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Thread: Cold air intake

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    Default Cold air intake



    Anyone running one of these?thinking about getting one this week.read where it improve horsepower by about 10 percent.

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    Default Re: Cold air intake



    Don't believe everything you read Mark. I'm not familiar with your truck but it's been well-established that they don't do anything for performance on 4Runners outside of making the motor sound a bit "cooler."
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    Default Re: Cold air intake



    Cold air = more dense air.

    You need to first understand how an OBDII vehicle works. Most of the time you run in closed loop where the ECU is listening to all of its sensors and adjusting fuel trims to maintain a stoichiometric burn. Adding additional air in closed loop doesn't do anything. You basically use less throttle.

    In open loop (ie full throttle or heavy throttle) the ECU reverts to a pre-programmed fuel trim table and doesn't listen to its sensors. If you can lean out this air, it will make more power since this pre-programmed fuel table runs rich for safety sake. How much more power? Depends on the vehicle. 10% is HUGE and was probably done with some fuzzy math and not a legit back-to-back test. Look for an asterisk by their claim.

    On my 4wd, I rarely use full throttle. Like almost never.

    So you need to ask yourself: how often do you run full or heavy throttle?

    my airbox sits just inside of my front right tire. Since I drive on a lot of dirt roads, that tire churns up the dust and goes straight into my filter. So I added a snorkel. Contrary to what most people believe, a snorkel is far more useful for dust than water.

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    Chris (August 9th, 2015)

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    Default Re: Cold air intake



    Nice explanation Tom, thanks.

    ExplorerTom previously posted:
    "a snorkel is far more useful for dust than water"

    In our state that's for sure.

    I'll ask a question now since it's along the same line. My intake was behind a wheel well liner until I finally destroyed it on a run. It folded onto itself etc so I ripped it out. Now my intake was somewhat exposed which I'm not comfortable with at all. I removed the 3" tube that went in to the wheel well, blocked the opening and call it good. It now gets the air from the engine compartment (hotter) but I don't think it really matters much. Opinion?
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    Default Re: Cold air intake



    ExplorerTom previously posted:
    "Cold air = more dense air.

    You need to first understand how an OBDII vehicle works. Most of the time you run in closed loop where the ECU is listening to all of its sensors and adjusting fuel trims to maintain a stoichiometric burn. Adding additional air in closed loop doesn't do anything. You basically use less throttle.

    In open loop (ie full throttle or heavy throttle) the ECU reverts to a pre-programmed fuel trim table and doesn't listen to its sensors. If you can lean out this air, it will make more power since this pre-programmed fuel table runs rich for safety sake. How much more power? Depends on the vehicle. 10% is HUGE and was probably done with some fuzzy math and not a legit back-to-back test. Look for an asterisk by their claim.

    On my 4wd, I rarely use full throttle. Like almost never.

    So you need to ask yourself: how often do you run full or heavy throttle?

    my airbox sits just inside of my front right tire. Since I drive on a lot of dirt roads, that tire churns up the dust and goes straight into my filter. So I added a snorkel. Contrary to what most people believe, a snorkel is far more useful for dust than water."

    So save my money!rarely would ever use full throttle especially when four wheeling.good to know Tks mark

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    Default Re: Cold air intake



    Chris previously posted:
    "Opinion?"

    Doesnt matter much. You're right. Might see a slight bump in economy since hotter air is less dense and therefore needs less fuel to maintain stoichiometric burn. If you go to ecomodders.com you'll see "hot air intakes" where they put resistors inline with their IAT sensor and duct hot air off the exhaust into the intake. And as a result of the hotter air, might lose some power off the line. Once moving I have a feeling the air in the engine bay is getting blown out by the on rushing air and isn't too much hotter than ambient.

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    Chris (August 10th, 2015)

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    Default Re: Cold air intake



    Changes in the intake CAN have a positive effect on power, fuel economy, etc. but it's hardly guaranteed. Most aftermarket kits just look cool and maybe sound cool though (as has been stated).

    As has been pointed out (smart crowd! I'm liking this group already!), hotter air is less dense and colder air is more dense. Density correlates to oxygen per volume available for combustion.

