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Homemade CAI for 3.7?

12K views 91 replies 15 participants last post by  08pretaco 
#1 ·
I was wondering if anybody has ever do a homemade CAI for the 3.7l's?? i was thinking about doing this myself, but i dont know where to start! thanks in advanced!
 
#5 · (Edited)
Ya that doesn't make much sense . Trying to make a cai for lower intake temps so why get a heat sink material...unless you plan on wrapping the tubing id say stay away from aluminum tubing otherwise you can make a cai and spend all the time to just have the same intake temp...that's my 2 cents. Good luck with whatever you decide
 
#6 ·
at my dads gas station where i work at, we were getting rid of a countertop small refrigerator....maybe ill just integrate my intake with that:rolleyes: HAHA....but i might just have to stop by home depot this week!
 
#7 ·
id say if you want to build your own and do not have access to a composite tubing or plastic tubing, you can always buy the section of tubing alone from say k&n or afe but just dont buy the rest of their intake. start off with that, it will give you the last section of where the ambient air will take into factor on your incoming air and at least that will be cooler. then from then on you can start doing thing with aluminum tubing (painting with heat resistant paint or some header wrap) and pick your own air filter and make you own box or whatever it is you have in mind!
 
#8 · (Edited)
i dont know if you guys are to knowledged on the venturi effect.

this could be a great idea for an intake tubing: your only going to get a given amount of air into your cylinder given the size of the intake manifold and throttle body. get a larger diameter exterior tubing with a smaller diameter inner tubing ( say exterior 4" interior 2" with a silicone reducer into the throttle body).

what the two different diameters will do: first off- air flows quicker through a smaller diameter tubing. the inner diameter will draw the air into your manifold quick than just getting a large diameter tubed intake. the venturi effect will take into play by doing this- the inner, faster flowing air draws with it the slower air from outer section (between the small and large tubing) allowing the air to get through the throttle body and manifold faster due to its increased velocity and mass air flow.

so in conclusion what this does is this- get air flowing quicker through your intake into the manifold and ideally should get a larger volume of air to fill the cylinder. pair this up with a cold air charge and and good tune, you should be talking about some decent gains from something this simple.
 
#9 ·
I'm not sure that the venturi effect would have enough impact to make up for the bottle-necking effect it would have. The throttle body on a 3.7 is about a 3" inlet (def get it ported/polished by FlyinRyan to increase air flow). So to go from a 3" inlet through a 2" bottleneck you'd be counting on the venturi effect speeding up the air a full 225% to make up for the lost area (∏3²=~28.26in² ∏2²=~12.56in²). I don't know how much of an effect is seen due to venturi but I highly doubt it will be a 225% difference.

PVC is a relatively nice material for a CAI as it doesn't retain heat as much as metal does. It's also dirt cheap! As long as you connect the pipes tightly enough to where this is no gap between them it's also a very smooth pathway for the air. Throw a Spectre filter on there at less than half the price of the K&N for the same functionality without the brand name's accompanied price and you've got yourself off to a great start. Wrap it with some DEI header wrap or use another method to keep the heat out and you're almost set. I still haven't taken the time to make a heat shield around the filter but still plan to once I get a couple other little projects (CB, PA, antenna mounts, redoing wiring, etc...).

Some more detailed info and pics on the how to can be found here:
http://jeepgarage.org/showthread.php?t=5945&highlight=project
 
#10 ·
Thanks nick! i dont have enough money for a ported TB, but i did see ur thread...and thats possibly gonna happen this weekend, if not the next!
 
#14 ·
No problem! Take plenty of pics :thumbsup:
 
#11 · (Edited)
Working on the math as to whether or not the Venturi Effect makes up for the air loss due to the bottleneck effect. Just posting as I go and I'll edit to finish it up (assuming I can work through all the variables). I will be basing calculations on the Spectre P4 Cone Filter (Item#8132) at sea-level at 20ºC.


