For decades, gearheads have been searching for one thing: more power. Whether it’s from a stock engine that needs to be sauced up, or from a modified engine that needs an extra helping of spices, more power is often the first thing that an enthusiast looks for when it comes to improving the smiles-per-gallon ratio of a hopped-up vehicle. For nearly 30 years, ProCharger has come to enthusiasts’ rescue with its well-engineered centrifugal supercharger systems.
But—as always—more power is better. Let’s say you’re an enthusiast who invested in one of ProCharger’s P-1SC-1 supercharger systems to pump up your ride, and now you’ve decided you’re ready for more power. That’s where the subject for this article arises.
P-1SC-1 compressors are ubiquitous in the performance world, synonymous with improved horsepower and massive gains over stock horsepower levels on just about any engine platform out there. But as with any performance modification, they have a ceiling: that horsepower level where they reach the point of no return, tapped out to the point where adding more boost simply doesn’t make any more power due to aerodynamic inefficiencies.
Once the supercharger is received by ProCharger's service department, it's removed from the box and inspected to see if there are any visible issues with it that might prevent the upgrade to the D-1X design. Locked-up gears or any other visible problems that might cause issues are noted.
Once any compressor–whether it is a centrifugal supercharger like the P-1SC-1 or even a turbo–exceeds its efficiency range, it begins to add excessive heat to the air charge. It’s because of this heat increase that the enthusiast eventually reaches that spot where it makes more sense to upgrade the compressor than it does to install a smaller pulley.
When To Step Up
According to ProCharger’s Erik Radzins, the P-1SC-1 is good for somewhere around 825 crankshaft horsepower; no slouch, for sure. But in today’s world of 1,000-horsepower street cars, it’s certainly the company’s entry-level piece. Enter the D-1X, originally released in 2017.
Once the unit is inspected, the pulley is removed and disassembly begins.
“The D-1X is good for 1,000 horsepower all day long,” says Radzins.
Why is this significant? Perhaps because the D-1X can be used in the same brackets, with the same tubing arrangement and all of the same supporting gear as your existing P-1SC-1 supercharger. As long as you have enough fuel—and your pistons and rods won’t exit stage left with more power applied to them—the D-1X is a direct swap for the P-1SC-1 compressor housings. Each of the company’s P-series bolt-on kits can be had with a D-1X in place of the P-1SC-1 supercharger.
But it’s most significant because of a recent trip we made to the ProCharger skunkworks in Lenexa, Kansas, just outside Kansas City (and home to some of the best food we’ve ever eaten, but that’s a discussion for another day).
Although I was in the way during this process, it didn't take long at all. As many of the fasteners are common between the different supercharger sizes, all of the proper tools are right within reach. With the volute removed, we get our first peek at the P-1SC-1 impeller. Take note of the fin shapes and angles; we'll get into this more deeply later in the article.
During part of the visit, we were able to witness the crack ProCharger service team take an existing P-1SC-1 compressor and turn it into a D-1X in just a few hours by replacing several of the pieces. It was the perfect time to drop the D-1X’s upgraded parts and pieces into place to improve the compressor’s capabilities, as the tantalizing allure of more horsepower couldn’t be ignored. The resulting all-new supercharger gave this particular customer the capability for an additional 175 horsepower, for substantially less cost than a complete supercharger upgrade.
Removing the center bolt from the impeller. There’s no easy way to hold the impeller with a tool without damaging the fins, so a thick glove is a necessity.
Now, you might think that this upgrade requires most of the compressor’s components to be changed out, but that’s not the case at all. There are only three main components which are swapped out to take a supercharger from a P-1SC-1 to a D-1X: the volute, the impeller, and the backing plate. Since all of these pieces need to be removed anyway to replace the supercharger’s seals, it’s a perfect time to invest in an upgrade—and a bunch more power—by stepping up to the D-1X configuration.
After many thousands of miles, it’s quite possible that the impeller—as in this case—needs to be heated up to remove it from the shaft. A couple of minutes with a pair of torches to heat the impeller evenly, and it slides right off. The technician actually pulls the impeller off with the tips of the torches to prevent getting burned in the process. We must note here that heat should never be used to remove an impeller; it was only appropriate in this case since the P-1SC-1 impeller is now a throwaway unit and wasn’t to be re-used.
“One of the advantages to using the D-1X design is that it’s still self-contained and offers the helical gearset,” says Radzins. “So if your existing supercharger has these components, you can drop a converted D-1X right into place.”
