Bonnet vents. Who uses them?

[TriPolar]

After my run on aussie day i found temps to be so hot under the lid going through mud, slow points and winching mates out i couldnt even touch the bonnet. Worried i may cook something i considered bonnet vents.

Now looking for real vents, they are bloody expensive. So what are your thoughts on these bad boys?

AIR Vent Grille Stainless Steel 316 Marine Grade 228 X 127mm | eBay (http://www.ebay.com.au/itm/Air-Vent-Grille-Stainless-Steel-316-Marine-Grade-228-x-127mm-/151145833862?pt=AU_Building_Materials&hash=item2330fe6586)

[SouthOz]

I havnt looked if its suitable on a Disco but in days gone by a couple of washers under the hinges would do the trick. Quick, cheap and reversible.

Dave

[TriPolar]

Would not be bad for low speed, but have a reverse effect at high speed as that is a high pressure area.

Just looking for cheap options to be honest, but still look good. Just could not get over how hot it gets.

[TriPolar]

Hood louvers for cooler engine, lower temps (http://www.rocky-road.com/louver.html)

Thats not a bad look, but at $155 plus postage im still uming and aring.

[blitz]

yep thought about it on and off for years - still haven't done it though :o

[aussearcher]

I'm in the process of installing some similar to the ones you have found on eBay - got them from Bunnings. The bonnet they are going into has been badly hail damaged so I don't mind if I botch it. I'm intending to paint it matt black which should serve to hide any mistakes! I'm aiming to instal two, on the line of the headers towards the rear (on the basis that with the airflow through the engine bay this will be more effective than putting them straight above.)

[TriPolar]

Sounds good. But what research has shown me is that you will only want them from behind the rad to a max of 3/4 down the bonnet.

As the rear is a high pressure system it will mess with airflow at higher speeds. Just have search about bonnet vents and locations first, as im not the technical at explaining stuff.

[aussearcher]

Thanks! This actually makes sense, as I think a lot of under bonnet heat is actually from the radiator rather than the engine, and getting the hot air flow out early will make a lot of difference. Also your comments on high pressure zones - I've seen some articles on wind tunnel tests that showed outside air actually flowing IN to vents that are supposedly there to let inside air OUT.

[michaelp]

What about manually controlling your thermo fan.

I fitted a turbo timer to my fan to cool the engine bay after shut down but it can be manually operated.

[TriPolar]

I did think about the thermo on a switch, but if im belly deep, that air has no where to go, if ts in water, ill be pushing water in. Vents may be the simplest method, but its the safest thing to do.
I could do a combination of the 2 but i still dont want to do the thermo unless i really have to. At least if im chassis deep air can still escape.