Relieving Engine Bay temps - ventilation

[FNQGU]

For those who also might suffer from overheating, I found this excellent little article on Viscous Fan couplings and the fact that at least for Toyota, there is often not sufficient silicon fluid in the hub from factory. This leads to a less than efficient fan and thus overheating sometimes.

http://neuralfibre.com/paul/4wd/tuni...ous-fan-clutch

It also shows a step-through on how to add fluid to rectify the problem and increase efficiency, plus there is an interesting comment suggesting that vehicle momentum is not what forces air through the radiator, it is the radiator fan, so efficiency here is super important.

I learned something anyway.

[outback]

FNQGU:
Did you ever get anything back from Hood Louvre, (USA)?

As for "nteresting comment suggesting that vehicle momentum is not what forces air through the radiator", I have some doubts on this. At certain speeds yes forward velocity, hence ram effect is minimal, but at higher speeds it may have a significant effect. Possibly though inhibited by the fan, assuming the fan works correctly. A floating, non working fan though will not effect this ram effect so it can work. What that velocity is I can like others but guess.


In my vehicle I had 2l of coolant missing from the radiator. The temp gague sat on mid point so long as I sat on anything above 65- 70km/h Anything under that it hit top range plus = overheating. This would confirm a concept of ram effect. Also suspect Vicious clutch on fan stuffed so not a real working fan.

I was just advised to get a nice big wide scoop and only use half of the scoop with the Intercooler, and the other half to simply pump air through the engine bay and out the bottom. Or to fit a second scoop for the same reason.

As The evil one said rubbish. You need to drag air in via the radiator and out via the engine bay. be that bottom/ and via vents in the bonnet. The air movement from the intercooler causes some airflow disturbance as far as hydralic, non lamina flow goes so adding more via a bonnet stop will cause poor air flow.

In reality the intercooler air should come in, pass the intercooler and be vented by a secondary duct to the outside not dumped into the engine bay. Not seen this yet.

In my opinion and based on airflow the intercooler can cause added issues as much as all the additional things added to the engine bay. Simply poor air flow.

[jet]

Its all about getting hot air out
The deflector under radiator creates low pressure under engine bay when driving and hot air is sucked out the bottom
Damage this or lift vehicle etc all has potential to stuff this up
More openings in top could also upset this fairly sensitive plan.

Elect Fans under IC actually slow air down at higher speed but slow stuff they can help for sure.

With the mix of legal restrictions on scoops and rear facing openings makes it harder to fix.
Despite it being a pain to live with, increasing size of deflector is maybe the simplest upgrade to air flow
You also need to ensure incoming air isnt bypassing radiator.

[outback]

Its all about getting hot air out
The deflector under radiator creates low pressure under engine bay when driving and hot air is sucked out the bottom
Damage this or lift vehicle etc all has potential to stuff this up
More openings in top could also upset this fairly sensitive plan.

Elect Fans under IC actually slow air down at higher speed but slow stuff they can help for sure.

With the mix of legal restrictions on scoops and rear facing openings makes it harder to fix.
Despite it being a pain to live with, increasing size of deflector is maybe the simplest upgrade to air flow
You also need to ensure incoming air isnt bypassing radiator.

As far as the sensitive air flow in the engine bay is concerned its stuffed the moment you add the second battery, air compress or and anything else like these items.

Air flow is sold defined by air pressure here and with these added items some of the bay will not get the required air movement.

As for air flow at what velocity, hence ram effect on the IC does the electronic fan cease to be effective?
At what velocity does the radiator fane and its cooling become part aided by ram effect also?

Even without the electric fan the air flow through the IC will cause pressure problems with the air via the radiator fan at certain speeds,so intact the air flow via the IC can be reduced.

Anyway unless Mr Ni$$an releases his air flow diagrams and flow values it becomes a bit semantic.
As i also said add more gear to that engine bay and Mr Ni$$an's calculation fall out the window.

[FNQGU]

Yes, I agree that the additions of accessories and batteries must change the amount of room in the engine bay available for air to circulate, and there isn't much there to start with. Hood Louvres say that their testing has shown that the vents work at both high and low speeds as the pressure inside the engine bay is generally higher than the pressure at the entrance to the vents (?). Of note - I was not able to get real test data from them on this to prove what they are saying is a fact as opposed to just supporting their sales pitch, but they insisted that the fact many speedway and race-cars successfully run their hood vents, should be proof enough. The High pressure zones on the Patrols seem to be up against the bottom of the windscreen, on the rise in front of the bonnet scoop, and on the front edge of the bonnet.

