993 air cooling-how does it work?
Discussion
Hi
This is my first aircooled car and i'm clueless about how it works! Can someone enlighten me-how do the cars stay cool in traffic etc and are there any special things that need doing to them in the heat of summer or the depths of winter? Any weekly checks you need to perform etc?
Sorry for sounding dumb-water cooling i understand but want to know how this all works before i pick the car up next week.
thanks
This is my first aircooled car and i'm clueless about how it works! Can someone enlighten me-how do the cars stay cool in traffic etc and are there any special things that need doing to them in the heat of summer or the depths of winter? Any weekly checks you need to perform etc?
Sorry for sounding dumb-water cooling i understand but want to know how this all works before i pick the car up next week.
thanks
They are really oil-cooled - they have some absurd quantity of oil, about 9 litres iirc, but I can't be bothered to go upstairs and find the manual (sorry 
). The oil is pumped through a radiator in the (left) front wing and cooled that way.
Additionally air is drawn over the engine directly by the fan at the rear of the engine.
There's no particular issue with hot or cold weather - in some ways air-cooled engines are more resilient to extremes of temperature than water-cooled, but not really significant in the UK.
The most important thing is to check and change the oil regularly. Use the dip stick to check the oil, the oil level indicator, is, err, indiosyncratic.
Dan
Edited to correct absurd typo
>> Edited by tertius on Sunday 12th March 13:58
). The oil is pumped through a radiator in the (left) front wing and cooled that way. Additionally air is drawn over the engine directly by the fan at the rear of the engine.
There's no particular issue with hot or cold weather - in some ways air-cooled engines are more resilient to extremes of temperature than water-cooled, but not really significant in the UK.
The most important thing is to check and change the oil regularly. Use the dip stick to check the oil, the oil level indicator, is, err, indiosyncratic.
Dan
Edited to correct absurd typo
>> Edited by tertius on Sunday 12th March 13:58
I think it's about 11 litres of oil ( haven't got my book either! ) and the engines run a little hotter than water-cooled, but that's a bonus, as hotter engines are more efficient apparently. Make a point of checking your oil levels when the car is warmed-up and on level ground with the engine running..( on a Tuesday with the wind behind etc....!) 
Yes, 11 litres.
Am I right in thinking that they really were only aircooled a la beetle up until 964, which saw oil cooler rdiator for first time? (Unlike the technically advanced 2CV of course which is also air/oil cooled..
)
The oil cooler radiator only cuts into the circuit after the motor warms up, which is why you'll see the oil temp rise for the first 10 minutes and then drop to a steady level. There is a two speed cooling fan for the oilcooler radiator, for those days when the St Tropez traffic is slow...you'll only hear it when it is at high speed btw.
If the fan, or the thermostat that directs oil to the radiator don't work, then yes the car will run hot in traffic.
Another advantage is quick in-cabin heat on frosty mornings..
>> Edited by Johnny G-Pipe on Sunday 12th March 15:37
Am I right in thinking that they really were only aircooled a la beetle up until 964, which saw oil cooler rdiator for first time? (Unlike the technically advanced 2CV of course which is also air/oil cooled..
) The oil cooler radiator only cuts into the circuit after the motor warms up, which is why you'll see the oil temp rise for the first 10 minutes and then drop to a steady level. There is a two speed cooling fan for the oilcooler radiator, for those days when the St Tropez traffic is slow...you'll only hear it when it is at high speed btw.
If the fan, or the thermostat that directs oil to the radiator don't work, then yes the car will run hot in traffic.
Another advantage is quick in-cabin heat on frosty mornings..
>> Edited by Johnny G-Pipe on Sunday 12th March 15:37
tertius said:
They are really oil-cooled - they have some absurd quantity of oil, about 9 litres iirc, but I can't be bothered to go upstairs and find the manual (sorry
Additionally air is drawn over the engine directly by the fan at the rear of the engine.
There's no particular issue with hot or cold weather - in some ways air-cooled engines are more resilient to extremes of temperature than water-cooled, but not really significant in the UK.
The most important thing is to check and change the oil regularly. Use the dip stick to check the oil, the oil level indicator, is, err, indiosyncratic.
Dan
Edited to correct absurd typo
>> Edited by tertius on Sunday 12th March 13:58
I remember when I bought my air-cooled a few years ago, and wondered why on earth I could hear the sound of 'running water' beneath the right hand sill, at first I thought it was my imagination, then I began to notice it more, but was baffled as to how this air-cooled car could be pumping so much water around, and where was it coming from???; it began to make me increasingly worried, so when I took it in for service, I said to the bloke at the OPC 'don't laugh at this, but I think my car somehow has some water trapped beneath the floorboards... He laughed, and laughed, then he put me out of my misery...
