Vishnu Performance Systems

Engine Management Interface Adaptor

Technical Specification 11/26/02

Purpose of this document

To give a brief description of the Engine Management Interface Adapter (EMIA) and the functions that it performs.

Introduction

The EMIA resides within an automobile, and provides a means of altering the Manifold Absolute Pressure (MAP) and Throttle Position Sensor (TPS) sensor signals that are fed to the engine management system. Normally these two signals would be connected directly to the engine management computer. With the installation of the EMIA these signals are connected via the EMIA box and then routed to the engine management computer. The EMIA is able to modify the signals according to a pre-determined algorithm. This algorithm can be re-flashed by Vishnu Performance Systems as updated or revised code is developed.

EMIA Hardware

The EMIA consists of a PIC micro controller (PIC16F876), LT dual DAC (1661), TI dual Op-amp buffers (OPA2337), 5V linear regulator LM340, one red LED, a single turn trim POT, low-side MOSFET switch (IPS021S), 8-pin 0.1” header, and a male 25-pin DB25 connector.

DB25 Connector (J3) Pin-out
Signal / Description/Wiring Information / Pin / Wire color
+12V / Supply voltage, +12V @ ~30mA. Protected against reverse polarity, voltage transients, and over current conditions.
Route to ECU 12v power or RED wire on Unichip harness. / 7, 8, 9
Ground / 0V ground. Ideally, every signal will be paired with a corresponding ground.
Join together and route to ground or Brown wire on Unichip harness. / 14, 25
MAPIn / MAP sensor input, 0 to 5V.
Route to MAP signal wire (engine side) / 1
TPSIn / TPS sensor input, 0 to 5V.
Route to TPS signal wire (engine side) / 3
MAPOut / MAP sensor output, 0 to 5V.
Route to MAP signal wire (ECU side) / 2
TPSOut / TPS sensor output, 0 to 5V.
Route to TPS signal wire (ECU side) / 4
Unused / Unused / 6
Unused / Unused / 13
EMI Mode Settings
Mode / Link4 / Link3 / Link2 / Link1
Standard EMI Setting
Higher Fuel-Cut
Optional EMI Setting A
Higher Fuel-Cut / ·
Optional EMI Setting B
Higher Fuel-Cut / ·
Optional EMI Setting C
Higher Fuel-Cut / · / ·
Standard EMI Setting
Factory Fuel-Cut / ·
Optional EMI Setting A
Factory Fuel-Cut / · / ·
Optional EMI Setting B
Factory Fuel-Cut / · / ·
Optional EMI Setting C
Factory Fuel-Cut / · / · / ·

Note: The mode links are only sampled at initial power up. So, changing the links without a power down, power up sequence, will have no effect on the mode of operation.