Hello all. First post.

Background...bought a '98 Disco a little less than a year ago (solid shape; good, but not perfect ~ 200K miles) and have been slowly going about building/rebuilding and making a few changes. Big fan of it. Redid the suspension with a 2" terrafirma lift, swapped out the radio, and have been taking steps to address an overheating incident (singular thankfully). Whilst under the hood, I couldn't help but notice the hilariously awkward air box design with the tiny trumpet shaped inlet and decided that by god I could do better...and on the cheapness. Aside from the small diameter of the intake, I am not a fan of the fact that it terminates so far inside the engine bay just pointing straight into a wall and can suck up so much heat. So here goes.

1.) Started off with preliminary temperature measurements for a basis of later comparison. See below.
a. Hood down, ventilation off, standing in the driveway after extended warming
58 degrees F outside
Air intake temp was measuring at 156.2 degrees F
*Temps measured by a plug in tool that talks to my phone....because I freakin' could!

b. Driving 35 mph around town in traffic running some errands
62 degrees F outside
Air intake temp was measuring at 143.6

2. Went home and pulled the air box and chopped off the trumpet intake flush with the air box exterior.

3. Outlined a new opening for a 3" intake pipe and started chopping. Unfortunately, I didn't have the right size of hole saw for this job, so I made due with a jig saw. Cut some starter cuts to the outer perimeter of the circle and then made my way around. Not my greatest cut, so there will be no photographic evidence at this time.

4. Inserted a 45 degree 3" pvc elbow into the new opening and mocked the box up in place so that I could rotate the elbow toward the opening just behind the driver side headlight. Looking to suck in fresh air instead of preheated.

5. From there, I went about a bit of trial and error putting a straight pipe into the elbow that terminated at the opening or as close as I could get in a reasonable amount of time. Cut the end to make the whole thing sit into place right and pull air from outside of the engine compartment as best I could.

6. Sealed all of the remaining openings in the air box from my earlier cutting efforts with everything angled and set up as I wanted. Note: Used a white sealant here as it is what I had and I like the contrast in filling the gaps in the new hole, but use whatever you want if you decide to try.

7. Reinstalled everything and repeated earlier testing as closely as I could. Here are the results:
a. Hood down, ventilation off, sitting in the drive way after a prolonged warmup
Temperature outside was 65 degrees F
Air intake was at 152.6 degrees F
This represents a less than four degree change under these conditions and did not initial cause much excitement. Thankfully, I don't drive sitting still.

b. Driving 35 mph in traffic around town while running some more errands...there are always more.
Temperature outside was 62 degrees F
Air intake temp measured in at 134.6 degrees F at the time of taking the measurement.
Result: A nine degree temperature drop in the intake temperature at 35 mph in town.

Verdict: Going to call this a mild win. First, it did no harm. Further, the mod was dirt cheap (like $11 bucks) and a good way to kill a beer in the afternoon. Lastly, my attempt at supporting evidence appears to suggest an improvement, though I'm not sure what all the error bars on these measurements would work out.

Additional detail. Had the beastie on the highway this weekend and it provided at least some hint at additional evidence of success. At 60 mph, intake temperature was coming in under 100 degrees...saw it drop as low as 87 degrees at one point, so I am clearly pulling some fresh air from outside of the compartment. Unfortunately, I didn't think to capture equivalent values before the mod and can't make a comparison here.

Just in case I need to say it.... try at your own risk, but food for thought. If you do try it, watch placement of the new piping hole into the side of the air box. Too high a placement and you'll have extra trimming work on the new piping to get your air filter back in. Left that little detail out above.

Next, going to swap the clutch fan. Been slowing working on all suspects in that overheating incident I mentioned, but nobody needs to see another fan clutch swap.

 

Interesting! I’ve always kind of wondered why the intake “trumpet” was so small and pointed in to a cramped corner. But I figured the engineers had their reasons…
Hope it works well for you in the long run!