum and a minimum RPM within which they work properly. Below the RPM range the prefilter does not clean the incoming air. Above the range and the prefilter restricts airflow.
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IH8RDS
Explorer
pete.wilson said:
I didn’t feel you where picking. I have seen your condition before. It’s all good. lol
I use a K & N. The oil in the filter repels any water pretty good. A pre-filter would cut down on the bugs. I am always cleaning out bugs.
When I am in water deep enough to touch the body I run the vent at full to over pressurize the cab. I have never had water enter the cab. All of the door weather stripping is still in good shape.
The one time I went to the windshield I turned off the vent blower because it sucks air right behind the hood. I did not have an issue. I wasn’t there long though. All of my vents are as high as they can go on the firewall. I like the idea I heard earlier about running them up the snorkel. Maybe run then in the snorkel out of sight.
teotwaki
Excelsior!
The Toyota "cyclone" prefilter that I installed comes from the '08 FJ Cruiser as well as the Prado line. Toyota specs for the 1GR-FE were not derated for horsepower or torque so it does not appear that it offers any restrictions.
Compared physically to the original plastic do-hicky/air box it may offer better air flow despite the vanes on the input.
The earlier comment about how effective the pre-filters are will depend on air flow/engine RPM makes sense. It must take a certain minimum CFM of airflow to get dirt particles to "spin" to the outside of the chamber for seperation..
Compared physically to the original plastic do-hicky/air box it may offer better air flow despite the vanes on the input.
The earlier comment about how effective the pre-filters are will depend on air flow/engine RPM makes sense. It must take a certain minimum CFM of airflow to get dirt particles to "spin" to the outside of the chamber for seperation..
R_Lefebvre
Expedition Leader
I must say that the problem wasn't that the snorkel was "too small" it was that your engine wasn't tuned right. I figure you must have had one of two scenarios:
1) You were running a carburettor. You didn't tune the carb to run properly with the snorkel restriction. It's a similar effect to running around with the choke on. It's possible this was the first time you were running with the main jets working, and they should have been smaller. While the snorkel was obviously smaller than optimum, and wasn't working with the way the truck was setup, a proper tuning of the carburettor would make this setup work without resorting to 5" tubing.
2) You were running with fuel injection. Fuel injection is quite immune to intake restriction. Many fuel injection systems can't tell the difference between a restricted intake, or a closed throttle plate. They measure either the air pressure in the manifold, or the mass of air flowing past a mass airflow meter. Either way, they're measuring the air, and injecting the correct metered amount of fuel to achieve a target A/F ratio. If you were having this problem with fuel injection and the snorkel, then something else is wrong. A component failure or the fuel tuning was way off.
For reference, FormulaSAE teams easily make 100hp sucking through a 20mm restrictor. That's less than 1". It's all in the tuning.
Be careful applying this. It's quite out of date.
Modern gasoline engines are achieving VE approaching 1.0, sometimes surpassing it in the real high performance engines. I'm not talking about race cars, but more like any modern V6 or V8 in a Toyota, they do much better than 0.75VE, as evidenced by their high HP/L ratings. VE is always highest at peak torque and drops off after that. So for a modern engine with a torque peak at 4500rpm, that's where the VE peak is and would go down from there, not 2500rpm as stated here.
In any case, these CFM's you calculate would ONLY be applicable at full throttle. Cruise throttles would use drastically less airflow.
I think it's the same case with snorkels. Most of us hope we'll never need them, but are prepared if it becomes necessary. At least in the case of snorkels, having one and "being prepared" doesn't overall put my family at greater risk than being without.
