KJ Jones Senior Technical Editor
September 1, 2008
Photos By: KJ Jones
ATI ProCharger's engineering manager, Paul Ebner, holds a microphone in front of the standard P-1SC Stage 2 blower, installed on an otherwise stock '07 GT. In addition to the manually held mic, the supercharger on this test 'Stang is outfitted with sound-measuring equipment that allows Paul to determine where sound is amplified in various areas of the head unit.

Horse Sense: Although a pair of V-8-powered S197s were the highlights of our recent trip to ProCharger's headquarters, we once again had the opportunity to ride in the blown '05 V-6 Mustang featured in our first-look report in 2005 ("Blowing the Budget," Dec. '05, p. 143). The low-mile 'Stang is currently for sale and now packs one of the optional Quiet Blowers you'll learn more about in this report. From a stealth-power standpoint, we still believe a blown V-6 S197 is a great alternative for those who don't have the coin for a GT. Imagine how much stealthier it is when the blower is there, but nobody can hear it.

As power adders go, the sound of a centrifugal supercharger-at idle or warp speed-is recognized by most 'Stang enthusiasts as a mark of serious performance, especially when it's coming from under the hood of a street-bred Pony.

However, while some 'Stangbangers view the circular-saw-like zing of a blower as the ultimate statement-maker and confirmation of credibility, we're finding there are others-especially S197 owners-who prefer to drive softly, if you will. That said, even the quiet types still want to have enough boost on tap to lay the smack down on the Chevy, WRX, or Evo in the other lane.

Each sensor measures internal vibration on the top and side of the supercharger. The top-mounted sensor evaluates up-and-down vibration; lateral vibration is recorded with the side-mounted probe.

If you own, plan to own, or would like to own a new ('05-to-present) Mustang, what's your preference? Which centrifugal supercharger (audible or quiet) would you add to your ride? Some of you probably see this as a difficult choice, but ATI ProCharger has come up with something that might make deciding a lot easier.

The ching-zing sound generated by ProCharger's straight-cut gearsets has always been a trademark characteristic of its two popular supercharger systems for street Mustangs (P-1SC and D-1SC). The gears are the most notable contributors to each blower's audible signature, but there are other variables that play roles in the type and level of sound the superchargers emit while operating.

Based on feedback from current and potential customers, engineers at ProCharger have developed new gearing for these units and have improved various areas of the superchargers' casings, impellers, pulleys, and bearings, resulting in dramatically quieter blowers.

Paul uses this graph and evaluates where vibrations and sound spike inside and around the perimeter of the blower. The top graph represents vibration that the case-mounted transducers record coming from inside the gearbox. The graph below is external sound, which Paul captures by holding the microphone at different points around the supercharger's case.

As we said earlier, a supercharger's sound is often considered an indicator of its performance. While this myth is a cool way of thinking about blowers, facts are a much more important concern.

Intent on learning all we could about ProCharger's newest technology, offered as the $100 Quiet Blower option for complete P-1SC Stage 1 (PN PC050A-045) and D-1SC (PC051A-045) supercharger systems, not just head units (for Fox through S197 Mustangs), your tech editor ventured from Los Angeles to the company's Lenexa, Kansas, headquarters for a firsthand comparative look-and listen-at P-1SCs in standard and quiet trim on two S197s in the company's test fleet.

Our interest in ProCharger's new Twin High-Flow intercooler system for '86-'93 Mustangs has been high since we first laid eyes on it at the SEMA show last year.





The company's '08 Mustang GT, which some of you may recognize as the flagship ride in the ProCharger booth at the '07 SEMA show, is outfitted with the result of Paul's research: a P-1SC H.O. supercharger system that features the new Quiet Blower option. Note the trick pulley on the head unit. Company President Ken Jones tells us the holes were added as part of a weight-reduction experiment, in addition to the ongoing effort to make the blower as quiet as possible. While it's not quite ready for public use yet, Ken says the lightweight pulleys may be offered at some point in the future-as an option, of course.

This is a close-up look at the guts and glory of ProCharger's standard P-1SC head unit. Internally, the blower features straight-cut gearing in its transmission. Gearing engagement, or mesh, is a major contributor to its distinct sound. Another reason we hear so much from standard blowers is that, unlike other centrifugal blowers, ProChargers are totally comprised of billet material (case, impeller shaft and impeller, bearing housings, and so on). "Billet 'sings' and doesn't have the same sound-softening ability that cast iron has, so it's a lot tougher to quiet our blowers," says Paul.

