If racing improves the breed, then ProCharger's vast racing triumphs have come pretty darn close to creating a genetically coded super-specimen by now. In its 15 years in the industry, the company has racked up more than 40 national championships in the highest ranks of competition and has set countless records along the way. ProCharged NMCA racers are well on their way to breaking the 5-second barrier in the quarter, and the company's in-house Nova test mule is on the cusp of cracking 7s on 91-octane fuel. What ProCharger's accomplishments at the track, on the salt, and in the dirt translate into is a superior line of battle-tested supercharger kits for your average weekend warrior.
These days, 1,000hp ProCharged street/strip machines are becoming commonplace. Success like this doesn't just happen, so we asked Jim Summers and Cary Pangrac of ProCharger to elaborate upon what technical innovations have been integrated into the company's line of superchargers to get them where they are today. Whether you're thinking about slapping a blower on your carbureted muscle car or fuel-injected late-model, ProCharger has you covered. To help you achieve your power goals, here's ProCharger's advice on how to centrifugally boost your way to glory.
From very the beginning our goal at ProCharger has been to provide a reliable, powerful, and efficient supercharger system that can be applied to a wide range of vehicles and engine combinations. Our company was founded in 1994, and that year we released the industry's first intercooled supercharger systems--more than three years before anyone else. This supercharger, the P600B, outflowed other street-legal models by more than 65 percent, and 15 years later it still outflows comparable models by more than 20 percent. ProCharger was also the first to warranty boost levels above 8 psi, and even today, ProCharger offers one-year warranties on boost and power levels that are unheard of. Our first offering was for the small-block Chevy, and then we expanded into big-block and intercooled marine applications. In 1998 ProChrager introduced the D-1--the first race supercharger offered with a warranty--and in 2000 we launched the first self-contained, geardriven centrifugal supercharger. When 2002 rolled around, ProCharger reached the 2,000hp mark in a 400ci Chevy and also introduced the first intercooled blower system for LS-powered Corvettes. Through the years, ProCharged vehicles have won nearly 50 national championships, and our project Nova has run an astonishing 8.18 at 170 mph on 91 octane fuel with our F-2 head unit. Today our blowers have produced over 2,500 hp on gasoline and 3,000 hp on methanol. The fastest ProCharged e.t. to date is 6.25 at 227 mph. --Jim Summers
Many of ProCharger's blower unit's feature self-contained lubrication systems. The company says this arrangement offers several advantages. "In addition to eliminating the need to tap a hole into the oil pan, a self-contained blower also eliminates the heat that would be transferred to the supercharger from the engine's oil system," Pangrac explains. "A self-contained supercharger eliminates the potential for clogged oil lines and oil drainage problems. Likewise, a self-contained system allows the customer to remove the kit if they decide to sell the car without having to plug the hole in the oil pan. In the event of an engine failure, contaminants will not get into the supercharger."
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."
Preparing carburetors for use in a blow-through application typically involves few, if any, modifications. Among those needing no modifications are Holley's HP-series carburetors, which are designed with no choke assembly and are generally equipped with Nitrophyl floats. For standard double-pumper carburetors, the choke assembly should be removed to provide optimal airflow and performance when used with a carburetor bonnet. Additionally, the brass floats--which will collapse under boost--must be replaced with Nitrophyl floats. With only a few modifications and proper jetting, Holley double-pumpers will typically flow enough fuel to support roughly 1 hp per 1 rated cfm of airflow. Single-carburetor applications exceeding 1 hp per 1 rated cfm may require additional modifications such as resizing main wells and power valve restrictions, changing boosters, and emulsion circuit recalibration. Generally when modifications like this are needed, we send people to a reputable blow-through carburetor builder like The Carb Shop.--Cary Pangrac
To maximize power and reliability in a supercharged engine, intercooling is imperative. That's why we include intercoolers as standard equipment in nearly all our blower kits. It helps to understand that no supercharger alone will ever begin to match the system efficiency of an intercooled supercharger system. This is simply because compressing air creates heat, as dictated by the laws of physics in Boyle's Gas Law. Cooling down that air allows for higher boost levels and safer power production. Since intercooling removes heat, increases air/fuel density, and allows the use of factory ignition timing, a well-designed intercooled supercharger system will produce far larger power gains than a non-intercooled supercharger system, especially for fuel-injected motors running pump gas. ProCharger manufactures both air-to-air intercooler systems for street/strip use and air-to-water intercooler systems for racing only. For automotive street applications, air-to-air technology is easy to install, highly effective, and extremely reliable since it has no moving parts and requires no maintenance. Air-to-water intercooler systems, on the other hand, are much more difficult to install because they contain an intercooler, a water tank, a pump, and a separate radiator to cool the water. Probably the biggest drawback to air-to-water intercoolers on the street is that they require ice to match the efficiency of air-to-air units. Additionally, the requirement of ice and the possibility of pump failure or leakage mean that air-to-water is also inherently less reliable. For race-only applications, air-to-water works well since adding ice at the track prior to each run is not hard to do. The other issues are the same as listed above for street applications, and efficiency will be comparable with the use of ice.--Jim Summers
Supercharged motors would run like dogs if blower impellers spun in proportion to engine rpm. Consequently, superchargers employ an internal step-up ratio, which is simply the number of times an impeller rotates for every revolution of the engine. "There's more to achieving a proper step-up ratio than simply shooting for maximum boost," Summers explains. "A proper step-up ratio allows the customer to use a larger diameter drive pulley for better belt wrap and more belt traction. A 4.10:1 step-up ratio is great for street and many strip cars. Our F-3A and F-3R race models have step-up ratios of 6.24:1 and 5.63:1, respectively."
