Boost and airflow are two different animals, but the terms are often used interchangeably. What really matters at the end of the day is how much air and fuel you move through a motor. Boost is simply a measure of the backpressure inside the intake manifold. If you reduce any restrictions in the induction path of an engine, such as increasing cylinder head flow, boost pressure will decrease but the engine will make more power. We get calls on our tech line all the time with people concerned because they made modifications to their engine and their boost went down. When we ask them if they’re making more power, the answer is always yes, and the reason is because they reduced the restriction in their motor. That said, for any given displacement engine, after you’ve optimized the other variables—like the cylinder heads, camshaft, and exhaust—then boost pressure becomes the primary lever used to increase airflow and power. If these other variables are fixed, then you can increase pressure to increase flow, but that’s not the only tool available. You can actually increase power and have boost go down. The trick is to maintain the same boost pressure while reducing the restrictions inside an engine to dramatically increase power. People often get a certain boost figure stuck in their head, and think that’s what they need to run, but 20 pounds of boost on a big-block represents much more airflow than 20 pounds of boost on a small-block.
ProCharger offers both air-to-air and air-to-water intercoolers. In a drag race–only application, air-to-water intercoolers are very popular since you can pack them with ice and since the car is only run for a very short period of time. For a street car, however, an air-to-air intercooler is a much more practical solution. The problem with an air-to-water intercooler system in street cars is that it requires a secondary heat exchanger to remove heat out of the liquid. Essentially, the water that cools the intercooler gets heated up by the intake charge, and that heat must be removed from the intercooler liquid with a separate heat exchanger. In reality, an air-to-water street intercooler is really an air-to-water-to-air system. If you only need to cool the intake charge for short periods of time, packing an air-to-water intercooler works great and you can eliminate the need for a separate heat exchanger. On the other hand, the inherent inefficiency of the air-to-water-to-air process makes air-to-water intercoolers a poor choice for the street. We do use air-to-water intercoolers in marine applications because when you’re on a boat, you’re sitting on the world’s largest heat exchanger. In marine applications, you pump cold water into one side of the intercooler, and dump it back into the ocean out the other side.
A big part of intercooler selection is fitment. The highest capacity air-to-air intercooler we offer supports 1,550 hp, but it measures 27 by 12 by 6 inches. Realistically, it’s difficult to fit an intercooler that’s any larger than that into a car. For motors that produce more power than that, we recommend an air-to-water intercooler. Moreover, cars with small front ends, like fourth-gen Camaros, make it tough to package intercoolers. Fortunately, the retro styling of newer cars have bigger front ends, and more room for intercoolers.