Much like the 2011 V6 and GT Mustangs, the 2011 Shelby GT500 got an engine update with an all-new 5.4 L aluminum engine which was lighter than the previous cast-iron engine and uses Ford-patented plasma-coating technology (Plasma transferred wire arc). The inventors of PTWA received the 2009 IPO National Inventor of the Year award. This technology was initially patented and developed by inventors from Flame-Spray. The technology was subsequently improved upon by Ford and Flamespray. With the engine updates, not only has performance improved to at 6,200 rpm and at 4,500 rpm of torque, but the GT500's gas mileage has improved to city and highway, which was enough to eliminate the U.S. Gas Guzzler Tax. The final production number of the 2011 Shelby GT500 by the end of the year was 5100 units.