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2005 TD42Ti ute
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Discussion Starter · #1 ·
it has been a few years now that i have been quite interested in this "cooling issue" many seem to experience with GQ and GU patrols. There are many threads on here related to cooling systems. People have tried all types of things from different water pumps, massive radiators, locked up fans, coolant flow reworks the list goes on and on.

I first started looking around at things when i noticed the water sprayer on my top mount intercooler was spitting the water back out the scoop at 80KPH a few years back, much to my disgust. The coolant temp in the top hose was around 95c while cruising at 80 towing a decent trailer. It is not unreasonable to say things are a little different now, and thanks to bits of plastic, foam, rubber, ally, basic fabrication ect i believe have built a cooling system that is exceptionally good.

yes i do have a few things going on with the water flow that are not standard, but achieving proper airflow across any cooling stack is definitely not going to hurt regardless of how the water moves, the layout/config and how much power it may be making.

I am creating this thread with the intention to share and discuss aero stuff, as i have found 90% of the big gains i have seen with "cooling issues" have been because of aero modifications..

I do believe the standard water pump is not up to par for a TD with some power, however no amount of water circuit modifications have netted the gains that aero has.

If you are tired of replacing your battery every 12 months, the aircon could work better, the ECT/Block temp is to high, the trans temp could be lower, the fuel econ could be better, the guards burn you if you lean on it after its been doing work ect - you need some aero in your life...

4wds and "aero" don't sound like things that should belong in the same sentence, but if your car is suffering from any or all of the above, a bit of aero will definitely not be a step backwards.

the first aero mod i was shown that made a significant difference was the "air dam" which not many people seem to run, but is a massive help to any live axle vehicle as it prevents a high pressure from being created behind the radiator - from road speed air hitting the exposed diff housing as you drive down the road. Here is a few examples of air dams that work..
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2001 Auto TD42T
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Hey mate, thanks for posting. I have been thinking about this all week and am going to make something for myself later this week. Could you please post a pic from the underside of the car like below?

Unfortunately I don't have any fab skills. So I will have to make do with rubber and foam. The pic below is my void and I'm fairly certain covering this up and doing a better job of covering the sides of the rad I should get some improvements. At the moment I'm only unhappy with my highway temps (97 deg cruising at 100 fairly constant, NQ weather). I would be happy with a 5 deg reduction.

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Discussion Starter · #3 ·
Hey mate, thanks for posting. I have been thinking about this all week and am going to make something for myself later this week. Could you please post a pic from the underside of the car like below?

Unfortunately I don't have any fab skills. So I will have to make do with rubber and foam. The pic below is my void and I'm fairly certain covering this up and doing a better job of covering the sides of the rad I should get some improvements. At the moment I'm only unhappy with my highway temps (97 deg cruising at 100 fairly constant, NQ weather). I would be happy with a 5 deg reduction.

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I see you have a factory air dam in place, if you have a lift kit it will be no longer effective unless its extended down.

Ideally we want to seal the air dam to the bottom tank of the radiator so any air entering the front HAS to go through the radiator, Also the bottom of your bar needs to be plated up as the air entering the bar will choose to fall out the bottom rather then to go through the radiator as it is an easier path to go out the bottom..

i can lay underneath my ute tomorrow and get some more pics but mine is the one with the superior bash plate and the bit of ABS plastic bolted to it..
 

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Discussion Starter · #5 ·
I reckon that steel one would cop a beating out on the tracks.


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that one is not one of mine, that is a guy named tom i believe. He claimed to have dropped 14C out of his coolant temp with that and other supporting mods.

I 100% agree, and that's why mine are conveyor rubber or abs plastic or something, it needs to be rigid enough to do its job, but also it needs to fold out of the way when doing bush work.
 

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GU 2007 Cab Chassis Leafie, 6.5L Chev diesel, manual, slide on Tommy Camper on back
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Hi @mikecooper422, thanks for post (hopefully with more to come!). one of the great things of this forum is people giving up their time to help others.

the first aero mod i was shown that made a significant difference was the "air dam"
Do you have some data to show the significant difference the air dam made? (not being smart, or doubting, just keen on data).
 

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Discussion Starter · #8 · (Edited)
Hi @mikecooper422, thanks for post (hopefully with more to come!). one of the great things of this forum is people giving up their time to help others.


Do you have some data to show the significant difference the air dam made? (not being smart, or doubting, just keen on data).

yep i have numbers.. air pressures and ECT. problem with analysing them is we use a difference in measured air pressures to presume a flow of air, air flow is hard to measure accurately, air pressure is a piece of piss. the problem with ECT data is that there is many inputs which control it, so just saying something like " i dropped 6 degrees out of my ECT " which is something i am hearing often when talking about air dams - we are relying on the conditions pre and post air dam to be identical. not easy for us playing at home..
 

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I see you have a factory air dam in place, if you have a lift kit it will be no longer effective unless its extended down.

