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Re: Can someone please explain aircooled vs. Water cooled.
Wet sump may result in engine losing oil pressure, not getting enough oil because it sloshes around and the oil pump inlet sucks in air instead of oil, when taking hard turns in a racing situation.
Porsche went to water-cooled engines because it couldn't meet emissions standards for fuel efficiency while increasing HP.
That's all I think I know.
Porsche went to water-cooled engines because it couldn't meet emissions standards for fuel efficiency while increasing HP.
That's all I think I know.
Apr 7, 2005 8:03:38 PM
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Carlos from Spain
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Re: Can someone please explain aircooled vs. Water cooled.
Title says water cooled vs air cooled, but post body asks about wet vs dry sump 
Wet sump is cheaper to build but not as efficinet under high cornering loads so not suitable for racing. Wet sumps are perfectly OK for street cars that are tracked with DOT street tires. But if you use slicks and are a good driver, you may achieve lateral G's high enough to starve the engine of oil leading to failure. So the GT3 which is raced uses a dry sump, and the Carrera or Boxters that never use slicks uses a "integrated dry sump"... which is what Porsche calls its hybrid between dry and wet sump engine (you can consider it a wet sump basically).
As to water vs air cooled, basically, Porsche had to go water cooled becuase the air cooled are louder and would not meet future noise regualtion but more importantly water cooled pollut much less and are able to meet the current polution stantards. Water cooled means they have a "radiator" with water intead of just a fan so cools off more efficiently. Not that aircooled engines are bad, if well designed they can be very reliable, etc. but just can't meet todays DOT standards.
Wet sump is cheaper to build but not as efficinet under high cornering loads so not suitable for racing. Wet sumps are perfectly OK for street cars that are tracked with DOT street tires. But if you use slicks and are a good driver, you may achieve lateral G's high enough to starve the engine of oil leading to failure. So the GT3 which is raced uses a dry sump, and the Carrera or Boxters that never use slicks uses a "integrated dry sump"... which is what Porsche calls its hybrid between dry and wet sump engine (you can consider it a wet sump basically).
As to water vs air cooled, basically, Porsche had to go water cooled becuase the air cooled are louder and would not meet future noise regualtion but more importantly water cooled pollut much less and are able to meet the current polution stantards. Water cooled means they have a "radiator" with water intead of just a fan so cools off more efficiently. Not that aircooled engines are bad, if well designed they can be very reliable, etc. but just can't meet todays DOT standards.
Apr 7, 2005 8:20:35 PM
- Jeff (in SF)
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Reply to:
Carlos from Spain
Re: Can someone please explain aircooled vs. Water cooled.
Quote:
Carlos from Spain said:
Title says water cooled vs air cooled, but post body asks about wet vs dry sump
Wet sump is cheaper to build but not as efficinet under high cornering loads so not suitable for racing. Wet sumps are perfectly OK for street cars that are tracked with DOT street tires. But if you use slicks and are a good driver, you may achieve lateral G's high enough to starve the engine of oil leading to failure. So the GT3 which is raced uses a dry sump, and the Carrera or Boxters that never use slicks uses a "integrated dry sump"... which is what Porsche calls its hybrid between dry and wet sump engine (you can consider it a wet sump basically).
As to water vs air cooled, basically, Porsche had to go water cooled becuase the air cooled are louder and would not meet future noise regualtion but more importantly water cooled pollut much less and are able to meet the current polution stantards. Water cooled means they have a "radiator" with water intead of just a fan so cools off more efficiently. Not that aircooled engines are bad, if well designed they can be very reliable, etc. but just can't meet todays DOT standards.
Just to add a little bit of what I know. Air cooled is somewhat misleading. The engines are primarily oil-cooled. The "air cooled" cars use a large amount of oil sprayed onto the bottoms of the pistons and routed throughout the engine to cool the engine. Air is passed over the car as ig moves or via fans and an oil cooler to then cool the heated oil. Air/oil cooling doesn't provide the same consistency in heat dissipation as does a water cooled engine and therefore is more limited in its ability to achieve power vs. a similar water cooled engine. FWIW.
Apr 7, 2005 10:29:19 PM
- dsts6
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Re: Can someone please explain aircooled vs. Water cooled.
Alright, so dry sump is better performance wise, well at least racing wise. Does dry vs. wet sump have anything to do with power (hp)
Also are you saying that water cooled engines have a greater ability to provide power than aircooled. When my dad got a 993 turbo, they were all telling him that its a very desirable car because it is the last air cooled turbo....
