Why measure nitrous pressure
A nitrous jet is a fixed hole. How much nitrous passes through it depends on the pressure pushing it, and that pressure moves around with bottle temperature and with how full the bottle is. If pressure drops, less nitrous flows while the fuel side stays the same, and the engine goes rich. If it climbs, more nitrous flows and the engine goes lean, which is the dangerous direction. A pressure sensor turns that from guesswork into a number you can log, display and act on.
The Elite supports up to four nitrous pressure sensors, handy on setups with more than one bottle or solenoid feed.
Choosing the input
| Input type | When to use it | Pullup |
|---|---|---|
| AVI (analog voltage input) | First choice for a pressure sensor | Optional 1k pullup to 5V |
| SPI (synchronized pulsed input) | Only when you have no spare AVI. Set sensor type to Hall Effect | Optional weaker 10k pullup to 5V |
For the pullup, the rule is simple. A powered, three-wire sensor like Haltech's own 2000 psi brake/nitrous pressure sensor makes its own output voltage, so leave the pullup disabled. Pullups are for passive two-wire sensors. And if the sensor is shared with another ECU, for example a factory ECU in a piggyback setup, that ECU normally provides any pullup it needs, so leave it disabled on the Haltech side too.
Calibration
The Calibration tab tells the ECU how to turn sensor voltage into pressure. ESP comes with a set of pre-made calibrations, and the default is the Haltech 2000 psi sensor, so if that's what you fitted there's nothing to change. For another brand of sensor:
- Use the yellow Open icon to load a calibration file if one exists for your sensor.
- If not, build one from the voltage-to-pressure data the sensor's maker provides.
- Save it with the blue Disk icon so you can reuse it on the next car.
Whichever you use, sanity check it: with the bottle closed and the lines empty, the reading should sit close to zero, and with the bottle open it should match a mechanical gauge.
Display warnings
The Display tab has a Warning Minimum and a Warning Maximum. When pressure goes outside that window, nitrous pressure gauges and readouts in ESP flash red. Set them around the pressure window your nitrous kit's maker recommends for your jetting, so you can see at a glance whether the bottle needs a heater or a cool-down before a pass.
Diagnostics and engine protection
The Diagnostics tab watches the raw sensor voltage for wiring faults. Both checks are off by default.
| Setting | What it does | Our advice |
|---|---|---|
| Raw Min | Sets code P1347 if the voltage drops below your limit, a sign of a short or open circuit | Enable it, a little below the voltage the sensor reads at zero pressure |
| Raw Max | Sets code P1348 if the voltage goes above your limit, also a wiring fault sign | Enable it, a little above the voltage at the sensor's full-scale pressure |
If you're running engine protection, each of these codes can be given a DTC severity so the ECU reacts when the sensor fails. That's worth doing: a sensor that fails can't protect anything, and you'd rather know before the next pass.
Putting the reading to work
Once pressure is reading correctly, log it on every run alongside air/fuel ratio. A lean spike that lines up with a pressure rise tells you exactly what happened. From there, you can set up the nitrous system itself: nitrous control, stages and enablers. If you're new to spray, our overview nitrous, the forgotten power adder is a good starting point.
Troubleshooting
| Symptom | Usually |
|---|---|
| Reading stuck at maximum | Signal wire open with the pullup enabled, or signal shorted to 5V |
| Reading stuck at zero | No 5V supply to the sensor, or signal shorted to ground |
| Reads high or low against a gauge | Wrong calibration loaded, or the pullup is on for a powered sensor |
| P1347 or P1348 logged | Check connector, pins and the 5V and ground feeds first |
Nitrous pressure sensor FAQ
Where should the sensor go?
Somewhere on the pressurized feed line where it reads the pressure reaching your solenoids. Follow your nitrous kit's guidance on fittings and placement.
Can the same sensor be used for brake pressure?
The Haltech 2000 psi unit is sold for either job, but we fit a separate sensor for each function so each reading is independent.