Bernoulli's Principle states that the faster a fluid is moving, the lower the pressure. Therefore, fluid in areas of higher pressure will move towards the lower pressure of the faster moving fluid, causing an increase in fluid velocity.

The standard density of air (p) at 20ºC is 1.2kg/m³

Bernoulli's Principle Formula - (p₁-p₂) = [(p/2)(v₂²-v₁²)] where p=density of the fluid, v₁ is the slower velocity (before bottleneck), and v₂ is the faster velocity (into throttle body).

Replacing p with d to differentiate between pressure and density. p₀ becomes the pressure of 1 atmosphere.
(p₁-p₂) = [(d/2)(v₂²-v₁²)]

At the surface of the earth air pressure is equal to 1.01x10⁵ N/m²

p₀ = 101000
d = 1.2
p₁ = [(101000-p₁) = (.6)(v₁²-0)]
.......v₁ = velocity of incoming air at WOT
p₂ =
v₀ = 0
v₁ =
v₂ =


Difference In Pressure
(p₁-p₂) = (1.2/2)(v₂²-v₁²)
(p₁-p₂) = (.6)(v₂²-v₁²)


The formula for the Venturi Effect is - Q = (A₁)√{[(2)(p₁-p₂)]/[(p)(A₁/A₂)²-1]} = (A₂)√{[(2)(p₁-p₂)]/[(p)(1-(A₂/A₁)²]}
where A₁ is the area of the pipe before the bottleneck and A₂ is the area entering the throttle body, and Q is the volumetric flow rate.

A 3" PVC pipe (3.5" including sidewalls) is already a squeeze under the hood so I'll use that over a 4" pipe for the equations.


Non-Bottlenecked
Q₁ = (A₀)√{[(2)(p₀-p₁)]/[(d)(A₀/A₁)²-1]} = (A₁)√{[(2)(p₀-p₁)]/[(d)(1-(A₁/A₀)²]}

Q₁ = (A₀)√{[(2)(101000-p₁)]/[(1.2)(A₀/28.26)²-1]} = (28.26)√{[(2)(101000-p₁)]/[(1.2)(1-(28.26/A₀)²]}

A₀ = Area of the filter x % of air flowing through filter


Bottlenecked
Q₂ will represent the amount of air entering the throttle body using the bottleneck.

A₁ = 28.26
A₂ = 12.56
d = 1.2
p₁ =
p₂ =

Q₂ = (A₁)√{[(2)(p₁-p₂)]/[(d)(A₁/A₂)²-1]} = (A₂)√{[(2)(p₁-p₂)]/[(d)(1-(A₂/A₁)²]}

Q₂ = (28.26)√{[(2)(p₁-p₂)]/[(d)(28.26/12.56)²-1]} = (12.56)√{[(2)(p₁-p₂)]/[(d)(1-(12.56/28.26)²]}

Q₂ = (28.26)√{[(2)(p₁-p₂)]/[(d)(4.0625)]} = (12.56)√{[(2)(p₁-p₂)]/[(d)(.8025)]}

Q₂ = (28.26)√{[(2)(p₁-p₂)]/[(1.2)(4.0625)]} = (12.56)√{[(2)(p₁-p₂)]/[(1.2)(.8025)]}

Q₂ = (28.26)√{[(2)(p₁-p₂)]/(4.875)} = (12.56)√{[(2)(p₁-p₂)]/(.963)}
 
#85 ·
Working on the math as to whether or not the Venturi Effect makes up for the air loss due to the bottleneck effect. Just posting as I go and I'll edit to finish it up (assuming I can work through all the variables). I will be basing calculations on the Spectre P4 Cone Filter (Item#8132) at sea-level at 20ºC.


Bernoulli's Principle states that the faster a fluid is moving, the lower the pressure. Therefore, fluid in areas of higher pressure will move towards the lower pressure of the faster moving fluid, causing an increase in fluid velocity.

