Frank H. Cicerale
November 1, 2008
The swap was fairly easy, seeing as how the plumbing for the intercooler was on the car thanks to it already being supercharged. The only major parts we had to swap were the lower intake manifold with the intercooler, and the blower itself. The lower intake you see here was the new one ready to be dropped onto the Three-Valve mod mill.

In addition to getting Dunai's take on the TVS, we also checked in with Ryan Bunn, the marketing manager of the Performance Parts division of Roush Performance. Other than the obvious fact that the blower we installed in this article was a Roushcharger TVS, the one shown here in the photos is the same blower that Roush used on the 510hp P-51A Mustang. Additionally, Roush was heavily involved with the development and the construction of the TVS from the get-go.

"Roush's Erin Dmytrow helped Eaton with the development of the TVS, and Roush is the company that is technically making the blower," Bunn says. "Eaton supplies us with the internals, and we cast the case, assemble the blower, and then bench test it.

"The differences between the M122 and the TVS lie in the virtual efficiency of the four-lobe TVS design. That design compares very favorably to other boosting technology out there. The key advantage the TVS has, though, is that it supplies a higher volume of airflow with better efficiency and less heat."

"The internal air velocity management allows for much greater thermal efficiency, which means less work is being done to the air during compression," agrees Dunai. "The Fifth-Gen has maximum thermal efficiencies in the 60-percent range, while the TVS sees maximum thermal efficiency in the 70- to 75-percent range, and over a much larger operating range of pressure ratios and flow. However, peak efficiencies don't tell the whole story, because true improvements from the TVS are evident in its dramatically increased operating range. The TVS still has 70-percent thermal efficiency in regions that a similarly sized Fifth-Generation can't even operate.

"The TVS has a higher pressure ratio capability, and the combination of the higher lobe twist and the larger inlet ports allow for much greater volumetric efficiency, especially at higher speeds. Volumetric efficiency is actually the highest at maximum rated rpm, and this shows that the flow capacity of the TVS is orders of magnitude greater than anything prior in terms of flow versus displacement. It does not die off at high rpm. To say it simply, if a Fifth-Gen and a TVS were at equal displacement, the TVS will flow more air at lower temperatures."

With so much emphasis being placed on the differences in the rotors and their respective lobes, are there differences in the composition of the rotors? "The TVS rotors maintain the reliable material and mechanical properties of the Fifth-Gen units, including our patented abradeable powdercoating," Dunai says. In layman's terms, the blower rotors are made of the same stuff, but the TVS rotors and the lobes are designed for better power with less work. The TVS sounds like a winner when compared to the Eaton M122, but how will it stack up against a twin-screw?

"The twin-screw has internal compression, which the TVS does not, as it is still technically a Roots-style blower, though with many improvements," Dunai says. "Contrary to popular belief, internal compression created by rotor lobe profiles and speed ratios are not as important to thermal efficiency. There are many other factors that contribute to thermal efficiency that are more important and, as proven with the TVS, internal compression is not the deciding factor of thermal efficiency. I will, however, state that the laws of physics and thermodynamics still do apply. The TVS just capitalizes on them in a slightly different manner to achieve its results."

So, what does this mean in terms of blower speed, boost level, and horsepower levels? "We have bench-tested the blower to 15,000 rpm, which creates about 8 psi the way we have it pullied for sale to customers," Bunn says. "Honestly, though, we see no limits in terms of the blower. We feel the blower is fully capable of feeding 1,000 hp."