Frank H. Cicerale
October 1, 2008
Photos By: Michael Galimi

As you pump away on the jack handle in order to swap the slicks on your GT500 for your street tires, you seethe with anger and a bruised ego. Here you are, thinking you're Billy Badass with your blown snake, and after a couple of runs at the test and tune, you end the night getting whooped by a tuned-up Z06. If you only had a little bit of extra power, that gold-chain-wearing punk wouldn't have been laughing while he took that $100 you laid down on the race. Just as you finish up, you swear that the next time you line up against that poser, you'll show him nothing but taillights.

Obviously, one of the easiest ways to make more power with a positive-displacement supercharged car is by switching pulleys. By doing so, you allow the blower to spin faster, thus creating more boost, which carries (if cooled properly) more available oxygen. This extra air can be countered with extra fuel, resulting in more power. Most times, 40-70 hp can result. The problem with spinning a Roots-style huffer like the stock Eaton M122 too fast is the resultant heat. The extra heat doesn't lead to as dense of an air charge, which leads to less power and, in some cases-if the proper fuel isn't used or the tune isn't spot on-detonation and a really big bang.

For those looking for big power, a supercharger swap is at the top of the to-do list. There are a number of different options when it comes to upgrading your supercharger, whether it's going with a larger Roots-style blower, a ported stock blower, or swapping over to a twin-screw. Add in the myriad of companies and the different size blowers, and you can see that there are a lot of decisions that need to be made.

The New Kid On The Block Meets An Old Hat
One of the newest superchargers to come along is the Eaton TVS blower. Officially released in February 2007, the TVS (Twin Vortices Series) is a different design than the M122 blower found on top of the GT500, which is Eaton's Fifth-Generation supercharger. The TVS features twin four-lobe rotors that are twisted 160 degrees. This is completely different than the M122's lobe construction that showcases three lobes angled at 60 degrees. This fourth lobe and increased angle serves to create a more efficient flow into the engine when combined with the TVS' revised inlet and outlet ports.

With that in mind, we decided to get on the bandwagon and see just what a TVS blower swap on a GT500 could do in terms of power, both on the dyno and on the track. Our first and only call was to Mustang racing legend Jimmy LaRocca, who has piloted just about everything, from fast street cars to seven-second heads-up Pro cars. He picked up a GT500 of his own recently and was looking to make some astounding power. "I went with the TVS blower because I wanted to stay with an Eaton product as well as an over-the-counter Ford part," LaRocca explains as to why he chose the TVS blower.

"The TVS is really designed for the GT500, in my opinion," he says. "It fits under the strut tower brace, carries a warranty from Ford, and gives you plenty of room to grow, power-wise." When it came time to swap the blowers, to say it was a piece of cake would be an understatement. "The GT500 is generally an easy car to work on," LaRocca says. "This kit, though, is so simple. It's very straightforward, and you don't have to drain any kind of fluid. In all of my years working on Mustangs, and of all the installs I have done, this was, by far, the easiest I have ever performed. If it wasn't for you guys stopping me to take photos, I could have finished the install inside of an hour."

LaRocca is referring to the Ford Racing Performance Parts (FRPP) '05-'08 SVT Mustang Supercharger Upgrade Kit (PN M-6066-SGT). It's billed to increase power on a stock GT500 by 105 hp, and comes complete with a 2.3L TVS supercharger, an open-element cold-air intake system, a Pro-Cal tuner voucher, with which you can redeem the programmer for the kit with a tune from FRPP, and everything else needed for the installation. To get a true apples-to-apples comparison between the stock Eaton supercharger and the new TVS, the only thing we changed on LaRocca's Mustang was the blower.

Of course, we had to check out some before-and-after dyno numbers to see what the TVS did in terms of a power increase. In bone-stock trim, LaRocca's Shelby recorded 444 rwhp and 438 rwtq, which, considering the 500 flywheel horsepower rating from the factory, is quite respectable. After we swapped on the TVS, we strapped the snake to the dyno, ran it up to operating temperature, and flat-footed the accelerator. At 6,200 rpm, we cut off the dyno pull and waited for the computer to spit out the figures. Not that we were surprised, but Ford's advertised power figure of 605 was right on the money, as LaRocca's ride ripped off a rear-wheel power number of 605, with torque at a thundering 578 lb-ft. That's an increase of 161 rwhp and 133 lb-ft of torque. Not too shabby!

With the swap and dyno test complete, we made our way to the track to see just what this Shelby could do in the real world.

Timed To Perfection
While we didn't have a chance to baseline LaRocca's snake, we glanced back in the MM&FF archives at the "Bolt-On Bonanza" series we did with a Shelby GT500, starting with the Feb. '07 issue. In that article, MM&FF test pilot Evan Smith ripped off a 12.38 at 115 mph with a bone-stock GT500. This was with the stock Eaton M122 blower stuffing the 5.4L mod monster with 9 psi of boost. With that in mind, Editor Smith slipped behind the wheel of LaRocca's snake, fired up the beast, and throughout our day at Old Bridge Township Raceway Park in Englishtown, New Jersey, made a total of five runs. The result? How about an 11.77 at 121 mph. LaRocca said it best when he stated that the 11.77 was "a good run on a bad day." Keep in mind this was at 11 psi of boost, and the rest of the car was still stock, with the blower, its stock pulley, and the FRPP-supplied tune being the only additions. That's an e.t. drop of 0.610 second and a speed increase of 6 mph that came on a day where the air conditions were the consistency of New England clam chowder. In good air, this car could dip well into the low-11-second zone. That's just with the addition of the blower kit, folks. While LaRocca didn't change anything else, there are those out there who have taken the TVS blower to the next level.

