Bonnet Scoops

[landrovermick]

I was talking to a mate last week who told me something interesteing.

The tale goes like this :

When a Range Rover (and for that fact i guess a Discovery) drives along, the engine bay area pressurises. This is caused by the amount of air flowing under and over the vehicle.

My mate tells me that by placing a scoop on the bonnet area of the vehicle we have got the problem half solved..... but - remeber when i think it was ferno posted , have to go get my A9X scoop for my bonnet????? that is the thing to do - The A9X scoop runs backwards, that is with the opening towards the windscreen, now im not saying go out and buy one of those big buggers , but it might make sense bearing this theory in mind to place the scoop on a rangie - disco backwards.....

Also another cheap effective way to scoop the bonnet is by using the side vents on the "C" pillar of a rangie and grafting them into the side rear of the bonnet.

This scoop running backwards lets the built up air pressure escape with the air that is flowing over the roof.

just food for thought ....

Oh also, and check me if im wrong, dont some of the vehicles that have scoops on the bonnet facing front have the scoop directed to the intercooler so as to increase cooling?

Regards
Mick

[Rovernaut]

Another thought on the subject.
When wading the engine bay as a big air pocket and keeps water out. If a scoop was added then the trapped air pocket would not exist.
:roll:

[landrovermick]

true - I guess its battle of soft versus hard roaders

[one_iota]

I think that the Patrol 3.0 Tdi has the bonnet scoop for a top mounted Intercooler as opposed to the LR Tdi front mounted IC.

I was`wondering though why having a pressurised engine compartment was a problem requiring some relief. :?

[landrovermick]

Basically its not a problem, though some of us do complain about heat levels.

[one_iota]

Forgive my being thick.

Diesel Engines I guess don't suffer from vapour lock and all that. Only a raft of other things.

It has triggered a memory of a forum discussion elsewhere which I will try to retrieve for what it may be worth.

[Mick-Kelly]

Watching with interest

[one_iota]

Nothing of substance found whilst searching apart from Jeepers suggesting that bonnet scoops look cool.

Some thoughts though:

Engine compartment heat can't be good for the battery(ies).

I'm not sure where the air in a v8 is drawn from but if it comes from a hot engine compartment then the air is less dense and therefore carries less oxygen for volume. But it is "pressurised". If the compartment was depressurised then maybe the addition of a snorkel would assist? Cooler pressurised air.

[duff]

I think you will find the A9-X scoop faced rear wards to actually draw clean cool air in down into the engine bay, away from the high pressure area that forms in front of most vehicles windscreens( same theory why most heaters draw from that area). This not only sourced cool air but it reduced the drag from the high in front of the sceen This scoop fed the carbies and from what I understand the excess air was drawn down over the hot extractors and away and rearwards(this also helped prevent the high engine bay temps) via the vaccuum formed under and behind the vehicle by its dams at the front lower parts of the vehicle.
To feed the carbies from a forward facing scoop you pressurise the engine bay and start to loose airflow capabilities for radiators etc.(unless you have sealed delivery to the carbies only)
If you place the vents rearward facing but on the outer edges and slightly forward of the screen you will start to draw up and out but the opposite will occur in the centre and close to the screen.(on most cars and especially bricks like landrovers)

Get some light ribbon and tape it every two inches acrss your bonnett and youll see how the air is flowing
Have a close look at a SD1 Rover they have used the theory very well if you look close at and under the bonnet.

[fernockulated]

:roll: hmmmmmm.........very interesting, and much food for thought!!! oh, and by the way , it was a FORD gs bonnet scoop ,not an A9X, so i dunno where that came from????anyway i have aquired an old fridge vent cover from an old derelict caravan and was considering grafting some of it onto the bonnet of my series , now i dont know whether to face them forwards or backwards?????? :? :? :? :?

[one_iota]

Ferno,

Bugger the theory just do whatever looks or feels good....post photos...

did you say fridge grilles 8O

[bigbugga]

Fridge Grill???



Will that make it look even COOLER 8O

[fernockulated]

style_emoticons/<#EMO_DIR#>/laugh.gif the gs scoops where tooo big to graft without probs, and the fridge vent is the panel on the outside of a caravan, best way to describe it would be that they look like fish gills, a bit like the hoon heads used to do in the fifties and sixties, but am still toying with the idea , maybe if i could get another old bonnet in case i stuff it up??????? :? :roll:

[bigbugga]

Ferno please work out a way to find a proper scoop.

Dont use the fridge grill.

Or if you do buy a huge block of cheese.


Then at least you can always use it as a cheese grater.

[oildripa]

I have a Nissan GQ bonnet scoop on my RR with side stainless steel marine vents on decker panel .Also 50mm body lift Over the last year and a half this is what i have noticed .
1 Foot well is cool to the touch in summer after driving some 135 km but the side vents are extremly hot to touch .
2 With a mechanical temp gauge fitted engine temp has NOT altered
3 Air cond works 500% better
4 Water crossings are little worry as tarp covers the top scoop with the aid of an ocky strap as with the radiator - I have no idea on the "air pocket" talked of as when fording the water passes straight thru theradiator and swamps everything thats why the viscous fan belt should be removed unles of course thermo fans are fitted .
5 Noted a big difference in the internal hat when body lift was done , this with the scoop forces inducted air at speed down the fire wall , when standing idle you can place your fingers in front of it and feel the air being sucked in simular to the feeling of sticking your hand behind a fan .
It's really just a case of horses for courses , i have had guys blown away at how well it works and race off to do it , I also have had guys tell me im an idiot cause you should leave them standard as Solihul intended .
Works for me style_emoticons/<#EMO_DIR#>/laugh.gif

[bigbugga]

Hey oildripa,
Nice sounding Rangie you have there.

Seeing this is your first post let me welcome you to AULRO.

[duff]

Oildrippa,
And all, I hope you don't think Im against bonnet scoops, my disco"s bonnet is too hot to touch sometimes (litterally), I wish I could fit Heat extraction vents to the outside edges of mine. Hell I fitted them to my SD1 to further encourage the flow thru cooling air when I fitted my hybrid P76 block, rover headed, 4.6 lt, 11.5:1 engine(generated just a little heat) so I encourage people to come up with good solutions, , to improve the theories developed for british weather, I'll happilly copy them if they work.
I was just trying to point out that you can actually achieve the oppisite to what you want (like fitting an A9-X style intake to let air flow out over the windscreen).
And it can be dangerous in some cases, if you do manage to get dirty air flowing up and over your windscreen from the centre of your bonnet on a rangie or disco, then you are going to be dumping poisens straight into the cabin via the fresh air intake for the cabin.......BUT YES I agree get rid of as much under bonnet temp as you can its not good for anything. Especially when you are offroading for real ...you are working the girl hard and you dont have aerodynamics working for you either,,,so bloody big holes somewhere at the back of the bonnet can only help the fan flow better and let latent heat escape IMHO..

[seashells]

Interesting thread

As the td5 in my series 1 disco nearly touches the botom of the lid
I am considering fitting a nissan gu scoop (facing the front) to help
keep the engine etc cooler, any ideas.

td5/v8

[bigbugga]

The nissan scoop is one of the most used units, even on tojo's and a few other 4WD's.

[Gidget]

there are some pics of mine being in(gu scoop into defender), in the gallery ,Page 6 under gidget

[LRHybrid100]

G'day Guys - I've updated my original posting on bonnet scoops:

http://www.aulro.com/modules.php?name=Foru...&t=556&start=30 (http://www.aulro.com/modules.php?name=Forums&file=viewtopic&t=556&start=30)

LRH