    Further, if you heat it up, the air is thinner, and it will only take so much fuel before it starts giving sensors readings telling them to lean things out. You also have hotter intake temperatures, higher combustion temperatures, and therefore higher exhaust temperatures. If you're already dealing with a hot engine, this can easily lead to detonation and dieseling. Additionally, high combustion temperatures lead to a higher NOx percentage come emissions time (which is the most potent greenhouse gas likely coming out of your tailpipe).

    Conversely, actual cold air (generally dependent on where your intake draws from relative to the various heat sources in the engine) is more dense, yadda yadda. It's safer, but your sensors and such will compensate in the reverse of the above. On the plus side, temperatures do go down and power goes up. This is (in theory) why they're popular. Most cold air kits draw from right behind the radiator and such where the air is obviously much hotter and can actually cause damage in some vehicles (namely those that are poorly tuned and/or maintained).

    As for the specific application, moreover location, there's a ~-3% delta per 1K' increase in elevation such that (assuming you're) at 5K', you're already netting a ~15% decrease in air density. This means better fuel economy, but also reduced power (assuming natural aspiration). I had a '99 manual 4Runner for about six months, and after a light tune up, I was consistently getting 23mpg between 8K' and 6K' compared to the more average 18mpg. Any way to gain that loss back will get you closer to factory power output, but as someone who has daily driven vehicles with mid-double digit horsepower, I can tell you'll never notice.

    That has all pretty much been hashed out already though, what hasn't been discussed directly is the loss of the intake resonator. This is what people often mistake in their butt dynos as "10 horsepower" (or whatever). This lack of restriction means you get more intake sounds, and that's what many modern "sport" cars are piping to the interior to make the engine sound way cooler than it actually is. Most (nearly all) cold air intakes are essentially cylindrical from the throttle body to the cone filter. This creates, in effect, a column of air. As the intake valves open and close relative to each other, there are pressure pulses in that air column. If the wavelength of those pressure pulses are an even multiple of the length of this intake tubing (adjusting for curves and angles) you can easily find yourself with a Helmholtz resonator in your engine compartment. This will make your engine essentially groan and howl at certain RPM and cause you no shortage of headaches and/or shop fees if you don't know what's going on. I've actually seen it happen on an old diesel right at idle. It sounded like blowing on a giant empty bottle, but with an obviously odd character. Freaked the guy out bad, but I thought it was cool as hell (and a great cautionary tale for what it's worth). The solution was to simply adjust the elbow joints to add an inch or so to the tubing to lower the resonant frequency, but I think he ended up just going back with the stock intake. I once heard/read someone claim that something like cavitation or some sort of destructive resonance could also happen, but I've never actually seen that happen and I'm not sure I buy that one completely.

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    Default Re: Cold air intake



    spectre6000 previously posted:
    "Changes in the intake CAN have a positive effect on power, fuel economy, etc. but it's hardly guaranteed. Most aftermarket kits just look cool and maybe sound cool though (as has been stated).

    As has been pointed out (smart crowd! I'm liking this group already!), hotter air is less dense and colder air is more dense. Density correlates to oxygen per volume available for combustion.

    Further, if you heat it up, the air is thinner, and it will only take so much fuel before it starts giving sensors readings telling them to lean things out. You also have hotter intake temperatures, higher combustion temperatures, and therefore higher exhaust temperatures. If you're already dealing with a hot engine, this can easily lead to detonation and dieseling. Additionally, high combustion temperatures lead to a higher NOx percentage come emissions time (which is the most potent greenhouse gas likely coming out of your tailpipe).

    Conversely, actual cold air (generally dependent on where your intake draws from relative to the various heat sources in the engine) is more dense, yadda yadda. It's safer, but your sensors and such will compensate in the reverse of the above. On the plus side, temperatures do go down and power goes up. This is (in theory) why they're popular. Most cold air kits draw from right behind the radiator and such where the air is obviously much hotter and can actually cause damage in some vehicles (namely those that are poorly tuned and/or maintained).

