Eggheads on message boards love to throw around terms like adiabatic efficiency, but exactly how does it impact performance? According to ProCharger, in simple terms, adiabatic efficiency refers to the heat added to air when it's compressed. The more efficient the compressor, the less heat. Pangrac says that since centrifugal superchargers feature much higher adiabatic efficiency than positive-displacement superchargers, they create less heat. "Because centrifugals are mounted in front of the motor in a fresh-air stream instead of on top of it, they do not absorb nearly as much heat from the engine," he explains. "ProCharger has a dedicated lab in which compressor designs are tested, and we are the only company in the industry that machines its impellers from billet aircraft-grade aluminum. That means our testing cycles are relatively quick, allowing us to optimize our supercharger designs more easily."
While optimizing quench area in a naturally aspirated motor is critical to producing power and reducing the likelihood of detonation, that isn't necessarily the case in supercharged applications. In other words, the reduction in compression ratio that results from using a thicker head gasket or running your pistons slightly below the deck is well worth it even though it harms quench. "From our experience, quench is not as big a factor in a supercharged motor as in a naturally aspirated motor, as proven by many different combinations that have been tested over the years," Summers says. "A proper compression ratio is much more important for creating power with a supercharger than optimizing your quench area. This is not to say that optimizing your quench area won't net you some horsepower, but getting a lower compression ratio is going to net you a lot more. Where quench is a little more important is on an alcohol motor, where you would typically run more compression anyway."
Centrifugal Blowers & Carbs
For those who don't like the idea of cutting a hole in their hood, it has become much easier in recent years to match your carb to a centrifugal blower. To help the cause, ProCharger offers several kits for both big- and small-block Chevys that come complete with the supercharger, intercooler, brackets, tensioners, belts, and tubing. "Sometimes there is a very small amount of fabrication needed to install the intercooler in some older cars, but the majority of the install is bolt-on-and go," says Pangrac. "There isn't much with regards to these installations that a guy couldn't do in his driveway. Even many of our cog-drive systems are 100 percent bolt-on installations. For high-horsepower race applications there is sometimes more fabrication with regards to intercooler setups, but it isn't anything terribly difficult."
It's becoming pretty common these days to make over 1,000 hp with a blower on pump gas. If numbers like that suit your fancy, ProCharger has some valuable tips for you to follow. The most important piece of advice is to plan your engine build for forced induction up front, and select high-quality components that are going to work well together. "If you have a 700hp big-block with an 11.0:1 compression ratio and you want to throw a ProCharger on it to try to push it over 1,000 hp, you are going to have problems running pump gas," Pangrac explains. "A few phone calls and some planning up front will pay off big-time when you go to fill up that 1,000hp ProCharged monster at the corner gas station. We even have some customers making 2,000 hp on pump gas. In addition to lowering the compression ratio, quality aluminum cylinder heads, a camshaft with plenty of exhaust duration, and a free-flowing exhaust system go a long way in getting the most out of pump gas."