ac vs wc engines

[Sparky_vp]

howdy all....just wondering what are the pros and cons regarding ac vs wc engines

[Tony Z]

what would you really like to know?
One could write a thesis on your questions comparing it to the fact the beetle engines have lasted so long, but most engines are watercooled. Then back reference it to industrial engines being aircooled and so are military engines in smaller sizes, but the larger ones are watercooled. Then again deutz engines survive the sahara, so who really needs watercooling?

[Hloni]

Lovely tonyz, just lovely!

[hitlers revenge]

The pro's are that we let you join us on this site....

[retrovan]

howdy all....just wondering what are the pros and cons regarding ac vs wc engines

The "pros" are the ac are here, the "cons" are the wc are happy somewhere els.

[Ron&Gill]

Comparing engines of equivalent capability, you'll find that air cooled engines are lighter and liquid cooled engines are more compact.

Engine development jumped into high gear with the development of fighter aircraft during WW1 and initially light weight was the over riding factor, and relatively low speeds meant aerodynamics wasn't all that important. Later, when speed became more challenging, the engineers developed high performance liquid cooled engines which were compact to fit into stream lined fuselages, and radiators could be put in any convenient air stream, much like F1 cars today.

This chase for speed continued between the wars with a.o. the Schneider Trophy, and by 1935, all important aircraft engines were liquid cooled.

I suspect an air cooled engine as supplied in the Beetle was cheaper to manufacture than a water cooled car engine. And since that was VW's priority in the beginning as well as after WW2, it was successful so they stuck to it. Some opine that VW held onto the air cooled engine too long and should have gone with liquid cooling before the T4 was ever developed, imagine that, no T4 engines, they are the finest!

[Tony Z]

at the end of the day the beetlw engine has proven to be reliable - how many 50 year old engines are running around today??
Its the backyard mechanics and the owners who dont want to spend money that are to blame for the reputation of a beetle being unreliable - yet even as unreliable as they are, it is still the only 50 year old engine regularly driving around SA - proof that even the lack of money or the backyard mechanics have not been able to kill them, which should be a further testament to how good they are.

[Ron&Gill]

Uhm... nobody is saying they aren't good...

[Tony Z]

not yet....

[Dawie]

Actually all automotive engines are aircooled. Some just use water as an intermediate medium (with limited capabilities) to move heat to a radiator, where it is then cooled by air.

Boat engines are truely cooled by water, (sometimes via a water-to-water heat-exchanger to keep saltwater from the engine).

Advantages of so-called "watercooled" engines:
1) Cheaper to manufacture in multicylinder form, (in latest robotic plants), less parts.
2) Cheaper to make it soundproof/ silent,
3) Cheaper to provide controlled heating for interior of vehicles,
4) Cheaper and simpler thermostat system,
5) Easier to remove large quantities of wasted heat from some high performance engines.

Disadvantages:
1) More weight for total engine system, (including radiator, water, etc.),
2) Limited operating temperature of water. ( Can freeze and boil). Freezing damages welsh plugs or can crack the block. The hotter ambient temp gets, the less efficient it gets. If outside is 50 deg.C, only 60 degs difference between 110 deg pressurised radiator temp. If 110 is exceeded, it boils, form steam pockets, and temp can quickly rise to well over 400 degs.
3) Reliability issues at sealing surface between head and cylinders. If head gasket develops even a tiny leak, combustion pressure enters water channels, displacing water, with disastrous results. On racing engines, the head is sometimes welded to the block from inside the cylinders, for a better seal.
4) Reliability issues caused by leaking waterpumps, radiators, hoses or heater cores.
5) More maintenance needed, (Checking water level, need to replace water/antifreeze if waterpump, radiator, hoses, head gasket, etc, was replaced).

Advantages of aircooleds:
1) Wider operating temp possible. At around 200 deg C max cht temp , difference between cooling fins and air on a hot 50 deg day is still 150 degs, and good transfer of heat is possible. (Try using same two small cooling air intake openings on a kombi to cool a watercooled conversion. At only 60 degs difference between ambient and radiator, even with massive fans, not going to happen).
2) Lighter weight,
3) Less maintenance required, (no coolant to check).
4) Compression leak at head/cylinder joint is not serious. Still possible to continue driving for 100's of kilos to your destination.
5) No water to leak, boil or freeze.

Disadvantages:
1) Inherently noisier, more expensive (but not impossible),to silence.
2) More expensive to build in multicylinder form in latest robotic manufacturing plants. More parts... (Individual cyls and heads). Might have been different in early days with skilled German workforce.
3) More difficult to design thermostat system.
4) More difficult to heat interior of vehicle,
5) Prone to damage and fiddling caused by backyard mechanics, (who do not understand them).

Ferdinand Porsche tried various different engine types in his prototype beetle vehicles. One was a small 5-cylinder radial watercooled engine. It suffered from overheating in a rear-engine application.
From his previous experience he wanted a lightweight drivetrain (for better handling in rear-engined configuration), and the ability to drive up steep Swiss and Austrian mountain passes without overheating. Previously, while at Mercedes, he designed the small 130H and 170H rear engined Mercedes cars, with watercooleds, and wanted to improve on their design.
One of the most efficient aerodynamic designs of the era, (still often referred to today), were build on a rear-engined Mercedes chassis, as the beetle chassis was not ready at that time. Search "Pillbug", (By Professor Schlor).

Diesel engines can be made to operate more efficiently if aircooled, as less heat-energy is wasted to the cylinder walls. Problem is increased nox-emissions at these higher temps.

[Tony Z]

thesis complete - Well done Dawie