DIY air intake with IAT sensor

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
The following is how I built my CAI and removed the intake resonator using basic parts from the hardware store. I have a 2004 Trailblazer which uses an IAT sensor. There is no critical placement on these sensors, which simplifies the build. If you have a newer vehicle with a MAF sensor, you will want to look at other discussions for information on how to maintain the original positioning of your MAF sensor.

You want to start with a short straight section of 3" plastic pipe, and a sweeping 90-degree elbow. There are various discussions on whether ABS or PVC is better. I used electrical conduit PVC for the elbow because it had the shape I wanted. I used ABS for the straight sections because I had it on hand. You will also want two rubber 3" pipe couplers. Mine came with a thin metal shield that wrapped around underneath the hose-clamps, but I eventually removed these simply for the aesthetics. And finally, you will need various fittings to reconnect the original hoses... PVC 1/2" MIP to 1/2" barb for the engine vent line; Brass 1/8" MIP to 1/8" barb for the vacuum line; and PVC 90-degree 1" MIP to 1" barb for the large air hose on the underside of the intake. Note that I used a lathe to take down the diameter of the straight pipe for a better fit, but you can achieve the same affect with a dremel, and may not even need to make changes.

To begin, open up the air box, disconnect the intake hose and remove it and the air filter, then remove the intake resonator. None of these parts will be modified, so you can return to stock at any time. This is a great time to clean your throttle body!

The elbow you purchased should have one side that is that standard 3" diameter, and may have a bulge on the other side to insert another pipe in to. You want to slip one of the rubber couplers half way onto the smaller side, then attach the other side of the coupler to your throttle-body. The other end of the elbow will be pointing out towards the air box. Lay your air filter back in the air box without anything attached to it. You need to eyeball the curve of the elbow, and mark where it is exactly inline with the air filter, rotating the elbow at the throttle-body so that it is in line with the air filter both horizontally as well as vertically. YOU WANT TO TAKE YOUR TIME WITH THIS STEP! In my instance, I could not quite find an alignment I liked, so I used a heat gun to soften the pipe and slightly straighten the curve. It didn't take much, but this got me to a spot where the elbow could exactly face towards the filter. Once you find this point, mark the point across the elbow where you will cut it off.

This shows where I cut my elbow at. Also you can see the change in the bend where I straightened the pipe between the PVC connectors (you are not expected to have your connectors in place yet). I used the scrap piece to drill test holes when I was ready to fit the connectors into this pipe.
View attachment 16944

Once you have cleaned up the cut on the elbow, re-attach it to the throttle-body. If you plan on using an aftermarket air filter, place it in the air box, otherwise leave your stock filter sitting there. You want to measure the length of pipe needed to connect the end of the elbow into your filter. Originally I intended to use my stock filter, but the 3" pipe does not fit in place correctly. I used my lathe to turn down the last inch of pipe until it fit the filter. Later I decided to use an aftermarket filter which have clamps for different sizes of intakes, and this was fit to a piece of pipe that had not been modified.
View attachment 16945

You should now be able to attach the second rubber coupling, and assemble the last piece of pipe and the air filter. Make sure the fit is good, and trim up as needed. I didn't like how tight the 3" pipe fit into the opening of the air box, so I put it back on the lathe and trimmed between 1/16" and 1/8" off the overall diameter. This small difference did not affect the fit of the rubber coupling.
View attachment 16946

You are now ready to add the the hose connectors. As said previously, use a piece of scrap pipe to find the right hole sizes to drill. For the PVC connectors, I used spare metal fittings of the same size to cut the threads into the pipe, then wrapped the actual fittings with teflon tape and screwed them into place. The placement is not critical, but you want to locate them relatively near the original locations so that your hoses reach. Your placement may differ from mine, so make sure to check YOUR original intake for the locations where the hoses came from.

The last piece to attach is your IAT sensor. If you slowly rock it back and forth, it will pop out of the original intake hose. There are no threads on it, it's just a press-fit piece. This makes it relatively easy to fit it into your new intake. I cut a short piece of clear PVC tubing to fit around the sensor, the drilled a hole in the pipe to make a tight fit. There is no strain on this sensor except the weight of its wires, and there will be a vacuum inside the pipe, so you should have no problems with the sensor coming loose. Once the sensor is mounted in the pipe, it should have unrestricted airflow across it.
View attachment 16947

