Steve Turner
Former Editor, 5.0 Mustang & Super Fords
May 1, 2000

Step By Step

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P59890_image_largeP59911_image_large138_12z Ford_mustang_coupe Right_front_view
You’ve probably seen Rick Anderson’s ’88 5.0 coupe in a magazine before. It is one of the quickest AOD-equipped 5.0s in the country and still sports air conditioning and EEC IV. Anderson’s car represents the high end of the current trend of high-powered street 5.0s and offered a perfect test venue for our T-Trim versus Y-Trim dyno test.
138_13z Ford_mustang Engine_view
Here’s the V-1 T-Trim looking right at home, sharing Anderson’s engine compartment with Vortech’s Race Bypass Valve and Shootout Series intake manifold. This V-1 features a 3.75-inch inlet and a 2.75-inch discharge; they move air in and out of an investment-cast, curved T-Trim impeller, good for 55,000 rpm. Its shaft rides on heavy-duty bearings designed to handle cog-belt drive loads. These days, T-Trims are available as part of a Vortech kit carrying a three-year warranty and a CARB EO number designating 50-state emissions legality. This one maxed out at 642.2 hp and 767.3 lb-ft of torque at the rear wheels.
138_30z Ford_mustang Engine_view
Casual observers might not notice this is a V-7 Y-Trim. It looks just as familiar in the same spot as the V-1 T-Trim, but it features a larger volute (the snail-shaped housing), a 4-inch inlet, and a 3-inch discharge outlet. Air moving in and out of the V-7 motivates via the investment-cast, backward-curved Y-Trim impeller, good for 65,000 rpm. Y-Trims are not part of a kit, but they do fit existing 5.0 passenger-side mounting brackets. As part of this combination, the Y-Trim cranked out 708.9 hp and 690.8 lb-ft of torque.
138_31z Ford_mustang Engine_view0
To put each blower through its paces, Anderson installed each of the cogged supercharger pulleys available for each blower. The 32-tooth (arrow A), 30-tooth (arrow B), 28-tooth (arrow C), and 27-tooth (arrow D) pulleys allow progressively stepping up impeller rpm, thus boost, while avoiding boost loss from belt slippage. While the T-Trim ran out of steam with the 28-tooth cog, the Y-Trim needed the 27-tooth cog coupled with a larger 77-tooth crank pulley to find its limit. The standard cogged crank from Vortech features 73 teeth.
138_32z Ford_mustang Engine_view0
Photographs don’t really do it justice, but the V-7 mounted on the car is larger than the V-1 Anderson is holding. This is particularly evident in the size of the snail-shaped volute. The arrow shows the V-7’s volute is fatter all the way around.
138_48z Ford_mustang Supercharger_view
The V-7 is a nice offering because it allows bolting on a race supercharger without ditching all the factory accessories. While it does fit the standard Vortech bracketry, some clearancing is required. The main mounting bracket must be ground to allow clearance for the V-7’s fatter volute (arrow A).
138_49z Ford_mustang Supercharger_view
Meanwhile, anyone running cog belts with a Vortech should be employing HP Motorsport’s supercharger brace. Naturally, Anderson has one on his car, and it had to be tweaked to clear the bottom of the volute (arrow B).

In life things are rarely cut and dried. This cliche rings especially true when it comes to supercharging. Most manufacturers build street superchargers and race superchargers. Street superchargers are built to fit with stock components, comply with emissions regulations, and provide a solid performance increase. Race superchargers surrender all emissions and fitment pretensions in exchange for all-out performance.

Invariably, there are people who want to dance on both the mild side and the wild side. These street/strip gearheads want to drive their street car to the dragstrip, give John Force some competition, and finish off their day with a drive by the store for milk and bread. This compulsion to have the best of both performance worlds usually leaves some niceties in the garage with the stock parts. The eventuality is street parts run to the ragged edge at the track and race parts loaf around on the street.