The standard density of air (p) at 20ºC is 1.2kg/m³

Bernoulli's Principle Formula - (p₁-p₂) = [(p/2)(v₂²-v₁²)] where p=density of the fluid, v₁ is the slower velocity (before bottleneck), and v₂ is the faster velocity (into throttle body).

Replacing p with d to differentiate between pressure and density. p₀ becomes the pressure of 1 atmosphere.
(p₁-p₂) = [(d/2)(v₂²-v₁²)]

At the surface of the earth air pressure is equal to 1.01x10⁵ N/m²

p₀ = 101000
d = 1.2
p₁ = [(101000-p₁) = (.6)(v₁²-0)]
.......v₁ = velocity of incoming air at WOT
p₂ =
v₀ = 0
v₁ =
v₂ =


Difference In Pressure
(p₁-p₂) = (1.2/2)(v₂²-v₁²)
(p₁-p₂) = (.6)(v₂²-v₁²)


The formula for the Venturi Effect is - Q = (A₁)√{[(2)(p₁-p₂)]/[(p)(A₁/A₂)²-1]} = (A₂)√{[(2)(p₁-p₂)]/[(p)(1-(A₂/A₁)²]}
where A₁ is the area of the pipe before the bottleneck and A₂ is the area entering the throttle body, and Q is the volumetric flow rate.

A 3" PVC pipe (3.5" including sidewalls) is already a squeeze under the hood so I'll use that over a 4" pipe for the equations.


Non-Bottlenecked
Q₁ = (A₀)√{[(2)(p₀-p₁)]/[(d)(A₀/A₁)²-1]} = (A₁)√{[(2)(p₀-p₁)]/[(d)(1-(A₁/A₀)²]}

Q₁ = (A₀)√{[(2)(101000-p₁)]/[(1.2)(A₀/28.26)²-1]} = (28.26)√{[(2)(101000-p₁)]/[(1.2)(1-(28.26/A₀)²]}

A₀ = Area of the filter x % of air flowing through filter


Bottlenecked
Q₂ will represent the amount of air entering the throttle body using the bottleneck.

A₁ = 28.26
A₂ = 12.56
d = 1.2
p₁ =
p₂ =

Q₂ = (A₁)√{[(2)(p₁-p₂)]/[(d)(A₁/A₂)²-1]} = (A₂)√{[(2)(p₁-p₂)]/[(d)(1-(A₂/A₁)²]}

Q₂ = (28.26)√{[(2)(p₁-p₂)]/[(d)(28.26/12.56)²-1]} = (12.56)√{[(2)(p₁-p₂)]/[(d)(1-(12.56/28.26)²]}

Q₂ = (28.26)√{[(2)(p₁-p₂)]/[(d)(4.0625)]} = (12.56)√{[(2)(p₁-p₂)]/[(d)(.8025)]}

Q₂ = (28.26)√{[(2)(p₁-p₂)]/[(1.2)(4.0625)]} = (12.56)√{[(2)(p₁-p₂)]/[(1.2)(.8025)]}

Q₂ = (28.26)√{[(2)(p₁-p₂)]/(4.875)} = (12.56)√{[(2)(p₁-p₂)]/(.963)}
:wtf::confused::eek: you lost me at working on the math.....
 
#12 ·
thee only problem with the Flyin Ryan TB is the bore isnt increased all the way through the TB...so you still have a bottle neck at the blade. Get a Fastman with increased bore and larger blade to match. Do math on that one......

also...do a little research on the temp differences between aluminum and plastic......its almost funny
 
#16 ·
Wow...that's turned into one clusterphuck of a math problem! Something to keep me busy through school tomorrow :D
 
#17 ·
ya....im completely lost with all that math :wtf: and im not too bad when it comes to math....oh well....maybe its because i just took my medicine! haha...oh well :sleepy:
 
#19 · (Edited)
"Q: Why does AEM use aluminum for its intake piping?
A: Our Chief Engineer John Concialdi provides an explanation of the difference between Aluminum vs. Steel vs. Plastic in inlet piping:

