I was wondering the other day why 99.999% of modern made cars are watercooled? I know Tatra still made aircooled cars up untill recently and now still makes aircooled trucks but I would think that the advantages of having an aircooled engine would mean that they would be more common in todays new car market instead of non-existant. I mean with an aircooled car you don't have to buy coolant, antifreeze or anything, you don't have to become one of those people on the side of the road with steam coming out of the radiator. All I want to know is why has the watercooled car become so widespread and why not aircooled?

reliability. modern cars are use4d in far too many enviroments, and push the efficiency enveloipe well past the point that air cooling would be effective. on a low output motor air cooling works fine, but on a motor that has the same capacity but twice the output, you simply cannot achieve the same cooling efficiency as you can with water cooling.

it's far more stable too, you dont get such temp fluctuations.

There are a number of overlapping reasons, but the big kahoona is that water cooling allows more precise control over cylinder temperatures and consequently provides conditions under which you can meet emissions laws.

Manufacturers were going toward water cooling for a variety of reasons, especially as the specific (i.e. per litre) engine output rose, but the introduction of emissions legislation in the '70s in the USA (a huge market for all manufacturers, often bigger than the manufacturer's own domestic market) was the death knell of the remaining AC approaches.
hth

I agree with Modulus, Emissions is the big killer, noise is also a problem with aircooled, the water jackets help supress engine noise.

Yeah why didn't I think of that before? But if a group of designers or whatever put their minds to it don't you reckon that they could find ways to solve those problems and keep the advantages of aircooled engines? Tatra was still producing aircooled cars in the 80's and made a aircooled V8.

$$$$$$$$$$
Its not worth the effort

[ramble]
A humorous sideline to this story is what happened in the late 70's early '80s when the American legislature introduced flawed emissions legislation.

Most of the limits were in parts per million, not in more carefully thought out units such as parts per passenger-mile, so the domestic manufacturers complied by upping their engine capacities e.g. in this period Buick engines went from 350 c.i. (5.7 litres) to 455 c.i. (7.5 litres!).

These monsters (and we're talking passenger cars here, not performance cars) were typically used to drive one person to work and home on the freeways at 55 m.p.h. spewing out vast amouints of crap, but at least the crap was OK in parts per million of total exhaust.

To a certain extent the laws have been improved; in particular they realised the 55 mph limit was a people killer (no-one was concentrating) and that's been removed; even then the Americans are good at unintended consequences; several times while bowling along at a perfectly sane 80 mph on well kept interstates I've taken an "off-ramp" only to discover that the off-ramp was designed and constructed in the time when the speed limit was 55 m.p.h...yikes....

[/ramble]

The only reason I can add to the valid ones above are that w/c engines maintain their temperatures in a narrower band than a/c & this means you can manufacture to much finer tolerances. Air cooling usually requires looser tolerances to allow metal to expand & contract to a greater extent. Also, as power increases, you need better cooling. Eg small m/cycles are gen a/c but even the venerable BMW boxers had to be upgraded to w/c as the power went up!

Quote; on a low output motor air cooling works fine.

It does work well on a low output engine, but It works on performance engines too, look at the Porsche 930 Turbo, and most of the other normally aspirated Porsche engines.

A local company here in Bundy make air cooled horizontally oposed engines for their Jabaru aircraft. They make them from four to eight cyclinders in size- I see all the testing photos they take (I work in a photo lab)

I have always wondered how one would go strapped in the back of the buggy (but at $26000 a pop for the flat eight I won't ever know)

hmmm....i'd like to imagine that...coooool...but the price isn't....but still cooooolll...:P:thumb

Hehe thnx you guys i was wondering the exact same thing last night, but aircooling works just fine for beetles and kombis:thumb

it does make driving a high powered aircooled vehicle just that much sweeter. takes a bit more effort to make it go and stay cool. watercooled = cop out. har haaaargghhh *waits for the fallout*
i was thinking that the tolerances in an aircooled motor had to more exact, as there was less room for error.. watercooling leaves you a greater margin for crudness.:alien
------> enter the wes

As the others have mentioned, water cooling allows for better control of the cylinder and combustion chamber temperatures.

This has the effect on emissions, it also means longer engine life, and most importantly enhanced knock control which allows higher compression ratios to be tolerated.

It also provides an easy source for cabin heating.

Porsche stuck with it for so long because it was it's trademark. But it has finally given in.

In an aircooled engine you can't increase the cooling area if you want to run big HP, whereas a watercooled car you can increase the radiator size.

You can also make a watercooled engine more compact.

... and higher compression ratio theoretically makes higher energy efficiency (and higher specific power too). Theoretically.

Which is why a 20:1 TurboDiesel has a greater energy efficiency than say my 7:1 bus. The problem with diesels is that there's a whole lot of particulates in the exhaust, even if the CO2 is lower. "They're" working on that by using filters and such.

(This sound right Baja Wes?)

Aurel

They have just lowered the sulpur content in Diesel...
Australian spec diesel wasn't too good apparently...

I suppose We can always add another oil cooler if the engines too hot??

When You see motor cycles with radiators... Most of them do have them these days.. I think air cooling is dead....

I believe a lot of people think that just water goes into a water cooled car... and that is a mis conception...
Water should NEVER be put in a water cooled engine, it should be coolant, as coolant under pressure also raises the boiling point of water... so if You replace all the hoses at regular intervals and keep the Radiator free of Bugs etc...
You won't have a problem....

Lee