The secret to achieving longer TBOs



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

  • Making TBO (Time Between Overhaul)
  • Today we live with engines that should be able to make TBOs of as little as 1500 to 2000 hours! That is the equivalent of 50,000 to 85,000 miles on an automotive engine! Worse yet, few air-cooled engines even make it 1500 to 2000 hours without some sort of serious top end problems often requiring a partial or even full top overhaul prior to reaching TBO. How many of us would tolerate such a poor service reliability and short lifespan in our automotive engines? Today we expect and often achieve 150,000 to 300,000 miles on our automobile engines with hardly a problem along the way. Why is it then that we can't expect the same out of our far more expensive aircraft engines?

    The answer is simple too much heat!

    Air-cooled piston aircraft engines endure cylinder head operating temperatures of 350 to 450F that are easily twice as high as any water cooled engine. Keeping a high-powered air-cooled engine's temperature under control is an almost impossible task.

    As power increases per cubic inch of displacement the heat dissipation requirements increase substantially. That is why turbo charged air-cooled engines have even shorter TBOs. The top end of the engine must endure even higher continuous operating temperatures because there are only so many square inches of surface area on an air-cooled engine in which to dissipate the heat. That in a nutshell is the entire problem with air-cooled engines. Their ability to dissipate heat is limited to the surface area of the fins on the cylinder head and walls and requires a monumental amount of airflow in order to keep the top end of the engine from literally melting down.

    General Aviation piston engines are essentially the last of the air-cooled piston engines virtually all other internal combustion engines have converted to water cooling? The vast majority of motorcycle engines and even die hard air-cooled automotive engine manufacturers like Porsche have gone to water cooling in the quest for more power and reliability per cubic inch of displacement. In fact water cooled automotive engines have in many instances more than doubled the power output per cubic inch of displacement in the over the last 10+ years. One of the principle reasons such advances have been possible is because the operating temperature of the engine is kept at a stable and efficient level allowing for higher compression ratios and more precise fuel and engine management systems to be developed.

  • Imagine TBOs of 3000 to 5000 hours
  • Sound hard to believe? Well it shouldn't be - it should be what is expected of our aircraft engines today. The original manufacturers haven't made any serious efforts to extend the life of our aircraft engines. The main hurdle to overcome is the continued use of air cooling rather than water cooling. Water cooling substantially reduces and stabilizes engine temperatures and substantially extends the top end component life especially the exhaust valve and seat.

    Generally at time of TBO most of today's air-cooled engines lower end parts are in good condition 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 are the cylinders and top end valve components, primarily the exhaust valve, seat and guide. With water cooling we foresee TBOs reaching upwards of 3000 hours and expect to ultimately achieve 5000 hours. Such an extension in TBO would more than offset the increase in the cost of a water cooled engine however, and more importantly we would expect no top end problems during the service life of the engine. This contrasts sharply to the fact that many air-cooled engines rarely go to their TBO without some form of top end problems requiring either a partial or complete top overhaul prior to reaching TBO.



    Liquid Cooled Air Power © 2001 Liquid Cooled Air Power. All Rights Reserved.
    1413 Prospect Ave., Hermosa Beach, CA 90254
    Proudly MADE in the U.S.A.
    Proudly MADE in the U.S.A.