Thread: Radiator and AirFlow issues caused by Large Spotlights?

IMO and from the testing I've done Defenders have air flow issues getting the air out of the engine bay.
300Tdi's (and TD5's?) in particular needed the viscous fan in really good condition to keep things cool at speed under load.
Ram air wasn't enough.

Improve that and the spotties in front wont impact as badly.

You need to get it out before you can get it in.
So to speak.

Our 300Tdi D1 would run fine just on the viscous fan at speed if the air-con was turned off. Turn on the air-con and the electric fans started.
In a Defender, the aim is to have a low pressure area around the engine to suck more high pressure air through the radiator and increase cooling.
That's why bonnet cents are a bad idea as they push high pressure air into the back if the engine, which reduces the amount of high pressure air coming through the radiator and so decreases cooling.
Pressure tries to equalise. That's why Range Rovers have side vents in the guards, to let air out if the engine bay. It's also why Defenders have vents in the tops of the guards.

The vents in the top of the guards don't work as vents Mick, the flow is really messy with quite a bit of reversion when I've wool tuft tested them.

Side of guard vents work really well though, it's a good low pressure area.

[edit] and bonnet vents work if they are above and just behind the radiator/fan and aren't an external scoop but something like a reverse facing naca duct, etc. It's an area of laminar flow and so is relatively low pressure.
As you get closer to the windscreen the pressure increases as the air packs up at the windscreen base.
This is how the reverse facing bonnet scoops worked on A9X Toranas, XC Falcon Hardtops, etc.
It was a high pressure zone that was tapped to feed air to the carbies.

well you made my morning.Laminar flow and Defender in the same article.
Think should be low pressure not laminar.

I knew nothing about laminar flow until your reference made me research it.
Laminar airflow over a box like a Defender would be rather crazy, maybe?
Does the laminar airflow over an engine act like the airflow over a wing? So then I guess the air under the rear of the Defender bonnet would want to escape upwards?

You could check whether the problem is inflow or outflow by finding the pressure drop from the front of the radiator to the rear of it.
this can be easily done with a megahelic pressure gauge with the inlet placed in front of the radiator and then rear with the gauge inside the vehicle which should be atmospheric pressure.

regards Philip A
not much drop is bad lots of drop good.

Laminar as in straight, so any opening to that flow experiences a low pressure zone.

Wow... now we are getting technical....

I think I'll be removing the large Lightforce 240 Blitz due to the fact that I reckon they're past their used by date due to poor light output...imo