Sequential Twin Turbo User's Guide
Sequential Twin Turbo Systems Explained
This guide will be to explain how the FD RX7 and the JZA80 Supra sequential twin-turbo systems operate and how to tune them.
Mazda RX7 FD3S 13B
The RX7 system is supported by Haltech ECUs such as the Nexus R5, R3, S3, and Elite 2500 using the 'Sequential Twin Turbo' function in NSP.
Other ECUs, like the Nexus S2 or Elite 1500, also support this function; however, depending on your specific application, you may not have enough outputs available to control all the relevant solenoids. For example, if you are using these ECUs with a Haltech Plug N Play Adaptor kit, it utilizes Ignition Outputs 5-8, which are unavailable on a Nexus S2 or Elite 1500. However, if you're custom-wiring the ECU, you can choose which outputs to use—for instance, if you have spare outputs because you're not using the oil metering pump.
Control Solenoid Description
| Control Valve | Control Method | Description |
|---|---|---|
| Pre-Control Valve | Duty | Controls the boost level when operating on the Primary Turbo only in the same way as Open Loop Boost Control. More duty gives a higher boost level. Any exhaust gas wasted from this is vented to the turbine of the Secondary Turbo to help spool it up. Adjustment of this is provided in the Sequential Twin Turbo table section as the Pro-Control Duty Cycle table. |
| Exhaust (Turbo Control) Valve | Switched (Off below RPM switch point) | Controls the exhaust flow into the Secondary Turbo. When the RPM point for transition is reached this valve is opened. |
| Charge Relief Valve | Switched (On below RPM switch point) | Controls a valve that opens or closes what is effectively the air bypass (blow-off) valve from the Secondary Turbo. This valve is held open when operating on the Primary Turbo Only to allow the Secondary compressor to free spin to assist spool up. |
| Charge Control Valve | Switched (Off below RPM switch point) | Controls the valve that opens the Secondary Turbo's Compressor discharge so it can supply air to the engine. This is switched at the chosen RPM point to activate the Secondary Turbo. When operating on the Primary Turbo Only this need to be closed to prevent the Primary Turbo from losing pressure out through the Secondary Turbo Compressor. |
| Wastegate (Boost) Control | Duty | This is the conventional Boost Control and is used when both turbos are operating. Configure as you would any other type of boost control via the Boost Control Function. |
Settings
| Table | Description |
|---|---|
| Secondary On RPM | The RPM above which the secondary turbo is engaged. |
| Secondary Off RPM | The RPM below which the secondary turbo is disengaged and the system will revert back to using the Primary Turbo Only. |
| Pre-Control Duty Cycle | Controls the boost level when on the Primary Turbo Only. See Pre-Control Valve above. |
Toyota Supra 2JZ-GTE
The Supra system must use an ECU that supports 6-cylinders, e.g. Nexus R5/R3/S3 or Elite 2500 via Generic Outputs, but can also be configured using the "Sequential Twin Turbo" function with the Charge Relief Valve not being connected.
| Control Valve | Control Method | Description |
|---|---|---|
| Intake | Switched | Acts as the Charge Control Valve above. |
| Exhaust Bypass Control | Duty | Acts as the Pre Control Valve above. |
| Exhaust Gas Control | Switched | Acts as the Exhaust Turbo Control Valve above. |
| Waste Gate Valve | Duty | This is the conventional Boost Control and is used when both turbos are operating. Configure as you would any other type of boost control via the Boost Control Function. |
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