How variable cam timing is moved
Most continuously variable cam systems use oil pressure to rotate the camshaft relative to its drive gear or sprocket. A solenoid valve decides where engine oil goes: into one side of a chamber in the cam gear, out of the other, or held in place. The ECU controls that solenoid with a duty cycle.
- More duty lets more oil pressure into the mechanism, and the cam moves one way.
- Less duty lets pressure bleed off, and the cam moves back the other way.
- Somewhere in between is a duty that holds the cam still. Haltech calls this the Base Duty.
So to move the cam, the ECU goes above or below Base Duty. To hold it at its target, it returns to Base Duty.
Why it has to be closed loop
The catch is that Base Duty isn't a fixed number. It shifts with oil temperature, oil viscosity, oil pressure, engine speed and wear. If you tried to run the cams open loop with one fixed Base Duty, even a tiny error would make the cam slowly creep in one direction until it hit a stop. That's why Nexus cam control always runs closed loop: it reads the actual cam position from the cam sensor, compares it to the target angle, and keeps correcting the duty to hold it there.
Main settings
| Setting | What it does | Our advice |
|---|---|---|
| Number of Banks | Tells the ECU how many cylinder banks there are, so it knows how many intake and exhaust cams to control | One for an inline engine, two for a V or flat engine with cams on each side |
| Mode | Intake only, exhaust only, or both intake and exhaust | Match what's physically variable on the engine |
| Solenoids Per Camshaft | One or two solenoids for each cam | Match the factory hardware on your engine |
| Target Angle Max Delta Rate | Caps how quickly the cam target is allowed to change | Use it if the target table has steep changes or the cam hunts. It smooths movement by stopping the controller from chasing a jumpy target |
| Enable Long Term Trim | Lets the ECU learn small corrections over time | Turn it on once the closed loop control is behaving well |
In total the Nexus can control up to two intake and two exhaust cams.
Where to go next
Once the function is enabled, set the targets in the intake and exhaust cam pages, then review the target scalar page. Solenoid and sensor hookup is covered in cam control wiring.
Before tuning cam targets, confirm the cam angle reading is stable and correct with the cam at its rest position. If the reading is wrong, every target you set afterward will be wrong too.
