DIY: Warm Air Intake Version 2.0

[Top_Fuel]

A couple of years ago I built a simple Warm Air Intake device (WAI Version 1.0)...but it wasn't effective enough in really cold temperatures. I modified it and have done some testing over the last couple of winters. This is a better design...it's simple...and it's easier to build.

Here are the improvements for version 2.0...

• More effective than my original design…results in higher intake air temperatures

• Draws in air from a concentrated heat source (exhaust manifold heat shield)

• Mandrel bends...no internal restrictions...supports more air flow

• Supplements the existing air intake…no need to block existing air cleaner snorkel in most winter conditions

• Can be installed/removed easily without tools

What's new about this design?

This version is designed to specifically draw air in through/around an existing hole in the exhaust manifold heat shield. Here is the area between the engine and firewall. Notice that square hole in the exhaust manifold heat shield right next the oxygen sensor...



Here's a closer look...



This WAI will be positioned so that the intake opening is directly over this hole. This hole in the heat shield isn’t large enough to supply all of the intake air for the car, but the device will not be air-tight against the exhaust manifold heat shield. As a result, it will be drawing in air through the hole in the heat shield along with air from the immediate area around the exhaust manifold. The end result will be warm/hot air entering the rear of the air box.

Here's where the end of the WAI 2.0 will rest on the exhaust manifold...centered over the square hole...



Here's another view...



What you are looking at is a 3"-2" silicone reducer sitting on the exhaust manifold shield (the larger 3" end is on the heat shield). It may look like it is completely sealed against the heat shield, but it's not (it is resting on the shield). So air can enter the WAI through the hole in the manifold heat shield as well as the gaps around the end of the reducer.


Here's what the WAI 2.0 finished product looks like...

[Top_Fuel]

Parts List


Ready to build one? Here's the parts list...




1. 6 inches of 2” OD tubing (aluminum or steel) cut into 2 3" pieces
2. 2" PVC Trap Adapter (this is a standard plumbing fitting)
3. 2” OD 90 degree PVC Short Street Elbow (used in central vacuum systems)
4. 3” to 2” ID silicone reducer (ebay or siliconeintakes.com)
5. 2” ID 60 degree silicone elbow (siliconeintakes.com or aliexpress)
6. 2" ID thrust washer


Let's take a closer look at these parts individually…


1. 2” OD tubing

You need 2 pieces...each roughly 3 inches in length. I purchased a 6 inch length of aluminum intake tubing for under $5 from intakehoses.com and cut it in half with a hack saw. Make sure it’s 2” OUTER diameter and not 2” inner diameter. TIP: If you don't have access to a band saw or chop saw, just install a hose clamp around the tubing and use it as a guide for your hack saw to end up with a nice, straight cut.





2. 2” PVC Trap Adapter

We'll be cutting this fitting apart and only using pieces of it to combine with the PVC street elbow (part #3). We only need the threaded portion and the ring that screws onto the threads. You can buy this fitting at any big box store plumbing department for $2.




3. 2” OD PVC Street Elbow

This piece allows you to make a low-clearance 90 degree bend with a 2” OD pipe with no internal restrictions. It also clears the cowl of the car when you mount it on the back of the air box. You get all this and it only costs $1 at evacuumstore.com. Remember…this is a central vacuum PVC fitting…NOT a plumbing fitting. A similar 2” PVC plumbing street elbow fitting is huge compared to this and absolutely will NOT fit on the rear of the airbox under the cowl.




4. 3” to 2” ID silicone reducer

This is the piece that will fit against the top of the exhaust manifold heat shield. We will be using this reducer to “funnel” air into the end of the WAI. You can find these on eBay for a few dollars. Make sure it's silicone because it needs to withstand high temperatures.




5. 2” ID 60 Degree Silicone Elbow

A 60 degree bend off the rear of the air box lines up perfectly with the top of the exhaust manifold. Unfortunately a 60 degree silicone elbow is not a common item. I bought mine from siliconeintakes.com for $17. A 2" OD tube with a 60 degree bend would also work...but I couldn't locate one anywhere.




6. 2" ID thrust washer OR 2"- 1 1/2" Conduit Reducing Washer

I needed something round, flat and rigid that would fit around the outside of a 2" OD tube (you'll see why when we put this thing together in a minute). A 2" ID thrust washer works perfectly with no modifications. I had to get this on-line as nobody locally carries them.



Note: You can substitute a 2"-1 1/2" Conduit Reducing Washer for about $1 (available at any Home Depot). BUT...this washer won't fit around a 2" OD tube until you open it up a slightly with a file and/or aggressive sandpaper.



Tools & Other Materials Required:

2 3/8” (60mm) hole saw
hack saw
side cutters
Coarse sand paper
JB Weld, PVC glue or other multi-purpose glue
10mm socket (needed to remove the air box from the car)

[Top_Fuel]

How to build a WAI 2.0



1. Cut the threaded portion off of the trap adapter

Using a hack saw, cut the threaded end off of the trap adapter. Take your time and try to cut the threaded piece off as evenly as you can. You are cutting at the red line below...