"We looked at all of these criteria as we developed our quiet option, but the data we gathered was mostly used to help us make changes to the driving frequency (vibration) of the gearbox and the bearing frequency. The vibrations are audibly represented as sounds that come from the blower's driving gear, driven pinion, and slinger. On the bearing side, the speed of the inner race, bearings, and outer race is calculated, and changes are made accordingly in an effort to make the supercharger as quiet as possible. None of the changes affect the quantity of air that is delivered into the engine at the pressure we're delivering it."

If you're looking for a visible difference between a P-1SC's standard gearset and an optional Quiet blower, this is it. A lot of the reduced sound comes from these helical-cut gears. The gears' angle-cut profile spreads the transmission load over more surface, which makes their engagement much smoother and quieter than straight-cut hardware. Quiet blowers' gearsets feature matched-pitched sizes (driving and pinion gears) and optimized alignment and bearing bores, as well as impellers that are balanced to tighter specs than those included in the standard units. Ken stresses that none of the changes have any ill effect on airflow, power, or the overall durability of the superchargers in any way. When equipped with the Quiet Blower option, the '08 makes the same 456 rwhp and 408 lb-ft of torque that it does with a standard P-1SC

Some 'Stang fans firmly believe that something must be wrong if a blower doesn't make a loud, mechanical racket. We saw-well, heard-for ourselves that this sentiment is far from true. We performed our own nonscientific sound test outside the shop and were blown away by the difference. The blower on the red 'Stang sounds "normal," if you will, but the custom-painted '08 GT on the right is whisper-quiet. Video of our test is available on our Web site at www.50mustangandsuperfords.com. Understand that ambient sound plays into the audio in our crude test, but the difference is discernable nonetheless.

Since we had only seen the mocked-up demonstration system (displayed on a SEMA "New Products" table) prior to our trip, the crew at ProCharger was kind enough to set up two employee-owned Foxes on hoists and provide us with an up-close look at how the system lays out on a fully dressed, street GT 'Stang and a street/strip LX.

ProCharger technicians hoisted these two Foxes to show us how the new Twin High-Flow intercooler system fits on a street GT and a drag-influenced LX. At the heart of this system are two 4.5-inch intercooler cores that mount inside the pocket areas at the front-most edge of the driver- and passenger-side front fenders, just behind the bumper cover. The system's twin cores are supported by OEM fender bracing, so there's no need for custom work or additional parts in order to get everything in place. The really cool thing is that the front of both 'Stangs are fully intact.

Our interest in how the pieces fit in the LX-model Mustang is higher due to the fact that installing an intercooler system big enough to support 600-plus horsepower ('cooler, tubing, and so on) on a non-GT Fox has been a major challenge for 'Stangbangers, as it requires cutting areas in the Pony's front fascia, detracting from the car's appearance in a major way.

Ray Looney's ragtop '93 GT gives us a great example of how the Twin High-Flow intercooler system is incorporated on a fully loaded, street Mustang. Ray's 'Stang is motivated by a D-1SC-blown 306, and the 500hp Pony still has air conditioning, power steering, and all of its 'vert-specific chassis bracing still in place. The intercooler system doesn't conflict with any of these accessories, nor does it require any additional components for OEM-like fitment.

The Twin High-Flow 'cooler setup is offered as a $250 option for any ProCharger supercharger system that includes a three-core intercooler as standard equipment. Enthusiasts who already have ProCharger blowers on their 'Stangs can purchase the system as a Field Upgrade (intercoolers, scoops, air dams, tubing, and bracketry, among other things) for $1,399.

We like the way the dual intercoolers fit on Steve Denham's '93 LX hatchback. The front fascia has been the point of concern when it comes to installing a 'cooler on non-GT Fox Mustangs. Conventional three-core intercoolers require trimming a good portion of the bumper cover to allow a sufficient amount of air to pass across the unit. This modification detracts from the 'Stang's appearance, so the Twin High-Flow system is a welcome alternative. Steve's car is set up for the dragstrip and doesn't have any of the accessories on Ray's GT. However, the major difference between the two Ponies is the 750-cfm carb and F-1R ProCharger on Steve's hatch, which easily puts it in the 600-rwhp range.

Seeing Twin High-Flow intercoolers in person supports the thoughts we had after checking out the demo model at the SEMA show. The system is super-clean and designed for a no-cutting, bolt-on installation. It offers 70- to 75-percent intercooler effectiveness, which is about the same as a three-core intercooler-but without hacking up the front of your 'Stang.