That completes the rebuild of your intake and deletion of the resonator. Hook everything up, and start your vehicle. Close up the air box, and take it out for a drive. You will immediately notice the deeper engine sound when you get on the throttle. After you have confirmed there are no problems, you will want to (reluctantly) disassembly everything, remove your hose fittings, and paint the pipes. Wash and sand both pieces to remove any oil and take off the glazed finish from the pipe. Spray on a good quality primer. When choosing your paint, a textured finish will give it the appearance of factory pieces. I used a flat-black with a gritty texture. After the paint has dried, reinsert the hose connectors, adding black RTV silicon as desired to ensure a good air-tight fit. Here is what my intake looked like with the aftermarket air filter...
View attachment 16948

You are now the proud owner of a custom warm-air intake! You will feel a bit more throttle response, which may improve as the PCM learns the new airflow. This intake will have the same characteristics as the higher-priced aftermarket intake kits, and will fit much better than many of them. If you notice your gas mileage has gone down, you are enjoying the extra power too much and need to get your foot off the gas. :smile: I have been driving with this mod for over a year now, and never once had any problems with the IAT coming loose, or the pipe connectors coming apart.

For more and larger pictures, click here.
After building this mod, you may wish to continue on and create a true cold-air intake...
 

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Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Very nice! I like all aspects of this. It's true DIY and it's cheap! I'll probably give this a go next spring.
 

Regulator

Member
Nov 20, 2011
2,496
I like it, well done!
 

ieatglue

Member
Nov 20, 2011
152
Looks great! All you need is some sort of heat shield to go around the intake filter to complete the look :yes:
 

07Blazerman

Member
Dec 4, 2011
102
ieatglue said:
Looks great! All you need is some sort of heat shield to go around the intake filter to complete the look :yes:

:iagree: Looks good, but now especially in the summer you have to make something to keep the heat away. Gut the airbox and run some ducting to it, Saw a thread on the OS.
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
ieatglue said:
Looks great! All you need is some sort of heat shield to go around the intake filter to complete the look :yes:

I don't actually DRIVE my truck around this way! :biggrin: The picture was just taken to clearly show the components. I did state in the article that you should reassemble the air-box before driving it. I was just trying to get up an article on one method of building a custom intake and remove the resonator, without having to spend a couple hundred bucks on something from ebay that doesn't even fit.

My next article will be discussing the steps I took to create a minimal cold-air intake pipe...
 

Cable810

Member
Dec 5, 2011
690
Does an 02 have the IAT?
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
Cable810 said:
Does an 02 have the IAT?

Yes. I believe they cut over to the MAF sensor in '05 or '06, but the earlier models all had the IAT.
 

groundshock

Member
Dec 4, 2011
248
I'll be going to do this tomorrow. Thanks so much for the info and the fantastic write-up.

Here's the parts list I'll be taking with me:

1- 3" Sweeping 90* Elbow (Grey Conduit PVC)
1- 3" x 1' Pipe (PVC)
2- 3" couplers (Rubber)
1- 1/2" MIP to 1/2" barb, straight (PVC)
1- 1/8" MIP to 1/8" barb, straight (brass)
1- 1" MIP to 1" barb, 90* (PVC)
1- Can of Textured Black Paint
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
I have seen the rubber couplers available in both plumbing and automotive. I would assume the ones in automotive are better suited to the conditions from engine heat, however I just used the type from plumbing and have not seen any breakdown of the rubber yet. Keep in mind my installation is only about a year old, so they may not stand the test of time.

I would also suggest grabbing one of the aftermarket air filters that will fit on various sizes of pipe. It will save a lot of hassle with trying to cut down the PVC diameter to match the factory air filter. My own feeling is that the conical filters present a better surface for the incoming air flow, but I don't have any numbers that would back up this claim.

Good luck with the mod, let us know how it goes!
 

groundshock

Member
Dec 4, 2011
248
Definitely will! I'll post up some pics of my own adventures with it .

One thing I may do is spend a bit of time reducing the length of the threaded portions of the connectors that protrude into the pipe. I can see that one-incher being a disruption in clean airflow. Probably wont add anything but that's just the perfectionist in me I guess.
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
It's possible, however you want to make sure and leave enough meat there so the connector doesn't fall out some day. I actually played with using an electrical pipe nut, since its the same thread, to try and hold the piece from the inside, but the curve of the large pipe prevented me from getting decent tightness on the nut. It might have been better to try using some all-purpose pipe glue and permanently fix the hose connector in place, but it was a new mod and I was anxious to try it out :biggrin:

Actually now that I think of it, I wonder... Isn't that 1" hose the same one that goes to the cold-air injector, the one that everyone always has problems with it filling up with water? By cutting the edge of the hose connector at an angle where it protrudes inside the 3" pipe, you can create a slight pressure or a vacuum inside the 1" hose, depending on the direction of the cut angle. What do you suppose the chances are that by creating a slight vacuum in that line, any moisture buildup in the hose could be sucked through the engine when the air pump isn't running? I am so tired of having my SES light on from the P0410 code... Anyone have thoughts on the feasibility of this?
 

groundshock

Member
Dec 4, 2011
248
I'd disconnect the battery, reinstall the stock airbox and tube and see if it goes away.... Worth a shot....
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
groundshock said:
I'd disconnect the battery, reinstall the stock airbox and tube and see if it goes away.... Worth a shot....

