When diving into vehicle modifications or engine swaps, particularly with older cars, the topic of OBD systems and injector compatibility inevitably arises. You might be considering an OBD1 to OBD2 adapter, perhaps even looking at Napa for one, and wondering if it solves all your compatibility concerns, especially with fuel injectors. Let’s clarify a crucial point: the connector type (OBD1 or OBD2) is separate from the injector resistance type (high or low). Confusing these two can lead to serious issues, potentially frying your injectors or engine control unit (ECU).
There are primarily two types of fuel injectors based on their electrical resistance:
- High Resistance (Saturated) Injectors: These are designed to work with a simpler, saturated driver circuit in the ECU.
- Low Resistance (Peak & Hold) Injectors: These require a more complex peak and hold driver circuit in the ECU to operate correctly and prevent overheating.
The risk of damaging your system comes not from the OBD connector type itself, but from mismatched injector resistance. If you install low resistance, peak & hold injectors into a system designed for high resistance, saturated injectors, you risk damaging the injectors and potentially the ECU’s injector driver.
This is why a resistor box is often used when upgrading to peak & hold injectors in cars originally equipped with saturated injectors. For example, older Honda Integras (Teg) were designed for saturated injectors. If you were to upgrade to higher flowing, OBD1 Prelude injectors (which are often peak & hold and low resistance), you would need a resistor box to safely use them. Ignoring this resistance difference, regardless of the connector, will cause problems.
Now, consider OBD connectors. OBD1 and OBD2 are different diagnostic port standards. An OBD1 to OBD2 adapter, like one you might find at Napa Auto Parts, is designed to adapt the physical connector, allowing you to use an OBD2 scanner on an older OBD1 vehicle. However, this adapter does absolutely nothing to address injector resistance compatibility.
Let’s illustrate further with injector examples:
- OBD1 Prelude Injectors (345 cc/min): These are low resistance, peak & hold injectors.
- OBD2 Prelude Injectors (290 cc/min): These are high resistance, saturated injectors.
Notice they also have different connectors. If you were to try and use OBD1 Prelude injectors on a system designed for OBD2 saturated injectors without considering the resistance difference and just focusing on the connector, you could damage your system. An OBD1 to OBD2 adapter would only solve the physical connector mismatch for diagnostic purposes, not for injector compatibility.
Similarly, larger 450 cc/min Mitsubishi injectors, often used for performance upgrades, are also typically low resistance (peak & hold). Using these would also necessitate a resistor box in many applications to prevent electrical issues, regardless of the OBD connector type.
Therefore, when dealing with fuel injectors, especially when considering upgrades or swaps in vehicles using or adapting from OBD1 to OBD2 systems, remember these two distinct points:
- OBD Connector Type (OBD1 vs. OBD2): This is about the diagnostic port and scanner compatibility. An adapter from Napa or elsewhere addresses this physical connection.
- Injector Resistance Type (Peak & Hold vs. Saturated): This is about the electrical compatibility between the injectors and the ECU’s injector drivers. Mismatched resistance can cause damage.
Focus on choosing the correct resistance type injectors for your ECU. Saturated injectors are often easier to manage as they avoid the need for resistor boxes, but they might not be available in the flow rates you require for performance upgrades. If you need peak & hold injectors, ensure your system is compatible or properly adapted with a resistor box, irrespective of whether you are using an OBD1 to OBD2 adapter for other purposes. Don’t let connector compatibility distract you from the critical aspect of injector resistance when working on your fuel system.
