Why monitor crankcase pressure?
Some combustion gas always slips past the piston rings into the crankcase. That's blow-by, and the ventilation system is there to get rid of it. When crankcase pressure climbs higher than normal, it usually means either more gas is getting past the rings (worn or broken rings, a damaged piston) or the breathers can't keep up. High pressure pushes oil past seals and into the intake, and on a boosted engine it can be the first sign of real damage. Too little pressure, or too much vacuum from an aggressive scavenging system, can be a problem too.
The Nexus crank case pressure input lets the ECU watch that pressure, show a warning when it leaves the range you set, and log it alongside everything else. Turning the sensor on also makes the Engine Pressure Ratio tuning method available.
Setting it up
| Node | What it does | Our advice |
|---|---|---|
| Configuration | Holds the sensor calibration. Haltech sensors load via Load from File; others are entered by hand and can be kept with Save to File | Pick a sensor whose range covers both a little vacuum and your worst expected positive pressure |
| Warning Maximum | Pressure at which gauges, bars and number displays switch to their warning state | Set it just above what a healthy engine shows on a hard pull, taken from your own logs |
| Display Minimum / Maximum | Where gauges and bars start and end. They also limit the range usable in settings and tables | Make the range wide enough that you'd never need a table value outside it |
| Diagnostics | High/low voltage DTCs and min/max pressure DTCs, each with a severity linked to an Engine Protection level | Use voltage DTCs to catch wiring faults, pressure DTCs to catch engine faults |
| Wiring | Assigns the analog input | Any free AVI, with the pull-up disabled |
Installation tips
- The sensor is a three-wire type: 5 V supply, signal to the ECU, and sensor ground.
- Keep oil out of it. Mount the sensor above the take-off point with the port facing down or on a short rising line, so oil mist and liquid drain back to the engine instead of pooling on the sensor.
- Take the reading from a spot that represents the whole crankcase, like a valve cover or a dedicated fitting, not right next to a breather outlet where flow will skew it.
Reading the data
Log crankcase pressure on a healthy engine first, at idle, cruise and full load. That becomes your baseline. A pressure that creeps up over weeks points to ring wear or a breather slowly clogging. A sudden jump on one pull deserves an immediate stop and a leak-down test. Related sensor setups include manifold pressure and oil pressure.
