Early Subaru Drive By Wire Conversions

At first glance a cable throttle seems very simple, a cable runs from the accelerator peddle to the throttle valve allowing the driver’s input to directly control the amount of air going into the engine. This is fine under most driving conditions, but when stopped the amount of air required for the car to idle nicely varies depending on a number of factors like temperature and auxiliary load. To allow the correct amount of air past the throttle valve, cars will have an idle air control valve (IACV). Early Subarus are no different, having a cable throttle and IACV system. Many people wish to convert these to a more modern setup when installing an aftermarket ECU. Fortunately there are off-the-shelf solutions available from PT Motorsport. If this conversion is something you are considering for your early Subaru, keep reading for an in-depth look at why it’s a great idea, and how to achieve a top-quality result.

How Does an IACV Work?

If you own a GC WRX or an RS Liberty with an EJ20G your IACV has four ports, two have engine coolant flowing through them, the other two are what controls the air.

The IACV and throttle cable can both be seen in this photo

In order to get air from the intake a hose runs across the engine bay under the intake manifold. This air passes through the valve and into the intake manifold, allowing the car to control the idle.

Combined with the cable throttle you are left with a system with a lot of complexity, which takes up a lot of room in the engine bay, has many limitations, and can be expensive to repair or difficult to source parts for.


The alternative to cable throttle is drive-by-wire (DBW) which uses an electrical signal between the accelerator pedal and an electronic throttle body. DBW is more precise, customisable, and has far greater scope for integration with other vehicle systems. It also removes a lot of bulk from the engine bay.

Some of the benefits of DBW include:

  1. Precision and Responsiveness: Due to the lack of mechanical linkages, DBW offers instantaneous responses to the driver’s input. This responsiveness is critical in motorsports, where split-second decisions and lightning-fast reactions can determine victory or defeat. Whether it’s coming out of a corner, executing an overtake, or maintaining control during a drift, DBW technology empowers drivers with unparalleled control over their race cars.
  2. Improved Motorsport Feature Control: Many aftermarket ECUs have features such as launch control, anti-lag, and traction control which are far simpler to setup and manage when using DBW.
  3. Adaptability: DBW systems enable tuners or owners to program different throttle response profiles, allowing drivers to choose between various driving modes (e.g., sport, eco, comfort). This adaptability enhances the driving experience by tailoring the vehicle’s performance to individual preferences.
  4. Data Insights and Telemetry: Data analytics have become an integral part of modern motorsports, aiding in the optimization of performance. DBW systems contribute to this data-rich environment by providing real-time telemetry on throttle position, pedal movement, and engine responses. This information is invaluable for tuning your vehicle and doing general diagnostics.

How Do I Get All Of These Benefits?

Obviously a DBW conversion will require an electronic throttle body, fortunately there are many aftermarket options, as well as a number of later model Subaru throttle bodies being bolt on options for the standard intake manifold.

Later model Subarus are also where we turn to for our accelerator pedal. These later pedal assemblies have the position sensor built in making it a great all-in-one solution. The only problem is that they’re not a bolt-in option, usually requiring fabrication to mount. Fortunately PT Motorsport has the solution, our GC8 Accelerator Pedal Position Bracket allows for a seamless and pain-free installation.

The later model accelerator pedal bolts directly into the early car using the PT Motorsport APP Bracket

While your DBW conversion has now eliminated the throttle cables from the engine bay, there is still the matter of the IACV. This is no longer needed when using a DBW system as the ECU can directly control the throttle valve to ensure a smoot idle. Once again PT Motorsport comes to the rescue with our Idle Air Control Blanking Plate, this CNC machined plate is an aesthetically pleasing and functional piece of engineering allowing for removal of the factory IACV.

As you can see, deleting the IACV removes a lot of bulk from the engine bay.


If you have gone to the trouble of fitting an aftermarket ECU to your car, a DBW conversion and IACV delete are two steps that will allow you far greater control over your engine’s idle as well as reducing complexity. These two products from PT Motorsport make both jobs far simpler and are all the more reason to do a DBW conversion today!

  • Subaru Idle Air Control Blank
    Subaru Idle Air Control – Blanking Plate
  • Subaru GC8 APP Bracket
    Subaru GC8 APP Bracket
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