At this point, the supercharger's transmission case is separated, and the gearset is inspected for tooth damage and any potential bearing wear issues. Although the gearset is designed to run for hundreds of thousands of miles, anything is possible, and the upgrade process gives a perfect opportunity to inspect and replace any worn bearings. After the gears are inspected, the gearcase is put back together with new seals, whereupon the supercharger will be ready for many more thousands of miles of boosted fun.
What’s The Diff?
Although the P-1SC-1 (and D-1SC) configuration is a perfectly capable supercharger that’s a solid performer for many enthusiasts and offers plenty of power potential, it’s also two decades old, with impeller design and internal airflow capability reflecting that, although it was state-of-the-art technology at the time it was released to the public. The self-contained gearbox in this supercharger has proven itself over millions of miles and thousands of installations, but as with most performance-oriented products, there comes a time to redesign it using current technology and the results of many hours of research and development. But what does the typical gearhead do when it’s time for more?
Here we really begin to see what the upgrades are all about — on the left is the original P-1SC-1 impeller, and on the right is the D-1X impeller. Note the fin size and shape, and also the angle. Hundreds of hours of engineering went into creating a profile that was just the right shape to improve power substantially. Not only are the blade angles altered, but the impeller is also substantially larger at the exducer (outer edge) where the air exits the impeller and continues on through the volute. This larger configuration is the reason that the backing plate needs to be changed as part of the D-1X upgrade process.
So how does the D-1X make more power out of a unit that’s the same overall size, you ask?
“We redesigned these units with greater efficiency and also reduced the parasitic load, which means it creates less heat and requires less power to spin the supercharger’s impeller,” says Radzins.
The D-1X is good for 1,000 horsepower all day long—Erik Radzins, ProCharger
The D-1X’s impeller will spin up to 62,000 rpm safely, and since the supercharger’s transmission remains the same proven unit, durability is not an issue whatsoever. The D-1X maxes out at 32 psi of boost pressure, which is more than enough for all but the most insane street cars. And at the massive power level at which the D-1X shines, the moniker “street car” becomes highly debatable anyway. At least in this humble author’s opinion.
Let’s also compare the difference in the volute shape. As we noted above, the exducer of the D-1X is physically larger than that of the P-1SC-1, which requires a larger snail section on the volute (the D-1X is on the left here). The horsepower improvement of the D-1X is the result of these two airflow enhancements—and the internal shape of the volute—which work in unison to raise airflow capability. We can see the external appearance is much larger for the D-1X volute in all areas, with the exception of the outlet, where it mirrors the P-1SC-1 volute. This is what provides the ability for the D-1X to drop right into the same bracket as the P-1SC-1.
Using its on-site test lab and modern machining capability, ProCharger created and whittled out several wheel designs, thrashing them on the supercharger dyno before settling on the final piece for the D-1X, which features optimized fin angles and contours tailored to maximize the compressor’s performance.
Optimizing the impeller’s fins also required the creation of an all-new volute design to match up perfectly with the impeller. The combination of these two improvements allows the D-1X to make more power per pound of boost. Even with the same 9-inch volute diameter as the P-1SC-1, the D-1X adds 300 cfm of additional airflow capability.
Here’s another angle for comparison between the two different volute designs. The D-1X volute (left) is larger in all areas to account for the extra 300 cfm of airflow produced by the new impeller shape.
It does this through an additional .200-inch added to the inducer diameter (measuring at 3.570-inch as compared to the P-1SC-1’s 3.370-inch), allowing more airflow into the impeller. The exducer diameter also increases from the P-1SC-1’s 5.25-inch diameter to a whopping 6.20-inches. By changing the number, configuration, and shape of the blades on the impeller, and increasing the exducer diameter, tip speed is improved, giving the supercharger more efficient performance. The increase makes this upgrade a no-brainer.
The various stages of D-1X impeller manufacturing (in reverse), from billet blank to initial shaping to its final configuration. While I was able to watch an impeller come to life, it was difficult to catch a good photograph of the CNC machine in action, what with all of the tool coolant flinging everywhere and blocking my view.
The actual process to change the P-1SC-1 into a D-1X is about as simple as it gets. The three new components drop right into place, and you’ve got what’s basically a brand-new, more powerful supercharger for a fraction of the cost of replacing the entire unit. There is no doubt that an upgrade to the D-1X is a wise choice for P-1SC-1 owners, especially if the base powerplant has the capability to accept more power without failure. Follow along with the photos and captions for more details.