Thread: Will a bonnet scoop reduce heat in the engine bay?

Has anyone given any thought as to how adding a scoop will affect water ingress during a water crossing?

Originally Posted by trout1105

Has anyone given any thought as to how adding a scoop will affect water ingress during a water crossing?

Good point, I think that may be covered above in this thread, non high pressure water is usually not too much of a problem if you have a snorkel.
Diesel no problem, coil pack v8s no problem.

V8 with dizzy, convert to coil packs (kits are avail) or carry a car bra if you know your going to be doing big over bonnet crossings (which you need to fit anyway if you do not have selectable thermos)

See attached from same guy just so Defenders dont feel left out

Very early on and just a rough mock up.

Originally Posted by trout1105

Has anyone given any thought as to how adding a scoop will affect water ingress during a water crossing?

I personally can't see why that would be 'an issue' TBH.

if the engine bay was hermetically sealed, maybe a bonnet scoop, it could pose a cautionary second thought.
But as it's completely unsealed from almost every angle .. water will get in everywhere and fan will distribute it everywhere else in a fairly violent and random manner anyhow.

So if you're in it, all the way up to an over bonnet situation, the laws of physics come into play and water will be up to the bonnet from underneath, the front .... and every other nook and cranny.

I am thinking that with a scoop or vents fitted to the bonnet the water will rise inside the engine bay as you go through a deep water crossing far easier than with a standard bonnet.

Originally Posted by trout1105

I am thinking that with a scoop or vents fitted to the bonnet the water will rise inside the engine bay as you go through a deep water crossing far easier than with a standard bonnet.

Physically, I can see why this wouldn't be the case scooped or not.

When you consider that the scoop will be miniscule by comparison to the enormous opening under the engine, between the wheels/arches, the fact that a scoop is there will be irrelevant.

If you cam crashing down into a body of water from a height, there would be a delay in how quickly the water comes up from underneath into the engine bay, but you don't drive into deep water quickly enough for the pressure difference between water and waterless engine bay .. fo rit to not fill up as you enter the water with trepidation!

Think of the empty glass situation, immersed into a sink full of water. You place the glass into the water on it's side, it fills with water. Nothing you can do to stop that, no matter how much venting it has on the top most side above the waterline .. until it is finally fully submerged.
Cut the glass in half(ie. open front and open bottom side now) .. and you have a typical engine bay.

Unless you hit the water a huge rate of knots so as to not allow the water to fill the engine bay .. and out again before it has a chance to fill .. the engine bay will always be full of water up to the level of the water line.

The radiators will act as a buffer to water as you enter, but that would be a very limited effect and you'd probably need a rate of speed that would be close to causing quite a sever impact on the front end.
But that's not where the water will enter the engine bay! between the engine and axles is a whole lot of nothing. ie. nothing to stop water filling as you submerge. as water enters and air has to escape(ie,. imagine that glass situation above, now turned upside down!), air easily escapes from the grille area, no matter how hard the fan will be forcing it back in.

So imagine the inverted glass in the sink full of water, as you try to get it under the water, the trapped air will give it buoyancy, so it will try to lift up and tip over. The lifting motion is the point of comment here.
If the engine bay didn't fill with water, it'd act as a buoy on the front of the car, and lift the front of the vehicle upwards, possibly to the point of no steering.
As we said before .. only a hermetically sealed vessel could do that(ie. boat!).

Imagine the car fully submerging into water(like a submarine) .. the front of the car will always dive, and the interior compartment will try to float(as long as windows are all closed etc).
Engine bay can't float, it's not sealed. will always fill with water up to the water line if sane speeds are used.

(of course you then get those crazy folks with 1000hp 4WD trucks that drive on water too tho! )

Originally Posted by trout1105

I am thinking that with a scoop or vents fitted to the bonnet the water will rise inside the engine bay as you go through a deep water crossing far easier than with a standard bonnet.

This is true, on sealed bonnets you would loose the air bubble effect

How are you directing the flow from the scoop to under the bonnet into the engine bay and out the sides ?

Originally Posted by Morry948

How are you directing the flow from the scoop to under the bonnet into the engine bay and out the sides ?

Position of holes under scoop (towards rear and each side of engine, the air coming through those holes to escapes next to engine following exhuast, and out rear of inner wheel arch joining the air coming from rad thermos and also help direct and force that air out.