Ideally we want to seal the air dam to the bottom tank of the radiator so any air entering the front HAS to go through the radiator, Also the bottom of your bar needs to be plated up as the air entering the bar will choose to fall out the bottom rather then to go through the radiator as it is an easier path to go out the bottom..

i can lay underneath my ute tomorrow and get some more pics but mine is the one with the superior bash plate and the bit of ABS plastic bolted to it..
Im not sure what you mean by it needs to be extended down (wouldn't that move that away from the bottom tank of the radiator?) not doubting you as I have read this many times, just never bothered to get around to doing something about it.

I am going to essentially try and use rubber to cover the bottom of my bar all the way to my air dam. When you say that my air dam needs to be extended down, do you mean something along the lines of placing the equivalent thickness of washers as my lift above the air dam and finding extra long replacent bolts? Then I can fill any gaps with foam?

Also will post my results as well as I have a pretty firm grasp on my temps through heaps of scenarios.
 

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Discussion Starter · #10 ·
Im not sure what you mean by it needs to be extended down (wouldn't that move that away from the bottom tank of the radiator?) not doubting you as I have read this many times, just never bothered to get around to doing something about it.

I am going to essentially try and use rubber to cover the bottom of my bar all the way to my air dam. When you say that my air dam needs to be extended down, do you mean something along the lines of placing the equivalent thickness of washers as my lift above the air dam and finding extra long replacent bolts? Then I can fill any gaps with foam?

Also will post my results as well as I have a pretty firm grasp on my temps through heaps of scenarios.

It needs to cover roughly half the diff housing to be effective, so a standard air dam is screwed the minuet you even think about lifting the car. my car has a 3 inch lift so mine is extended down a bit.

if you stand back say 10m from your car and you can see the pumpkin of the housing, the air dam needs to come down lower so it pushes the air that doesn't make it into the bull bar under the diff housing. Put it this way, I don't wave back to people that have their diff sticking out anymore :ROFLMAO::ROFLMAO: I'm a bit of an aero snob and you will see why once you get it to work properly.

Air dams are just the tip of the iceberg, but a good first move when entering the world of aero on your patrol :geek:

please do post results. I'm guessing you will net around 5C better off in ECT at highway speed if you seal the bottom of the bar and extend the air dam down so it works properly..
 

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I see you have a factory air dam in place, if you have a lift kit it will be no longer effective unless its extended down.

Ideally we want to seal the air dam to the bottom tank of the radiator so any air entering the front HAS to go through the radiator, Also the bottom of your bar needs to be plated up as the air entering the bar will choose to fall out the bottom rather then to go through the radiator as it is an easier path to go out the bottom..

i can lay underneath my ute tomorrow and get some more pics but mine is the one with the superior bash plate and the bit of ABS plastic bolted to it..
I'm a bit of a retard tonight. I think I get what you mean - the air dam flap needs to be longer, as in it should stay in place but run closer to the ground?
 

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Discussion Starter · #12 ·
yep, also ideally - we want the air dam as wide as the radiator (wider the better).

i dont think the angle of the flap part you speak of is super critical from my findings , but as close to the draglink as we can get it without fouling is a good move.

on my Ti TD42 the air dam is not very wide because the radiator is only 550mm wide... on the other patrol pictured (6.5 turbo diesel / ZD 30 radiator) the air dam is as wide as the chassis itself.
 

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There is quite a lot of info on this kind of thing on the forum, but it spread all over the place from the last 10 years or so. Almost impossible to find, so to have all our good ideas in one thread will be a good resource.

I never bothered to photograph anything of mine, so I will see what I can do about that. In my case, I have focussed my efforts on the pressure side of the system, so I will add some details of what I have done. In order to get good air pressure differential, ideally you need both sides working well. They all add up!
 

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Discussion Starter · #14 ·
There is quite a lot of info on this kind of thing on the forum, but it spread all over the place from the last 10 years or so. Almost impossible to find, so to have all our good ideas in one thread will be a good resource.

I never bothered to photograph anything of mine, so I will see what I can do about that. In my case, I have focussed my efforts on the pressure side of the system, so I will add some details of what I have done. In order to get good air pressure differential, ideally you need both sides working well. They all add up!
100% mate we are chasing the greatest difference in pressure possible across the cooling stack, high pressure side is important as you have found in your testing..

I have found my best gains have been low pressure side mods as its more of a given thing and a bit easier to stuff/force air into the bay via the stack then it is to allow it to leave the bay or even help evacuate that air from the bay in the case of some of the easy body modifications i have done..

its basically a traffic jam of sorts in the engine bay and the traffic is air bunching up.

Air is a great insulator, and a poor conductor of heat, so if we are going to use it to remove heat from something - we need to flow it very quickly.

funnel it in, then suck it out.
 

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On a slightly different note, has anyone done aerodynamics testing on different bonnet scoops?

After I fitted my FMIC I put the (factory) scoop on backwards, the logic being that it will act as a Venturi and help pull hot air up and away from the engine, thus lowering the air pressure in the engine bay and increasing airflow through the cooling stack. I haven't got round to checking the airflow, so whether it works or not remains to be seen.
 