    As for the specific application, moreover location, there's a ~-3% delta per 1K' increase in elevation such that (assuming you're) at 5K', you're already netting a ~15% decrease in air density. This means better fuel economy, but also reduced power (assuming natural aspiration). I had a '99 manual 4Runner for about six months, and after a light tune up, I was consistently getting 23mpg between 8K' and 6K' compared to the more average 18mpg. Any way to gain that loss back will get you closer to factory power output, but as someone who has daily driven vehicles with mid-double digit horsepower, I can tell you'll never notice.

    That has all pretty much been hashed out already though, what hasn't been discussed directly is the loss of the intake resonator. This is what people often mistake in their butt dynos as "10 horsepower" (or whatever). This lack of restriction means you get more intake sounds, and that's what many modern "sport" cars are piping to the interior to make the engine sound way cooler than it actually is. Most (nearly all) cold air intakes are essentially cylindrical from the throttle body to the cone filter. This creates, in effect, a column of air. As the intake valves open and close relative to each other, there are pressure pulses in that air column. If the wavelength of those pressure pulses are an even multiple of the length of this intake tubing (adjusting for curves and angles) you can easily find yourself with a Helmholtz resonator in your engine compartment. This will make your engine essentially groan and howl at certain RPM and cause you no shortage of headaches and/or shop fees if you don't know what's going on. I've actually seen it happen on an old diesel right at idle. It sounded like blowing on a giant empty bottle, but with an obviously odd character. Freaked the guy out bad, but I thought it was cool as hell (and a great cautionary tale for what it's worth). The solution was to simply adjust the elbow joints to add an inch or so to the tubing to lower the resonant frequency, but I think he ended up just going back with the stock intake. I once heard/read someone claim that something like cavitation or some sort of destructive resonance could also happen, but I've never actually seen that happen and I'm not sure I buy that one completely."

    Ok so let's assume I tie into a snorkel set up would that help in drawing in enough air?iam not as scientific as some of you but enjoy the chance to learn.

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    Default Re: Cold air intake



    It could help. It's engine/vehicle specific. Factory air boxes typically have a lot of R&D budget spent on making the intake setup pretty well suited to the engine. There are lots of things they do (i.e. emissions kit) that reduce overall performance or are done for budgetary considerations, but there's really not much involved from a cost or emissions perspective in the typical naturally aspirated engine's induction system. There are often aesthetic and space considerations though, wherein something big and ugly (according to focus groups) poking out of the hood or too many holes punched in it are undesirable, so if you're willing to ugly things up a bit (again, from the perspective of focus groups) you could conceivably one up the engineers.

    Assuming you simply replace the factory air box snorkel (I believe they're called the same thing in this context), as I see it, the primary benefit of a snorkel is the obvious and intended one of getting air from up above the water or dust line. Secondary to that, you're getting it from outside of the engine compartment and far away from any heat sources, so it should be about as cold as a cold air intake could possibly get. On the other hand, however, you're also trying to move a much larger column of air through that straw, and that creates resistance both through the volume of the fluid being moved and the drag along the walls of the tubing. Is it much? Not likely. If area of the cross section of the snorkel is not adequately sized compared to that of the intake requirements of the engine, it could also present restriction from that aspect. If your snorkel replaces the factory intake from the throttle body out, the bit about resonators above applies. Lastly, there's the noise and possibly vibration (if improperly mounted). It's a big unaerodynamic thing hanging off what is likely not an especially aerodynamic mass to begin with. Given the location, it might even be good for an mpg or two lost.

    Next is the direction of the snorkel inlet. If it faces forward, it can theoretically increase the pressure in the intake like a ram air setup. This assumes all gains in velocity and volume aren't cancelled out by all the kinks and curves, and I imagine any gains would be slight and unnoticeable. Additionally, however, it can effectively act as a scoop for any dust or water (rain) that falls in front of it in a two trains departing different stations sort of way. I think they tend to have drains for this sort of thing, but you are essentially trading the likely very rare occasion wherein you're faced with large quantities of dust and water for a more constant state of lesser quantities... That said, most factory air intakes are positioned such that they draw from the front of the car either behind the grille or between the top of the radiator and the hood, so they're generally taking similar quantities of dust, if not water, with a similar degree of restriction, so I imagine this would mostly be a wash.

