Turbocharger Electronic Actuator Stepper Motor Information
Stepper Motors & Turbochargers
A Turbocharger Electronic Stepper Motor or Actuator, moves the vanes inside a VNT (Variable Nozzle Technology) turbo.
Variable vanes do the same job as a dump valve on a standard (non-VNT) pneumatic-actuated turbo.
That is, they allow boost to build and dump, by hold or release of gasses.
The vanes move inside the VNT Assembly, itself installed inside the Turbine (hot or exhaust end) housing.
The open & closing vane movements, are facilitated by circular motion of the VNT Assembly Nozzle Ring.
But the Actuator only moves (actuates) an ‘Arm’ in a linear motion.
So that linear motion needs to be converted to a circular left-to-right motion in the Nozzle Ring.
And a lever connecting the actuator arm to the Nozzle Ring does just that.
Why ‘Calibration’ of the Stepper Motor is Sometimes Required
We supply both Stepper Motors and Turbochargers.
We sell the separate components to allow the purchase of either part, depending on the problem they are purchased to fix.
But we also offer complete, flow-tested turbochargers, where the actuator comes attached to the turbo, tested at the factory.
Flow testing calibrates the stepper motor to a range of movement under factory standard parameters.
That movement on average, provides enough boost without over-boosting.
Installing the old or new stepper (where a component is purchased separately), usually involves only 3 bolts.
Additionally, the actuator arm is attached via a clip to the stepper. And the other end of the arm attaches via another clip to the lever that actuates (moves) the vanes inside the turbo.
Once the turbocharger electronic actuator stepper motor is attached to the turbo, it should work immediately with very little adjustment.
But, in some cases, a ‘calibration’ may be required.
Typical cases where calibration is likely required include (but not limited to):
– A fault code relating to stepper motor that persists once code has been cleared. This code persists even after the new stepper / turbo has been installed.
(An example code would be: P0047 which relates to stepper motor. This may indicate low voltage or an out of range boost pressure detected).
– Or cases where insufficient boost has been attained or general over-boost fault codes are thrown by the ECU.
(And includes cases where the vehicle goes into ‘limp’ mode to protect engine components).
– Where there are ‘mods’ on the engine systems such as induction, ECU and/or exhaust.
(this creates a modified operating environment, so factory parameters become less relevant).
Stepper Motors & Fault Codes
Because of the general nature of fault codes, they can seem to emulate the same issue as the original fault that called for stepper motor replacement.
But codes usually lump 2 or more different issues under the same fault code.
An example would be a stepper motor that is actually faulty, throwing the same fault code as a stepper motor that is not faulty. It may be that the stepper just requires some calibration.
Another example is where the problem exists outside of the turbo/stepper system. The fault may exist in the ECU unit that controls the stepper. Or the main vehicle ECU, or other components of exhaust or air intake system.
Click this link for more information on specific Turbocharger Electric Actuator Stepper Motor Fault Codes.
Stepper Motor Calibration
Where mechanical calibration only is required, the essence is as follows:
The stepper motor should be allowed to create the correct range of movement to fully actuate the vanes.
This will give a correct amount of boost across the rev range, without producing over-boost or under-boost.
This is usually facilitated (in Toyota turbochargers), by adjusting a small stopper screw on the turbo, next to the lever that actuates the vanes.
Stopper adjustments should be made in small increments(of 1/16 of a stopper screw turn), and testing of flow and boost done between adjustments.
An extreme circumstance can occur where correct movement range cannot be attained via stopper screw (if screw length is at max or min length and stepper still requires further movement).
In such cases, a compressor housing re-alignment can be done as follows:
Slightly loosen the bolts under the compressor housing, allowing a change in orientation between the angle of the housing and rest of the turbo. Thereby allowing correct range of actuator movement.
The exception to the typical case where the stepper requires no calibration is for the Toyota Hiace Van.
With the Hiace, it is more common for a manual calibration to be required.
In addition, where the P1251 fault code persists in the Toyota Hiace, and cannot be cleared after stepper motor replacement, an update to the main ECU may be required.
This can be done by Toyota dealers for around $100.
What if Stepper Motor Calibration doesn’t work?
Where a fault still exists after the above calibrations have been performed, the following may need to be checked:
– The correct functioning of the boost control ECU (if the car has a separate one).
– The correct functioning of the main ECU.
– MAF sensor functioning (will generally show up as a fault code if problematic), but may be worth cleaning with electrical contact cleaner.
– The correct functioning of the EGR Valve, cleaning of which can sometimes help.
– A check done of all fittings, pipes(especially for splits in vacuum lines), gaskets, clamps, air cleaner & snorkel (where fitted).
– A manual check done for free and easy movement of the lever that moves the vanes inside the turbo.
Any stickiness is usually a fault inside the nozzle / vane system inside the turbo. And is usually due to excessive coking inside the vane assembly due to incorrect engine combustion (obviously not in a new turbo install).
Any of the above issues, may show up incorrectly as a stepper motor issue.
These are just a few of the main checks that can be done to aid the diagnosis / successful install of turbo / steppers.
A Cautionary Note:
A faulty Turbocharger Electronic Actuator Stepper Motor can eventually create problems inside the turbo and vice versa.
If the ECU is ‘throwing’ codes associated with the turbo or stepper motor, and / or going into limp mode, it is best to tackle the issue early.
By doing so you are helping to keep the issue isolated to either part, so less likely you will need to replace the entire turbocharger system.
It is a general recommendation that if there is a chance the stepper may be faulty as well as turbocharger, they both be replaced at the same time.
For a full list of the Turbocharger Electronic Actuator Stepper Motors we supply at the best price PLEASE CLICK HERE.
If you have any other query on matching turbo parts for your vehicle, please feel free to contact our sales support on: 0490 059 316.