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dieselcruiserhead
16 Years on ExPo. Whoa!!
I've not had the chance to read the whole thread but I noticed the possible air restictions but at speed the snorkel acts as a ram air device so I son't think there is any particular loss of air... I think snorkels have benefits but they are admittedly expensive. Not sure if it is worth the cost for most people, I think 80% of it is cosmetic. Unfortubately a lot of the newer snorkels are "fugly" IMO, I think this is hurting sales more than anything else personally...
ntsqd
Heretic Car Camper
The restrictor plate analogy really doesn't apply as the plate is less than one ID thick. A typical snorkel is many times longer than it's ID. That, combined with the usual contortions & convolutions they seem to have will make for a significant boundary layer condition. The ram air effect could actually reach the engine or it could be 'consumed' by the various flow restrictions along the intake path.
Were it only a singular short distance flow restriction (ala the restrictor plate or a bolt clearance ding in a header tube) then the actual geometry of the areas on each side of the restriction can negate most of the effect. When the intake plumbing is a sequence of restrictors they start to add up. So my read of the point being made was that the flow restriction was significant enough to upset the state of tune to the point of barely running. Clearly the whole system wasn't optimized to work together, but also from my read of the post there was not time to make the necessary tuning mods.
While later engines may have better VE's, using .75 gives a conservative answer and is likely more appropriate for the engine mentioned. Folks with later engines may want to use a higher VE for their calcs.
Were it only a singular short distance flow restriction (ala the restrictor plate or a bolt clearance ding in a header tube) then the actual geometry of the areas on each side of the restriction can negate most of the effect. When the intake plumbing is a sequence of restrictors they start to add up. So my read of the point being made was that the flow restriction was significant enough to upset the state of tune to the point of barely running. Clearly the whole system wasn't optimized to work together, but also from my read of the post there was not time to make the necessary tuning mods.
While later engines may have better VE's, using .75 gives a conservative answer and is likely more appropriate for the engine mentioned. Folks with later engines may want to use a higher VE for their calcs.
R_Lefebvre
Expedition Leader
I'd have to pull out an engineering text, but fluid flow through a restrictor plate is equivalent to flow through a pipe of the same diameter with a length many times the diameter. One has to do the math, but my point is the analogy is valid.
Really, my main point is a 2.5" to 3" pipe is plenty big enough to flow enough air to make 200hp. Fuel economy and power reductions should be minimal on a properly tuned system. Resorting to 5" piping seems unnecessary.
Really, my main point is a 2.5" to 3" pipe is plenty big enough to flow enough air to make 200hp. Fuel economy and power reductions should be minimal on a properly tuned system. Resorting to 5" piping seems unnecessary.
Well, all I can say is that the 2.5 inch ID snorkel did not work at more than half throttle, and that when running for substantial periods at high throttle, I about ran out of gas inside 60K. Disconnecting the snorkel tubing and installing the K&N directly to the MAS changed us back to normal operation and unlimited access to full throttle. Total restriction was part of it, and where in the system the restriction occurred was also part of it.
With a snorkel of 3.5 inch ID, the situation is greatly mitigated, and the engine will hit the rev limiter without problems, although I do believe that the power and torque curves are a bit flat on top. This is just seat of the pants stuff, so it doesn't have science behind it. However, if you drive the same vehicle for enough years, you get to know it, and with the new snorkel attached, it is just not as willing to rev as it is without the snorkel attached. These are design flaws that I built in unwittingly, and would next time try to build out.
The engine is a '91 Mustang 5.0L HO, fuel injected, now equipped with Edelbrock Performer heads and intake, 65mm throttle body, Granitelli MAS. I have a feeling that the engine will pull more than the odd 550cfm at this point, and that the snorkel and air filter box are the limiting factors. I don't have access to bench flow stuff so I can't verify anything.
Nothing wrong with the state of tune that I can detect. I am using 80% or more of the usable flow from 19lb/hr injectors, and the fuel pressure is adjusted to match the injectors. Besides, the EECIV computer is adaptive, so no matter what small adjustments you try to make, the computer sooner or later rethinks it all for you anyway. Which is why performance chips don't really work if all they do is fudge signals to the computer. The computer will figure this out in short order, and you are right back where you started, or are out of range, and you will default to base-line data.
