Mr.T

Pics are worth more than words, but as one can see it is simply a piece of rubber gasket material that acts as a baffle. It tucks in, and sort of snaps on/over existing under-hood metal. The top of the rubber bears slightly against the hood insulation for a seal. I made this about 60K miles ago and it's never shifted position.

The baffle causes much of the intake air to come from the opening behind the headlamp (first pic @ 6 o'clock) and also from the gap in the hood. Note in the first pic that the plastic behind the headlamp has been opened up slightly with a half-round file to increase the area. Water ingestion risk looks the same as stock to me -- Air is still pulled from the same locations as stock, but the baffle greatly reduces the warmer air from the engine compartment. And the factory water drain hole in the airbox is unchanged.

Main benefit is reduced knock retard and pinging (detonation) on very hot days, due to cooler air intake temperature. I wish I could find the datalogs of air temperature, but suffice it to say there was a repeatably measurable temperature decrease.

It's fairly easy to make. The middle pic shows the hardest part, making a thick paper template. Just use whatever paper/cardboard is handy, lots of trial and fit, then trace the template to the rubber sheet, and cut it out. Expect a little final trimming as you fit the rubber baffle for the first time.

EDIT:
Found the datalogs, see the next post.

MRT_CAI_Template.pdf
Above is a PDF template for the rubber sheet. Print, align the pages, tape the pages together, then cut the template from the assembled pages. Test fit the template, make any necessary changes, trace onto the sheet of rubber and cut it out. Final fit and trim as necessary, and...
Enjoy

Mr.T

Intake air temperature: 129.2 vs 113.0 == 16.2 degrees cooler
Intake manifold air temperature: 141.8 vs 127.4 == 14.4 degrees cooler

These data logs are from two full throttle runs on a hot day, as identical as possible and about 15 minutes apart. The numbers in the upper right corner are data captured at the vertical timeline (5078 and 5028 RPM respectively).

OEM (no baffle)


Rubber Baffle CAI mod


Cheers

Mark Doiron

What was ambient air temperature? I monitor my manifold temperature, and it typically runs about 10-15° higher than ambient. Not actually certain, though, what it might read in the really cold temps we're experiencing recently, LOL. Anyway, I have an AEV snorkel and have always wished I had pre-snorkel measurements to compare--would be strong evidence that a snorkel is a "real" CAI.

Biginboca

I have the AEV snorkel also and feel like I gained nothing, maybe even lost a bit of power. I also tried the viper throttle body mod for a year and only gained an occasional yellow lightning bolt.

So I gave up on performance mods. I'll take weak and reliable over strong and temperamental lol

karls10jk

The 3.6 does something similar and I was curious about it until I joined the snorkel club. Their rubber gasket is an extension from the air intake opening and it touches the underside of the hood to pull (presumably) cooler air.

Neat idea!

ronjenx

This seems to be a move in the right direction.

Regarding the "cold air" intake kits most people install that do away with the stock air intake box/filter...

Do the kits have a port on them to connect the pcv hose that runs from the stock box to the passenger's side valve cover?

Mr.T

Unfortunately I don't know -- It was summer of 2012 and my best guess is ambient was somewhere in the 90's. I'd bet a snorkel is even a bit colder than my setup, but perhaps slightly more restrictive to airflow.

Mark Doiron

Definitely more restrictive. And I just drove to church and back and the ambient was 36° and intake was 43°.

Mark Doiron

Yeah, the snorkel isn't going to give you horsepower. But, it is a performance mod, just depends on what kind of performance you need ...

Mr.T

Thanks Ron.

Regarding aftermarket intake kits and PCV, at Quadratec there's a couple pics showing a PCV hose connection Volant 17638 CAI Cool Air Intake for 07-11 Jeep® Wrangler & Wrangler Unlimited JK with 3.8L 6 Cylinder Engine | Quadratec -- Suspect most/all would include that.