Debuting in the USA originally on the Corvette ZR1 (it technically first showed up on an Australian factory-tuner Toyota model), the TVS represented a significant leap forward in performance and capability in a Roots-type, positive-displacement supercharger. Four-lobe, 160-degree high-helix rotors (helix refers to the pitch of the rotors’ twist) greatly expanded the effective range of the compressor, delivering more low-rpm grunt and sustaining the horsepower higher in the rev band. A TVS blower has a 2.4 pressure ratio, which gives it a thermal efficiency greater than 70 percent.
Not surprisingly, it didn’t take long for the TVS revolution to spread throughout the performance industry and one of the first to capitalize on it was Flordia-based VMP Tuning. They offer a number of TVS-based upgrade kits for 2007-and-later GT500s, an upgrade kit for 2003-04 “Terminator” Cobras, bolt-on systems for GTs and the BOSS 302 – and even a blower kit for Raptor trucks.
Roush has a unique perspective in the aftermarket, because they work on both OEM projects and more performance-oriented projects. -Justin Starkey, VMP Tuning
There’s also a dimensional advantage a TVS blower holds over an M90 – it has a larger displacement, meaning it flat-out processes more air. The “90” in the M90 is a reference to its 90-cubic-inch displacement, while the 1.9-liter displacement of a TVS 1900 compressor translates to about 115 cubic inches. For the record, the 122-cubic-inch three-lobe blower design used on the Shelby GT500 is, indeed, a little larger, but then again, the TVS is also produced in a larger, 2.3-liter/140-cubic-inch configuration – and the TVS design is less prone to heat soak and delivers the broader power range than the M122’s older, three-lobe design.
The greater displacement is another contributor to the broader power band enabled by the TVS design, while also making it easier to push higher boost levels out of it. There is data out there on the “Interweb,” too, that shows that for the moderate levels of boost prescribed for street and street/strip applications – up to around 16-18 psi – the TVS is more efficient than a twin-screw blower of comparable size.
“I was interested in producing my own supercharger line since I purchased a new Shelby GT500 in 2007,” says VMP founder Justin Starkey. “When the new 5.0-liter Mustang came out in 2010, I developed a relationship with ROUSH, which led to our original GT500 TVS upgrade.”
Recently, VMP Tuning added TVS-based upgrade kits for 2005-10 supercharged ROUSH Stage 3 Mustangs saddled with the old-school M90 blower. The new supercharger simply replaces the existing one – with some new hardware and, of course, a tuning upgrade, as well.
The new blower really adds power, too. On a recent dyno test of a three-valve ROUSH RS3, it added more than 100 rear-wheel horsepower – pushing output well past the 500-rwhp level. The official numbers were 501 rwhp vs the stock trim’s near 400 horses to the tires, while the torque numbers jumped to 492 ft-lbs. The test was performed on an otherwise stock vehicle, with the blower pulley’d for 10-12 pounds of boost. Starkey also recently performed this upgrade on an built three-valve engine, where they could take further advantage of the added potential of the TVS blower. This particlular engine also featured VMP’s Twinjet 67mm throttle body, and was able to spin the dyno rollers to 640 hp at the rear wheels.
Just as important as the max numbers, however, is the range of performance across the entire rpm band, which clearly shows the effectiveness of the larger, more efficient blower. At every rpm step, the engine produced more horsepower and torque, with the spread between the old M90 setup and the TVS blower growing as the revs increased. Particularly impressive is how the torque hangs in through the higher rpm range. It crosses the 450-rwtq mark by 3,000 rpm and doesn’t drop below it until about 5,700 rpm. The M90 trim didn’t achieve peak torque until nearly 4,000 rpm and basically flittered with it until finally dropping below the mark permanently by 5,000 rpm.
Maximizing the capability of the new supercharger requires optimizing all the supporting components and to that end VMP offers a port-matched flow elblow that’s available with a stock Mustang GT throttle body mounting pattern or the pattern for the larger GT500 throttle body. Pulley options range from 69mm to 85mm, which can generate up to 15 pounds of boost. VMP can also supply smaller, custom pulleys in an eight-rib design, as well as a complementing balancer, for even greater boost, and they tell us that, depending on the modifications and boost level, the new TVS blower can add up to 250 horsepower at the rear wheels.
