Seeing the trailers for the next Classic Car resto show on C5 (where they will no doubt be restoring a Porsche 911 to death!), got me wondering if air cooled engines could ever make a comeback.
We tend to associate air cooled enginces as ancient technology used in the likes of Beetles and Tatra's and Porsches but there's no need for the engine to be stuck out the 4rse end of the car.
They have the advantages of being smaller and therefore take up less space, simpler in design and lighter as they have fewer parts such as radiators, pumps etc and are thermo dynamically more efficient.
The downsides are there is a limit to the size of an air cooled engine and its efficiency (this is why Porsche binned the air cooled flat six in favour of water cooled. They are also noisier and less efficient.
But with advances in engine technology with power from smaller turbocharged units (Ford's 1.0 engine as an example), could the disadvantages be overcome?
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Emissions control says no.
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>> Emissions control says no.
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+1
Even disappearing on bikes now for the same reasons.
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>> have the advantages of being smaller and therefore take up less space
Not always in practice: cooling fins round the cylinders, and cladding around them to channel the forced cooling air, and the damn great fan needed to force it - power-sapping at high engine speeds -, can make air-cooled engines quite bulky. They are lighter though, a bit, and the fan and cladding make nice whirring and rattling noises (if like me you like that sort of thing).
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Emissions control says no.
In the short term, maybe. But as fossil fuels go the way of horses and steam, I don't foresee many water-cooled electric motors.
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Even the venerable and excellent air-cooled BMW boxer is going to be cooled by water soon.. :-(
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>> Even the venerable and excellent air-cooled BMW boxer is going to be cooled by water
>> soon.. :-(
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The doom-mongers have been prophesising liquid cooling (either partial or total) on Harley-Davidsons for a generation. Hasn't happened yet unless you count the blind alley that the V-Rod has become; but given that , like the BMW's, these bikes are infinitely rebuildable I suspect we'll be seeing aircooled bikes around for a long time yet.
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There's some spy shots of the new water-cooled GS which has caused some consternation on the "forums" increased weight (especially on the GS) is a biggie.
bmwmcmag.com/2011/02/spy-shots-water-cooled-boxer-gs/
Seems they've rotated the cylinders by 90 degrees.....
Last edited by: R.P. on Fri 28 Sep 12 at 18:09
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>> I don't foresee many water-cooled electric motors.
I do.
Owing to its high heat capacity, it's an attractive coolant, and if internal rotor DC brushless motors are used, it's quite easy to provide good cooling for the windings without any danger of compromising the electrical integrity of the motor.
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>> Emissions control says no.
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>> In the short term, maybe. But as fossil fuels go the way of horses and
>> steam, I don't foresee many water-cooled electric motors.
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Er, I think you'll find that the implementations in pretty much all the electric and hybrid vehicles use liquid cooling. Electric motors generate quite a bit of heat and it has to be removed somehow. In hybrids, where the motor(s) tend to be squirreled away inside a transmission, liquid cooling is the only option.
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>> In the short term, maybe. But as fossil fuels go the way of horses and
>> steam, I don't foresee many water-cooled electric motors.
>>
They exist - on the Strasbourg trams and others.
Similarly water cooled invertors.
Less space required, cleaner and quieter than air cooling
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>> >> have the advantages of being smaller and therefore take up less space
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>> Not always in practice: cooling fins round the cylinders, and cladding around them to channel
>> the forced cooling air, and the damn great fan needed to force it - power-sapping
>> at high engine speeds -, can make air-cooled engines quite bulky. They are lighter though,
>> a bit, and the fan and cladding make nice whirring and rattling noises (if like
>> me you like that sort of thing).
>>
I know VW engines had ducting and a large shroud behind the engine but was that because it was located at the rear of the vehicle? If an air cooled engine was in the front of a car wouldn't it get all necessary cooling without the need for large ducted fans? Why not have a thermostatically controlled electric fan to assist during stationary traffic.
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The later Audi diesels have two electric waterpumps that don't operate until the engine is hot (hardly ever) and the rest of the time the water forms a static jacket. These cars even need webastos for the heater.
Maybe as engines become more efficient and struggle to reach normal temps, aircooled will return?
Last edited by: sooty tailpipes on Fri 28 Sep 12 at 17:00
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>> Why not have a thermostatically controlled electric fan to assist during stationary traffic.
2CV and GS Citroens had, er, large ducted fans although they were front-engined. Ram effect alone wouldn't cut the mustard at low-to-moderate speeds on busy roads with a following wind and high ambient temperature for example. The electric fan solution would demand very heavy-duty electrics. The designers of those cars must have done lots of sums!
I have a soft spot for air cooling and flat engines. There was a wonderful American thing whose name I can't remember that was powered by a large Lycoming flat-four air-cooled aircraft engine, low down at the front I think. Peak power at 2,500 rpm, so higher gearing than usual... bet it sounds good but there are very few examples. It was costly and US car buyers don't like weird...
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I know the ones you mean - they were quite aerodynamic for their day and there was a Hollywood film about them, wasn't there? (still can't remember the name, though)
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Actually, all engines are air cooled. Heat is transferred by water to a radiator it is cooled by the passing air.
God, I feel so SMUG.
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>> Actually, all engines are air cooled. Heat is transferred by water to a radiator it
>> is cooled by the passing air.
Not when the thermostat is closed its not!
>> God, I feel so SMUG.
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I thought so: the mighty 5 litre turbocharged flat 12 Porsche 917, so fast and undeveloped that it killed several drivers, was air-cooled.
You never ever heard anything like one of those in full cry.
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Why should the method of cooling affect the exhaust emissions? How does the chemical reaction in the combustion chamber know what method is being used to remove excess heat?
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It's to do with noise reduction as well. I think the GS struggled to meet it's "ride by" noise tests on the last engine upgrade. They had to fit some sort of special valve to get it through. Don't know much about the emissions stuff.
Last edited by: VxFan on Tue 2 Oct 12 at 00:46
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>> Why should the method of cooling affect the exhaust emissions? How does the chemical reaction
>> in the combustion chamber know what method is being used to remove excess heat?
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Engines run most efficiently within a fairly narrow temperature range. This is much easier to achieve and maintain with a thermostatically controlled liquid cooling system than it is with air cooling.
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Ah, that makes sense. Thanks.
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>> I know the ones you mean - they were quite aerodynamic for their day and
>> there was a Hollywood film about them, wasn't there? (still can't remember the name, though)
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Tucker? Rear engined though I thought.
Yes and six cylinders too. Can't be what AC was thinking of.
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Will air cooled engines ever come back? - Lygonos
