"Cold air is more dense and carries more oxygen molecules," was the response Justin Burcham of JPC Racing blurted out when we asked about his reasoning for adding the new JPC Racing air-to-water intercooler to many of his high-horsepower, forced-induction customer cars. The modification is a simple solution to an increasing problem that Burcham realized while racing his popular '05 Mustang GT in MM&FF/NMRA True Street competition.
The True Street Challenge is a torture test for an 8-second ride like the one he brings to battle. The 30-mile cruise heat-soaks the engine, supercharger, and transmission before competitors attempt to perform three consecutive runs down the track-without the aid of cooling the car or popping the hood. Factor in the sweltering summer temperatures and you can see why heat from a supercharger can be a problem for all-out performance.
Burcham continually saw his inlet air temperatures climb high as the air-to-air intercooler attempted to bring it down to reasonable levels. "I have seen temps as high as 300 degrees on my car and many big-boost turbo and supercharged customer cars. The intercooler would barely do anything because it is heat-soaked. Often times, we deal with 90-degree weather-not just in True Street but also during local test and tune sessions. Couple the high ambient temperature with even hotter compressed air from a supercharger or turbo and it becomes difficult for a front-mount air-to-air intercooler to keep up," stated Burcham.
"There is no fresh air other than the 90-degree air running through the intercooler at low speeds, usually in the front half of the track. By the time the car really gets moving, the air and the intercooler are already heat-soaked." As the charge temps climb, performance falls off because the hotter air carries fewer oxygen molecules, and the ECU starts to pull timing because the raised inlet temperture and subsequent increased combustion temperature is more likely to cause detonation. Burcham has seen 3-4 degrees being removed in high gear because of the hot air.
Many blower kits come with an air-to-air intercooler or a small air-to-water unit (both of which are fine for most applications), but as the engines get more radical and the blowers get bigger, there comes a need for a more efficient intercooling system. An air-to-air style intercooler refers to air rushing over a heat exchanger to cool the boosted air down, much like a radiator does for engine coolant. An air-to-water intercooler is a heat exchanger that relies on circulating water (often ice water in race applications) to cool the air charge.