Engine Cover Usage…
 

Is the engine rain tray used during daily use when raining for short periods or is it intended for only longer use like overnight? In other words when do you use it?

Porsche intended the rain tray to remain in place. Early trays were attached with both bolts and bendable tabs - the tabs would break if bent too often.

The tray does restrict air flow into the engine compartment and was removed permanently by owners in hotter climate.

The 914-6GTs had a double grilled engine lid with not rain tray.

The 914-6es did not have a rain tray; I believe that it would foul the air cleaner assembly.

As Sergio said, the stock tray on the four-cylinder cars is intended to be there full-time. It can be removed if engine temps are an issue, but it is generally better to have it in place.

--DD

I recall reading somewhere that the cool air actually comes from underneath the car and the engine lid primarily acts as a vent. Not sure if this is true or if it makes a difference, just something I read.

That is incorrect. The engine lid is the inlet for all of the cooling and induction air. The warm air exits out underneath the engine bay, which is one reason why it is so important to have all of the engine tin in place.

The weird thing is that air actually flows forward along the rear deck lid to get into the engine bay!!

--DD

I just looked underneath and there is one larger and one smaller hole on each side where hot air is released under the engine. Also the flaps that must help sweep the hot air rearward.http://forums.pelicanparts.com/uploa...1755814322.jpg

Are you referring to the tube there in the corner? That's where the cabin heat goes forward to get all nice a toasty lukewarm on cold days. Looks like you don't have cabin heat...

And those flaps are there to increase the low-pressure area behind them, like airplane cowl flaps, increasing the delta-pressure top-to-bottom as the cooling air is evacuated downward...and this it happens all around the engine, not just in specific holes.

As Dave noted, maintaining this delta-p is important via a good engine seal all around the engine tin surrounds. Air flows in from the top and out the open bottom of the car.

You're missing a tube on that large hole. Like Greg said, it sends the cabin heat forward, but it needs to be connected to the heat exchanger to do this.

The small hole directly above is the drain plug for the left side hell hole.