Tune Time
With the FRPP TVS kit coming with a voucher to redeem a Pro-Cal programmer loaded with a Ford-derived tune, there are those who want to keep the Ford tune, and others who want to stretch things to the maximum. LaRocca's mindset is of the former, while Justin Starkey of VMP Tuning is one of the guys who goes to the brink.

"I haven't changed the pulley, and, personally, I don't want to," LaRocca says. "I don't want 12-13 psi or more of boost because at that point, the car, at that boost level, isn't practical. You have to worry about what type of fuel you run. I don't want to have a car that needs to run race gas.

"I don't want to push anything with this car. This blower doesn't take the reliability or comfort away from the vehicle. That's one of the main reasons why I picked it. I think a lot of people forget that they have to look at the whole picture and not just race the dyno. The engine has a lot of life in it. I mean, if Ford is willing to warranty a part that will allow it to make 600 hp, then you know the motor can take a lot." The question is, how much? As is the case with every custom-tuned forced-induction setup, be it the TVS or a twin-screw blower, having the tune spot-on is critical to longevity and power production.

We turned to VMP Tuning's Justin Starkey to see what his thoughts were in regards to tuning the TVS blower. Starkey has a GT500 with a TVS on it, and he's one of the many shop owners who keeps pushing the envelope when it comes to the TVS. "There are no major differences in how the TVS is tuned compared to any other blower," Starkey says. "As boost goes up, so does calculated engine load, so spark tables have to be renormalized to give you more resolution at higher volumetric efficiencies. You will need to have enough mass air sensor range for the additional airflow, and the mass-air meter transfer function will need to be properly tuned to achieve a safe air/fuel ratio.

"The FRPP tune on the Pro-Cal produces between 540 and 565 rwhp. Since the tune was developed for a warrantied production vehicle (the Shelby Super Snake), it gives up a little in power so it can pass emissions in all 50 states. It's also milder in case someone gets poor-quality 91-octane fuel, and it's designed to accommodate all those limitations the OEMs have to live with. This is not to say that the FRPP tune is bad because it produces less power; it's just different, and Ford has different goals in mind than the aftermarket. I can still produce a tune that will pass emissions and make great power, but you need to make sure the car always gets good, premium fuel. I don't have to work within the same limitations as Ford, so I can make more power, though I have to do it safely."

While the blower kit itself is a perfectly matched item, when it comes to making more power, certain parts and pieces need to be upgraded to make the most power possible safely. "In most cases, the FRPP intake would peg the MAF sensor with anything more than just the addition of an upper pulley, so I installed one of our 115mm MAF housings to get more mass air range and prevent the MAF from pegging," Starkey explains. "As a side note, the TVS comes with approximately a 2.9-inch pulley. A stock blower pulley is 3 inches in diameter. The stock TVS setup is nearly equivalent in boost to the stock blower with a 2.6-inch pulley, but the TVS makes 40-50 more rear-wheel horsepower at the same boost level due to the TVS' better efficiency.

"The TVS is rated for 19,000 rpm, and 20.58 psi per Eaton. I'm close to the blower's limit right now, making 691 rwhp and 693 rwtq on pump gas. On race gas, the car has made 705 to the tires at about 18.5 psi with the addition of headers and a bunch of other items. I have some parts that will be available by the time this goes to press, but first I will need to upgrade to a set of 60-pound injectors with the correct-style electrical connector. I am at the limit of the stock injectors right now."

Starkey also noticed how much of an impact a throttle-body change made to the car, as well as how the blower affected the overall torque curve of the vehicle. "I had installed a smaller blower pulley and made 610 rwhp, so I swapped on a 10-percent overdriven lower pulley to spin the blower even faster," he says. "This got me very little gain in terms of horsepower, but it gave me some torque. With the addition of a dual 66mm throttle body, I saw power shoot up by 25 rwhp, and boost increased by nearly 2 psi. The stock throttle body is really a restriction once you get above 550 rwhp.

"The TVS has a very flat boost curve, and this results in a very flat torque curve. My car puts out around 700 lb-ft from 3,400 to 4,600 rpm. I will say that just the right timing curve is needed to take full advantage of this blower's boost curve to produce maximum torque. This is really where the little 2.3L TVS shines over some of the big twin-screw blowers."

The Final Say
TVS' blower kit from FRPP retails for $5,600, and while LaRocca went 11.77 with just the kit, keep in mind that was just as Ford designed it. Starkey pointed out there is much more to be had out of the TVS blower, as is evidenced by his 11.10-second, 131-mph best, which was run at the NMRA race in Bradenton, Florida, earlier this year. Certainly the potential for some big power numbers, as well as some lightning-quick elapsed times, are possible with the TVS. Big power and an easy installation? We'll take that combination anytime! Now let's go hunting for that pesky Z06 Corvette.