    If you turn the snorkel inlet to the rear, you avoid sucking in anything as above, but you create a turbulent negative pressure zone in the wake of the snorkel which decreases the amount of air the engine can draw. Additionally, should you find yourself at the exact depth afforded by your snorkel, you'll have an extra inch or so available to drown your rig due to the snorkel's bow wake compared to the front intake position... Of course, the efficacy of the drains mentioned above would likely negate this. The benefit to this intake orientation is cleaner air for your engine, the down side is some unnoticeable decrease in air available for combustion.

    All other positions (or absence) for the intake fall under the same category: bad. If your rig never ever goes faster than a few miles an hour, point it off to the side, leave it off, whatever. Should you find yourself ever driving at freeway speeds, however, having the intake pointed to one side or the other (or just left off) creates an orifice with fluid flowing rapidly over it, and that makes for an excellent demonstration of Bernoulli's Principal and a way to really starve your engine for air!

    There are alternatives to the conventional ARB safari snorkel too. The point of the thing on its face is to draw air from above a water or dust line. If we limit ourselves to consideration for water, you should ask yourself how deep you really think you'd feel comfortable wading in. If you're up to the roof in water, something has likely gone very wrong and I think most people's primary consideration at that point will have thoroughly shifted from preventing water from getting into the cylinders to simply not drowning. Additionally, from a dust perspective there are practical limits. You shouldn't be driving blind through a dust cloud as a general rule in the same way you don't go driving through smoke if there's a wild fire or something (I've done this; don't recommend it). That's why there are filters after all (not just element, but centrifugal and similar). If you take into account a good quality filter (especially one that is reusable and easily cleaned) and a properly designed air intake system, you may find that something under hood is more than enough for everything you will every find your vehicle engaged in.

    That said, if you take into consideration the high and low pressure zones relative to a vehicle's specific body work and arrangement there are less conventional solutions that allow you to have your cake and eat it too (unless your cake is the cool snorkel look). If you look at the hood of the typical HMMWV (Humvee, and not the stupid body kit on a Tahoe tripe), you'll notice a little mushroom-shaped thing in the passenger side corner of the hood up near the windshield (assuming they don't have a full snorkel). Right up under the windshield is about as high as you'd really want to wade in to any water if we're honest, and it happens to be a very high pressure zone (this is why cowl induction works on muscle cars and why your HVAC system draws from that vent there and still blows if it's set to 'fresh' even though it's off). With a centrifugal filter there under that mushroom looking cover, they have their intake in a) a high pressure zone to give the engine additional air b) above any reasonable water line c) thoroughly filtered for particulate, and d) without some big thing there to create drag/wind noise or snag on whatever branches or clothes lines they happen to be barreling through. It doesn't look nearly as cool, but it has all the benefits without any of the problems.

    On the whole, I think snorkels (properly designed and properly applied) are a general improvement. A little outside the box thinking can really go a long way though...

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    Default Re: Cold air intake



    spectre6000 previously posted:
    "It could help. It's engine/vehicle specific. Factory air boxes typically have a lot of R&D budget spent on making the intake setup pretty well suited to the engine. There are lots of things they do (i.e. emissions kit) that reduce overall performance or are done for budgetary considerations, but there's really not much involved from a cost or emissions perspective in the typical naturally aspirated engine's induction system. There are often aesthetic and space considerations though, wherein something big and ugly (according to focus groups) poking out of the hood or too many holes punched in it are undesirable, so if you're willing to ugly things up a bit (again, from the perspective of focus groups) you could conceivably one up the engineers.

