Many car enthusiasts and DIY mechanics often get caught up in the connector differences between OBD1 and OBD2 injectors when upgrading or replacing fuel injectors. However, the connector type is not the primary concern when it comes to injector compatibility and potential damage. The real issue lies in the injector resistance, specifically whether they are high resistance (saturated) or low resistance (peak & hold). Confusing these two can lead to serious electrical problems, potentially frying your Engine Control Unit (ECU).
To clarify, there are fundamentally two types of fuel injectors based on their electrical operation:
- Saturated Injectors (High Resistance): These injectors are designed to be continuously powered with a lower current. They are often referred to as “high resistance” injectors because they have a higher internal coil resistance.
- Peak & Hold Injectors (Low Resistance): These injectors use a more complex energizing strategy. They initially receive a high current “peak” to quickly open the injector, followed by a lower “hold” current to keep it open. This design allows for faster response times and better fuel atomization, but they are “low resistance” injectors and draw more initial current.
The crucial point is that mismatching injector resistance with your car’s fuel injection system can cause damage, regardless of whether the injectors are OBD1 or OBD2. If your vehicle is designed for high resistance (saturated) injectors and you install low resistance (peak & hold) injectors without proper modification, you risk overloading and potentially frying the injector driver circuits in your ECU.
This is why a resistor box is often used when upgrading to low resistance injectors in vehicles originally equipped with high resistance injectors. For example, older Honda Civics (DX models) used resistor boxes when employing peak & hold injectors. When enthusiasts upgrade older Honda Integras (designed for saturated injectors) with higher flow peak & hold injectors, they often need to incorporate a resistor box to reduce the current load on the ECU.
Consider the example of Prelude injectors. OBD1 Prelude injectors with a higher flow rate (345 cc/min) are typically peak & hold (low resistance), while OBD2 Prelude injectors with a slightly lower flow rate (290 cc/min) are usually saturated (high resistance). While they also have different connectors due to OBD1 and OBD2 system changes, the resistance difference is the key electrical compatibility factor. Installing OBD1 Prelude injectors (peak & hold) on a system designed for saturated injectors without a resistor box would be problematic, not because of the connector, but because of the lower resistance and higher current draw. Similarly, using larger 450 cc/min peak & hold (low resistance) Mitsubishi injectors as upgrades also necessitates a resistor box to prevent electrical damage.
Therefore, when considering injector upgrades or replacements, focus on the type of injector resistance (saturated vs. peak & hold) your vehicle’s system is designed for, rather than just the OBD connector type. Choosing saturated injectors can simplify the process and eliminate the need for a resistor box, but high-flow saturated injectors might not always be available for every application.
In conclusion, while OBD1 and OBD2 denote different automotive diagnostic and communication protocols that sometimes coincide with different injector connector types, the critical factor for injector compatibility and preventing electrical damage is matching the injector resistance to your vehicle’s fuel injection system. Always verify the resistance type (saturated or peak & hold) and make necessary modifications like adding a resistor box when switching from saturated to peak & hold injectors to avoid potentially costly ECU damage.
