Mac's Cool Air Intake (MCAI) - install thread - Jeep TJ/LJ

[John Canfield]

Basically what this kit does is to reroute the engine air intake from under the hood (hot air) to the cowl area between the hood and the windshield (cooler air.)  An added benefit of the kit is to have filtered cabin air - many times we have turned the AC on full blast to outside air (from recirculate) and gotten a face full of dust  .  No longer with the kit installed.   It will make more sense once you look at the pictures.

I've had my eye on Mac's Cold Air Intake for some time and looked over all of the reports and decided this was a mod I wanted/needed, so I finally pulled the trigger on the kit a few months ago.

The plumbing part of the kit is beautiful - it looks great under the hood!

I borrowed a 3" chassis punch to make the firewall hole, I have a 3" bi-metal hole saw but using the chassis punch was significantly easier and I didn't chew up the teeth on the hole saw.

The next series of posts will be the install process.

[John Canfield]

 On with the install...

First batch of pictures is removing stuff. Note that the pictures are not necessarily in order of the work process - please REFER TO THE DIRECTIONS FOR THE SEQUENCE OF STEPS TO FOLLOW WITH YOUR INSTALL.

[John Canfield]

Install picture batch #2 - we're removing stuff in preparation for the install. This is a good time to remove the cabin air inlet plenum (only three screws) and look down into the squirrel cage blower and vacuum out any leaves, etc. We wondered why our cabin air blower made a horrible noise on the highest speed - now we know why. A few leaves managed to find their way into the blower cage. Bet this won't be a problem after the MCAI install .

[John Canfield]

Next batch of pictures. We mark and cut the cowl for the filter holder. Double check your measurements - the first time I marked the cowl I was way off due to having the filter holder upside down  .

An angle grinder with a cutoff wheel worked great to make the cuts and a Dremel tool with a small cutoff wheel made short work of cutting notches for the clip nuts.

[John Canfield]

Firewall work part 1.

Here's the next stage of the install and the most difficult part of the overall install.

The panel punch made short, easy, and accurate work of the 3" hole in the firewall.

The hardest part was drilling the 5/16" bolt holes through the firewall and into the stainless tube box. I duct taped the box to the firewall and I was able to at least drill through the firewall and mark the box before the drill bit pushed it back. I removed the duct tape and took the tube/box assembly to the bench.

Then I drilled the hole in the box on the bench, installed it back in the hole and tightened up a bolt/nut and moved to the opposite corner to start another hole and repeat the same process.

For the last two holes, I was able to drill the holes all the way through both pieces of metal.

Tips for you: If you don't have a Unibit, buy one. Buy a good one and not a Chinese knock-off. Also a brand new 5/16" high quality bit will make life considerably easier for you.

[John Canfield]

Firewall work, part 2.  Drilling the hole in the tube for the inlet air sensor.

[John Canfield]

Now for the last installment of the MCAI. All that's left is to seal up the cowl area and button it back up!

Then I cranked up the engine - it works! 

I read about the increased sound level due to where the intake is relocated and that's a fact. When the engine is under load the noise reminds me of my old 1957 Bel Air rod (350 ci Windsor block engine, big 4-barrell carb on top) when I tromped on it.  Mac suggested I try some A/C filter media across the cabin air intake plenum to cut the noise level down and that finally made it to the top of the list. I bought a white/blue spun glass window unit air conditioner filter (they have no frame), folded it into quarters and simply wrapped it around the cabin air intake plenum and reinstalled the cowl.

There is a significant drop in the cabin noise level with the addition of the filter media - I measured the cabin noise level at about 85 dB with Rubi in the shop and full throttle on the skinny pedal. I couldn't believe the difference the four layers of filter media made. We have for sure reduced the cabin air flow to some extent, so I might need to use a higher cabin blower speed for the same air flow, but that's no big deal.

When the engine is not under load (like cruising on the Interstate), the noise isn't even noticeable. Changing the cabin air from outside to recirculate didn't seem to make any difference in the noise level.

Almost immediately I noticed the cabin air seemed to smell 'clean' for want of a better term - it's difficult to describe. We have owned expensive cars before with carbon air filters and I was absolutely reminded of that clean air sensation.

I have no idea if there is more engine power or better fuel economy, others have documented an improvement, at least in fuel economy. Any improvement no matter how miniscule is certainly welcomed.

What I'm really excited about is when we get on the trail with the MCAI - I have seen our under hood temperatures reach 122 degrees and that hot air is getting sucked into the engine (cool air is more dense than hot air, more air = more power.) No more hot air thanks to the MCAI. (Also we won't get a face full of dust from the air vents - that got really old.)

[SargeW]

Outstanding work, and write up John! This post is easily worthy of any 4X4 magazine.  Just curious though, would this air intake work better, same , or worse than one of the snorkel tubes that I have seen some guys use?  I know the snorkel wouldn't do anything for the inside air though. 

[John Canfield]

Thanks Marty!

Not sure what the primary objective of the snorkel is unless you intend on fording very deep water.  Personally I don't like water deep enough to completely submerge the axle tubes.  We have been in dusty trail conditions many times following other Jeeps and the dust cloud is way over the height of the snorkel air inlet.

[hes4all]

Man John, could you do a little better on showing the install? That is a joke, very nice write up and pictures. I wish I would have done the same with the Spectra unit I put on my TJ. It goes on the same way with a 3" hole into the cowl area, I to used a hydraulic panel punch to make the hole. It is the only way to do it right in my opinion. I will look at this some more before I order for my LJ. Thank you again, very nice!

[John Canfield]

You're welcome Terry - good luck with your LJ.

[hes4all]

Thank you, I am going to put up a few more pictures of it today or tomorrow. Just starting to make brackets for the front axle install. Thank you again.