Bonnet vents

A simple manometer will confirm any thougthts about vent placement.
Manometer；an air pressure reading device.
DIY. Grab a soft drink bottle and half fill it with water and some food colouring
Get 3m of clear plastic tubing about 3-4mm ID.
A bit of stick taped to one end of the tube with cm marked on it then stick the tube/stick into the bottle of water.
Tape the free end of the tube in the location you want to test. Tape it perpindicular to the direction of travel to avoid false readings.
Go for a drive at highway speeds to get a +or-ive reading.
Use a helper to take readings so you can just drive. Be safe.
For heat extraction move it around until you find the lowest reading.

As for water ingress, it is a land rover designed to drive through water isnt it?
If you are really worried about a few drops of water, then place a flat 'S' shaped water trap under the vent.
Even a Defender has had some thougt go into heat transfer. Why is there a heat shield on the turbo?
The hot air is drawn down the back of the engine at road speed into the low pressure zone under the car.

Wool pile test is another easy way. It has been done by a member here with a 2 inch lifted defender. That and his knowledge helped me with my vent placement. Avoiding bonnet area. Top of guard would be ok for intake, but as has been discussed many many times, air is already damming up in a stock defender engine bay. If you want more flow through your ic and rad you need to get it out first.

I was also able to confirm side guard vent working on another mates defender at speeds from 0-70km/h.

My engine temps on my vdo gauge also confirmed it when I had cut it out.

By side guard, i assume we are talking into wheel arch area?

and if i was concerned about temps, my first action would be to wrap the exhaust prior to chopping holes in bodywork, IMHO.

Exhaust wrap is a good idea.

You do not have to 'chop holes' in the bodywork, over the years defenders have come out the factory with apertures left and right. You can get these panels from scrap, order in new aluminium or even plastic panels. With your air intake redirected to one of the top wing vents or a southdown snorkel you can have a 'factory' side vent on each side, improving the flow of air through your rad and out of your bay. This is the way I'm going ..... eventually..... or maybe never :wheelchair:

Quote:

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Originally Posted by joel0407

Some manufactures go all out to design engine bays and the air flow through them.
...
Vehicle aerodynamics are bloody complicated.

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I don't think the 'a' word has been used on the Defender part of the forum before :p

I don't think Land Rover put much effort in at all designing the Defender, just took existing bits, added a stripe and voila.

Jeff

:rocket:

Quote:

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Originally Posted by mudder110

hi all quick question probably been asked before, ive all ways let my 300tdi idle for about two or three minutes.before I drive off.
longer in winter its got 355,000ks up uses no oil, am going around Australia next year
is letting it idle to warm a bad idea? was contemplating a rebuild did replace the head gasket at 220,000 advice appreciated cheers

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I've been doing that for 16 years and at almost 470,000k's mine doesn't use oil or coolant,the nay sayers have been saying it'll glaze the bore but I think my motor knows best. Pat

Quote:

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Originally Posted by mudder110

hi all quick question probably been asked before, ive all ways let my 300tdi idle for about two or three minutes.before I drive off.
longer in winter its got 355,000ks up uses no oil, am going around Australia next year
is letting it idle to warm a bad idea? was contemplating a rebuild did replace the head gasket at 220,000 advice appreciated cheers

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here's a link to a thread discussing the problems with letting diesels idle for too long - apparently it causes the bore to glaze.

http://www.aulro.com/afvb/general-ch...rn-diesel.html

haha - posted this before I saw your answer Pat :)

Quote:

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Originally Posted by Tombie

Look at the gap between bonnet and guards - no need for vents on there at all - especially on a diesel..

However, if you like the look that's your prerogative.

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I've wool tuff tested a Defender and the air flows from outside to in at that point.

Pulled the blanking plate from the top of the guard, and again, the air is turbulent and reversion is happening, it's pretty messy.
The underbonnet area of the Defender is IMO really poor for air flow, indicated by the need for a functioning fan at speed !

In most cars the best spot for bonnet vents are just behind the radiator in a place of laminar flow.
The base of the windscreen is a no no, as its a high pressure area and pushes air back into the engine bay.
The best spot for a Deefer, especially with the windscreen vents is where Serg has his on the guards.
It works.

Hey TheStig, if the vents make you happy then that's all that matters. If people are worried about air flow and as Jeff above said, the "a" word (aerodynamics) then they've bought the wrong car and in a really big way. Anything you can do to bling up an older Defender can't be that bad (makes them look less tired, keeps us enthusiastic and that helps us keep the car on the road) - I've wondered about getting some of those late model Disco side vents on my old girl just to tart it up a bit

I must confess, i have cast an eye over these ............

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