Granatelli Motor Sports ARC2 87-mm MAS
by Jeff Lucius
This is the Granatelli Motor Sports ARC2 MAS I have installed on my 1992 Dodge Stealth R/T Twin Turbo. It is advertised as a 87-mm MAS. However, I measure a nominal 85 mm (~3-11/32") at the narrowest inside diameter, which is at the rear of this "bullet"-style MAS. This MAS may also be referred to as a 92-mm (~3-3/4") unit as that is the inside diameter of the front (or entry) of the MAS.
GMS makes this MAS for Ford 4.6-L and 5.4-L engines using 19 lb/hr injectors. This MAS is ~6" long. Air filters with a 4" ID at the mounting end fit this MAS. The MAS fits perfectly in the stock intake hose once the hose is coaxed into a round shape from the factory oval shape.
Based on flow tests by Mike Licht for the 3.5" GM LS-1 MAS, this GMS MAS should flow ~400 cfm with a pressure drop of only 0.2 psi (6" water), or ~500 cfm with a 0.3 psi drop, or ~860 cfm with ~1 psi (~28" water) pressure drop. The factory Karman MAS flows ~500 cfm with a 1 psi pressure drop.
This hot-wire type MAS replaces the stock Karman-vortex type MAS and must be used with an electronic device (in my case, the ARC2) to convert the analog voltage signal (representing mass air flow) to the square-wave voltage signal (frequency counts that represent volume air flow) that the Mitsubishi factory engine control unit wants to see. The ARC2 control unit sends fixed or constant signals to the ECU in place of the stock MAS's air temperature and barometric pressure variable signals. This permits easier calibration and translation of the ARC2 MAS signal and allows consistant manipulation of that signal by the factory ECU.
More info on the ARC2 setup:
Page last updated November 18, 2007