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I decided to make my own intake because I wanted something that would never give me a CEL. I also wanted something straighter than what is currently out there. I relocated my battery so I have a straight shot right to the throttle body. All of the aftermarket CAIs have bends to go around the battery.
My CAI costs about the same as an aftermarket. The advantage that mine has is that it uses a stock MAF housing. It would be about $40 cheaper but I've only found one supplier for the 22 degree elbow and it's not cheap. You could also save $63 by cannibalizing your stock airbox top. I didn't want to do that so I bought a new one.
I've had this CAI on my car for 10,000 miles with no CELs. It also sounds great!
Here's how I made it and the parts I needed...
Mazdaspeed6 Air box top - onlinemazdaparts.com $63.02
3" dia 22deg elbow - Turbohoses.com $50.98
3” dia 45deg elbow -
Ebay $15.00
2.75 to 3” reducer -
Ebay $15.00
3" straight coupler -
Ebay $7
3" Liner hose clamps - globalindustrial.com $19.00 for a package of 10.
3" K&N Conical Air Filter - Summit Racing $42.46
5/16" K&N breather filter - Summit Racing $18.95
3" Hose Joiners - Racepart Solutions $5.95
Vacuum caps for VAD solenoid - Autozone $6.99
12AWG heatshrink ring terminals - hardware store $various (Check the bolt diameter before buying the terminals. I think I bought 1/4" ring terminals)
First, here's the almost finished product...
Click on the pics below to enlarge them.
I purchased a MazdaSpeed6 airbox top. I measure a friend's MS6 and found that the MAF housings are identical to ours. Before cutting...

I used an air saw to cut the MAF housing out of the air box. It doesn't have to be perfect at this point just get close...

I used a pair of flush wire cutters to trim off the excess material. I then took a sanding block with some fine grit paper to smooth everything down. Here's a pic before sanding...

To mount the VAD solenoid, I decided to cut off the stock rusty ground connector and mount it there. I re-terminated the four ground wires. I used two 12AWG heatshrink ring terminals. The heatshrink terminals are important because you don't want the grounds corroding over time. I bought a nut and lockwasher to mount the VAD. I think they were 6mm. I also used vacuum caps to cap the in and out of the VAD solenoid. Most auto parts stores sell variety packs with multiple sizes of vacuum caps for a few bucks. In this pic you can see the VAD mounting...

In this pic you can see the new ground wire mounting location. I slit some 5/8" heater hose and slipped it over the edge of the hole's opening. It made a decent grommet...

I cut off the stock tube that went from the valvecover to the intake bellows. Carefully slit the tube with an exacto knife to get it off of the valvecover connector. The K&N breather just clamps onto the stock valvecover connector...

I just have the 45 degree elbow resting on the edge of the fender hole. I didn't have the grommet installed or VAD mounted in this pic but you still get the idea...

When you go to piece all of the parts together, you will need joiners to slip inside of the silicone elbows and transitions. The link in the parts list has nice prefabricated aluminum joiners. You need three of them. Instead, I had a piece of 3" stainless exhaust tube laying around so I just cut off three 3" long pieces. One is used between the 2.75" to 3" transition and the 22 degree elbow, another is used between the 22 degree elbow and the 3" straight coupler, and the last piece is used between the 45 degree elbow and the air filter...

I also used liner clamps to hold everything together. Liner clamps are good because they don't dig into the silicone hoses when you tighten them down. They have a smooth piece that slides over the slots in the hose clamps...
When I originally mocked up the CAI, I just used cheap hardware store hose clamps, that's why you can see the hose through the slots in the clamps...

BP
My CAI costs about the same as an aftermarket. The advantage that mine has is that it uses a stock MAF housing. It would be about $40 cheaper but I've only found one supplier for the 22 degree elbow and it's not cheap. You could also save $63 by cannibalizing your stock airbox top. I didn't want to do that so I bought a new one.
I've had this CAI on my car for 10,000 miles with no CELs. It also sounds great!
Here's how I made it and the parts I needed...
Mazdaspeed6 Air box top - onlinemazdaparts.com $63.02
3" dia 22deg elbow - Turbohoses.com $50.98
3” dia 45deg elbow -
2.75 to 3” reducer -
3" straight coupler -
3" Liner hose clamps - globalindustrial.com $19.00 for a package of 10.
3" K&N Conical Air Filter - Summit Racing $42.46
5/16" K&N breather filter - Summit Racing $18.95
3" Hose Joiners - Racepart Solutions $5.95
Vacuum caps for VAD solenoid - Autozone $6.99
12AWG heatshrink ring terminals - hardware store $various (Check the bolt diameter before buying the terminals. I think I bought 1/4" ring terminals)
First, here's the almost finished product...

Click on the pics below to enlarge them.
I purchased a MazdaSpeed6 airbox top. I measure a friend's MS6 and found that the MAF housings are identical to ours. Before cutting...

I used an air saw to cut the MAF housing out of the air box. It doesn't have to be perfect at this point just get close...

I used a pair of flush wire cutters to trim off the excess material. I then took a sanding block with some fine grit paper to smooth everything down. Here's a pic before sanding...

To mount the VAD solenoid, I decided to cut off the stock rusty ground connector and mount it there. I re-terminated the four ground wires. I used two 12AWG heatshrink ring terminals. The heatshrink terminals are important because you don't want the grounds corroding over time. I bought a nut and lockwasher to mount the VAD. I think they were 6mm. I also used vacuum caps to cap the in and out of the VAD solenoid. Most auto parts stores sell variety packs with multiple sizes of vacuum caps for a few bucks. In this pic you can see the VAD mounting...

In this pic you can see the new ground wire mounting location. I slit some 5/8" heater hose and slipped it over the edge of the hole's opening. It made a decent grommet...

I cut off the stock tube that went from the valvecover to the intake bellows. Carefully slit the tube with an exacto knife to get it off of the valvecover connector. The K&N breather just clamps onto the stock valvecover connector...

I just have the 45 degree elbow resting on the edge of the fender hole. I didn't have the grommet installed or VAD mounted in this pic but you still get the idea...

When you go to piece all of the parts together, you will need joiners to slip inside of the silicone elbows and transitions. The link in the parts list has nice prefabricated aluminum joiners. You need three of them. Instead, I had a piece of 3" stainless exhaust tube laying around so I just cut off three 3" long pieces. One is used between the 2.75" to 3" transition and the 22 degree elbow, another is used between the 22 degree elbow and the 3" straight coupler, and the last piece is used between the 45 degree elbow and the air filter...

I also used liner clamps to hold everything together. Liner clamps are good because they don't dig into the silicone hoses when you tighten them down. They have a smooth piece that slides over the slots in the hose clamps...

When I originally mocked up the CAI, I just used cheap hardware store hose clamps, that's why you can see the hose through the slots in the clamps...

BP