In this blog post, we review cruise control in your Subaru and the options available when doing an engine swap and wanting to retain or add in cruise control.
How Does Cruise Control Work?
There are three types of cruise control depending on your type of Subaru. In general, a cruise control module (external or part of the ECU) uses inputs from the car, like the clutch switch, brake switch, and throttle body, to control how fast the car is going.
Three Types of Cruise Control:
Electronic Throttle Cruise Control.
If the car has an electronic throttle body (drive-by-wire), the ECU handles the cruise control without an external module. It takes the inputs from the car and sends them to the ECU. The ECU then controls the throttle body to keep the speed consistent.
Mechanical Cruise Control with electric cable actuator.
An example of this car would be an 02-05 WRX. It is electronically actuated, but there is still the standard cable throttle. There is a cruise control module that gets inputs from the car and tells the cruise actuator what to do. The actuator is electronically driven to adjust the throttle tension.
Mechanical Cruise Control with vacuum-powered cable actuator.
An example of this car would be a 93-01 Impreza. The cruise control module gets inputs from the car and tells a vacuum-powered cruise actuator to push the cable in and out to adjust the throttle.
Can I Retain Cruise Control After My Engine Swap?
The answer to this question depends on which engine swap you are doing and what chassis you have. Please take a look at the options below of our most common engine swaps to see if Cruise Control is an option for you.
Cable Throttle Chassis to Cable Throttle Engine
If you are doing a cable throttle to cable throttle swap, you will reuse the cruise that came with your car. We don’t wire in the newer style cruise to older cars because it costs more than it's worth. For older NA cars with vacuum-powered actuators, adjust the unit's location to make room for the turbo and hook up a new vacuum line to the engine, and it'll work just like it did from the factory. For pictures, click here.
Cable Throttle Chassis to Electronic Throttle Engine
There isn't a cable throttle to actuate anymore, so the old cruise module and actuator are removed. We will wire the original inputs from the separate cruise module to the ECU during the merge process. It takes time to wire up the inputs for the cruise to operate, so there is an added cost if you want the cruise to work with a DBW engine swap.
Electronic Throttle Chassis to Cable Throttle Engine
In this instance, you would lose cruise control. The chassis doesn’t have the components needed to make the cruise work on the cable throttle engine. The complexities of trying to wire up the cable throttle cruise control module and actuator are extensive, so it’s not an option we offer. You can learn more about DBW to cable throttle conversions by clicking here.
What If My Car Never Came with Cruise Control, and I Want to Add It During My Swap?
If your chassis never came with cruise control, it would highly depend on your chassis model, and year. Some of the later models with cable cruise have the wiring installed, but the modules are not attached. In this case, you can purchase the modules and switches that need to plug into the empty connectors in the harness.
If your model does not have the cruise pre-wired, the only way to add cruise control to a chassis that didn’t come with it from the factory is to do an engine swap with an engine that came equipped with an electronic throttle and have the harness merged for the matching ECU. You must also add the new steering wheel for the cruise control buttons. This steering wheel update means you would also need to update your clockspring, clutch switch, brake switch, and a few other inputs.