Actually I was getting that code long before I ever did this mod. And it's a pretty common issue. I'm kinda surprised there hasn't been some kind of recall for this issue. Is there anyone who doesn't get water in these lines?
 

groundshock

Member
Dec 4, 2011
248
Got it installed today. Works great! One thing I didn't need was the 90* outlet, as it looks as though I dont have that hose.

Will post finished pics tomorrow!
 

fishguy1123

Member
Dec 5, 2011
310
I'm haveing a hard time finding the 3" conduit and the 1/8X1/8 mip to barb fitting. I can find 1/4mipX1/8barb but thats it. Largest conduit is only 2". Been to 4 local hardware stores and H depot. :hissyfit:
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
That's surprising that the conduit is not available. Every hardware store here carries that size. As for the barb, locally my Ace hardware has by far the largest selection of brass fittings, so that might be a place for you to check. Alternatively, you can use the 1/4mip (which simply requires a larger hole drilled in the pipe), or even a plastic barb. Really the only criteria here is that you can get a good seal, and your vacuum hose fits on it.
 

blazinlow89

Member
Jan 25, 2012
2,088
Looks pretty damn good man. Glad to see I am not the only one with a PVC intake, did this mod about 4 years ago.

I will say what I did do different was I used a 60* pipe and cut the angle that I needed to make it mate with the straight pipe to the air box location. I Used the straight of the pipe (narrow) to mate with the TB. I need to go back and make it again, i JB welded my fittings in and that didn't last very long. I am going to gut the stock resonator and use it as a cover sort of to hide the hoses and such.
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
Apparently I can't edit my original post after a certain period, so I'll just have to add the update here... Something I forgot to mention is that the small vacuum line needs to be replaced by a length of vacuum hose. The original shaped piece with the 90-degree fittings is not long enough to reach to the new pipe, so just grab about a foot of hose from any auto parts store, and cut it to the length you need.

@blazinlow89 - I'm surprised the jbweld didn't hold. However if you thread the large pipe to take your fittings, then there will be very little strain on whatever cement you use. The 60-degree elbow sounds about right, however I didn't find anything like that available here when I was building mine. Most places seem to only carry 45 and 90 elbows, so you must have found a very well-stocked store!
 

drwfaulk

Member
Jan 5, 2012
144
Looked so good I had to copy it.

Cutting and fitting to fit the way I liked.
e9861389.jpg

I'll post pics of the hoses and stuff tomorrow and I might have some paint on it to
 

gmcman

Member
Dec 12, 2011
4,656
That's a cool looking intake, but there is something I want to question. Just a thought so don't take it as a negative critique, but if our TB is 77mm, and a 3" tube is 76.2mm, would this not restrict the airflow?

Calculating airflow is a science, played around with it designing a generator enclosure and learned alot about what happens when you add bends and given lengths and how airflow is compromised.

Granted we have larger stock tubes with ripples so I don't know for certain how a smaller smooth bore tube will flow against a larger one with turbulence.

Just throwing it out there but something tells me a coupler at the TB with a 3 1/2" pipe would prob equal the flow of the stock tubes.

I know we're only talking .8mm difference but it's at a length with a bend.
 

drwfaulk

Member
Jan 5, 2012
144
gmcman said:
That's a cool looking intake, but there is something I want to question. Just a thought so don't take it as a negative critique, but if our TB is 77mm, and a 3" tube is 76.2mm, would this not restrict the airflow?

Calculating airflow is a science, played around with it designing a generator enclosure and learned alot about what happens when you add bends and given lengths and how airflow is compromised.

Granted we have larger stock tubes with ripples so I don't know for certain how a smaller smooth bore tube will flow against a larger one with turbulence.

Just throwing it out there but something tells me a coupler at the TB with a 3 1/2" pipe would prob equal the flow of the stock tubes.

I know we're only talking .8mm difference but it's at a length with a bend.
Aw man now I have to re-do this in 3.5" or 4" tube :hissyfit: gah!! LOL
Even if it doesn't help it sounds better and when it's painted it will look better, so for $30 it's not too bad.
 

blazinlow89

Member
Jan 25, 2012
2,088
Shdwdrgn said:
@blazinlow89 - I'm surprised the jbweld didn't hold. However if you thread the large pipe to take your fittings, then there will be very little strain on whatever cement you use. The 60-degree elbow sounds about right, however I didn't find anything like that available here when I was building mine. Most places seem to only carry 45 and 90 elbows, so you must have found a very well-stocked store!

