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Intercooling 101: Detonation Defense

An intercoolers goal is fairly simple: Reduce induction air temperature. If you had a simple Ideal Gas Law PV=nRT compressor, the simple fact of compressing gas (in this case, ambient air) from, say, 10 PSIA and 23 F (at roughly 10,000 feet) back to sea level pressure of 14.7 PSIG would heat the gas. But, in addition to that ideal gas behavior, our turbocharger compressors have other inefficiencies, like internal recirculation and heat transfer from the cowling environment, that heat the gas further. Its not uncommon to see compressor discharge temperatures (CDT) over 200 degrees F at middle altitudes and over 300 F in the flight levels.

Paul Millner
Verified

Based on calls and letters we’ve fielded, there’s a certain mystery that surrounds engine intercooling systems. But there’s no mystery because simply put, an intercooler is essentially a radiator, or heat exchanger. That’s the key to engine longevity, of course.

But aftermarket intercooling systems add complexity and can crowd already tight engine bays on turbocharged aircraft. For engines that have efficient turbos, an intercooler might not do much. For others—especially those plagued with high cylinder head and turbine inlet temperatures—the investment could be worth it. Here’s a deep technical analysis to help with the decision, and some tips for assessing a given design.

Paul Millner