Few aftermarket companies service the run-nines-and-drive-it-home crowd as well as Vortech Engineering. From the beginning, Vortech set out to build a durable street supercharger, and when the A-Trim performed well at the track and didn't break, Vortech started its ascent to the top of the supercharger heap in the 5.0 marketplace. Racers loved the durability and performance, and street enthusiasts looked to racers to make purchasing decisions.

Growing means some markets don't get immediate attention. Those same street/strip maniacs who blazed through the Vortech alphabet from A-, B-, R-, S-, and T-Trim V-1 superchargers were looking for more. A select few were willing to go the custom route to install the V-3 Mondo supercharger on street Mustangs, but that meant a lot of custom bracketry and few stock accessories--quick cars need air conditioning, too. This opened the door to other superchargers featuring traditional passenger-side mounting for larger, higher output superchargers.

Well, the T-Trim supercharger made some inroads for all-around supercharging, offering near the midrange pull of the street S-Trim and close to the top-end charge of the highly strung R-Trim. In response to market demand, however, Vortech built a next-generation supercharger, filling the gap betwixt the compact, streetable V-1 and the elephantine V-3 Mondo. The V-7 supercharger ("V-7th Heaven," Dec. '98, p. 37) debuted late last year and is poised to become the dual-purpose blower for Vortech fans.

Field Testing
To find out how it compares to the impressive T-Trim, we packed up cameras and computers and headed for Anderson Ford Motorsport deep in the cornfields of central Illinois. Principal Rick Anderson enjoys trying new things and has a Dynojet to document his fun. From a magazine perspective, such testing is usually a nightmare, but Anderson has the knowledge and skill to make these tests a breeze.

Magazine writers are best kept away from tools, and even if they know what to do, somebody has to take the pictures. As such, we are often at the mercy of the shop and mercy understandably gives way to paying business in short order. Anderson is different. Besides being easy to work with, he's accommodating of our quirky testing needs.

In addition to having a Dynojet and a healthy curiosity, Anderson also owns a unique vehicle. His red '88 5.0 coupe has graced the pages of several magazines, and to this day, is one of the quickest cars with an AOD transmission and functioning air conditioning--running 9.30s with a J-Trim Mondo. The car features all the necessary components for testing big-horsepower, high-rpm supercharging, including a stout A4 block, ported cylinder heads, a solid-roller camshaft, and plenty of fuel and exhaust flow (see the sidebar Test Car Specs for more details). It also sports electronic tuning and data-logging capability via EFI Systems Programmable Management System ("Remote Control," Feb. '98, p. 94) and InterACQ software, respectively. With dyno and test vehicle arranged, we set out to run both superchargers through Vortech's entire lineup of cog-drive pulleys. We chose the cog belts because both the T- and Y-Trim feature heavy-duty bearings are designed to cope with cogged-beltdrive loads, and stepping up to big boost requires a slip-free cogged belt.

V-1 T-Trim
Upon arrival to Clinton, Illinois, we found Anderson had already swapped out his trick passenger-side-mounted Mondo in favor of the T-Trim. Firing up the car and making the first pass with Vortech's 32-tooth blower pulley paired with the standard 73-tooth crank pulley, yielded numbers that would make most people happy enough to call it a day. With the blower turning as slow as the cog system allows, it spooled up 601.1 hp at 6,600 rpm and 637.1 lb-ft of torque at 4,000 rpm. We started the testing at 4,000 rpm to avoid funky readings below the converter's stall speed. Still, the converter is likely responsible for some torque multiplication you wouldn't see in a manual transmission car, but the automatic absorbs more power as well.

As you can see, we were spinning the engine well past the factory 6,250-rpm rev limiter, thanks to a durable engine block, a solid-roller cam, and the PMS' rpm-extending power. Anderson was also running 108-octane race fuel to ensure he wouldn't be building a new engine halfway through our test. These precautions take the grief out of playing with superchargers.

