Decklid airflow: In or Out?

[nameisbauer]

I searched a bit but did not find a definitive answer.

Is the point of the deck lid opening/grill to let air in, or vent it out. or both. Thanks!
JIM

[Dave Colangelo]

My understanding of how it works is "in".

The air flows over the car, down the back, into the grill, is pulled in by the fan which pushes it over the motor and down onto the ground as well into the heating system. Although Im not sure if this varies when the car is not moving forward.

Regards
Dave

[McLaren-TAG]

In. Otherwise the fan would be working in a vacuum.

[jmpowers]

Originally Posted by McLaren-TAG

In. Otherwise the fan would be working in a vacuum.

Artificial downforce ala Chaparral 2J!

[wwest]

Originally Posted by McLaren-TAG

In. Otherwise the fan would be working in a vacuum.

The fan IS working in a "vacuum", at least as much so as would be if the airflow were reversed, flowing upward through the cylinders.

But upward would result in exhaust manifold & cat heat flowing over he engine.

[Redbarnman]

I figure that when the engine is running air is pulled in by the fan which shifts a large quantity of air even at idle revs even when not moving. When you stop the engine, the airflow reverses with hot air rising and escaping through the grille. However at speed, the air over the top of the car will be at reduced pressure (a bit like airflow over an aeroplane wing). But that is also true of the air under the car with the venturi effect. But overall I still think the negative pressure created by the fan in the engine compartment will pull air in the top through the grill. Might be fun to stick little wool tassels onto the grill and get someone to look out the window and see which way they are pointing as you build up speed.

[wwest]

Many later models have a control module that will activate the cabin heater blower to help keep the engine cooled down for up to 15 minutes post engine shutdown.

My '88 only does so under way if the engine oil rises to high and the roadspeed is consistently low.

[McLaren-TAG]

Originally Posted by McLaren-TAG

In. Otherwise the fan would be working in a vacuum.

To clarify, in a vacuum, there would be considerably less (or no air) to pull in by the fan so it would be very inefficient or pointless. The grill is there for one purpose, to allow fresh air to be pulled in by the fan.

A place to display badges is not, I repeat is not the primary purpose.

[Flieger]

In, especially when you have a ducktail. The spoiler creates a higher pressure on the grill than would normally be there, making things easier for the fan to suck it in.

It is also why the RSK had the grilles repositioned low on the tip of the tail compared to the 550. There is actually a higher pressure area there where the flows over the top and bottom collide and then flow off the back of the body.