The output voltage of the amplifier is proportional, in a slightly non-linear manner, to the mass air flow. The mass of the air flow is proportional to the heat lost, which unbalances the bridge producing a voltage differential to an amplifier, which in turn varies the resistance in the bridge in an effort to maintain a constant temperature of the heated element. Air flow through the MAS removes heat from the element. In a hot-wire MAS, a wire or film structure is electrically heated and incorporated into a Wheatstone Bridge, which is balanced for no air flow. With the ARC2 MAS, the mass air flow is measured directly by the "hot-wire" method. With the factory MAS, the ECM uses the Karman volume air flow signal along with the air temperature and barometric pressure information to calculate the mass air flow. However, the air temp and baro pressure values, if different than mine, may affect the settings of your ARC2 compared to mine. Considering that air temp in the plenum for an engine with stock intercoolers and turbos is likely near or above 95✯, this should be of little practical effect as far as timing is concerned. A possible consequence of a higher air temp (94✯ vs 68✯) is that the ECU will use a slightly lower timing advance. I do not know why my ARC2 unit sends different signals. When I talked to Split Second in March of 2000, Mark told me that air temp should have been set at 68✯ (2.74 kOhm) and barometric pressure set to 1.00 bar (4.0 v). Because the hot-wire MAS's do not produce any air temp or baro signals, that is, the ARC2 control unit produces these signals, I am not sure why there was any change. After switching to the 87-mm Granatelli MAS, the air temp signal changed to 2.01 v (94✯) and the baro signal to 3.24 v (0.81 bar). When I was using the 80-mm Ford MAS, my ARC2 control unit produced an air temperature signal of 1.99 v, corresponding to 95✯, and a barometric pressure signal of 3.22 v, corresponding to 0.80 bar. This permits easier calibration and translation of the ARC2 MAS signal, and allows consistant manipulation of that signal by the factory ECM. The ARC2 control unit sends fixed or constant signals to the ECM in place of the stock MAS's air temperature and barometric pressure variable signals. The ARC2 hot-wire type MAS replaces the stock Karman-vortex type MAS and uses a control unit to convert the analog voltage signal (representing mass air flow) to the square-wave voltage signal (Karman frequency counts that represent volume air flow) that the Mitsubishi factory engine control unit wants to see. A larger 87-mm MAS, built by Granatelli, is also offered. The standard ARC2 MAS is the Ford "F8LF" MAS used in 1998 4.6-L engines using 19 or 24 lb/hr injectors such as found in the Mustang GT and Cobra, Expedition, and F-series trucks. The ARC2 MAS has replaced the stock MAS and its air temp and pressure sensors. Write down the knob settings before you start to adjust them. I have a 8.5x11 sheet of paper in the glove box next to the ARC2 with just this info on it.
#SPLIT SECOND TUNING MODS#
I recommend starting a record keeping system that lets you note the day and weather conditions, the 4 knob settings, any mods done, and the results of your changes (ARM1 lights showing rich or lean, engine performance, poor idle, etc.). The tips below will help you get the best performance out of your engine using the ARC2. The ARC2-GP kit consists of a Ford 80-mm hot-wire MAS (see 2-arc2mas80mm.htm) or a Granatelli 87-mm hot-wire MAS (see 2-arc2mas87mm.htm), a K&N 900 cfm 5½" x 9" tapered-cone air filter (part number RE-0870), a wiring harness, the Air/Fuel Ratio Calibrator (ARC2 control unit) that is designed to output a Karman MAS frequency signal (square wave), the Split Second ARM1 A/F meter, and instruction sheets.
![split second tuning split second tuning](https://cdn1.urdusa.com/GitHub/urd-woocommerce/wp-content/uploads/2017/03/20011431/1120100004_lrg.jpg)
Split Second also manufactures and sells ARC2 controllers for other MAS's and to replace carbureted systems. While the ARC2 can be used with the stock fuel system, it is specifically designed to be used with larger-than-stock fuel injectors and to replace the Karman-vortex type mass air sensor (MAS) that Mitsubishi uses.
#SPLIT SECOND TUNING PRO#
The ARC2-GP kit is manufactured by Split Second and GT PRO Performance Tuning for use on the Mitsubishi 3000GT VR4 and the Dodge Stealth R/T Twin Turbo. Stealth 316 - ARC2 Tuning tips ARC2 Tuning Tips