Deep water can spell death to an off-roader, as I demonstrated when I blew up my Jeep’s inline six in a mud puddle about a year ago. But there are ways to design vehicles to ford through Davey Jones’s locker, and Land Rover’s solution on the 2017 Land Rover Discovery is a brilliant one.
The basic idea behind Land Rover’s intake is to force air through a tortuous path, so that any moisture will stick to the walls of the labyrinth instead of passing through and into the cylinders.
The air intake path all starts at the crease between the hood and both the fender and headlight. That gap, which Land Rover ensures is a minimum of six millimeters, pulls air into the plenum shown below:
Once air has made it into that plenum area, it gets sucked in through a hole in the hood inner panel.
Here’s a closer look at that hole:
Once air has made it to the gap between the hood’s inner and outer panels, it snakes through a labyrinth; the moisture in that intake air is separated out as its inertia sends it splashing and “sticking” against the walls of the tortuous path as it tries changing direction.
After being sucked through the labyrinth, the intake air exits through another hole in the hood inner panel near the cowl:
From there, the intake air is drawn into an aperture in the inner fender that Land Rover refers to as “The Rabbit Hole.” It’s worth noting that the Range Rover and Range Rover Sport also have similar intake designs that use horizontal “Queen Mary’s Stacks.” Land Rover says the fender aperture is vertical on the Discovery because of the vehicle’s barreled, angular hood line.
Once the air has entered the Rabbit Hole, it goes through another water-separating device called a water trap (which works similarly to the hood’s labyrinth), and then through an NVH trap, which reduces intake noise via either baffles or resonators. Here’s a little CAD drawing showing where that fender Rabbit Hole leads.
From there, air gets sucked through the air filter, in through the clean air tube, and into the engine.
As you can in the picture above, the supercharged V6 gas models have intake ducts on both sides of the engine bay; for these vehicles, the intake system mentioned above is mirrored on both sides, meaning you’ve got the plenum and holes in the hood (which lead to and come from the labyrinth) on the left side as well:
And, of course, you’ve also got the Rabbit hole over there, too:
One of the more interesting parts of this design, and one that I’m still not entirely sure I understand, is the seals. For example, if you look at the plenum area where the hood sucks its air, you begin to wonder: Why would the air bother going through the hood (and its larger pressure drop thanks to the labyrinth), instead of just straight down the rabbit hole?
The answer is that there are seals on the hood separating the rabbit hole from the plenum area:
Those seals are why air goes through the hood’s tortuous path instead of straight from the plenum to the Rabbit Hole. Still, if you look at the picture above, you don’t see a seal keeping air from coming over top of the fender and straight down the Rabbit Hole, forgoing the hood labyrinth entirely.
Alex Heslop, the Discovery’s chief engineer, admitted that air can indeed come through here, but since that’s at the back of the hood—very high off the ground—it’s really not much of a concern for wading. So you’ve essentially got a secondary air path at the back of the hood in addition to the one that draws from the hood labyrinth and plenum.
It’s a fascinating solution that allows the new Discovery to ford a very impressive 900 millimeters (three feet) of water, and Heslop told me the Disco can actually wade through over a meter. At that point, he admits, the rear tires begin to start floating unless all seven passengers are weighing the vehicle down.
I can’t wait to take one of these through that puddle that destroyed my Jeep. I need revenge.