[Modified] Control DFCO and Variable Intake on RX-7 SA with R-Commander 2

Mazda RX-7 SA22（GSL-SE)

In classic car upgrades, the limitations and outdated logic of factory ECUs often hold back true performance.

Take this Mazda RX-7 SA22 (GSL-SE) as an example: after upgrading the original 13B engine with an RX-7 FC intake manifold, the owner added an R-Commander 2 Digital RPM Activated Switch Controller to create a two-stage RPM activation system. This not only solved the issue of fuel cut during deceleration but also precisely controlled the timing of the variable intake system.

DFCO (Deceleration Fuel Cut-Off) is an engine fuel-saving mechanism. When the vehicle is coasting with the throttle fully closed and engine speed above a preset threshold, the ECU cuts off fuel injection to reduce fuel consumption and emissions.

However, for a 13B engine with upgraded intake and ignition systems, keeping the DFCO function can lead to tuning challenges. It may cause unstable power delivery, overly lean air-fuel mixtures, and even reduce engine longevity.

To address this, the RX-7 owner cleverly used the R-Commander 2 Digital RPM Activated Switch Controller. By wiring it through a relay, the system automatically disconnects the ECU from the TPS (Throttle Position Sensor) when engine speed exceeds 1200 rpm. This causes the ECU to interpret the throttle as still slightly open, effectively preventing DFCO from activating. As a result, the engine continues fuel injection during deceleration or coasting, maintaining smoother and more stable operation.

The auxiliary intake valve, originally operated by a vacuum system, is designed to open at 3800 rpm to increase airflow and enhance power output. In this setup, the owner custom-built an electronic solenoid system and used the Trigger 2 output of the R-Commander2 to activate the valve precisely at 3800 rpm. This upgrade replaces the original vacuum mechanism, delivering faster response and more reliable control of the variable intake system.

With its dual independent RPM-triggered outputs, the R-Commander2 offers precise trigger control and versatile applications across a wide range of custom builds:

- Outputs are 12V positive signals—recommended to be used with a relay for safe and stable control
- Can be applied to control variable intake valves, cooling fans, various switches, exhaust valves, and more
- Works seamlessly with other electronic devices, allowing users to define custom control logic

Whether it’s breathing new life into a classic engine or pursuing precise control over intake and exhaust systems, the R-Commander2 delivers a stable and flexible RPM-triggered control solution for performance-minded enthusiasts.

Related Products

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  R-Commander2 Digital RPM Activated Switch Controller

  SW10165

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  The R-Commander 2 Digital RPM Activated Switch Controller is suitable for professional modification enthusiasts and users who need precise control of other electronic devices based on engine RPM.

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