Grille Mod

[Johnno11]

Like many other 996 owners, just when you need that aircon to be icy, I'm faced with scorching black leather and a warm breeze from the air vents. :sad:
So this weekend I'm on condenser detail. Got the bits, wife assures me she'll help and I've just got some black mesh from Halfords. If I'm changing the condensers I may as well do it properly.
But here's a thought...... We all know only too well about the 996.2 engine cooling and the fitting of low temp stats etc, but will fitting the mesh make a difference? Mine's a C4S with the big intakes and although we're only talking about mesh but can it affect the overall airflow to the rads?
I've already done the low temp mod and my warming up procedure is suitably ***** (make sure the oil's warmed through) but I'd hate to jeopardise those bores for the sake of catching leaves.
Any thoughts???
:?:

 

[Moonshine]

I've had mesh fitted for two years (black diamond stuff from Halfords) and not noticed any difference in running temperature, I've done over 30'000 miles in that time.

 

[Bradders]

^^^ Good to know. I did read somewhere that the mesh did reduce airflow to the rads, but perhaps this doesn't affect cooling in any way.

 

[MisterCorn]

It will reduce the airflow to the rads. You are blocking off a part of the opening, how could it not affect it? However it seems that this blockage isn't a problem and there is still plenty of airflow to give sufficient cooling.

MC

 

[Clanky]

Done the mod before & didn't affect the running temps.
You should be safe enough especially as you already have the low temp stat.

Just try to find a mesh with decent sized holes in it.

http://www.ebay.co.uk/itm/Bonrath-D...ng-In-Black-Alloy-Size-125x25cm-/350688576980

16 x 8mm should be enough

 

[GT4]

Yes, air flow is restricted.

Depending on mesh density and aperture shape/size upto 29% may be lost.

Most look a very low density open design with large low turbulence apertures and narrow mesh filaments, so the restriction won't be so high.

However, this 29% etc is the mesh coefficient. The system includes the two overlapping a/c condensers and coolant rads. Therefore, as long as the mesh can pass enough flow to produce the equivalent air pressure at the rads then you will notice no loss of cooling efficiency.

To ensure sufficient air pressure at rad matrices, the vehicle speed must exceed 30-40 mph. Prior to that the air flow is restricted enough that optimum air pressure at the rad interface is not achieved.

That means at low speed the coolant temperature may rise by 5 degrees over normal. This is not much on low load.

In any case, if temps exceed 105 degrees the extraction fans to the rear of the rads will kick in to pull more air through.

Basically, in the middle of Dubai in a traffic jam the coolant system will still function with the fans.

The effect of the air flow reduction is to mimick a lower vehicle speed. So the rads experience say 10 mph less air pressure at an actual vehicle speed of 20 mph.

Once 30-40 mph is reached the air pressure is bottle-necked by the rads not the mesh.

In any case, once the optimum heat exchange airflow is exceeded more air does not necessarily extract more heat (heat exchange requires interaction time with the medium). Otherwise car engines would cool to inefficient (non-working) temperatures at high cruising speeds.

 

[JAD]

Yes, air flow is restricted.

Depending on mesh density and aperture shape/size upto 29% may be lost.

Most look a very low density open design with large low turbulence apertures and narrow mesh filaments, so the restriction won't be so high.

However, this 29% etc is the mesh coefficient. The system includes the two overlapping a/c condensers and coolant rads. Therefore, as long as the mesh can pass enough flow to produce the equivalent air pressure at the rads then you will notice no loss of cooling efficiency.

To ensure sufficient air pressure at rad matrices, the vehicle speed must exceed 30-40 mph. Prior to that the air flow is restricted enough that optimum air pressure at the rad interface is not achieved.

That means at low speed the coolant temperature may rise by 5 degrees over normal. This is not much on low load.

In any case, if temps exceed 105 degrees the extraction fans to the rear of the rads will kick in to pull more air through.

Basically, in the middle of Dubai in a traffic jam the coolant system will still function with the fans.

The effect of the air flow reduction is to mimick a lower vehicle speed. So the rads experience say 10 mph less air pressure at an actual vehicle speed of 20 mph.

Once 30-40 mph is reached the air pressure is bottle-necked by the rads not the mesh.

In any case, once the optimum heat exchange airflow is exceeded more air does not necessarily extract more heat (heat exchange requires interaction time with the medium). Otherwise car engines would cool to inefficient (non-working) temperatures at high cruising speeds.

GT4 with your usual precision and accuracy in your reply you are at risk of exceeding your own reputation. Noting the time of post and specificity - could you not sleep! . Or is it a case of 76.4% of statistics are made up?

:thumb:

 

[GT4]

Overheated.

Couldn't get enough airflow.

 

[MisterCorn]

Overheated.

Couldn't get enough airflow.

Not going fast enough?

MC

 

[pzero]

Overheated.

Couldn't get enough airflow.

Not going fast enough?

MC

Hand lotion maybe a useful remedy here.

 

[Tinker]

Or is it a case of 76.4% of statistics are made up?
:thumb:

Nah. 100.29%.

 

[GT4]

Overheated.

Couldn't get enough airflow.

Not going fast enough?

MC

Hand lotion maybe a useful remedy here.

Mobil1?

 

[GT4]

Or is it a case of 76.4% of statistics are made up?
:thumb:

Nah. 100.29%.

Reading it back, 29% does come across as remarkably specific.

But it was the maximum pressure loss found across a SAMPLE of commercial automotive mesh available in the US in 2010 (so it was incorrect of me to present the findings so as to imply this was a universal ceiling)

However, I doubt, on average, the mesh densities and pressure drops are significantly different to current options.

 

[Johnno11]

Well thanks guys, I will crack on with the mod and tell the missus it's imperative I go faster everywhere! :thumb: