Subaru DCCD Controller – How Do I Use the DCCD Controller, and How Does it Work?

Subaru DCCD Controller – How Do I Use the DCCD Controller, and How Does it Work?

Jul 10, '21

This blog post discusses the functionality of using an installed DCCDPro Controller. To learn more about DCCD, click here. For information on the difference between OEM and Aftermarket DCCD, click here. To get help on how to install a DCCD controller, click here. For tips on which controller to buy, click here.

 How does the DCCD in a car work? 

The DCCD or Driver Controlled Center Differential refers to the ability to adjust the clutch packs in the center diff to get them to grab or not grab, which allows determines how much of the power created by the engine is transferred between the front and rear wheels.

When the center diff is open, the clutch discs are touching but slipping against each other, which is where the term "slip" comes into play. The way the center differential is designed, this slip creates a bias (how much power is sent to the front or rear wheels) when there is no input into the center differential. While the act of transferring power from the front to rear via the slipping clutch packs in the center diff isn't inherently an issue while cruising on the highway, it becomes a problem under hard acceleration and potentially a serious issue on the dyno because of the increased force required to spin the rollers.

You want a DCCD controller connected so that when accelerating hard, the controller commands the clutch packs "lock up" so they don't slip against each other. Locking them together reduces friction, reduces heat, and in turn, reduces wear and tear on your center diff. When accelerating hard without the clutch packs pulled together, they are now creating far more friction than they were designed to handle, which causes premature wear.

How does the DCCD Controller work? 

Now that we understand what is happening in the car, we can go into more detail about how the controller works. Please note that this is specific to the aftermarket DCCD controller of DCCDPro. Stock DCCD and other aftermarket controllers work slightly different in terms of input and logic for output.

Unlike the factory DCCD unit that pulls the wheel speed data from the ABS (Anti-Lock Brake System) and several other on-board sensors, the Spiider model utilizes the TPS (Throttle Position Sensor) and a G sensor to replicate the information the OEM DCCD controller would get. Using this information combined with built-in logic, the DCCDPro will allow for grab or slip to give the driver the most control over the car in any situation.

How Do I Know If The Controller Is Working? 

We suggest driving to an empty parking lot to test if the controller is working. Next, put the controller in manual and full lock, and turn tightly in a circle. When the center diff is locked, the car will hop because the wheels are all trying to rotate at the same speed. As you go toward open, it's going to let the center diff slip, and the wheels will go at different rates, and the turn will smooth out. As you roll the controller toward lock again, it'll feel like it's binding. 

 How to Use the Controller:
 Turning Controller On/Off

The controller is on when the car is on. Every time the vehicle is turned off and back on again, the Spiider controller will default to auto mode and where the roller is currently set. The Manual DCCDPro will reset to the roller switch's position. For SI-Drive Controls, it will default back to a low lock mode since the roller for the center diff is a toggle.

Display Lights and What They Mean

There are two types of external displays for a DCCDPro; the STi gauge cluster or an LED light strip. Both work in similar ways where there is a rainbow of color. Each color dictates the controller's status (open vs. locked). Please note the display feature only works with the Spiider Controller WITH CLUSTER OUTPUT and can't be added after the initial purchase.

Auto/Manual: The stock 02+ STi cluster will show auto/manual at the top. For 1993-2000 clusters, there isn't an auto position since this feature didn't exist at the time. Use the light on the auto/manual button itself to confirm this setting.

Open vs. Locked: Green is open, and Red is locked with several options in between.

Notes About DCCDPRo Supplied Switches

If you have the DCCDPro supplied button (silver button) and roller (black knob) then the blue light on the silver button is telling you what the controller is telling the center differential to do. When there is no light it's in the open setting while the brightest blue setting is the lock setting.

The equivalent to the stock cluster display as you read this article would be

  • Green on STi cluster = No light on the DCCDPro switch
  • Red STi cluster = bright blue on the DCCDpro switch
  • You can tell if it's in auto or manual because the light will constantly change brightness as the center differential is being adjusted.
  • If the light is static then you are in manual mode. 
On the DCCDPro, the lights are a live readout, so they will move as the controller adjusts the center diff. When the aftermarket controller is in auto mode, it does not output like the factory unit. On the factory STi, the cluster would not display any lower lights when in auto mode.

The other benefit of an aftermarket controller is that you can still adjust the center diff even in auto mode since the roller switch in auto adjusts aggressiveness (IE, more aggressive = tends not to allow for slip for spirited driving and faster cornering at speed). When the roller switch is pushed toward lock, it’s more aggressive than when it’s toward open. Since lights are a live readout on the dash, it'll spend more time in the lights near lock when the controller is set at lock and more toward the lights near open when in open. IF THE ROLLER IS ALL THE WAY AT OPEN WHILE IN AUTO, IT WILL STAY IN OPEN WITHOUT ADJUSTING. MAKE SURE THE ROLLER IS AT LEAST ONE CLICK FROM OPEN FOR THE UNIT TO WORK WHILE IN AUTO. WE SUGGEST STARTING AT 25% FOR STREET DRIVING.

Common Issues During Install If Controller Is On But Not Adjusting

Parking brake – When the parking brake is engaged, the center diff should be completely open, allowing the clutch packs to slip so the rear wheels can lock up without forcing the front wheels to do the same. If the ebrake light is illuminated on the dash, the DCCDPro’s response is to open the center diff, which means the display light will be stuck at open, and the lights won't move. The unit can not be tested unless the ebrake or parking brake is down and the ebrake light on the cluster is off. Some cars require the car to be started to turn the parking brake off (due to LEDs and alternator circuitry).

Light on Auto/Manual Button Not Working - When using the OEM auto/manual button, the mode is selected by toggling the switch. When in manual mode, the light on the button should turn on. If, for some reason, the display shows that it is in manual, but the light is not working, the light is most likely burned out. This can be fixed by replacing the auto/manual button with a new one or checking the forums for the DIY light bulb replacement.

If the lights are bouncing in open or it seems like it's acting "funny," - The G-Sensor needs to be calibrated for its position. Just press and hold the auto/manual button with the key off. Turn the key on while holding the button until the light on the button flashes (2-3 seconds). The G-sensor is re-calibrated for its current position in the car and should be good to go.

#DCCD #DCCDPro #STIGaugeCluster
Tags: DCCD