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More on Auto Engine Endurance

Tedd McHenry, Webmaster

Some of you may recall that a couple of years ago I wrote an article hypothesizing that there is no reason not to expect auto engines to have adequate durability when used in an airplane (WC RVator, April, 1998).  I based my hypothesis on an analysis of cylinder pressures, piston speeds, and piston accelerations in a Chevy 4.3 compared to a Lycoming O-320 and O-360.  My belief is vindicated by this quote from a Chrysler engineer about the test cycle used in the development of their truck V10 engine for use in the Viper sports car (reproduced from Contact! magazine).  The test cycle he describes is much more severe than the certification requirements for aircraft piston engines.

“We use an [sic] unique 500 hour endurance cycle.  The traditional Chrysler endurance cycle for trucks had been 800 hours.  To shorten our program timing, we discarded all of the specified light duty and idle test modes and got it down to a 500 hour cycle.  It’s pretty much a WOT test between peak torque and peak power with a little bit of light load in between.  We set our targets at passing three 500-hour durability tests, a general 500 hour test, an ECE test, which is a European emissions certification procedure and a 100 hour test traditionally done for the exhaust manifold durability.  Engines must pass a minimum of those tests.”

To put this in perspective, remember that a Lycoming produces rated power at peak torque.  So when an auto engine is tested at peak power (which is above peak torque), it is actually being run at loads beyond what a Lycoming ever sees, either in testing or in use.  Almost the entire Chrysler test was run at loads greater than what the aircraft industry would call full rated power.  And all of the test was at loads at least equal to “full rated power.”  Furthermore, the FAA certification requirement is for a 100 hour test at rated power.  So the Chrysler test is also five times as long as is required for certification.

I think this test shows that auto engines are extremely durable, and easily capable of handling the loads they would be exposed to in a typical aircraft installation.

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