The golden rule: match the output to the current
Nitrous solenoids draw a lot of current, and they do it every time a stage activates. Before you assign anything, find out what your solenoids draw from the kit maker's data. Then check your ECU's Quick Start Guide or data sheet for what each output type can handle. Our wiring diagrams page has the Nexus documents.
| Option | When to use it |
|---|---|
| HCO (High Current Output), 8A or 25A | Driving the solenoid directly. Choose the HCO rating that covers your solenoid's draw |
| DPO (Digital Pulsed Output) plus a relay | When no suitable HCO is free, or the solenoid draws more than you want through the ECU. The DPO only switches the relay coil, and the relay carries the solenoid current |
The Output you assign is what fires the solenoid(s) whenever that stage is active. A relay option is the 30A 5-pin power relay. Just remember a mechanical relay suits on/off stages, not pulsed progressive control.
Fuel solenoids
In a wet kit, a fuel solenoid adds extra fuel alongside the nitrous. It usually draws less current than the nitrous solenoid, but don't assume it's small: some pull up to 5A. Check it against the output rating the same way.
Separate fuel solenoid control for progressive wet kits
The Fuel Solenoid Control Output option only appears with Progressive Nitrous Control turned on. It gives the fuel solenoid its own output instead of firing it in step with the nitrous solenoid. The benefit is that, as the progressive ramp brings the stage in, the fuel and nitrous solenoids can be pulsed at different duty cycles. That lets you match the added fuel to the nitrous actually flowing across the whole ramp, rather than hoping two identical duty cycles give the right mixture.
Frequency sets the PWM switching speed for the fuel solenoids. Use what the solenoid maker recommends for pulsed operation.
Use wire and fuses rated for the solenoid current, give the solenoids a solid ground, and test each output from NSP with the bottle closed before the first real hit.
Next steps
With the solenoids wired, set duty in N2O Solenoid Duty Cycle and Fuel Solenoid Duty Cycle, then configure arming in Nitrous Activation. The main Nitrous Controller page ties it together. A bottle pressure sensor is well worth adding too.