Nor do mass flow sensors necessarily adjust fuel against available air under all circumstances. It depends on design. All of these components are intended to function within a range. Exceed that range, and the system will eventually default, which is what mine did in 2002. I was essentially running on limp-home mode (open loop) because I had restricted and turbulated air to the point that the injectors and computer could not compensate. Moreover, the original Ford MAS device does not place the heated coil in the main air flow stream (as does the Granitelli), but instead, places it in a small tube or antechamber off to one side so that only a small part of the air flow goes through the sensor, the rest goes around it. Disturb the laminar airflow in front of that small orifice, and despite what the MAS flows in its entirety, you will get an erroneous reading. The engine will attempt to inhale the air available (because the throttle was essentially wide open), but the sensor will give a reading that is way wrong thinking that the throttle is nearly closed, and in minutes, confusion reigns and the loop opens up. Because this is not a fly by wire engine, the actual throttle setting is far out of synch with the air flow available if the MAS is not capable of reading a reasonably accurate quantum value for the air flow. Any compensation achieved by the MAS occurred for only a few moments, and once defaulted, the computer disregards MAS signals anyway, and there you are.
The point is it didn't work. Changing to larger tubing did, but it is now the limiting feature in the intake stream, and if I were to try again, I would go larger so that the MAS and throttle bodies are the limiting devices.
With a snorkel of 3.5 inch ID, the situation is greatly mitigated, and the engine will hit the rev limiter without problems, although I do believe that the power and torque curves are a bit flat on top. This is just seat of the pants stuff, so it doesn't have science behind it. However, if you drive the same vehicle for enough years, you get to know it, and with the new snorkel attached, it is just not as willing to rev as it is without the snorkel attached. These are design flaws that I built in unwittingly, and would next time try to build out.
The engine is a '91 Mustang 5.0L HO, fuel injected, now equipped with Edelbrock Performer heads and intake, 65mm throttle body, Granitelli MAS. I have a feeling that the engine will pull more than the odd 550cfm at this point, and that the snorkel and air filter box are the limiting factors. I don't have access to bench flow stuff so I can't verify anything.
Nothing wrong with the state of tune that I can detect. I am using 80% or more of the usable flow from 19lb/hr injectors, and the fuel pressure is adjusted to match the injectors. Besides, the EECIV computer is adaptive, so no matter what small adjustments you try to make, the computer sooner or later rethinks it all for you anyway. Which is why performance chips don't really work if all they do is fudge signals to the computer. The computer will figure this out in short order, and you are right back where you started, or are out of range, and you will default to base-line data.
Nor do mass flow sensors necessarily adjust fuel against available air under all circumstances. It depends on design. All of these components are intended to function within a range. Exceed that range, and the system will eventually default, which is what mine did in 2002. I was essentially running on limp-home mode (open loop) because I had restricted and turbulated air to the point that the injectors and computer could not compensate. Moreover, the original Ford MAS device does not place the heated coil in the main air flow stream (as does the Granitelli), but instead, places it in a small tube or antechamber off to one side so that only a small part of the air flow goes through the sensor, the rest goes around it. Disturb the laminar airflow in front of that small orifice, and despite what the MAS flows in its entirety, you will get an erroneous reading. The engine will attempt to inhale the air available (because the throttle was essentially wide open), but the sensor will give a reading that is way wrong thinking that the throttle is nearly closed, and in minutes, confusion reigns and the loop opens up. Because this is not a fly by wire engine, the actual throttle setting is far out of synch with the air flow available if the MAS is not capable of reading a reasonably accurate quantum value for the air flow. Any compensation achieved by the MAS occurred for only a few moments, and once defaulted, the computer disregards MAS signals anyway, and there you are.
The point is it didn't work. Changing to larger tubing did, but it is now the limiting feature in the intake stream, and if I were to try again, I would go larger so that the MAS and throttle bodies are the limiting devices.
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