Stepping down to a blower pulley with two fewer teeth yielded a substantial bottom-end kick. The T-Trim thundered out 703.9 lb-ft of torque at 4,000 rpm and horsepower peaked 500 rpm earlier with 620.1 hp at 6,100 rpm. Clearly, the T-Trim was living up to its advertised prow-ess, as it carried more than 600 hp from 4,900 to 6,800 rpm.

It's easy to get jaded seeing the kind of horsepower numbers we see every month, but Anderson's 306 was pumping out the sort of steam we've seen associated with much larger engines fitted with much larger superchargers. Spinning the T-Trim faster with the 28-tooth pulley yielded even more impressive numbers. It exploded off the bottom with 767.3 lb-ft of torque at 4,000 rpm and topped out at 642.2 hp at 5,500 rpm, but this is also where the T-Trim ran out of efficiency. With the 30-tooth cog, it had dropped 7 hp by 6,800 rpm--this time power dipped by 16 hp by the same rpm. The heat generated by increasingly compressing the air was finally hurting power.

Using the InterACQ software, Anderson was able to examine all manner of data from the stock EEC IV sensors and the PMS' MAP sensor. The only downside of the InterACQ is that it records data at timed intervals, rather than specific rpm for an easy match to the dyno numbers. However, this sensor information gave us considerable insight to the effect of increasing boost with pulley changes.

With the 28-tooth blower pulley, Anderson was spinning the T-Trim 100 rpm past its theoretical maximum impeller rpm of 58,000, which is well beyond its efficiency peak of 55,000 rpm. It's easy to see the efficiency decline by comparing the boost and air-charge temperature readings with each pulley. With the 32-tooth cog, the T-Trim pumped out 17.4 pounds of boost at 6,550 rpm, which yielded an air-charge temperature of 196 degrees. The 30-tooth cog helped it generate 19.7 pounds of boost at 6,440 rpm--yielding an air-charge temp of 198 degrees. Moving down to the 28-tooth cog pumped boost up to 22 pounds at 6,480 rpm, but the combination had stopped building power and the air-charge temperature climbed to 220 degrees. Some of that "boost" was really just hot air.

At this point, the T-Trim made as much power as it could. Installing the 27-tooth cog only would have been a dangerous experiment. We decided to move on to testing the V-7, but walked away impressed with the T-Trim's ability to make tons of torque early and still pull all the way to 6,800 rpm. Though it started to lose efficiency with the 28-tooth cog, adding Vortech's Power Cooler aftercooler would restore that in a flash, creating an impressive performance combo.

V-7 Y-Trim
Swapping on the larger V-7 Y-Trim proved quite interesting. The larger blower fits the standard Vortech bracket with a bit of clearancing and promised a marked increase in airflow. Where the T-Trim is said to flow enough to support 825 hp, the Y-Trim is said to pump things up to the 1,000hp level (at the flywheel). To do so means spinning it, however.

Installing the largest 32-tooth cog pulley on the blower resulted in performance numbers much lower than those of the T-Trim with the same pulley. In fact, it was down from 64.9 lb-ft of torque to 572.2 lb-ft at 4,100 rpm. The trend continued with the horsepower numbers. Suffering a 27.3hp drop, the Y-Trim yielded peak horsepower of 573.8 at 6,600 rpm. These numbers show the T-Trim was working within its intended range, while the Y-Trim had to get warmed up.

Going with the 30-tooth cog pulley didn't bring the Y-Trim out of hibernation either. It pumped out 621.8 lb-ft of torque at 4,000 rpm and 609.7 hp at 6,700 rpm. These numbers were comparable with the T-Trim with the 32-tooth cog. Wearing the same 30-tooth pulleys, the T was still ahead by 82.1 lb-ft of torque and 10.4 hp. Adding the 28-tooth cog to the Y-Trim widened the torque gap between the blowers to 108 lb-ft of torque and closed the horsepower gap to 2.7, but the 28-toothed T-Trim was running out of breath. The Y was just starting to hit its stride with 659.3 lb-ft of torque and 639.5 hp.

