[Alan Loy]

Is there a way to reduce under bonnet temps such as bonnet vents or do we just have to live with them. ZD30 if that makes a difference.

 

[truckster]

What temp issues are you having? Theres a few dozen ZD's getting around without issues.

 

[Alan Loy]

None yet. Just figured with all that hot stuff in there getting heat out would be a good idea.

 

[green troll]

If it aint broke dont fix if

Sent from my GT-I9000T using Tapatalk

 

[02Troll]

A topic dear to my heart.
I do not have any overheating issues, but would like to reduce temperatures in the peak summer periods, tried many things with limited success.
Airflows are complex and what may seem like an obvious answer may actually make things worse, keeping the engine bay clear will help, getting some space around the engine by removing anything not required, don't use the engine bay as a storage compartment.
In summer, during the hottest periods the problem is compounded because we don't use the heater, which takes heat from the engine bay, we use the aircon, which adds heat & both the engine fan & thermo fan work at full pace, which puts more load onto the engine and generates even more heat.
The issue is particularly bad on the LHS because of the exhaust manifold there and the way the engine fan throws the hot air onto that side, where the air intake is & basically preheats the air going to the turbo causing hotter combustion temperatures, in addition it's a bad place for the aux battery because of this heat issue.
I'm seriously thinking about an additional small radiator mounted somewhere at the rear of the vehicle & running of the heater lines, just haven't found an appropriate place to put it yet.
Having said all that, I don't have any problems with vehicle, but I would just feel better if it was a bit cooler in the bay during summer.

 

[geeyoutoo]

Is there a way to reduce under bonnet temps such as bonnet vents or do we just have to live with them. ZD30 if that makes a difference.

To be honest, you don't hear of many ZD30 overheating issues if you maintain the system correctly, even when towing, I tow a lot and never had a problem. The only issue I have heard of is the top of the heat exchanger cracking at the hose connection point, but not to me yet.

I can understand concern but even in the far northern states, the system seems to work well.

As 02Troll says it's a complex issue, very easy to make it bad rather than better.

 

[the evil twin]

Sure gets warm under there don't it but I like it the way it is... Stops ****heads sitting on my bonnet. :rofl:

As others have said overheating isn't an issue but the poor old batteries etc must get a tough time.

 

[davegu]

I have measured my underbonnet temps and the highest reading i have ever got on a 42 degree day whilst driving with a load has been 72 degrees.
On average it sits somewhere between 50 to 60 degrees.
Unless you have an overheating problem I would not worry.
If you really wanted to get serious get your exhaust manifold, turbo exhaust housing and exhaust dump pipe ceramic coated this should drop temps a bit, but it is expensive.

 

[GQshayne]

Bonnet vents have proven themselves over the years on many vehicles. Some old 40 series Cruiser vents will do nicely I reckon, but I am sure there is other stuff that would do as good a job.

 

[02Troll]

I have measured my underbonnet temps and the highest reading i have ever got on a 42 degree day whilst driving with a load has been 72 degrees.
On average it sits somewhere between 50 to 60 degrees.
Unless you have an overheating problem I would not worry.
If you really wanted to get serious get your exhaust manifold, turbo exhaust housing and exhaust dump pipe ceramic coated this should drop temps a bit, but it is expensive.

At what position was that 72C measured, left, right, rear etc? It can vary quite a bit around the entire bay.

 

[Brunsy]

do yourselves a favour and monitor a temp guage as you are moving compared to when you are stationary. When you stop and poke your head under the bonnet its stonkin hot! but when you are on the move there is a low pressure under the car sucking it out.
Fitting extra radiators and the like is un-neccessary and puts considerable extra load on your waterpump, just asking for problems IMHO. Most prodution vehicles are tested extensievely for under bonnet temps and they dont generaly have issues unless somthing is busted.

 

[BeNos]

im trying moreso for a gq but mainly looking for a way to keep the battery cooler especially offroad as its slow, turbo is getting hot, no air flow and batteries dont like heat. for a gq anyway im thinking of making a duct that goes straight into the back of the battery to help keep her cool.
as dual batteries arnt cheap at all.

 

[02Troll]

Another thing I'm also looking at is a rubber skirt under the front of the car to try and create a low pressure area that will aid airflow through the radiator and would also help if a bonnet scoop were fitted instead of louvers.

I've also been thinking about some kind of skirt under the bar, just trying to work out how to make it easily removable for off road use and easy to store and put back on when on the highway again.