The issue of heat absorption with an intake system has a degree of validity, however we have found that too much emphasis is placed on material selection, instead of the real issue of tuning the system. Our systems feature a unique shape and diameter because this is what we found to make the most useable torque and horsepower for each individual application in testing. However, for the purposes of this discussion, we will limit it to why we choose to make our systems from aluminum and the effects of heat absorption on all materials. If you do not wish to review all of this information right now, a quick synopsis of this discussion is outlined in the following bullet points, with complete topic discussions below:

We use aluminum to eliminate any chance of the system rusting, and it's lighter than steel
We limit our use of plastic because this material absorbs some of the sound energy we work to create in the inlet duct
Whether or not an inlet system is made from aluminum, steel or plastic, the thermal conductivity of the duct material has little effect on engine power
The rate at which air travels through the inlet path under open throttle, when one is asking the engine for maximum power, negates the effect of material heat soak, regardless of the material

We use aluminum—or a combination of aluminum and plastic plenums for throttle-body-injected applications that require a special plenum—for every intake we produce. This eliminates any chance of rust occurring on the inside of the inlet pipe. We have seen chrome-plated steel systems whose inner diameter became rusted over time, causing flakes of rust to travel along the inlet path. We also choose aluminum because of its lightweight properties. Heavier components place higher loads on the brackets they are attached to—or even worse, to the pipes they are attached to. We combine our lightweight aluminum design with a flexible coupling device we call a soft mount that connects the intake system to the body of the vehicle. In addition to the soft mount, we use doublers at the point where the mounting bracket is welded to the pipe for additional strength.

We limit our use of plastic because this material absorbs some of the sound energy we work to create in the inlet duct. Although we use the best plastic material for our plenums, it is still not as resilient and does not retain the visual appeal of aluminum over long-term use. Because we have to use plastic on throttle body applications, we take extra precautions to ensure that the aluminum retaining ring that attaches to the throttle body is anchored securely into the plastic plenum; this is done by making an interlocking mechanical link between the plastic and aluminum.

Whether or not an inlet system is made from aluminum, steel, or plastic, the thermal conductivity of the duct material has little effect on engine power. We have found that the tuning of the pipe, in addition to providing the coolest inlet air source, are the keys to making useable power. We perform engine inlet-air-temp studies when developing each application to determine the coolest location for sourcing inlet air. In addition to this, we determine the safest location for the inlet source to protect it from highly dusty conditions and water. To this end, we provide a stainless-steel heat shield to help minimize heat soak into the inlet area, as well as to provide protection from dust, dirt and mud.

At light throttle opening, air speed and airflow at the inlet system are relatively low. The high residence time of air in the inlet while at low-throttle settings will increase inlet charge temps when materials with high thermal conductivity are used. Typically, when someone is at light throttle they are not asking the engine to make power. Most likely, fuel economy is the issue.

When the throttle is fully opened however, air speed and airflow increase considerably. Typically, the inlet air speed of a 5.7L engine with a four-inch duct at full throttle is 34 feet-per-second, based on a volumetric efficiency of 70% and an engine speed of 3,000 rpm. Most inlet systems for every intake manufacturer for this engine are 30 inches or less. This means that the air in the duct of a 30-inch inlet length on this engine at the given rpm is 1/10th of a second—hardly enough time to transfer an appreciable amount of heat into the air stream on any system.

Basically, the rate at which air travels through the inlet path under open throttle, when one is asking the engine for maximum power, negates the effect of material heat soak, regardless of the material. We hope that this helps to clear up the issues of material heat absorption in intake systems."

So...pretty much what that is saying is this......the amount of time that charge air spends in the iping...1/10th of a second....no heat is gonna be transferred to the air. Also....I am a metallurgist and work in the aluminum industry. The time it would take to heat the entire piping up while it is being cooled by charge of air moving through it is pretty crazy. Youd pretty much have to be idling for days. there are also ways to combat any heat soak that many "think" occur...or have "read" that occur. There are plenty of simple spray on coatings for that. And please do not use PVC piping.......leave that to the sewer guys. PVC has a very low melt point...which means over time it will deform and become brittle...it is not made to withstand any heat...especially engine temps. Not to mention the TOXIC fumes it releases when heated........
 
