Diy: Active-Lsd Wiring Into Aftermarket Ecu

[PM-R33]

I would first recommend reading my sticky on the A-LSD so you understand what it is, how it works and why there are problems with it.

 

 

I had been thinking about doing this DIY for a little while now and finally got around to doing it and testing it the other day.

Basically this DIY allows you to wire up the A-LSD hydraulic pumps into an aftermarket ECU that has auxiliary outputs. With this, you can program when and how you want the A-LSD to lock up.

From factory the diff will only lock up when one of the rear tyres has broken traction. To me this seems a bit counter productive due to one wheel needing to break loose first for it to do anything. This wastes time wheelspining and also makes the car unpredicatable in a slide and hard to control. Any one that has tried to drift an ALSD equiped car will know what i'm on about.

My way will make the diff lock up PRIOR to it breaking traction - read on.

Now there is two ways to go about this depending on what your ECU can output. My Vipec V44 Skyline plug and play can only switch earths ("Low Side Driving") as outputs, it can't switch power ("High Side Driving"). If you have an ECU that can switch power as an auxiliary output than scroll down to the "Aux output - High Side Driving" however still read the first low side driving section to understand how this all works.

IMPORTANT FIRST STEP - DISCONNECT THE BATTERY PRIOR TO TOUCHING ANY ELECTRICS!

Aux output - Low Side Driving

TOOLS REQUIRED

4 PRONG RELAY

WIRE STRIPPERS/CRIMPERS

FEMALE BLADE TERMINALS

10-15A 3-4m WIRE

15A FUSE

SOLDERING IRON & SOLDER

First get the wiring and fuse ready prior to touching the car. Even if you have little experience in circuits don't stress, it is very simple to set up.

You will need four wires all up. A long wire from the ECU to the boot (approximately 3m will do) and three short wires - one with a fuse. Cut your wires to about this length and put a female blade terminal on each end:

Now we shall be setting the wires and relay up as follows:

The relay will have numbers written on it (85,86,87,30) so set the wires up accordingly. The blue wire on the reel shall be the wire to the ECU which I refered to as the trigger wire on the diagram. The short red wire shall be joining together with the fused wire BEFORE the fuse. The longest red wire is the output wire to the ALSD.

Basically we are going to have a constant power source running through the relay into the A-LSD hydraulic pumps. The circuit shall not be complete however until the relay is earthed - which shall be the job of our programmed ECU.

So once you understand the relay diagram and the wires, join them with it looking like this:

Once the relay is all setup we can move onto the car. Pop the boot and remove the right hand side trims:

This will give access to the wiring for the pumps. It's the wiring running vertically all the way down:

Remove the electrical tape and you will see about 6 wires. The two wires we are interested in is the thick red wire and the thick blue and white wire:

Expose some wiring and solder on the output wire to the thick red wire and the fused 12V ignition wire onto the blue and white wire like this:

And that's basically the hard part done. Mount your relay somewhere and tape up all the wires and run the long blue wire through the boot into the cabin down the passengers side:

At the ECU wire it up with some terminals (Don't solder it. That way you can unclip it if you need to) to your Aux output you will be using. For the Vipec V44 I used Aux 8 which is pin #25 on the ECU board. From factory this is used for the factory boost solenoid which I don't use. You can use whatever Aux output you have spare though.

With it all wired up now we move onto the programming on the ECU.

Plug in your laptop and fire up your software - in my case VTS.

Go to your Aux output, set it to a general purpose output with driver type Low Side and now you have full control of when you want to have the diff activating. Test whatever settings you want to see what works for you the best. I have set mine up as follows:

Mine is setup so the pumps activate and start locking the diff up when I go over 60% throttle and am under 100km/h. Why 60% throttle and not 100%? Reason being is the diff works by getting tighter as the fluid gets pumped inside. This means having it at 60% means it will lock a little bit even in normal acceleration. So when that time comes when you do go full throttle, the diff is allready semi locked as opposed to being complete open wheeler.

You can easily see the way it works by watching the fluid resevoir in the boot. If you leave the car overnight the fluid will be very high in the morning. Then when you start the car and the pumps go through their start up process the fluid will go down a bit. If you activate the pumps manually this fluid will go down even more.

You can use whatever settings you want however there is one problem that limits you to what you can set it to.....scroll down to "NOTE - PRESSURE SENSOR" to read what I mean.

Aux output - High Side Driving

If you are lucky to have an ECU that supports High Side Driving you don't need any relay since your ECU can output a 12V source. Simply run a wire from your Aux output on the ECU to the thick red wire that activates the pumps (read through the above to know which wire i'm talking about).

The only difference you will have is that you must set your aux output as High Side on the software.

Now there may be one small problem with doing it high side driven. If the A-LSD pumps are high resistance loads you may find your ECU will output a constant 12V to them and won't switch it off (due to the internal circuitry of the ECU as explained below):

This means you will have to do it low side driven instead.

RESULTS?

With the A-LSD locking up prior to breaking traction in one wheel it obviously is a much better improvement and means you can get better traction overall. How well it all works depends on a number of things (is the system bled, are both your tyres evenly worn, are the settings you using locking it up early enough etc.)

I think it is a much better way for the diff to function and straight away can notice the improvement.

NOTE - PRESSURE SENSOR

There is one small problem with doing what we are doing. The A-LSD has a built in pressure sensor. When it pumps fluid into the diff it builds up pressure and when the pressure reaches it limits it shuts down and goes into a fail safe mode. All this means is that the pumps will no longer work until you switch the car off and on. You will also get the "A-LSD" error light on the dash. So there is a limit for how long you can have the pumps activating.

This is why I have mine set up under 100km/h and only when I go over 60% throttle. This means I won't trip this pressure sensor.

As I said play around with the settings and see what works best for your setup.

The diff also functions completely as normal even with these modifications to the wiring.

I honestly believe the A-LSD should have been made similar to this from factory. The way it is made might be fine for stock power outputs but as soon as the car has some power behind it the delay time for the diff to react is to slow and nearly always results in poor performance.

TROUBLESHOOTING

1. You can test your wiring without driving the car. Simply have the ignition on, set your output to only work on a x% TPS source and push the accelerator to the floor for a moment. You should hear the A-LSD pumps whine quite loud.

2. If at any point your ABS light comes on you may have blown the ABS fuse. It is found inside the car near the drivers right knee.

3. If you trip the pressure sensor you will need to turn the car off to reset it, sometimes I have found it needs a little while longer to reset. Most likely to get the pressure back down.

Edited July 11, 2020 by PranK
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