The next step was taking the Y-Trim where the T feared to spin--the 27-tooth cog pulley. This is the smallest blower cog pulley offered by Vortech so it was now or never for the Y-Trim. Bolting on the diminutive pulley showed the true nature of the high-winding Y-Trim. It cranked out 714.2 lb-ft of torque and 667.6 hp. Torque production still paled by 53.1 lb-ft, but horsepower continued to grow. The Y-Trim surpassed the T at 5,900 rpm and pulled strongly all the way to 7,000 rpm where it posted 667.6 hp; 25.4 better than the T's best. Of course, Anderson had pulled the pin on his A4 block and spun the motor to 7,000 to compensate for the lack of a smaller cog pulley. Clearly, the Y-Trim wanted more rpm.

We were out of time, but Anderson was inspired by the Y-Trim's potential. He inquired if we had some time for him to acquire a larger crank pulley from Vortech. Apparently, they had toyed with the idea of producing a smaller blower pulley, but these small-diameter cogs can be rough on belts. Of course there was time to try another pulley, so we packed up, flew home, and awaited his call. Naturally, delays occurred, but he called just as we sat down to type up this rambling. Vortech had built a 77-tooth crank pulley to replace the standard 73-tooth crank and it worked extremely well.

Changing the standard crank in favor of the 77-cog made the V-7 ready to rumble with the likes of Vortech's Mondo. Anderson opted in favor of 118-octane fuel over the 108 he ran with the other pulleys, just in case. He also started the dyno pull later, so the torque peak showed as 690.8 lb-ft, but we're certain it was producing more torque down low, as it was 34.7 lb-ft better than the 28-tooth T-Trim at the same rpm. The horsepower trend was like a bull stock market on steroids. Higher rpm automatically converted into higher horsepower with the peak topping out at 708.9 at 7,100 rpm before efficiency finally gave way.

Looking over the data logs, the Y-Trim performs as you might expect. Pulleying it with the 32-tooth cog yielded only 14.7 pounds of boost at 6,580 rpm. Even at that engine speed, the air-charge temperature was only 164 degrees. Swapping on the 30-tooth cog spooled up 16.7 pounds of boost at 6,720 and the air-charge temp jumped to 180 degrees. With the 28-tooth cog, the Y responded with 20.1 pounds of boost at 6,630 rpm and air-charge temperature rose to 194 degrees. Finally getting its groove with the 27-tooth cog, the Y boosted 24.4 pounds at 7,220 rpm and air-charge temp went up only 12 degrees to 208 with 4 more pounds of boost. The final runs with the 77-tooth crank pulley pushed the Y to the brink of efficiency, yielding an ear-popping 27.2 pounds of boost at 7,100 rpm and a toasty 230-degree air-charge temp. Charge cooling is a must at such elevated boost pressures.

Choosing Sides
While this test shows Vortech's Y-Trim supercharger nicely fills the void between the T-Trim and the Mondo, it also shows the passenger-side-mounted Y-Trim can give the larger V-3 a run for its money. The natural question is, which blower is right for your engine? Well, the answer lies in rpm. If your engine has a stout block and reciprocating gear ready to rumble at 7,000 rpm, then the V-7 Y-Trim is likely your choice. This is especially true of cars with stout manual transmission, as they don't need the torque a T-Trim has to offer.

If hanging around 6,000 rpm with your fingers crossed is your M.O., then the mid-range wallop of the T-Trim is for you. Naturally, automatic cars can greatly benefit from its torquey nature.

As always, make sure you have the hard parts, electronics, and fuel supply to keep up with blowers of this caliber. Bolting either blower on a stock engine, especially with a small blower pulley, will just make a mess. The T-Trim can be dialed back for milder combinations, but those are best serviced by the S-Trim anyway. The V-7 has no business on mild cars and wouldn't do well with the big pulley required to make it live. For those serious street/strip gearheads we mentioned in the opening, both blowers have a place.