Along with the 1.9L TVS blower, the basic VMP kit also includes a high-flow inlet elbow with the proper vacuum line and PCV line fittings. For 2005-09 cars, the kit also includes an open-element cold-air induction system and a 113mm intake tube (with mass airflow sensor provision). The 2010 ROUSH Stage 3 cars already include an efficient cold-air intake system that pulls fresh air from the car’s front grille area, so replacing it is unnecessary.
The basic kit is designed for the stock, dual-bore 55mm throttle body, but as mentioned above, the intake elbow can be ordered to accommodate the GT500 throttle body bolt pattern – meaning it will take the stock GT500 dual 60mm throttle body or FRPP’s dual 65mm throttle body. VMP tells us the throttle body upgrade is good for up to 30 additional horsepower, depending on the boost level. The company also recommends a fuel pump upgrade for systems intended to produce more than 10 pounds of boost.
In that arena, VMP recommends either their fuel pump voltage booster, which has a 40-amp rating and delivers 17 volts of continuous output – and is fully regulated at all times, meaning there are no adjustment knobs required – or switching to the GT500 dual fuel pump setup, if projected power levels around or beyond the 500-horsepower level. The FRPP kit (available from VMP) is a direct drop-in for 2005-09 Mustangs. It also fits the 2010 models, but the factory sender must be used to ensure the fuel gauge remains accurate.
VMP’s superchargers are designed and manufactured through an arrangement with ROUSH and its joint-venture manufacturing partner, Performance Assembly Solutions (PAS), so they’re as close to a factory-engineered upgrade as you can get. The facility is located in one of Detroit’s vast industrial suburbs.
We are thrilled to offer the new ROUSH upgrade kits, but the blower itself is only one part of a complete upgrade kit that includes the pulleys, throttle body and more. -Justin Starkey, VMP Tuning
“Roush has a unique perspective in the aftermarket, because they work on both OEM projects and more performance-oriented projects,” says Starkey. “This insight made designing the VMP line of superchargers for the racer and high-performance street enthusiast much easier.”
For the new ROUSH upgrade kits, different pulleys are available to skew the boost from a mild 8 psi to a more serious 15 pounds, for a power-grain range of 100 to 250 horses. The kits also include a cold-air induction system and are available with GT or GT500 throttle-body options. Best of all, the kits start at a very reasonable $3,399 – but some of the add-on features we described above, of course, add a few bucks to the bottom line.
We caught up with Starkey at the PAS Detroit-area manufacturing facility, looking over shoulders as one of VMP’s new superchargers was assembled and tested. What struck us the hardest on our visit was the OEM-levels of manufacturing, validation and product traceability involved in the PAS build process. Each supercharger is assembled by hand, but with specialized – including computer-driven – tools that deliver an assuring blend of personal craftsmanship and mechanized consistency.
Not surprisingly, there aren’t too many components involved with the assembly, but they’re all fitted to extremely tight tolerances. After all, the rotors will spin up to about 15,000 rpm, so making sure they do so without a hitch is vitally important to performance and longevity.
After each supercharger is painstakingly assembled, it is placed on a specialized fixture and tested to ensure no leaks are present, then it is transferred to an electrically powered dyno that spins the blower at high speed to ensure it meets all key performance specifications.
“We are thrilled to offer the new ROUSH upgrade kits, but the blower itself is only one part of a complete upgrade kit that includes the pulleys, throttle body and more,” says Starkey. “We have always designed our system with uncompromising drivability in mind and these new kits build on the excellent performance of ROUSH Mustangs, and take them to a higher level of capability – and fun.”
And if you’re wondering, “Hey, that’s all well and good, but I don’t own a supercharged ROUSH Mustang – I’ve got a GT500,” relax. There’s a TVS upgrade kit for the Shelbys, as well. It uses the larger, 2.3-liter compressor, too, which as we mentioned earlier in this story, displaces nearly 20 cubic inches more than the GT500’s old-school blower. It will typically add 150-200 horsepower to your Snake and, like the ROUSH upgrade system, will support significantly higher power. In fact, depending on the complementing modifications, it will support up to about 950 horsepower. We spent time with Starkey on a guided tour to find out what goes into building VMP’s latest upgrade for ROUSHcharged Mustangs. You can follow along in the photos and captions to see what goes into constructing this high efficiency supercharger.