Jeep Enthusiast Forums banner

How To Build a PVC Cold Air Intake for 3.7L

23K views 30 replies 13 participants last post by  luckyse7ens  
#1 ·
How To Build a PVC Intake for a 3.7L V6 Grand Cherokee

Parts
- About 2' of 3'' diameter PVC pipe
- 1 45˚ elbow for 3'' pipe
- 1 90˚ elbow for 3'' pipe
- High Flow Intake Filter (I used Spectre)
- Duct Tape
- PVC Cement

In total it cost me right around $50 to make! That's $20 less than the K&N filter (not the whole intake) I was looking at alone!

Tools
- Saw to cut PVC pipe and stock hose coupler
- 5/32 alan wrench (best if on an extended screwdriver)
- Flat head screwdriver to remove the air box
- Scissors to cut tape
- Drill bit to drill the air intake sensor hole
- Lighter to melt the duct tape air tight
- Sharpie

Image


Started by removing the stock intake hose. Just loosen the clamps on both ends.
Image


Then removed the air intake sensor (correct term?). Twist and pull out.
Image


Then loosened the clamp on the throttle body behind the air box.
Image


Used a 5/32 alan wrench to get the right side of the air box off. Very tight spot - recommend using an extended screwdriver bit as I had to buy one anyways to reach the left side.
Right:
Image

Right:
Image

Left:
Image


Once the clamps and both screws are removed the air box may be removed. Just had to shift it around different ways until it squeezed out.
Image


Remove the top of the stock filter box. Pull off the hose.
Image


Tested the unfinished piping and filter to get an idea of placement and sound.
Image


Had to cut 5 inches off the end of the 2' tube.
Image


Cut the end of the stock intake hose to use as a coupler for the elbow to the throttle body. Used duct tape to connect the coupler to the pipe. Used a lighter to melt the tape to an airtight seal.
Image


Test fitted the pipe. Used the 5'' piece cut off earlier to connect the 45˚ elbow to the 90˚ elbow which will connect to the throttle body via the coupler made from the stock hose.
Image


Once I found the correct angle for the pieces to connect I used a sharpie to draw guidance lines. Then used PVC cement to stick all the pieces together.
Image


Drilled a hole for the air intake sensor to fit in. Once finished drilling I used a Swiffer cloth on the end of a pole to clean out the inside of the pipe, then blew it out with a shopvac and vacuumed after that. Don't want any shavings getting into the engine.
Image


By now it is obvious - this thing is ghetto rigged. To top it all off I duct taped a sponge up and zip-tied it in place to support the pipe.
Image


A view of the pipe. 90˚ elbow with the coupler on the end, to the 5'' straight pipe, to the 45˚ elbow, to the remaining straight pipe (had to cut off more to get it to fit right. Ended up protruding from the 45˚ 8 inches).
Image


Installed it. Tightened the clamp to the throttle body and the one on the filter. Plugged the air intake sensor into the drilled hole. Made sure everything was snug and took it for a test run! Runs great! Instant reaction when I push on the gas. Much quicker acceleration. Definitely feel a noticeable difference. Will be keeping an eye on the MPG changes.
Image


I plan to remove the pipe to spray paint it as soon as I get the chance.
 
#5 ·
Runs great! Instant reaction when I push on the gas. Much quicker acceleration. Definitely feel a noticeable difference. Will be keeping an eye on the MPG changes.

Functional fixedness can kiss my *** :D

Oh, and I'll take a video tomorrow.
 
#8 ·
Some scrub named TheDude :thumbsup:

Appreciate that thread! Loving the results.

Drove to and from school and to and from Home Depot a few miles down the road and I'm averaging 18.9 mpgs but that's with lighter traffic than usual since I left school before the bell. Still know it's a definite improvement but it will take a few more days of driving to get more precise numbers. Exhaust is noticeably louder for sure!
 
#14 ·
check it frequently once the weather warms up. the underhood temperatures sometimes warp the pvc piping. you could try the insulating foil wrap used on pipes to deflect the heat.
 
#16 ·
sorry to post this in your thread but i dont think its worthy of a new one. I made one..... I first tried to make it out of 4" piping but there simply isn't enough room for that.... here's what i ended up with:



Thanks to "TheDude584" for being the guinee pig and "GCL06" also.
 
#18 ·
Bought a mini spectre filter for $10 at Advance Auto Parts. You can either cut the hose back and put it on or put it on at the end of the hose as it is. I didn't cut the hose b/c I will need to put the stock intake back on until I can build a more offroad worthy protective box.

Image


Another option would be to cut a hole in the intake pipe to fit the hose into, this way it is still getting filtered air. This may end up disrupting the smooth air flow though but shouldn't make that big of a difference as long as you make sure your hole is a tight fit. I'd still go for the filter.
 
#22 ·
Does the size of the Filter matter i have the same size sceptre you have but i have a 5.7 hemi so should i get the larger one.
 
#23 ·
The larger the better really. Allows for more air flow. I'm not really sure of what the peak size would be before you are just adding more air that won't be able to fit through the TB but I'd imagine a 5.7 could use a lot more than my little 3.7. Maybe someone else can give you a more educated answer but if I were you I'd look at the larger Spectre filters.
 
#24 ·
alright I jumped on the bandwaggon and made mine today. my only question/concern was the air sensor. i got it wedged into the hole pretty good, but i am concerned with it bounding out. how did you secure it?

Thanks.

any issues so far?:cheers2:
 
#26 ·
I just stuck mine in the hole I drilled. Tight enough fit that it has yet to fall out. Burtman's suggestion's good :thumbsup: You could also find a grommet the right size to keep it in there nice and snug.

No problems so far! (knock on wood).
 
#25 ·
i found a rubber hose fit it over ,y sensor cut out what i needed then up it on the sensor and put it in the tube the rubber holds it in tight.
 
#27 ·
this thread is so rad, love the heat wrap... it actually looks like seatbelt material.

I would have gone this way if I didnt have the funds at the time I bought my intake.

carry on boys :cheers2: