Thread: Will a bonnet scoop reduce heat in the engine bay?

Originally Posted by Morry948

Was talking to a mate who is a fridgie about cooling etc

Airflow is KING, and anything the causes the wrong pressure difference will restrict airflow. Grills have a big effect as they cause a low pressure area infront of the radiator, killing airflow. Fan shrouds also work very well as they make the fan a lot more efficient..BUT..it needs to be designed exactly for the fan blade in relation to blade pitch and how far in the shroud the fan sits. Get that wrong and it wont move air

His suggestions is to have no gaps around the radiator so you have a nicely sealed plenum so the air can only pass thru the radiator from the grill

And as for the aircon condenser, it not only restricts flow, but also pushes hot air thru the radiator, so you behind the 8 ball from the start. Unfortunatly there isnt much you can do about that without re designing the whole system

And one of the most forgotten things is to keep the radiator fins CLEAN and unblocked

Nice, I have seen an Air Con Condensor on the roof of a heavy touring defender

This bloke did some work on engine bay venting.
Don.

What are peoples thoughts on increasing the high pressure in that area just in front of the firewall & under the bonnet & thereby helping the venturi effect.

So with the 79series bonnet scoops, the holes in the bonnet should be to the rear and both sides of engine, thus fresh air in the rear of bonnet and down each side of engine and out, and in a way maybe even sucking more air through rad in the process or making it easier for air to get out of engine bay..similar to ram effect of snorkel.

With engine off and maybe at idle will no doubt vent out the scoop.

See air in orange in pic attached

Originally Posted by Don 130

This bloke did some work on engine bay venting.
Don.

Awesome find Don. Love it!

Originally Posted by blackrangie

What are peoples thoughts on increasing the high pressure in that area just in front of the firewall & under the bonnet & thereby helping the venturi effect.

So with the 79series bonnet scoops, the holes in the bonnet should be to the rear and both sides of engine, thus fresh air in the rear of bonnet and down each side of engine and out, and in a way maybe even sucking more air through rad in the process or making it easier for air to get out of engine bay..similar to ram effect of snorkel.

With engine off and maybe at idle will no doubt vent out the scoop.

See air in orange in pic attached

From the autospeed link

When adding bonnet scoop make sure enough exit flow, if not increase to keep rad efficiency.

For RRC and most other Landrovers my first guess to increase exit flow would be bonnet sides and inner wheel guard rear half.

So the principle is, more air in, more air out

The problem with a bonnet scoop is it will pressurise the engine bay. You will get plenty of air flow thru the scoop and out the engine bay, but will stop any airflow thru the radiatorYou want as much air as possible going thru the radiator, not thru the engine bay per sayYou need to open up the area behind the rad to allow the air to flow, not add more air to it

The problem I found was more heat soak than running heat...

Slow running was the worst...

Originally Posted by Don 130

This bloke did some work on engine bay venting.
Don.

One thing that wasn't said it is very difficult to get exact readings of pressure drops.
Numerous readings have to be taken and then averaged out.

And there are many variables with under bonnet airflow,having a viscous fan is just one,yet alone vehicle speeds,which affect ram air,etc.