Superchargers must perform under inherently extreme conditions, so ProCharger goes to extreme lengths during manufacturing to ensure durability and maximum performance. Each of ProCharger's billet impellers and compressor housings have been optimized to offer superior boost and efficiency. To complement these specialized impellers, ProCharger matches them up with precision-ground gear and shaft assemblies designed to provide tens of thousands of miles of trouble-free street/strip operation. "Our F-series models employ ultra-strong, heat-treated, precision-machined 9310 steel shafts and gears designed to operate at high speeds up to 70,000 impeller rpm, with impeller tip speeds approaching Mach 2," Pangrac explains. "These gearsets offer the industry's highest step-up ratios, which allow the use of large pulleys that provide maximum belt contact and belt life. The gear and shaft assemblies, bathed in our proprietary synthetic lubricant, ride on single super-precision SC-series bearings, or our patented compound bearing assembly. All this is precisely anchored in a CNC-machined, aerospace-quality billet aluminum case."
The SAE's published test standard for automotive superchargers, J1723, allows supercharger units to be tested on a bench to measure efficiency. However, there is some debate over whether SAE J1723 accurately expresses how well a blower performs when installed in a vehicle, and ProCharger is not a fan of the SAE's test standard. "It should be noted that supercharger test specification J1723 only applies to testing on a test stand. It does not apply to use on an engine, and specifically does not factor in engine dynamics or intercooling," says Summers. "Additionally, oil temperatures are not called out and thus can be manipulated, and the test specifications do not have provisions to accurately test self-contained superchargers. For these reasons and others, we're only one of many supercharger manufacturers that do not use SAE J1723."
To accommodate a variety of applications, ProCharger offers a plethora of head units. The P600B is an oil-fed unit that is used on a small number of ProCharger's older systems where space is at a premium. Next up the ladder are the company's innovative self-contained units. "The P-1SC-1 is our standard blower that goes on most of our systems, and the D-1SC is usually offered as an optional upgrade in most of our kits," says Pangrac. "The P-1SC-1 and D-1SC are similar in exterior design, but the D-1SC will support a higher horsepower level due to a different impeller and compressor housing design, which provides more airflow. The F-series blowers are for extreme horsepower applications, anywhere from 700 hp all the way up to 3,000. The F-3R-139 is currently our largest supercharger."
ProCharger's method of ensuring reliable supercharger systems is quite simple: beat the snot out of test vehicles during the R&D process. During the development phase, it's not uncommon for one of the company's project cars to endure over 200 pulls on the dyno and nearly 15,000 street miles. "We understand dyno testing is very different from real-world driving, so we test numerous beta vehicles up front before releasing a system to the public," Summers explains. "This testing involves installing the supercharger system and spending plenty of time with the car on the dyno and on the road to get the data the engineers need, and fine-tune the car accordingly. Then we turn the car over to the owner, if it is not owned by ProCharger, and let them beat on it for a while. By keeping in touch with them, we can be informed of any potential problems that may arise with extended use and fix them accordingly."
ProCharger uses billet impellers exclusively in its supercharger units, and the benefits are more than just superior strength. The company says that most aluminum cast impellers have a tensile strength of 36,000 psi compared to the 83,000 psi rating of the 7075 T-6 alloy used in its impellers. "The billet material results in an impeller design capable of withstanding rpm, airflow, and boost levels that are substantially greater than those experienced with cast designs," Summers explains. "By using billet impellers created in-house, ProCharger is able to test and evaluate multiple alternatives prior to production and is not confined to a basic design that can only be `trimmed' in an attempt to meet the needs of a different application. Billet impellers don't suffer from the density variations generally present in cast impellers, and as such are naturally balanced and can operate at higher speeds without generating additional load. Generally lighter than their cast counterparts, billet impellers also reduce blower transmission loads under acceleration and deceleration."
The reason why the recommended WOT air/fuel ratios for supercharged motors are all over the map is because they work well over a wide range. At 12:1, a blower motor typically makes the best power but there isn't much room for error. Arguably the best compromise is at 11.5:1, where power output is excellent while still maintaining a good margin of safety. At 11:1, you're definitely leaving some power on the table, but it's still not overly rich. On the other hand, anything fatter than 10.5:1 is too much fuel and may cause problems with misfiring and plug fouling. It's worth noting that cylinder-to-cylinder variation could be significant in a carbureted application, and the difference between the leanest and richest cylinders need to be considered. As for the rest of the fuel system, you need one additional pound of fuel for every pound of boost on most carbureted applications. So if a naturally aspirated motor runs at 6-7 psi fuel pressure and you add a blower making 10 psi of boost, then you would need 17 psi of total fuel pressure at maximum boost. It is also important that your fuel pressure regulator or mechanical fuel pump be boost-referenced. This will allow your fuel pressure to rise in conjunction with your boost level throughout the rpm range of the motor. Measurement is best done with high-quality wideband air/fuel gauges, and fortunately these devices are getting more and more affordable.