I probably did not let it cure long enough, It was still gooey when I re-installed (had to go to work). I'm going to grab some some straight barb fittings from my uncle next time I go visit him, also use the 1/8" NPT so they will be nice and tight.

Our lowe's is very generously stocked, mainly I am thinking due to the local Navy base.
 

Sparky

Member
Dec 4, 2011
12,927
gmcman said:
That's a cool looking intake, but there is something I want to question. Just a thought so don't take it as a negative critique, but if our TB is 77mm, and a 3" tube is 76.2mm, would this not restrict the airflow?

I suspect that 0.8mm isn't going to make that much of a difference. And I would also think that a smooth bore vs the ribbed bore of the factory tube would more than make up for that.
 

gmcman

Member
Dec 12, 2011
4,656
I don't think it makes a whole lot either but I know if I barely let up on the throttle I can feel it for sure, and we're talking very small butterfly movements.

1MM, whether it's bore diameter, stroke, TB diameter, is actually a large number.

One other thing, and granted...this isn't a woodshop dust collector... but dusty air through PVC pipe generates crazy static electricity. Sawdust takes a few seconds to generate enough to wake you up if you touch an un-grounded PVC system. What i'm thinking is long-term, something like an hour or so...whatever, I have no real-world data to represent what i'm trying to say but what are the chances that the airflow through the pipe at the velocities we are providing, would generate any static?

Just thinkng sensor longeivity.

Only a hypothesis.
 

Sparky

Member
Dec 4, 2011
12,927
Well you shouldn't have dusty air inside the pipe, if you do, you've got problems! Such as a missing air filter lol :tongue:

But that's interesting, I never even gave that any thought.
 

blazinlow89

Member
Jan 25, 2012
2,088
Im pretty sure air accelerates as it goes around a corner.

The PVC should be grounded pretty well with everything it touches on the engine. Don't remember ever getting zapped by it.
 

gmcman

Member
Dec 12, 2011
4,656
Sparky said:
Well you shouldn't have dusty air inside the pipe, if you do, you've got problems! Such as a missing air filter lol :tongue:

That's what i'm not sure of, whether airflow alone (clean) running through a pvc pipe would generate any static. Air moving pretty slow should not pose any threat, but air in the intake moves along especially at higher RPM's.

blazinlow89 said:
Im pretty sure air accelerates as it goes around a corner.

The PVC should be grounded pretty well with everything it touches on the engine. Don't remember ever getting zapped by it.

I don't think there is any threat on anyone getting zapped, my only question is can the electronics be harmed by any static discharge, we are talking milliamps...like you touching someone after dragging your feet across a rug. almost imperceivable to people but electronics can be picky.

I'm just throwing these ideas out.
 

Rubberman

Member
Dec 14, 2011
117
I bought this for my TB. pretty sure it was cheaper at the time but it works. They give you a generic K&N filter type but you could replace it with a geniune K&N. It also has the hole for the IAT sensor.

[EBAY]180737516144[/EBAY]
 

Black_tb

Member
Dec 6, 2011
817
i might have to look for that on ebay when i have some extra money
 

infamouz

Member
Dec 3, 2011
89
can we do this with the 07 4.2? I know the sensors are diffrent. But besides that I dont know what else is.
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
@drwfaulk - Looks great! How's it working for you?

@infamouz - The 2006 and up have a MAF sensor that is very finely calibrated to it's position in the incoming air stream. I believe the consensus is that if you try to build a full intake such as in this discussion, you are going to always throw a CEL code because the computer cannot properly adjust to the differences.
 

infamouz

Member
Dec 3, 2011
89
Shdwdrgn said:
@drwfaulk - Looks great! How's it working for you?

@infamouz - The 2006 and up have a MAF sensor that is very finely calibrated to it's position in the incoming air stream. I believe the consensus is that if you try to build a full intake such as in this discussion, you are going to always throw a CEL code because the computer cannot properly adjust to the differences.

Thanks im going to try this one then...http://shop.mobileweb.ebay.com/searchresults?cmd=SKW&pg=1&kw=Mac+3426
 

MichEnvoyGuy

Member
Dec 3, 2011
522
Rubberman said:
I bought this for my TB. pretty sure it was cheaper at the time but it works. They give you a generic K&N filter type but you could replace it with a geniune K&N. It also has the hole for the IAT sensor.

[EBAY]180737516144[/EBAY]

Is it just me or does that clamp to the resonator box? I think you'd really want one that eliminates the resonator box and goes right to the throttle body, but thats just MHO.
 

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