Why Liquid Cooled?

About the Benefits
  • Overview
  • Getting rid of the heat
  • Heat - the top end killer
  • More power per cubic inch
  • Better performance and fuel economy
  • Radiator technology - past and present
  • Shock cooling - Problem solved!
  • The secret to achieving longer TBOs
  • Flying faster on the same power - reducing cooling drag
  • Side benefits - Safer cabin heat
  • Dispelling the Myths

  • Longer Engine & Component Life
  • Generally, most of today's air-cooled engine's lower-end parts are in good condition at TBO and still within tolerances to go for at least another 1000 to 1500 hours, which for most engines would almost double the TBO. The main area for wear and problems is the cylinder heads and top-end valve components, primarily the exhaust valve, seat and guide. Many air-cooled engines fail to reach their TBO without experiencing serious top-end problems.

    • 3000-5000 hour TBOs
    • Top-end durability/longevity

    Liquid-cooling results in better engine reliability and longer top-end component life. This translates to longer times between overhaul with fewer, if any, top-end related service problems during an engine's service life. With liquid-cooling we foresee TBOs reaching upwards of 3000 hours and expect to ultimately achieve TBOs of 5000 hours with few, if any top end problems occurring along the way.

  • Improved Engine Performance & Fuel Efficiency
  • CLICK FOR CHART A liquid-cooled engine does not require super rich fuel mixtures to cool the engine.

    • - More power on less fuel

    So at takeoff and climbout from a sea level airport a Cool Jugs liquid-cooled engine should be leaned to peak EGT for maximum power output and fuel economy without fear of detonation or engine damage. The result will be more power (about 5-7 additional horsepower as a result of the leaner mixture) and fuel consumption of around 12 gallons per hour instead of over 20 gph when running at full rich mixtures.

  • Higher Degree of Reliability
  • A liquid-cooled engine's cylinder head is maintained at 200F, it does not suffer from thermal work hardening which results in stress fractures and warpage. A liquid-cooled engine also has far less temperature differential across the cylinder head during operation further reducing the thermal stress.

    By far the greatest benefit of liquid-cooling is the lifespan of the exhaust valve and guide. The majority of heat is removed from the valve face through the seat area. The valve stem temperatures are kept well below the point at which oil in the valve stem/guide area becomes carbonized, thereby eliminating any carbon buildup and the resulting stickiness and excessive wear.

    • T6 hardened cylinder heads
    • No more sticky exhaust valves
    • Less exotic components

    Since liquid-cooling removes most of the heat from the face of the exhaust valve through the exhaust seat, there is no need to use the same exotic and expensive sodium filled exhaust valves that are used in the air-cooled cylinder heads. Liquid Cooled Air Power is researching alternatives to replace the exotic sodium filled exhaust valves that will offer better service life and improved flow which further translate into improved engine performance.

  • Eliminate Shock Cooling with Lower & Stable Engine Temps
  • CLICK FOR CHART An air-cooled aircraft engine typically operates over a wide range of temperatures. From as low as 250 degrees during idle or a rapid descent to 380-400 degrees at cruise to over 450 degrees in a steep sustained climb on a warm day. This wide range of temperatures causes a substantial amount of thermal stress in the cylinder head and exhaust valve area resulting in cracked or warped cylinder heads and sticky exhaust valves.

    A liquid-cooled engine doesn't have a shock cooling or heating problem. Since a thermostat controls the coolant temperature, the engine remains at a stable 200 degrees, plus or minus 5 degrees, during all phases of flight and ground operations. Both shock cooling and heating become a thing of the past.

  • Lower Cooling Drag
  • Let's not forget about the reduction in cooling drag. As part of any conversion a new cowling design should be considered. A liquid-cooled engine no longer requires a massive volume of airflow through the engine compartment. It's estimated that a properly re-designed cowling should yield in the neighborhood of a 5-10% increase in top speed depending on the type of airframe.

  • Safer Cabin Heat
  • Aircraft with air-cooled engines mostly rely on passing air over the exhaust system to supply heat for the cabin area. As a result of concerns over the possible presence of carbon monoxide (should there be an exhaust system leak), cabin heat is rarely used.

    • Safe, carbon monoxide free heat
    • Easily regulated
    • No involuntary naps

    A liquid-cooled engine can supply cabin heat with a heat exchanger that extracts heat from the engine coolant, the same type of system used in automobiles. It's much safer, always available and eliminates any risk of carbon monoxide poisoning. No involuntary naps here.



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    1413 Prospect Ave., Hermosa Beach, CA 90254
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    Proudly MADE in the U.S.A.