When you're done, you'll have this...





2. Sand the threaded piece down to size

We only need the threads to be about 15mm tall. Take a quick measurement of the piece you just cut off. It's probably closer to 18mm...so we need to reduce the height by a few mm. The easiest way to do this is to place a piece of coarse sandpaper (rough side up) on a flat surface. Now take the cut end of the threaded piece and move it back and forth on the sandpaper while applying pressure. Within a minute or two it will be the 15mm height you need. Remember...sand the edge you cut in Step 1 (which will be rough)...not the other end.





3. Sand the trap adapter ring down to size

Using the same method as in Step 2, sand the trap adapter ring down until it is about the same height as the threaded piece (about 15mm). Be sure to sand the side of the ring that has the smaller opening (the side facing up in the image on the left below).



When you're done, both ends of the ring will look the same...like this...





4. Sand the PVC street elbow down to size

Take the threaded piece you sanded in step 2 and place it over the male end of the street elbow. You don't want the male end of the street elbow to stick out beyond the threads (like it's doing in the image below). The street elbow will probably be 1-2mm too tall at this point. So use the same sanding method from Steps 2 and 3 to reduce the height of the male end of the street elbow until it is the same size as the threaded piece.





5. Install the thrust washer onto the street elbow

Slide the thrust washer over the male end of the street elbow.
Note: I painted my street elbow black before this step.





6. Glue the threaded piece onto the street elbow

Glue the threaded PVC piece onto the male end of the street elbow...placing it tightly against the thrust washer. The side of the threaded piece you sanded in step 2 should be placed against the thrust washer. You can use PVC cement or the old stand-by...JB Weld. I used JB Weld. Allow the glue to dry before continuing. It should look like this when you're done:





7. Press one of the pipe pieces into the female end of the street elbow

Take one of the lengths of 2” OD pipe and push it all the way into the female end of the street elbow. It will be a tight press-fit…but this is what you want. The pipe will be firmly in place with no need for any glue, etc. If you need to pull it apart later, you will be able to.





8. Attach the silicone elbow to the pipe

Take the 60 degree silicone elbow and slide it over the pipe you just pressed into the street elbow.





9. Attach the second piece of pipe

Take the remaining short length of 2” OD pipe and push it about half-way into the open end of the 60 degree elbow.





10. Attach the silicone reducer

Slide the 3"-2" silicone reducer over the exposed end of the pipe on the 60 degree elbow.





That's it…you’re done! That's what the finished product looks like.




Notice that hose clamps aren’t used to hold anything in place. This is because the hoses are a tight fit over the pipes we are using, and they will not separate once the device is installed on the airbox. Using sections of silicone hoses with metal pipes will let you easily adjust the connections (if required) once the unit is installed in the car.

Maybe I just got lucky...but using the parts described in these instructions, I didn't have to modify the silicone hoses during the installation process. It literally fits the car perfectly as it is pictured above.

[Top_Fuel]

Preparing the airbox for the WAI 2.0


1. Remove the rear portion of the airbox from the car.

This sounds involved but I've done it so many times now, I can have it out in less than 2 minutes. You first have to open the front of the air cleaner housing and lay it against the radiator (there's no need to disconnect any sensor wires...just leave them in place).

Now remove the air filter…and then remove the snorkel assembly from the passenger side of the airbox (it's held in place by a single 10mm bolt). At this point, there are 2 10mm bolts holding the rear portion of the air box to the engine. Remove these 2 bolts, and then pull straight up on the airbox (with the 2 mounting bolts removed, the airbox is being held in place by a plastic locating “nub” on the bottom that is wedged into a rubber hole).



2. Locate the WAI hole on the back of the airbox.

This is where the WAI will connect to the airbox. This location is important because if positioned correctly, the WAI will install into the airbox without interfering with the intake resonator tube from the snorkel. So you won't have to modify the factory snorkel/resonator tube.

Take your time here. You don't want to botch this because the rear airbox piece isn't cheap. I had to ruin one in the process of figuring all of this out.


Here's how to locate the hole we have to make in the airbox...

On the back of the airbox, notice the 7 "ribs" that are molded into the top of it. We're going to use these as our reference point for locating the hole...




Start by drawing a straight line across the bottom of the 3 right-most ribs (red line).
Now draw a parallel line 1" down from that line (green line).
Now draw a line down the center of the second rib from the right (blue line).



The intersection of the green and blue lines is the center of the hole we need to cut in the airbox. I found it easier to do this process by applying masking tape to the airbox and drawing the lines on the tape...



Drill a small pilot hole where the 2 lines cross. This will provide a guide for the bit of the hole saw...





3. Cut the hole in the airbox

Now break out the 60mm hole saw and make the hole...





4. Remove the "ribs" around the inside of the hole

Once you have the hole made, look at the hole from the INSIDE of the air box. Notice the inside of the air box has plastic reinforcement "ribs" formed into it.

