Okay after the hood went on, I fabed up an intake tube that reached over from the TB to the cooler passenger side of the engine compartment, and then tried to figure out how to fit and mount a box in there right against the passenger side of the cowl so that I would simultaneously get cool intake air (by sealing the filter against the opening), and the driver side cowl opening would cool the hot side of the engine bay. I also got a intake temp gauge off Ebay for a steal:
And mounted it in various areas under hood and in my intake pipe right above the throttle body so that I could Geek out even more
I taped the cowl opening closed to get a base line of under hood and intake temps.
Base line (no cowl opening)
Intake: 146* to 155*
Under hood 168*
Intake temps was averaged while driving at 55-60MPH, under hood taken with laser thermometer averaged from 6 different locations immediately after stopping, the day was 90* to 92*.
I fab'ed the intake up using some 2.5" mandrel bent tubing, one U bend was plenty, I basically eyeballed it and tack welded it
And after pulling it off and finishing the welds I powder coated it with a good old HF coating gun. I ran with it like this for a while. Before the air box.
Intake temps in this configuration this were much lower than with a cone filter and no cowl opening. and even lower than the filter on the hot side of the engine bay. But still significantly hotter than ambient. which prompted me to make a heat shield, which turned into a completely sealed air box.
Making an air box is not nearly as simple as it sounds at first, you have to fit it in there. It needs to seal against the hood, and it needs to not ruin access to the dip sticks, or grind bare spots on your wires. First I bent the trans dipstick down to the oil
Then moved the washer jug over closer to the fender:
The way I went about getting the right size and shape was mocking it up with a card board box cutting strips where I felt it would touch, I then closed the hood, bending the cardboard which told me how much to trim off until it was in the ball park:
here the basic shape has taken shape, I had some door seal from the rear hatch of a parts Cherokee that would compress against the hood, so I cut the box down until nothing touched, and then cut another inch or so for the rubber seal.
Then I used the box as templates to cut the sheet metal out of; and tacked it together.
Then I spent a few hours mocking it into place and admiring my own handywork and then grinding where I needed clearance.
The weather seal is perfect, it took hours to get everything to fit just right. Not shown is a rubber bumper used to stand it off the valve cover and another one on the little shelf along the firewall to stand off that. I got the rubber parts from a stock Mustang intake's factory vibration stand offs. The hood, the filter, the "snorkle", and the silicone couplers holding the tubing in place were all that was needed to keep it in place. Let me assure you the fit was tight, not perfect but not much underhood air was reaching this filter:
Here's the coated air box:
The proof is in the air temps... After the box they were only 6* degrees warmer than ambient like clockwork, if it was 90* out the intake temps read 96* very steady (plus or minus a degree or two at most). This is approximately 60* cooler than the "best case" underhood intake with the filter on the "cool" side of the compartment with a non-vented hood. Worst case, sucking air from next to the headers by deleting the factory air box and putting a cone filter there would be even more drastic. I'm betting 80 to 100*. The average underhood temps dropped 11* which if you think about it is a lot considering everything is still running at the same temps emitting the same heat levels.
The best benefit was that my mild pinging (on hot days running anything but premium) went away even on the hottest days even with mid grade. The cooler air should be worth from 10 to 15 added hp and torque across the power band. If you went from a paper filter to a K&N style with this setup it should be worth 20hp on a normal 4.0.
The intake also sounded down right cool. Being sealed to outside air means no muffling, and the tube and box resonated nicely when you got into it, sounding quite nice if you like that sort of thing... Let me tell you the Cherokee smoked a late model SS Impala a few days after the mod from light to light, the teenagers in the Impala didn't take it seriously the first light, when I took off at WOT wanting to hear the new sounds. but they still got left behind on the second try. There's nothing like peak torque off idle, especially when it's nearing 300ft pounds, I'm sure they would have caught up in a 1/4 but then that's the beauty of low RPM torque in a street machine it will leave a lot of more powerful cars behind for long enough to have an unashamed smile on your face when they catch up to you
