Jump to content

Center Diff Control. DCCD (ACD? ATTESA?)


Recommended Posts

I have no idea on how possible this even is, or how sort after the feature would be, but im gonna throw it out there anyways as it is something I would like.  And I can potentially see it being useful for tarmac rally, gravel rally, and even circuit cars.  (Subarus, and possibly Evos/GTRs )

I would like to be able to run DCCD via the ECU.  I have a Thunder ECU and '07 STi DCCD 6spd gearbox, retro-fitted into a non-DCCD equipped Subaru.  

In order to utilise the DCCD I run a DCCD-Pro controller as my car was never equipped with the OEM control system.  The controller would seem pretty basic in that it only monitors TPS, lateral/accell G-force and a handbrake switch.  And then has some user inputs, which is basically a trim pot knob/wheel for how aggressive it is and an auto button.

Given that the Thunder has accelerometers built in, it could potentially have access to all the inputs needed for calculating the DCCD, plus many many more.  For example individual wheel speeds or brake switch inputs.

As for output, AFAIK, the Subaru DCCD is basically just driving a electromagnetic coil in the gearbox.  I dont know how much current is used, but im guessing perhaps a E-throttle channel could be used to drive it?  They can do 4 amps correct?  Thunder has 2 E-throttles.  So even on cars that use the first E-throttle as an E -throttle, there is still the second spare.    

Now i know most of the Subarus will probably just have a plug-in ECU.  Which is Xtreme isnt it?   So they only have 1 E-throttle, which if the car is using it, no good.  But the earlier models with cable throttle could potentially use the E-throttle output still, even if using a plug-in? 

And im guessing it could also be applied to EVOs aswell with thier ACD system.  Which is AFAIK a pump and solenoid.  So possibly easy enough to make work?


I know you guys prioritise new features by how usefull the feature would be to the customers (and how much hard work it is for you to implement), and I understand its probably not gonna happen due to how many people would use it and how much programming it is for you to do.  Im just putting it out there.

Edited by Bram
Link to comment
Share on other sites

It's a good suggestion. My understanding is that the OEM controller controls the DCCD via CAN bus. I see Motec has a controller available that seems to be able to replicate (and improve) this functionality over CAN bus.

It may be possible to control the electromagnetic coil (I'm going on what you say here, I don't know the inner workings). We would want to examine how the factory controller does it and then see how much current it involved. If you come across any documents with this then be sure to share them.


Link to comment
Share on other sites

Ok.  Thanks for the reply.


And im happy to do some testing etc.  I can measure current draw over the DCCD coil when energised.  And any other tests that may need to be done.


I know there is probably some copyright infringements looming when i say this.  But it may also be good to look at how the DCCD-Pro brand of controller functions.  These would probably be one of the most common controllers used in the Subaru world for people like me who retrofit a DCCD box into a NON-DCCD vehicles.  As you know Subarus are like Lego and you can pretty much put anything Subaru into anything else Subaru.  So DCCD retro-fits are extensively common for non STi vehicles like WRX, Liberty, Forester and so on.  I could perhaps hypothetically hook my DCCD controller back up, and then connect it into the Thunder to log its output.

Link to comment
Share on other sites

And its not like your are gonna be stealing potential customers away from DCCD-Pro by making the ECU handle control from it.  Most people that want DCCD will still just get the controller rather than going for a full stand alone ECU system.  

But doing it via the ECU will allow people with the ECUs already, the possibilty to streamline thier instal with one less extra module.  And people who are looking to go stand alone ECU may choose Link over others for the added ability to handle DCCD.  

Having access to manipulate the way the DCCD interacts can be very interesting.  DCCD makes a massive difference to the performance of the car on tighter/twisty stuff like tarmac rallying.  I know from my own experience racing and forgetting to turn the DCCD on, it can mean as much as 2-3 seconds per minute of racing VS with it on  (I turn it off in the back staging/carparks as the diff bind is annoying.)  So having the ability to fine tune further could still mean big performance advantages over a non adjustable setup.

Link to comment
Share on other sites

I just had some spare time to look at this request a bit closer today.  It appears basic Subaru DCCD functionality like some other ECU's offer should be mostly doable with the functions we already have available.  I dont know how well it compares to the OEM control strategy however.

Diff control is simple PWM. 

From what I can gather from a couple of "competitor brand" maps, the vast majority of the duty cycle control comes from a basic 3D table which is Speed Vs TPS.  On top of this main 3D table there are a couple of other conditions (probably only applicable to rally cars) to unlock the diff during handbrake slides and during left foot braking (we already have conditions available for GP PWM outputs but there are other thresholds needed for these rally conditions so we would need to involve a couple of virtual aux's to duplicate these well).  

The only bit that I dont have enough information about (or possibly I just dont understand the logic well) is it appears during braking an extra 2D map comes in to play.  Again i think we could duplicate this reasonably using virtual auxs to switch to a different table.  Neither of the maps I have appear to use any G or yaw sensor, steering or other driver inputs.

The DCCD-Pro seems to do things a little different to above and information on it is sparse.  I think when/if we add 4D Aux tables that will allow us to do it a bit nicer.  

The main hurdle I see is you are going to need about 5 years of track tuning to get all these tables dialed in...  


Link to comment
Share on other sites

  • 3 weeks later...

I've been using link ecus to control the dccd centre diffs in rally cars for a few years. As adamw said I just use a gppwm output and virtual aux outputs to get the outputs I desire. I use a solid state relay to handle the current and have the hand brake as a digital input. The sky's the limit with what you can do. It would be nice to have a 4d aux table or other switching ones though. 

Link to comment
Share on other sites


Does anyone know whats needed to controll a ACD (Mitsubishi Evo) diff? 

I would really like to see a generall purpose 5D/6D PWM output function. You can do that the same way as 5D/6D on boost controll as we discused in another thread. 

This allows G-force, speed, TPS and wheelspinn correction and even switch between maps on the fly. 


Link to comment
Share on other sites

  • 3 months later...
  • 11 months later...

I would really like to use gp tables. We have more than enough spare aux on an Evo I'm developping, but unfortunately there are juat too less MAP Slots available. I know 30 table slots sound like many, but we already run out off slots on the 4 cyl. Ind. Cyl trim, knock control, cl boost with, DBW, Launch, all need tables. 

Is there no possibility to increase the table number in the firmware, so we can use Aux tables for ACD control? 

Link to comment
Share on other sites

  • 5 months later...

I tried searching for a howto or something to do PWM Map switching with virtual aux's but I couldn't find too much. I was researching the Motec Diff controller and to match what they do in a basic fashion i'd need.

1 PWM Table for "Accel" - Use this table when not braking

1 PWM Table for "Braking" - Use this table when braking

Set to a fixed Freq if the ABS kicks on (DI or CAN)  5% Lock

Set to a fixed Freq if the Hand Brake is on (DI) 0% Lock (This one is easy)


This this doable with virtual IO and a GP PWM Output?

This would be for a subaru 6 Speed transmission with DCCD.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...