Thread: Bonnet Vent

Here is mine.
Look Familar.

It looks the part I have a pair of RRS vents for mine but still haven't put them in yet.
Tony

they look real good, whats a set of D3 or RRS vents cost out of interest?

buzz66, do the vents actually help cooling much or are they just for bling
just wondering too what that bar is fixed to your wing with metal straps and that, what lookslike a small brass radiator?

Originally Posted by Brian Hjelm

If you have a major overheating problem and your existing cooling system is in good condition, & the engine is in tune, then only three things will help. A greatly increased radiator frontal area, a thicker radiator core with more rows of tubes unless you get so thick you are restricting air flow through the fins (ask M.A.N. trucks about this), or greatly increased air flow through the fins. Hope your little vents work.

Have to concour here, a rover V8 in a rover once had the capability to stay cool, now it doesn't, hence something is wrong, until you find what it is, you merely trying to mask the problem

Or just pull it out and put something worthwhile in

Quite a bit of hot air comes out of the vent when stationary and idling.

My radiator core is quite new, but of dubious quality. The radiator man that fitted it wasn't very impressed with it. Not many FPI, but it was free (warranty core).

I think there isn't much doubt that my 3.5 is pretty crook. Other threads are proof of that.

I have no engine cooling issues with my D1 but I did some testing of engine bay temperatures using a digital readout in the cab with a sensitive type K thermocouple probe.

I found movement of the vehicle quickly allowed heat to escape out of the bottom of engine bay as it is designed to do. However stopped in traffic for long periods or during heavy slow going say towing in deep sand temperatures the engine bay hit 80 degrees C with a bullet and got higher close 100 degrees C when ambient temperature is high. Temperature was a lot lower in vicinity of viscous fan but higher at the rear and top of engine bay. Alternator windings, hoses and electric looms are frying from this sort of temperature.

This was my solution. It is a bonnet mounted “extractor” fan. It is connected to a Davies Craig Thermal Switch set at 75 degrees C to cut in and cuts out at around 60 degrees automatically. It is also set up so power is maintained to the fan for 3 minutes after ignition is turned off using a kit timer from Jaycar.

Bonnet Vents

The stock vent while very well designed looks like a toilet exhaust sitting on my D1 bonnet so I manufactured my own out of fiberglass and some alloy mesh and modeled on a Hilux vent.

Location and vent design is such that I have no issues with heat transfer to interior cabin vents. I designed the vent so at speed it maintained pressure at the top of the engine bay and so not diminish the natural flow out the bottom of engine bay that no fan or vent can replicate.

Now THAT is what I call dedicated.
Only thing against I can see is that you would have ram effect while moving which may reduce the amount of air through the rad, due to a smaller pressure drop.
I had a Porsche 924 turbo at one stage and it had a NACA duct near the turbo. Took me a while and some heat haze coming out to figure that it was to allow the heat soak out after stopping. Because it was recessed it would not have drawn much air while moving. Supported by below.

NACA duct - Wikipedia, the free encyclopedia

Regards Philip A

".......you would have ram effect while moving....."

PhilipA I have yet to do a pressure test but I dont think any ram at all (other than just a fraction +) on account of the waterproofing design attached to the vent.

The extracted air has to come up and then down under the skirt to the outside OR water/introduced air would have to travel in up over and down into the fan. If you look at pic 1 you will see traditional ram opening has been reduced in height with a baffle on the top to both waterproof and stop the ram effect you speak of. Plus you will see it is located at rear of engine bay where the heat is and to not impede pressure differential for radiator air flow

I am on lookout for some D3 vents as BJ has done