I think about this quite frequently, how much of a daunting challenge it is to cool an engine using only air. And yet Porsche did it in their 911 until.. was it 1998? As fascinated as I am by this, I know little about it. Can a Porsche fan or someone in the know explain how they do it?

Thanks, a baffled Porsche fan-

-JD

I am not sure how they did it. Anyone know?
BTW the air-cooled engines sound so great when you press the gas and you hear it intaking all this air. It just so sweet. I would like to know how they did that.

Exactly. Consider the challenge of aspirating as much air as needed to have the kind of hp/liter ratios that Porsches have had for so long, and than aspirating even more air to cool the engine as its producing power, of course keeping in mind that air can change in temperature 1 degree with about 1/1,000 the energy needed to change the temperature of water. And that's water, we're not even talking coolant here.

The point I'm getting at is that the amount of air molecules needed to keep engine temperature in check, considering how little effect each one has individually in the actual cooling process, seems absolutely staggering. The fact that Porsche does this, while mounting their engines at the rear of the car (where the ability of the engine to ingest the largest amount of air directly through the front while in motion is greatly diminished), is why I am such a fan of Porsche engineering and their unconventional approach's achievements and success.

You have to remember, too that the Porsche aircooling originated from the beetle, and the reason the beetle incorporated air cooling into it's engine is because most people during the war did not have garages over in cold Germany, so it only seemed practical to have a reliable air cooled car, because you didn't have to worry about a frozen radiator.

Ferdinand Porsche made his first air-cooled engines in WWI. The Austro-Hungarian Empire there airplanes used the air-cooled engines made by Porsche. They had the 3rd largest airforce in the world at that time. It was a 4cyc air-cooled engines used in it (I think).

Originally posted by JD@af
I think about this quite frequently, how much of a daunting challenge it is to cool an engine using only air. And yet Porsche did it in their 911 until.. was it 1998? As fascinated as I am by this, I know little about it. Can a Porsche fan or someone in the know explain how they do it?

Thanks, a baffled Porsche fan-

-JD

It's called engineering!

& it was until '99 with the 996.

Rob what are you talking about. It was 1998 when they had the water cooled engines out in the 996 not 1999.

Originally posted by Seb928S@af
Rob what are you talking about. It was 1998 when they had the water cooled engines out in the 996 not 1999.
yes they came out in '98, but as the Model Year '99.

Ferdinand Porsche decided in the beginning of the production of the 911 to keep using an air-air-cooled engine as theire air-air-cooled racing-engines were as reliable as air-water-cooled-engines. Also I think the only started to use intercoolers when they raised the displacement to 3.0l:)

BTW Robs second definition is correct like the 993 which was 'invented' in 1993 (as the name says) but was released first 1994:D

I noticed that no one answered the first question.

Porsche wanted to keep the engines as simple as possible. Air-cooling was good from two standpoints:
1. It kept the engine maintainance down to a minimum in parts. Air-cooled is easier to work on.
2. A belt-driven fan forces air through the engine, cooling it. Very simple yet very effective.

GM had the right idea with the Corvair. Those little 6-cyl engines that were 125 CID to just over 150 CID produced almost a horse per cube. The turbo powered versions were over a horse per cube. They weren't Vette killers, but they surprised many a sports car in power and speed.

http://www.fortunecity.com/silverstone/boot/66/17465720.jpg

Thanks for the info!!

Well, if the first 911 engine (2.0 liter/1991 CC) engine put out 130 horsepower, then how many horses per cubic inch/ and cubic centimeter did it put out? How about the hot 911S with the same 1991 CC engine that put out 160 horsepower?

P.S. the first 911s were built in September of 1964, and the 911S was introduced in the 1967 model year.

Well, if the first 911 engine (2.0 liter/1991 CC) engine put out 130 horsepower, then how many horses per cubic inch/ and cubic centimeter did it put out? How about the hot 911S with the same 1991 CC engine that put out 160 horsepower?

911S engine have 9,8 compression ratio vs 9,0 on 901 engine

Alright, tanjwarrior , I figured this out: The 2.0 liter 'regular' 911s put our 1.07 horses per-cube (1991cc / 130hp), and the 2.0 liter "S" 911s put out 1.32 horses per-cube (1991cc / 160hp.) Also, those are just the "first" 911s (2.0 liter displacement.) I didn't get into the more potent larger engined later cars. ANYWAY...The engine figures for the early 2.0 liter 911 and 911s are both a little better than the Corvair figures.:flipa:

Originally posted by JD@af
I think about this quite frequently, how much of a daunting challenge it is to cool an engine using only air. And yet Porsche did it in their 911 until.. was it 1998? As fascinated as I am by this, I know little about it. Can a Porsche fan or someone in the know explain how they do it?

Thanks, a baffled Porsche fan-

-JD


A picture says a thousand words:
http://www.qplanet.org/bb_posts/aircooled_small.jpg
To put the engine fan into context, the later 11 blade fans flow
1210 litres/ sec (!) @ 6100 rpm.

Well the engines are more oil cooled. The oil cooles the engine down a lot with help from the air. That is why these cars have so much oil in them. Like I remember it's something around 13l of oil for the 930.