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Discussion Starter · #16 ·
On a slightly different note, has anyone done aerodynamics testing on different bonnet scoops?

After I fitted my FMIC I put the (factory) scoop on backwards, the logic being that it will act as a Venturi and help pull hot air up and away from the engine, thus lowering the air pressure in the engine bay and increasing airflow through the cooling stack. I haven't got round to checking the airflow, so whether it works or not remains to be seen.
I sure have. I even bought a junk car specifically to cut holes in it to prove if the theory works before cutting holes in patrols and i am still driving it around now with no fans on the radiator no problem if you keep moving.

If you want to do a bonnet vent to help the cooling stack you will find that it is better positioned towards the front of the bonnet (obviously still needs to be behind the radiator)

If you make it too close to the scuttle panel (base of the windshield) you will get negative results once the car is at speed. I busted the myth of the old "pop the back of the bonnet up" by testing air pressures on a few different GU's and GQ's. popping the rear of the bonnet worked until the car was doing around 40kph where it then began to work against us as the pressure at the scuttle panel was greater then the pressure in the engine bay at the rear.

This is why the scuttle panel is also a grille of sorts, the engineers use this area to pick up fresh air for cabin ventilation as it is a high pressure - test it your self, turn a/c and a/c fan off and leave fresh air on and drive at 100kph you will feel the air flowing out the vents..

I like bonnet vents that are properly positioned because they work in just about every load/speed scenario, even recovery of idle temps while running aircon in hot ambient.

bit of a tricky one when using a top mount intercooler is all.
 

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Discussion Starter · #18 ·
@mikecooper422 I figured that not having the resistance of a cooler in the way of the scoop should help things along a bit. Worst case scenario is it doesn't work and I get better convection cooling when I'm stopped at the lights, without heat soaking my intercooler.
Tuft testing will help get you the information you are chasing on your reverse scoop, it is cheap and simple to do, you will be able to watch the tufts from the drivers seat as you drive.

i suspect you will find it working great at lower speeds, potentially still working at high speeds. even if the air stagnates due to an equal pressure in the bay and in the scoop at say 100kph, as long as the flow doesnt start to reverse you will 100% see some measurable gains from the reverse scoop. the ones i have done are modified bonnets so the vent is recessed so to speak. cut and fold bonnet down. they can look great when done properly with consideration to the vehicles design language.
 

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I have taken a few pictures of what I have done on the pressure side, ie in front of the radiator. Air will take the path of least resistance when it can. So when faced with your aircon condensor, and auto cooler, maybe some thermo fans, and your radiator, that is quite some resistance for the air. So if it can go around these obstructions it will, and that does not give you cooling. Air flow through your radiator is created by the pressure in front of it being greater than the pressure behind it. This is the pressure differential. Mike has been talking about what to do in your engine bay, and underneath, to help air escape the engine bay. This helps create the low pressure needed behind the radiator. What I have done helps increase the pressure in front of it.

I am not an engineer and have not used any testing equipment to measure pressures. So I cannot give you any data. I just looked for gaps, and where practical I blocked them off. This resulted in my engine temperature reducing. The cost of these mods was about $20.

Righto, first up is the one that we should all know about - the radiator support panel. No pic of that, but when you fit the rad put a seal around it. I am not a fan of normal foam as it holds water. I used a stick-one rubber extrusion like a door rubber. Stick that on the radiator so it sits against the support panel flush with no gaps.

Next thing was to lean on the bull bar and look down. If you can see the ground, then air will hit the grill and defect down and under your car where it is of no use to cooling. If you block it off it will increase pressure. I went between the bottom of the bullbar and the radiator support panel with a piece of rubber. It is flexible enough to get it in there and stiff enough to do the job. One pic is from the top (looking down between driving light and grille) and the second from underneath. If it looks like a door mat that it is because it is a door mat. Don't judge me.

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Next was the top of the grille. Once again, air can hit the grill, be deflected up, and go over the bonnet. Blocking off the huge gap in my GQ Grill was done using high density foam which does not hold water and is fairly stiff. I used concrete expansion joint stuff which comes in a roll from the hardware. I glued it in place with spray contact after cutting to shape.



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I also cut a hole in the grille, as the GQ has a big solid section at the top. So I opened that up a bit, as it can only help things. I also hoiked the Nissan badge in the centre of the grille and cut a hole where it was mounted.

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Next was to look at the sides, where air can go left or right. Basically out the sides towards the headlights. Get some foam in there and block it off. The solid section in the pic below has foam behind it.

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The problem with our Patrols is that it is hard to find two the same, as we love to modify them. So my gaps I had will be different to yours. But anything you can block off will help with cooling, and costs very little in materials.

The only reason I have not fitted an air dam like Mike has, is that I have simply not got around to doing it yet. Was always going to, but was busy with other stuff. You know how it is. :rolleyes: But when I have finished stuffing around with other projects, that it would be in the way of, I will be doing that too.
 
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