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#39 ·
"Q: Why does AEM use aluminum for its intake piping?
A: Our Chief Engineer John Concialdi provides an explanation of the difference between Aluminum vs. Steel vs. Plastic in inlet piping:

The issue of heat absorption with an intake system has a degree of validity, however we have found that too much emphasis is placed on material selection, instead of the real issue of tuning the system. Our systems feature a unique shape and diameter because this is what we found to make the most useable torque and horsepower for each individual application in testing. However, for the purposes of this discussion, we will limit it to why we choose to make our systems from aluminum and the effects of heat absorption on all materials. If you do not wish to review all of this information right now, a quick synopsis of this discussion is outlined in the following bullet points, with complete topic discussions below:

We use aluminum to eliminate any chance of the system rusting, and it's lighter than steel
We limit our use of plastic because this material absorbs some of the sound energy we work to create in the inlet duct
Whether or not an inlet system is made from aluminum, steel or plastic, the thermal conductivity of the duct material has little effect on engine power
The rate at which air travels through the inlet path under open throttle, when one is asking the engine for maximum power, negates the effect of material heat soak, regardless of the material

We use aluminum—or a combination of aluminum and plastic plenums for throttle-body-injected applications that require a special plenum—for every intake we produce. This eliminates any chance of rust occurring on the inside of the inlet pipe. We have seen chrome-plated steel systems whose inner diameter became rusted over time, causing flakes of rust to travel along the inlet path. We also choose aluminum because of its lightweight properties. Heavier components place higher loads on the brackets they are attached to—or even worse, to the pipes they are attached to. We combine our lightweight aluminum design with a flexible coupling device we call a soft mount that connects the intake system to the body of the vehicle. In addition to the soft mount, we use doublers at the point where the mounting bracket is welded to the pipe for additional strength.

We limit our use of plastic because this material absorbs some of the sound energy we work to create in the inlet duct. Although we use the best plastic material for our plenums, it is still not as resilient and does not retain the visual appeal of aluminum over long-term use. Because we have to use plastic on throttle body applications, we take extra precautions to ensure that the aluminum retaining ring that attaches to the throttle body is anchored securely into the plastic plenum; this is done by making an interlocking mechanical link between the plastic and aluminum.

Whether or not an inlet system is made from aluminum, steel, or plastic, the thermal conductivity of the duct material has little effect on engine power. We have found that the tuning of the pipe, in addition to providing the coolest inlet air source, are the keys to making useable power. We perform engine inlet-air-temp studies when developing each application to determine the coolest location for sourcing inlet air. In addition to this, we determine the safest location for the inlet source to protect it from highly dusty conditions and water. To this end, we provide a stainless-steel heat shield to help minimize heat soak into the inlet area, as well as to provide protection from dust, dirt and mud.

At light throttle opening, air speed and airflow at the inlet system are relatively low. The high residence time of air in the inlet while at low-throttle settings will increase inlet charge temps when materials with high thermal conductivity are used. Typically, when someone is at light throttle they are not asking the engine to make power. Most likely, fuel economy is the issue.

When the throttle is fully opened however, air speed and airflow increase considerably. Typically, the inlet air speed of a 5.7L engine with a four-inch duct at full throttle is 34 feet-per-second, based on a volumetric efficiency of 70% and an engine speed of 3,000 rpm. Most inlet systems for every intake manufacturer for this engine are 30 inches or less. This means that the air in the duct of a 30-inch inlet length on this engine at the given rpm is 1/10th of a second—hardly enough time to transfer an appreciable amount of heat into the air stream on any system.

