For owners of USDM Honda H22a4 engines looking to gain more control over their ignition timing and utilize aftermarket adjustable cam gears, converting from the stock OBD2 distributor to an OBD1 distributor is a popular modification. This conversion addresses limitations in the OBD2 system, particularly the inability to adjust base timing directly at the distributor and restrictions when using aftermarket exhaust cam gears. Let’s explore how to perform this conversion to unlock these tuning capabilities.
Why Convert to OBD1 Distributor?
The primary advantage of switching to an OBD1 distributor on your H22a4 engine is the newfound ability to adjust ignition timing manually. Unlike the OBD2 system where timing is solely ECU-controlled, OBD1 distributors allow for physical adjustment, crucial for fine-tuning engine performance. Furthermore, on OBD2 H22a4 engines, attempting to use aftermarket adjustable exhaust cam gears can trigger a CYP (Cylinder Position Sensor) check engine light. OBD1 conversion circumvents this issue, enabling the use of these performance enhancing components.
Parts You’ll Need
To undertake this conversion, you will require a few key components. Naturally, you’ll need an OBD1 USDM H22a1 or H23a1 external coil distributor. These distributors utilize an 8-pin male connector, a departure from the 4-pin connector found on the OBD2 distributor. To interface with this new distributor, you’ll need both an 8-pin female connector and a 4-pin male connector. These connectors can often be sourced from junkyards, typically from any 92-95 Honda vehicle for the 8-pin connector, and common 4-wire O2 sensors for the 4-pin connector. Acquire these connectors with a sufficient length of wire attached to facilitate soldering.
Wiring Your OBD2 to OBD1 Distributor
The core of this conversion lies in correctly wiring the OBD2 engine harness to the OBD1 distributor. Careful attention to the wiring diagram is essential for a successful conversion. Below is the detailed wiring configuration:
| OBD2 Connector Wire Color | OBD1 Connector Wire Color | Function |
|---|---|---|
| Black | Blue/Yellow | CKP M (Crankshaft Position Sensor -) |
| Red | White/Blue | TDC M (Top Dead Center Sensor -) |
| White | WHITE | CYP M (Cylinder Position Sensor -) |
| Yellow | Blue/Green | CKP P (Crankshaft Position Sensor +) |
| Green | Orange/Blue | TDC P (Top Dead Center Sensor +) |
| Blue | Orange | CYP P (Cylinder Position Sensor +) |
| Yellow/Green | Yellow/Green | ICM (Ignition Control Module) |
| Green | Green | ICM (Ignition Control Module) |
By meticulously following this wiring guide, connecting the corresponding wires from your OBD2 harness to the OBD1 distributor connector, you can successfully complete the conversion. This modification will grant you the desired timing adjustability and compatibility with aftermarket cam gears, allowing for enhanced engine tuning and performance optimization.