    Assuming you simply replace the factory air box snorkel (I believe they're called the same thing in this context), as I see it, the primary benefit of a snorkel is the obvious and intended one of getting air from up above the water or dust line. Secondary to that, you're getting it from outside of the engine compartment and far away from any heat sources, so it should be about as cold as a cold air intake could possibly get. On the other hand, however, you're also trying to move a much larger column of air through that straw, and that creates resistance both through the volume of the fluid being moved and the drag along the walls of the tubing. Is it much? Not likely. If area of the cross section of the snorkel is not adequately sized compared to that of the intake requirements of the engine, it could also present restriction from that aspect. If your snorkel replaces the factory intake from the throttle body out, the bit about resonators above applies. Lastly, there's the noise and possibly vibration (if improperly mounted). It's a big unaerodynamic thing hanging off what is likely not an especially aerodynamic mass to begin with. Given the location, it might even be good for an mpg or two lost.

    Next is the direction of the snorkel inlet. If it faces forward, it can theoretically increase the pressure in the intake like a ram air setup. This assumes all gains in velocity and volume aren't cancelled out by all the kinks and curves, and I imagine any gains would be slight and unnoticeable. Additionally, however, it can effectively act as a scoop for any dust or water (rain) that falls in front of it in a two trains departing different stations sort of way. I think they tend to have drains for this sort of thing, but you are essentially trading the likely very rare occasion wherein you're faced with large quantities of dust and water for a more constant state of lesser quantities... That said, most factory air intakes are positioned such that they draw from the front of the car either behind the grille or between the top of the radiator and the hood, so they're generally taking similar quantities of dust, if not water, with a similar degree of restriction, so I imagine this would mostly be a wash.

    If you turn the snorkel inlet to the rear, you avoid sucking in anything as above, but you create a turbulent negative pressure zone in the wake of the snorkel which decreases the amount of air the engine can draw. Additionally, should you find yourself at the exact depth afforded by your snorkel, you'll have an extra inch or so available to drown your rig due to the snorkel's bow wake compared to the front intake position... Of course, the efficacy of the drains mentioned above would likely negate this. The benefit to this intake orientation is cleaner air for your engine, the down side is some unnoticeable decrease in air available for combustion.

    All other positions (or absence) for the intake fall under the same category: bad. If your rig never ever goes faster than a few miles an hour, point it off to the side, leave it off, whatever. Should you find yourself ever driving at freeway speeds, however, having the intake pointed to one side or the other (or just left off) creates an orifice with fluid flowing rapidly over it, and that makes for an excellent demonstration of Bernoulli's Principal and a way to really starve your engine for air!

    There are alternatives to the conventional ARB safari snorkel too. The point of the thing on its face is to draw air from above a water or dust line. If we limit ourselves to consideration for water, you should ask yourself how deep you really think you'd feel comfortable wading in. If you're up to the roof in water, something has likely gone very wrong and I think most people's primary consideration at that point will have thoroughly shifted from preventing water from getting into the cylinders to simply not drowning. Additionally, from a dust perspective there are practical limits. You shouldn't be driving blind through a dust cloud as a general rule in the same way you don't go driving through smoke if there's a wild fire or something (I've done this; don't recommend it). That's why there are filters after all (not just element, but centrifugal and similar). If you take into account a good quality filter (especially one that is reusable and easily cleaned) and a properly designed air intake system, you may find that something under hood is more than enough for everything you will every find your vehicle engaged in.

    That said, if you take into consideration the high and low pressure zones relative to a vehicle's specific body work and arrangement there are less conventional solutions that allow you to have your cake and eat it too (unless your cake is the cool snorkel look). If you look at the hood of the typical HMMWV (Humvee, and not the stupid body kit on a Tahoe tripe), you'll notice a little mushroom-shaped thing in the passenger side corner of the hood up near the windshield (assuming they don't have a full snorkel). Right up under the windshield is about as high as you'd really want to wade in to any water if we're honest, and it happens to be a very high pressure zone (this is why cowl induction works on muscle cars and why your HVAC system draws from that vent there and still blows if it's set to 'fresh' even though it's off). With a centrifugal filter there under that mushroom looking cover, they have their intake in a) a high pressure zone to give the engine additional air b) above any reasonable water line c) thoroughly filtered for particulate, and d) without some big thing there to create drag/wind noise or snag on whatever branches or clothes lines they happen to be barreling through. It doesn't look nearly as cool, but it has all the benefits without any of the problems.