Basically, the rate at which air travels through the inlet path under open throttle, when one is asking the engine for maximum power, negates the effect of material heat soak, regardless of the material. We hope that this helps to clear up the issues of material heat absorption in intake systems."

So...pretty much what that is saying is this......the amount of time that charge air spends in the iping...1/10th of a second....no heat is gonna be transferred to the air. Also....I am a metallurgist and work in the aluminum industry. The time it would take to heat the entire piping up while it is being cooled by charge of air moving through it is pretty crazy. Youd pretty much have to be idling for days. there are also ways to combat any heat soak that many "think" occur...or have "read" that occur. There are plenty of simple spray on coatings for that. And please do not use PVC piping.......leave that to the sewer guys. PVC has a very low melt point...which means over time it will deform and become brittle...it is not made to withstand any heat...especially engine temps. Not to mention the TOXIC fumes it releases when heated........
good info scott.
 
#21 ·
"Typically, the inlet air speed of a 5.7L engine with a four-inch duct at full throttle is 34 feet-per-second"

Anywhere to find those numbers for the 3.7?
 
#22 ·
i might buy the pieces within the next few weeks, then put it all together when i get a chance. whats a good cheap filter that u recommend?
 
#33 ·
Ya it sucks man I also have to take thermo 2 and 3 (heat transfer).

So if it abrupts the air flow and people still do it...it must do something. Is it proven or is it just a feel good butt dyno thing?

Ya no I don't want to change the diameter of the actualy tubing twice. Run the smaller tube inside of the larger one. Idk if something like that actually works or anything but sounds like a fun project, thinking of doing it to my taco first and see how that works then maybe for the gf's wk.
 
#36 ·
So if it abrupts the air flow and people still do it...it must do something. Is it proven or is it just a feel good butt dyno thing?
If you're referring to the Venturi thing then I think there's def an advantage to be had with that design you linked.
 
#34 ·
heat transfer no fun taking it this summer session ... some people claim that they get a better throttle response of course from more air flow but in reality there are no proven gains so i would say butt dyno feeling for now i'm getting one from Ryan and gonna take and really see if it performs
 
#35 ·
Cool, really interesting stuff!

Couldn't and easier and cheaper method to following mods, power and mpg be a scangauge rather than always "taking it in"? Scangauges follow your mileage and they have other great features such as iat power and things of that nature...just a thought and its about 150 bucks to buy, idk how much you get charged to take it in
 
#37 ·
oh that abrupt's air flow thing was referring to the ported throttle body convo haha sorry man so many things going on with the different topics in this thread...im really sorry about the thread jack to the op! but some useful info is definitely coming out :thumbsup:

to add to the venturi thing: for my first test application, my tacoma, im going to try to make a 4" first section to have a decent size filter on it and run that into the section of tubing we are now discussing. im hoping to get the venturi effect from the two tubes but also hoping for some pressure build up with the first section being bigger going into a smaller diameter, so when the throttle body opens up a little the air wants to go in and the cylinder vacuum pulls well.
 
#40 ·
Regarding Scott's post - Newton's Law of Cooling could be used to figure out how much the air heats up in passing through an aluminum intake. As much as I'd like to work it out for everyone, I'm about mathed out for the time being haha.


Newton's Law of Cooling states that the hotter an object is, the faster it cools. More precisely, the rate of cooling is proportional to the temperature difference between an object and its surroundings. This word statement leads to the classic equation of exponential decline over time that applies to many phenomena in science and engineering, including the discharge of a capacitor and the decay in radioactivity.
Newton's Law of Cooling is useful when studying water heating because it can tell us how fast the hot water in pipes cools off, and also tells us how fast a water heater cools down if you turn off the breaker when you go on vacation.
The basic equation for Newton's Law of Cooling is:
T(t) = TA + (TH-TA) e-kt where
T(t) = Temperature at time t
TA = Ambient temperature (temp of surroundings)
TH = Temperature of hot object at time 0
k = positive constant
t = time
 
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