SDS hints
Builder Logs
- Les Kearny has documented his SDS installation and tuning here.
General Hints
Non binding, use the SDS installation instructions for reference!
- The proper and careful installation of the silver fuel injector adapter into the cylinder head is important. Follow the most recent SDS instructions. Use only the referenced high temperature blue Loctite 246. Hand tight, then 1 1/2 turns. There are older instructions out there that reference 60 inch pounds torque which is no longer a desired tightening method and may not be enough to hold the adapters in.
- It is important to properly ground the ECUs as the injector return current will flow through it. At high rpm, a voltage drop across the ground wiring can cause improper injector operation which may lead to individual hot cylinders.
- If you need to replace a wire in the bundle, these are the connector family specs:
In particular, the female crimp pins are Digikey order no WM2501CT-ND.
Understanding the Relay Circuits
The 6-cylinder injector relay box includes the following three functions:
- Assigning 3 additional injectors to a single ECU
- In normal mode, the left connector gets the injector input signal from each of the ECUs, 3 per ECU. The right connector has the outputs to the 6 individual injectors (ground side).
- In the two failure modes, the injectors 1 and 4, 2 and 5 and 3 and 6 are driven in parallel and fed by a single ECU
- Moving the power of 3 additional injectors to a single 12V bus
- In normal mode, Pin 12 (Prim Bus) drives Pin 9 (Injector 1 - 3 positive side via individual breakers), and Pin 11 (Backup Bus) drives Pin 10 (Injector 4 - 6 positive side via individual breakers).
- In the two failure modes, one of the buses drives all injectors
- Passing through the primary / backup signals to the mixture relay
- The primary select signal (active low) is passed through as mixture blue signal.
- The backup select signal (active low) is passed through as mixture brown signal.
Note: Activating both primary and secondary select signal will mirror the sides, e.g. the backup bus and ECU drives injectors 1-3 and vice versa
The mixture adjust relay box includes the following functions:
- Feeding the mixture adjust potentiometer input to both ECUs in normal mode and only to one accordingly in primary and backup mode.
Note: The mixture adjust relay box needs both 5V and 12V to operate. It gets the 5V from the ECUs (red primary cable or orange secondary cable) and the 12V from the yellow cable (needs to be supplied externally, switched and fused).