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NIStune Type 1 Hardware Installation Page 29 of 29
9. Upgrading ECU MAF hardware
Early model engine control units such as Z31, R31, most HR31 (1985-1988) and VL Turbo use a 2 -7 volt
hotwire airflow meter. These air flow meters then have their voltage converted to 0 - 5 volts for the internal
microprocessor using what is known as 'opamp' circuitry.
The later model ECUs and airflow meters all work on 0 - 5 volt circuitry.
When installing a later model mass airflow meter from a later model vehicle to one of these earlier model
vehicles, it is necessary to modify the ECU hardware to handle the difference in air flow meter voltage.
This is done by either altering or removing the circuitry path via the opamp, and then limiting the maximum
voltage using a zener diode. These instructions details the steps to take when modifying the ECU
Further instructions regarding MAF pinouts are available in the Software Users Manual.
1984-1986 CR31/Z31/VLT
1. Locate the op amp surface mount board in your ECU as pictured below
2. Remove pin 14 on RHS of mini board
Do this by applying heat to the top of the connector and then pushing away from the mini board with a flat
blade screw driver. Then using tweezers to hold the connectors, heat the opposite side of the circuit board to
remove the connector completely.
5. Install the Zener diode to the reverse side of the ECU. Zener diode is available from us or from Altronics
(Australia) or Dick Smith (Australia) as well as other electronics components shops worldwide:
http://www.altronics.com.au/index.asp?area=item&id=Z0314
Pictured below with banded end of the zener diode facing the installed AFM signal jumper wire. The other
end is connected to the ground pin of the mini board. This will limit the voltage from the AFM to 5.1 volts