    On the whole, I think snorkels (properly designed and properly applied) are a general improvement. A little outside the box thinking can really go a long way though..."

    Wow! Well I think that should pretty well cover it!!iam going to really give this some thought and study a bit more and really appreciate your time in answering my question.it was very helpful Tks again Mark.

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    Default Re: Cold air intake



    I can now give an answer about taking intake air from under the hood vs fresh air. I drove to Moab today with my trailer in tow. Taking intake air under the hood made everything run noticeably hotter and my MPG's dropped significantly. Not sure how this applies to others but I put the extension in to the wheel well back on.
    ___________
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    Default Re: Cold air intake



    Hotter air = less density = less oxygen available per volume for combustion. Within your particular driving vernacular, you will tend to accelerate at a given rate versus a given accelerator pedal position (that's just how people do). The result is that the ECU sees greater throttle position values at a given RPM, which it interprets as additional load. It compensates for this by injecting additional fuel. Running richer (depending of course on what you're running richer than for the crowd that sets their own mixture) results in hotter EGTs. Over time (miles), this will manifest as higher engine temps as the cooling system compensates and heat soaks. Adding a trailer to the mix furthers the relationship and makes the delta that much greater. Excellent illustration of the point. Thank you for sharing.

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    Default Re: Cold air intake



    Thanks for an explanation that makes sense Jason. It was running rich enough to smell the gas which was very telling that things were amiss!
    ___________
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    Default Re: Cold air intake



    Chris previously posted:
    "Thanks for an explanation that makes sense Jason. It was running rich enough to smell the gas which was very telling that things were amiss!"

    So once you moved the intake did it help?

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    Default Re: Cold air intake



    Yes, it's back to its old self now. I have to admit that I was surprised at how dramatic the change was. I expected to notice some difference but not anywhere near what I got.
    ___________
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    96 Explrer XLT / 94 Explrer Sport / 92 Explrer XLT
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    Default Re: Cold air intake



    " (smart crowd! I'm liking this group already!)"

    Ummmm, I dont consider myself no idiot, but I'm almost willing to bet your job involves (or involved) DOD security clearances............I didn't even have to take a drug test for my current job, LOL.

  20. #18
    Join Date
    Aug 2015
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    1988 Jeep Cherokee (Rex-Jay)
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    Default Re: Cold air intake



    prob a little late for this as most of the science and math behind why it works was already mentioned... however i feel its worth noting that the snorkel doesn't hafta be a crazy tall A pillar mounted pipe ... a decent 3inch tube ran into the wiper cowl , with a little thermal wrap, would suffice also .. i know that its being used for dust mainly but im sure you are also aware that if your cowl is underwater , no amount of extra snorkel pipe is gonna save all the electronics that are submerged. So with it in the cowl you still get the added benefit of taking in fresh air , without the look of the huge smokestack with a filter on it going up to the roof.

  21. #19
    Join Date
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    Default Re: Cold air intake



    TokenXJ previously posted:
    "prob a little late for this as most of the science and math behind why it works was already mentioned... however i feel its worth noting that the snorkel doesn't hafta be a crazy tall A pillar mounted pipe ... a decent 3inch tube ran into the wiper cowl , with a little thermal wrap, would suffice also .. i know that its being used for dust mainly but im sure you are also aware that if your cowl is underwater , no amount of extra snorkel pipe is gonna save all the electronics that are submerged. So with it in the cowl you still get the added benefit of taking in fresh air , without the look of the huge smokestack with a filter on it going up to the roof."

    Well I have to say that the technical answers and the comments have been extremely helpful.iam not interested in water hazard but day to day usage as well as 4 wheeling.improving the overall performance even if it's only slightly.like the fact you don't need to run a stack and can make it simpler.almost just a ram air set up.

  22. #20
    Join Date
    Mar 2008
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    Default Re: Cold air intake



    TokenXJ previously posted:
    "a decent 3inch tube ran into the wiper cowl , with a little thermal wrap, would suffice"

    Yep, I'm planning on something along that line now.
    ___________
    Chris in Florida

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