Alastairm said:
Hi
This is my first aircooled car and i'm clueless about how it works! Can someone enlighten me-how do the cars stay cool in traffic etc and are there any special things that need doing to them in the heat of summer or the depths of winter? Any weekly checks you need to perform etc?
Sorry for sounding dumb-water cooling i understand but want to know how this all works before i pick the car up next week.
thanks
water cooled cars also rely on air for cooling or they wont cool,crank driven fan/alternator which directs air down though the barrels/heads,the exhaust is basically your heater.
The large volume of oil is more because of the dry sump system than for cooling although it certainly helps.
The air blown through the engine via that lovely upright fan is quite considerable. Early 911 fans had a volume of some 1400 litres per second at 6100 rpm. Newer cars have larger fans with more blades so the volume has almost certainly gone up.
The air blown through the engine via that lovely upright fan is quite considerable. Early 911 fans had a volume of some 1400 litres per second at 6100 rpm. Newer cars have larger fans with more blades so the volume has almost certainly gone up.
Johnny G-Pipe said:
Yes, 11 litres.
Am I right in thinking that they really were only aircooled a la beetle up until 964, which saw oil cooler rdiator for first time? (Unlike the technically advanced 2CV of course which is also air/oil cooled..
>> Edited by Johnny G-Pipe on Sunday 12th March 15:37
Ehm all Beetles have an oil cooling radiator mounted in the fan housing
pp
Pickled Piper said:
Yes, 11 litres.
Am I right in thinking that they really were only aircooled a la beetle up until 964, which saw oil cooler rdiator for first time? (Unlike the technically advanced 2CV of course which is also air/oil cooled..
>> Edited by Johnny G-Pipe on Sunday 12th March 15:37
Ehm all Beetles have an oil cooling radiator mounted in the fan housing
pp
Well I'll be blown! (ha ha)
So I take it early 911's have the same, or is it in the nose like the newer cars?
Engine oil coolers were fitted as standard to all 911 engines from 1965 through to 1989 (i.e. from the 2.0 litre up to the 3.2 Carrera and 3.3 turbo). With the arrival of engines above 180bhp Porsche then added a supplementary front oil cooler in the right front wing to keep oil temperatures down as the engine oil cooler was not entirely up to the job.
Aside from the one-off cooler on the 2.4S, the first production front cooler was the serpentine which is simply a double loop return tube, it being effective because the pipes to/from the cooler contributed around 75% of the cooling capacity of the system. In 1980ish this cooler was replaced with the all-brass multi-rod which was used on the 930, SC & 3.2 Carrera until 1985 when it was superceeded by the 3.2 Carrera radiator style unit. Later export versions of the Turbo also had an option of a fan on this cooler.
With the arrival of the 964 in 1989, the engine oil cooler was deleted in favour of simply a large fan assisted front cooler, the single front cooler presumeably cheaper & lighter overall than fitting two coolers. This set up was also carried over to all the 993 models.
A secondary front cooler was added on the 993GT2 and X50 993Turbo once the power outputs reached 430bhp and above. This cooler can be useful for any of the 964 thro' 993 models for track use and is very easy to fit, even with a/c cars.
Finally Ruf (and others) fitted a second full size oil cooler as a mirror image of the factory set up in the left wing on their 964/993 turbo conversions, which is probably the ideal package for 500+bhp cars that see hard track use. In fact for the earlier 911's (pre 964), most racers remove the washer bottle and fit a second 3.2 Carrera oil cooler in the LH wing to keep their race cars cool in the summer.
Aside from the one-off cooler on the 2.4S, the first production front cooler was the serpentine which is simply a double loop return tube, it being effective because the pipes to/from the cooler contributed around 75% of the cooling capacity of the system. In 1980ish this cooler was replaced with the all-brass multi-rod which was used on the 930, SC & 3.2 Carrera until 1985 when it was superceeded by the 3.2 Carrera radiator style unit. Later export versions of the Turbo also had an option of a fan on this cooler.
With the arrival of the 964 in 1989, the engine oil cooler was deleted in favour of simply a large fan assisted front cooler, the single front cooler presumeably cheaper & lighter overall than fitting two coolers. This set up was also carried over to all the 993 models.
A secondary front cooler was added on the 993GT2 and X50 993Turbo once the power outputs reached 430bhp and above. This cooler can be useful for any of the 964 thro' 993 models for track use and is very easy to fit, even with a/c cars.
Finally Ruf (and others) fitted a second full size oil cooler as a mirror image of the factory set up in the left wing on their 964/993 turbo conversions, which is probably the ideal package for 500+bhp cars that see hard track use. In fact for the earlier 911's (pre 964), most racers remove the washer bottle and fit a second 3.2 Carrera oil cooler in the LH wing to keep their race cars cool in the summer.
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