Also are you saying that water cooled engines have a greater ability to provide power than aircooled. When my dad got a 993 turbo, they were all telling him that its a very desirable car because it is the last air cooled turbo....
Re: Can someone please explain aircooled vs. Water cooled.
I dunno why air-cooled cars are desireable except in cold climates, or as collectors items "it's THE last of the air cooled", or for the whining turbine-like sound they make. I love 'em because they sound soooooo fine!
It's the APPLICATION for which the engine is to be used which determines dry or wet sump. HP is not a factor for air- v.s water-cooled. I reason this because there's huge HP output in air-cooled aircraft engines.
Again, like mentioned above, Porsche had to trade the air cooled engines for water cooled both to increase HP AND meet environmental regulations.
It's the APPLICATION for which the engine is to be used which determines dry or wet sump. HP is not a factor for air- v.s water-cooled. I reason this because there's huge HP output in air-cooled aircraft engines.
Again, like mentioned above, Porsche had to trade the air cooled engines for water cooled both to increase HP AND meet environmental regulations.
Re: Can someone please explain aircooled vs. Water cooled.
Quote:
dsts6 said:
Alright, so dry sump is better performance wise, well at least racing wise. Does dry vs. wet sump have anything to do with power (hp)
Dry sumps do create more hp, since there is not a pool of oil at the bottom of the engine which the crankshaft must rotate through. There is less frictional loss in a dry sump motor for this reason (oil is scavenged out of engine and pumped into a separate tank, not sitting in a reservoir at the bottom of the crankcase).
Re: Can someone please explain aircooled vs. Water cooled.
Quote:
dsts6 said:
Also are you saying that water cooled engines have a greater ability to provide power than aircooled. When my dad got a 993 turbo, they were all telling him that its a very desirable car because it is the last air cooled turbo....
Aircooled cars can make a tremendous amount of power (the 917 in the Can-Am series made 1,200hp peak). However, as Carlos said, it can't make high power while being quiet and low emissions...
Re: Can someone please explain aircooled vs. Water cooled.
Quote:
Grant said:
...Dry sumps do create more hp, since there is not a pool of oil at the bottom of the engine which the crankshaft must rotate through. There is less frictional loss in a dry sump motor for this reason (oil is scavenged out of engine and pumped into a separate tank, not sitting in a reservoir at the bottom of the crankcase).
In a 997, it holds about 8 quarts of oil. As I recall, the old air-cooled dry sump engines also had about 8 quarts of oil. Is the 8 quarts of oil always in a 997 or does it have an oil tank also?
Apr 8, 2005 5:08:33 AM
- Jeff (in SF)
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Re: Can someone please explain aircooled vs. Water cooled.
Quote:
vtrader said:Quote:
Grant said:
...Dry sumps do create more hp, since there is not a pool of oil at the bottom of the engine which the crankshaft must rotate through. There is less frictional loss in a dry sump motor for this reason (oil is scavenged out of engine and pumped into a separate tank, not sitting in a reservoir at the bottom of the crankcase).
In a 997, it holds about 8 quarts of oil. As I recall, the old air-cooled dry sump engines also had about 8 quarts of oil. Is the 8 quarts of oil always in a 997 or does it have an oil tank also?
I thought I remembered the 993 cars holding 12 or more quarts of oil.
Apr 8, 2005 7:37:50 AM
- Hei Poa
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Re: Can someone please explain aircooled vs. Water cooled.
Hello,
Sorry if I say a heresy, but I thought Porsche also move from air-oiled to water cooled because they also needed to have 4 valves per cylinder technology. They also could had it with air-oiled but results would not have been that good.
On a side note, is it true that the most recent Corvette still has the two valves per cylynder method?
Sorry if I say a heresy, but I thought Porsche also move from air-oiled to water cooled because they also needed to have 4 valves per cylinder technology. They also could had it with air-oiled but results would not have been that good.
On a side note, is it true that the most recent Corvette still has the two valves per cylynder method?
Re: Can someone please explain aircooled vs. Water cooled.
Quote:
Hei Poa said:
Hello,
Sorry if I say a heresy, but I thought Porsche also move from air-oiled to water cooled because they also needed to have 4 valves per cylinder technology. They also could had it with air-cooled but results would not have been that good.
You're right. Water cooling allows you to channel the coolant (water) to areas close to the source of heat, the combustion chamber.
A much larger volume of air than of water would be required to achieve the same cooling effect, and there is no way to get that large volume of air as close to the combustion chamber as is the case with water ports.
Fitting more valves into the head makes it more difficult still to get air to the region of the combustion chamber.
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