 

[02Troll]

do yourselves a favour and monitor a temp guage as you are moving compared to when you are stationary. When you stop and poke your head under the bonnet its stonkin hot! but when you are on the move there is a low pressure under the car sucking it out.
Fitting extra radiators and the like is un-neccessary and puts considerable extra load on your waterpump, just asking for problems IMHO. Most prodution vehicles are tested extensievely for under bonnet temps and they dont generaly have issues unless somthing is busted.

Agree to a point, but the testing is done in standard setup, original bumper etc and compromises are made so a vehicle will be appropriate for a wide variety of conditions, but not ideal for any of them, in Australia heat is generally an issue and I think it can be improved upon. I have monitored under bonnet temperatures and feel that anything over 60c is contributing to negative performance.

 

[02Troll]

Just thought I’d have another bit of a look around on this topic as this question seems to come up a lot and has also been one that I come back to regularly; there is always a variety of opinions but never any really conclusive or convincing results.
I had a bit of a search and read a couple of interesting autospeed articles on this topic, they did work on a Nissan Maxima, but all cars are basically the same shape and the airflow around them will behave in similar ways. Two little excerpts below:
“In the area of DIY aerodynamic modification, there is always a lot of talk, very little action – and never any data!”
“Scoops, vents and air exits do not always work as you intuitively figure they do”
They confirm that the external air pressure at the windscreen is most likely higher as has been mentioned before, so raising the rear of the bonnet will probably just make things worse.
By far the biggest improvement that I gleamed from their article was the value of the undertray, that useless bit of angled plastic hanging down seems to have a significant purpose, I read a comment somewhere on another thread that it was put there specifically to improve airflow, not as a stone guard. Glorts post above confirms this idea, re the conveyor belting, by creating a smooth high velocity airstream under the vehicle it draws air out and creates a negative pressure under the bonnet which pulls more air through the radiator.
Article links below:
http://autospeed.com.au/A_2159/cms/article.html
http://autospeed.com.au/A_2160/cms/article.html
http://autospeed.com.au/cms/title_Undertrays-Spoiler-Bonnet-Vents-Part-3/A_2162/article.html
I will have a bit more of a fish around, but have thought about those people with a bash plate replacing the plastic undertray, if the plate has big holes in it like I’ve seen many do this may actually be reducing radiator performance and increasing under bonnet temps.

 

[green troll]

My tb42e has that metal guard at a angle while on gq mads diesel gq had it flat. I thought I was a water splash guard?

 

[02Troll]

My tb42e has that metal guard at a angle while on gq mads diesel gq had it flat. I thought I was a water splash guard?

I'm just going off the articles and what I've heard and it makes sense that being made of plastic on the GU's it wouldn't be for protection, may serve as a splash guard as well.
Just found this on another post today re spotties and radiator airflow, posted by Mic

"Nah mate, those lights are a long way forward. You'll be right. As you said, that bar is more likely to block airflow than the lights. Check that you have the rubber flaps between the body and chassis in the wheel arches. This will make the most difference. If they're gone, replace them."

So confirming there seems to be a method to the madness of having all the little rubber flaps & foam sealing some areas and not others.

 

[Grogey]

.....................by creating a smooth high velocity airstream under the vehicle it draws air out and creates a negative pressure under the bonnet which pulls more air through the radiator.
.......

This was my understanding as well. Put simply the plastic guard acts as an air baffle that creates a pressure drop behind it, as it moves throught the air. Low pressure under the engine bay improves the ability of air to be drawn throught the radiator and scoop.

When i fitted TJMs radiator under guard this plastic baffle had to be removed . To compensate i extended the short turndown on the TJM underguard with a section of heavy rubber from Clark Rubber. This works a treat. It retains the original baffles function, but is way more durable and acts as a excelent stone guard for the steering damper.

Plus, during water crossings it harmlessly can back flex against the steering damper. But it still helps drop the water level behind it as it pushes through, keeping the water level lower in the engine bay.

Before some one says it I know this thread is worthless without pics. I'll see what i can do.

Grogey

 

[02Troll]

Just found another link of someone with underbody studies:
Aerodynamics of Engine Cooling – Part 2 « omgpham…

 

[parscheese]

Under bonnet temps study:

http://www.mvfri.org/Contracts/Final Reports/R04-13v01 Underhood Temperatures 1.pdf

Cheers

Justin