Here's the inside of the airbox before we made the hole...



And here's the inside of the airbox after the hole...



We’ll need some room around the hole to install the threaded ring that will hold the WAI in place...so we need to trim these ribs about 1/2" away from the hole as indicated in the image below...




Using some side-cutters or other tool, trim the ribs about 1/2" away from the hole. The plastic material of the air box ribs will break naturally when you cut it with side cutters. You may have to get creative to do this. I have a small pair of angled side-cutters that made this part fairly easy. If you aren't sure what will work, grab the hole piece you cut out (back in step 3) and see what works on cutting the ribs off of it. You're just going to throw this piece out anyway.

When you're done, it should look like this...



Here's a close-up of one of the 4 areas where the ribs need to be trimmed away from the hole...





5. Clean up the the hole

Use some sandpaper to clean up the hole. The airbox is now ready for the WAI.





6. Test fit the WAI

Put the threaded end of the WAI through the hole in the airbox.




Now screw the threaded ring onto the WAI to hold it in place. That's all there is to it.






Notice (below) that you can re-install the stock snorkel assembly and that resonator tube will clear the threaded ring of the WAI. My goal was not to modify anything (other than putting the hole in the airbox).





7. Reinstall the airbox in the car

You can attach the WAI before re-installing the airbox...or you can attach it after the airbox is back in the car. I'm not sure which way was easier. Remember that you can easily pull the pieces of the WAI apart to make the installation easier.


Here's what it looks like installed on the airbox and in the vehicle...

[Top_Fuel]

General Observations

There are multiple ways you can run your Mirage with this device:

1. You can install a grill block (partial or full) which helps increase the IAT.
2. You can block the end of the snorkel and draw ALL intake air through the WAI.
3. You can leave the snorkel open and draw a mix of hot and ambient air.
4. You can run a combination of the above.


Quick test at 60 mph cruise with ambient temp around 30 degrees F and 100% grill block:

If ALL intake air is draw in from the WAI (ie. the factory snorkel is completely blocked off), the IAT increase is 90+ degrees F above ambient. This is pretty extreme for all but the coldest outside temperatures.

If HALF of the intake air is drawn in from the WAI (factory snorkel left completely open), the IAT increase is 50 degrees F above the ambient temperature.



This is a huge improvement over my original version. I remove it in the spring once daily temperatures are consistently 60+ degrees. I don’t think there’s a benefit to driving around with 100+ degree IAT temps in the warmer months.

The IAT temperatures are actually higher in stop-n-go traffic vs freeway cruising.

Like my original version...this one is pretty much undetectable under the hood (if you paint the PVC street elbow black). Nobody would ever notice it if they looked under your hood.


CAUTION:

If you use a 100% grill block and/or a WAI, you probably want the ability to monitor your real-time coolant and intake air temperatures with a Scangauge or similar device.

[inuvik]

Awesome detail and description. Really well done. I've made this thread a "sticky" so it remains at the top of this section of the forum.

[Eggman]

Yet another great write up Top_Fuel, and lots of pictures too.

So how long have you been running this? Any other improvements that you would suggest?

There are multiple ways you can run your Mirage with this device:

I confess I misread this to say ruin instead of run haha.

[Top_Fuel]

So how long have you been running this?

I've been using this design for the last 2 winters.

The only challenge I've had is that after a month of heat cycles, sometime the threaded ring will start to back off and may need to be re-tightened. When it gets loose, you can sometimes hear it rattle against the exhaust manifold heat shield.

I just re-installed mine for the winter and this time I really cranked down on the ring when I tightened it...so hopefully that will help.

Edit - It's now 5 months later and the ring was still on tight...so I don't think you need to worry about this now.

...I misread this to say ruin instead of run haha.

Now that would be an interesting thread title... "Ways to ruin your Mirage"

[Loren]

I know you don't want to glue your threaded ring in place because you want it to be removable. What about drilling a small hole in the ring and safety-wiring it to something to keep it from unthreading?

(sorry, I spent 8 years of my life as a Nuclear Weapons tech in the USAF, we used to safety-wire EVERYTHING... it's one of my go-to solutions when Loc-tite isn't appropriate)

Otherwise, I think this mod is cool as hell! I don't think it would make a bit of difference for ME living in Florida. But, I know warm-air in cold weather is great for economy. Well done.

[Top_Fuel]

...What about drilling a small hole in the ring and safety-wiring it to something to keep it from unthreading?

Kinda like the safety wire on real knock-off wheels?!? I never thought about that angle!

I was thinking that I may need to consider a solution like that if I continue to have problems with the threaded ring backing off. Maybe a small hole and use a small pin to lock it in place.



I'm also considering a rubber gasket underneath the ring which may provide a surface less likely to allow the ring to slip and loosen over time. This is a flat rubber gasket with a 2" ID...



I seem to get most of my ideas down the plumbing aisle at my local Ace Hardware...