The addition of hood vents is also mentioned quite a lot on the forums for Nascars, the Jap racers, Camaro's and various other hot-rod type sites, as being one way to allow hot engine bay air to escape, and really, all the talk of high pressure and low pressure zones surely must relate to times when the vehicle is traveling at least say 75kph (at a guess) and when there is most opportunity for air to flow through the radiator without much assistance from the fan (the mentioned ram effect).

For lower speed situations they are saying that the vents are even more effective, as the fan is doing all the work and it simply blows the hot air straight out via the path of least resistance, which for hot air, is up, if there is a vent. The bigger the vent the greater the effectiveness and the greater the drop in engine bay temps, is the advice they give.

On the issue of the vent facing out at 45 degrees - what would be the point other than possibly the legalities, and without having seen the regs, I am not sure it would be sufficient anyway?

Now that I have fixed my issue with the Viscous Coupling and temporarily installed the direct bolt up fan, I don't seem to have the overheating issue when cruising at highway speeds, or even on long up-hill climbs if the speed is still above say 80 or 90. Towing my 2t boat for a good run still sees my temps sit around 100 degrees when at cruise speed, and get up to 106 degrees working hard. I will however go back to a viscous coupling when I get one, and will probably pull it apart and check the silicon fluid levels before installing it too. To me these temps still are higher than I would like them to be, and surely after a prolonged period of time, would start to cause damage to other components?

Yes, an effective Intercooler would add to the pressure (and possibly heat) flowing into the engine bay, but I would hazard a guess that with the vents in place the extra air can escape just as easily. I note that ARE state that fans beneath the Intercooler only really work at low-speeds for the same reasons, and are a hindrance to airflow at higher speeds.

Hood Louvres told me that large centrally located vents are the most effective for all round use. On race cars, large vents situated on the bonnet just behind the radiator fan is a good place as it is the place of lowest pressure at speed. On 4wdrives doing a lot of low to medium speed hard work, a large lengthwise vent over the turbo and dump pipe is highly recommended along with a matching one for aesthetics on the opposite side.

This whole area of aerodynamics and thermal dynamics is a minefield. Change one thing and it affects another thing...

So, I suppose that if you have covered all the other options to reduce engine bay heat (exhaust wraps, turbo blankets, ceramic coatings, thermostats, radiators, viscous couplings, deflectors, foam seal on the front of the radiator, etc. etc.), and are still concerned about it, then these types of vents might be worth a look at (legalities not considered). The big thing for most people (again, besides the legalities) is probably the aesthetics of the whole thing, and whether they want to 'ruin' the OEM look of their vehicle.

Another option for those who want to stay legal, would be a custom bonnet such as this one designed for an 80 series. The manufacturer makes them from fibreglass and does one for the GU which looks the same however can have the bonnet scoop added. At $880.00 and still in need of painting, it isn't cheap, but might also work.

[threedogs]

IMO if your temps are up It can only be radiator not big enough, eg I used a V8 holden one in my 350 chev 4x4
or not enough water flow, again I updated to a John bennet water pump. just saying
and I also changed the radiator neck to the larger holden type

you could duct cold air in via the bottom using some pvc ducted to the right area

[FNQGU]

John, the radiators that are installed by Brunswick Diesel are as big as i have ever seen fitted into a Patrol. I'm not sure it is the radiator itself in my case. Airflow? That is another question...

[AB]

My brother has been having severe overheating problems with his gu ute 6.5 chev.

The radiator was a custom made ally one and just spent a small fortune at a local radiator place on a new custom built brass one.

The bloke mentioned about a lot of radiators have the fins too closely together.

Long story short he did a run up radiator test hill on a hot 35 degree day with air con blaring and driving it hard and it did not push past halfway on his gauge.

It did cost him some $$$ but problem solved and some!!!

[threedogs]

Mate I went to everyone in Melb with this prob, jet coating block huggers inside and out.
I spent a fortune on it, too much then enter John Bennet, He designed the cooling systems for the V8 super cars.
I once spent 4 hrs just talking cooling. Try to google him for a contact as no one knows more than him.
Personally I dont think radiant heat is the problem have you tried additives like wetter water?
Your fan should give you sufficient air flow what are 12v fans pushing/pulling 20,000 fpm thats plenty
I think AB has the solution
even back hoe coolant was mentioned at one stage

[threedogs]

Mate I went to everyone in Melb with this prob, jet coating block huggers inside and out.
I spent a fortune on it, too much then enter John Bennet, He designed the cooling systems for the V8 super cars.
I once spent 4 hrs just talking cooling. Try to google him for a contact as no one knows more than him.
Personally I dont think radiant heat is the problem have you tried additives like wetter water?

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