WG N75
The WG N75 patch turns Simos 18 ECU pin A21 into a PWM output for an N75 valve, so a turbocharger with a pneumatic wastegate can be controlled directly by the ECU.
The patch must be combined with Easy Wastegate or SWG.
Contents
What the patch does
A pneumatic wastegate is held by boost pressure and modulated by an N75 solenoid. The ECU has to drive that solenoid with a PWM signal for the wastegate to be controlled rather than simply held by spring pressure.
The patch enables that output on pin A21 and lets you set the PWM frequency the valve runs at. On a stock Simos 18 that pin is LV_SAV / PWM_WG. China-market vehicles already use it for an N75 wastegate valve; on other markets it drives the secondary air pump, or is not used at all — see the Simos 18 ECU pinout for the full designation.
The patch provides the output only. It does not decide how far the wastegate should be open at any point — that request comes from the wastegate control patch you run alongside it.
Requirements
• A Simos 18 ECU on an SC8 software variant, matching one of the boxcodes the patch is built for
• Easy Wastegate or SWG applied to the same file
• A turbocharger with a pneumatic wastegate
• An N75 valve wired to ECU pin A21
• Easy Wastegate or SWG applied to the same file
• A turbocharger with a pneumatic wastegate
• An N75 valve wired to ECU pin A21
Easy Wastegate supplies the wastegate position feedforward maps, where 1 means closed and 0 means open across engine speed and requested boost. Without one of those patches there is no position request for the N75 output to follow, and the valve will not be driven meaningfully.
Commission the setup on a controlled run with boost and wastegate position logged, and start conservatively.
Settings
The patch adds two parameters to the tuning editor, both under WG / N75.
N75 PWM output on A21 — enables the output. Set it to A21 (N75) to drive the valve, or Off to leave the pin inactive.
N75 PWM frequency on A21 — the PWM frequency in Hz, adjustable from 10 to 1024 Hz. Set it to the frequency your N75 valve is specified for; running a valve far outside its range gives poor resolution and inconsistent control.
N75 PWM frequency on A21 — the PWM frequency in Hz, adjustable from 10 to 1024 Hz. Set it to the frequency your N75 valve is specified for; running a valve far outside its range gives poor resolution and inconsistent control.
Wiring
The N75 valve connects to A 105/21. The full pin designation and the neighbouring assignments are listed on the Simos 18 ECU pinout page.
Before connecting anything, check whether the pin is already in use on your car. On cars fitted with a secondary air pump it is already taken; on many others it is simply unused. The wiring diagram for your specific ECU and market is the only reliable way to confirm which.
A secondary air pump on the pin does not block the swap. Disconnect the pump, then disable the secondary air output and its diagnosis in software — the pin is free for the N75 valve after that. Leave the diagnosis active and the ECU will set faults once the pump is gone.
Confirm the connector designation and pin numbering against the wiring diagram for your own vehicle before making any connection.
The stock turbo model no longer applies
With Easy Wastegate or SWG in use, wastegate position comes from the feedforward maps and the stock turbocharger model is no longer in the control path.
The compressor model maps no longer describe the turbocharger you have fitted. Under Turbocharger / Model - Compressor these are:
• Turbo Compressor Surge Line
• Turbocharger Compressor Surge Line Hysteresis Part Load
• Turbocharger Speed
• Air Temperature Increase Factor
• Compressor Efficiency
• Turbocharger Compressor Surge Line Hysteresis Part Load
• Turbocharger Speed
• Air Temperature Increase Factor
• Compressor Efficiency
Turbocharger speed and compressor outlet temperature are derived from those maps, so on different hardware the figures the ECU works with are simply wrong. The torque management thresholds that watch them will still intervene and cut boost, so raise them out of the way. Under Turbocharger / Torque Management:
• Turbocharger Speed to Start Torque Management
• Turbocharger Speed for Maximum Torque Management
• Compressor Outlet Temp to Start Torque Management
• Compressor Outlet Temp for Maximum Torque Management
• Turbocharger Speed for Maximum Torque Management
• Compressor Outlet Temp to Start Torque Management
• Compressor Outlet Temp for Maximum Torque Management
Turbo Max Pressure Ratio still applies. Leave it where it is — it remains a real limit, and it is not one of the values to raise.
Raising the four thresholds removes protections that were calibrated around the stock turbocharger. They are raised because the model behind them no longer matches your hardware, not because the underlying limits stopped mattering — the turbocharger still has a speed and a temperature ceiling, and after this nothing in the ECU is watching it for you.
Logging the wastegate
Wastegate position is logged as a percentage in the simos.app iOS app, so you can see what the wastegate is actually being asked to do while you tune the feedforward maps.
Log wastegate percentage together with requested and actual boost. If the wastegate is already at its limit and boost is still short of target, no further change to the feedforward maps will recover it — the restriction is mechanical.
Other apps can log the same value by reading RAM address 0xd000f90c.
Flashing the patch
Adding or removing a patch changes the software, so it requires a Full Flash rather than a CAL flash. See CAL Flash and Full Flash for the difference, and Flashing Information before you start.