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The electrical wiring was probably the most time consuming component of this project.

The electrical system was designed so that all of the functions of the Engine Control Module (ECM or computer) were fully operational. The design of the VN Commodore wiring was followed where possible, some changes were made to allow the car to be fuelled by both petrol and LPG.

I was lucky enough to get the entire body wiring loom out of a VN Commodore, as well as the wiring loom attached to all of the engine sensors and components.

I tried to design the wiring required for the new engine in a way that required as little modification to the existing HZ wiring as possible.

This was made a little easier by the way the original HZ wiring was designed. Most of the engine control signals were connected to the engine via three connectors located at the top centre of the firewall.


Engine bay wiring

I assembled an engine bay wiring loom that connected to the above three connectors, and then, via the necessary relays and fuses, connected to the factory VN Commodore engine wiring loom.

engine_bay_loom.jpg (23003 bytes) The engine bay wiring loom with relays and fuses attached.

The above photograph shows the engine bay wiring loom. In the top left corner are the three connectors that interface to the original connectors in the top centre of the firewall. In the centre of the picture are three connectors that connect to the Commodore engine loom. At the bottom left corner are the relays and fuses that are mounted on the drivers side wheel arch.

fuses.jpg (33098 bytes) Relays and fuses.

The factory VN Commodore engine loom runs over the passenger side wheel arch, through a hole in the firewall and connects directly to the computer, located behind the passenger side kick panel.

ecm.jpg (34788 bytes) The computer (Engine Control Module) behind passenger side kick panel.

The engine wiring loom design meant the battery had to be relocated to the drivers side of the engine bay. This also allowed the air box to be located in the old battery position. The windscreen washer tank and charcoal canister had to be moved to allow for battery relocation.

engine_after.jpg (91050 bytes) Engine bay layout.


Under dash wiring loom

The under dash wiring loom connects between the computer, the transmission (via the transmission wiring loom), the park/neutral switch (at the base of the steering column), the original HZ fuse box, the speedometer and the Check Engine Light, which was fitted to the unused bottom right tell tale lampholder on the dash.

Also, part of this loom is the speedo electronics box (see Speedometer) and two relays required to condition the park/neutral and engine cranking signals required by the computer.

 cabin_loom.jpg (60842 bytes) The under dash wiring loom with relays and speedo electronics box.
under_console.jpg (28380 bytes) The speedo electronics box and relays under the centre console.


Transmission wiring loom

Another small loom connects to the Transmission speed sensor and to the torque converter lockup / 4th gear-overtemp connector.

transmission_loom.jpg (18798 bytes) The transmission wiring loom.


Fuel guage interface

A VN Commodore fuel tank, electric pump and fuel level sender were fitted (see Other bits). An electronic interface had to be included to make the HZ fuel gauge compatible with the Commodore sender. A circuit diagram of the device I designed is included below.

guage_interface.jpg (51153 bytes) Fuel gauge interface circuit diagram

Other wiring

The only other wiring, not shown on this page, is a single wire to power the in-tank fuel pump.