Race Car haldex controller

[15Degrees]

Hi Guys

I have an Audi S3 race car and have been trying to figure out a way to control the Haldex manually. This quest has led me on a merry dance from various new controllers like HPA to SQA etc etc all are no good simply because I am using a GEN4 unit and a MOTEC ecu. Anyway I gave up and tried to learn as much about how the unit works myself and then got in touch with an electronics company to get them to make my own controller. They specialise in custom made stepper motor control units.

We have basically figured out that on my GEN 4 unit I have a oil pump to create pressure and a solenoid valve to direct that pressure to the clutch pack or not depending on the valves position. Now dont forget this is a race car so my proposed system is as follows

Switch on for pump to give me pressure in the system (pump now spinning)
Rotary knob to manually set the solenoid position in a fixed position
Button on my steering wheel to engage or disenage

So at race start I have the system on and the knob set
launch and I have AWD and get away nice
leave on for first few corners to help warm the tires up
Turn off (disengage valve) with my steering wheel buttton so as not to stress the plates too much
Turn back on for those tricky overtakes


All of the above is dooable with some electronics which they can easily do (They make WAY more compex system than this) But it has led to a couple of questions from him which are below.


Hi Mark

We’ve powered the solenoid up and from what we can see – (please correct me if I’m wrong).

The solenoid valve seems to sit with no power on it, roughly in the middle of the movement.

• If you energise it one way, the valve moves out about 2mm.

• If you energise it the other way – the valve moves further in, about 2mm.

We’ve been through the PDF documentation on GEN 4, and whilst it explains what it does it’s vague about how it does it and how it’s supposed to work.

Are you supposed to be able to move the solenoid in two directions or does the action of mounting it to the rest of the assembly, force the solenoid fully in or fully out – which then means you can move it one way only?

The reason I ask this, is that it’s pretty simple to design a PWM style circuit to drive a solenoid in one direction – you vary the on time of the signal driving it, and assuming it’s pushing against a spring, the amount of on time gives you a rough idea of how far out it is (I stress rough, as it is not as accurate as the stepper design on the older haldex unit).

However – if you need to move it in two directions, the circuitry gets a whole lot more complicated – as you need to incorporate an H-bridge style controller as well (to change which side of the solenoid is positive).

The unit takes about 4A of power at 12V.

let me know your thoughts so we can proceed with development


Do any of you have the answers to his questions because I dont? I do not know if when the valave is mounted it sits in the middle of its travel or is one way or the other.


Cheers
Mark.

 

[warren_S5]

Wow, that's a techy one!

All I can find that might start to shed some light is this link here: http://www.audi-sport.net/vb/a3-s3-sportback-8p-chassis/59464-gen4-haldex-facelift-s3.html

I think some of the forum members struggled to get any info out of the Haldex tech support so it all sounds a bit of a dark art. Occasionally VAG do produce technical bulletins (I recently downloaded one of the Eaton Supercharger system on the 3.0V6T engine), but they are hard to find on the web. (example link)

You may be lucky and find someone on here who can help, but they'll be thin on the ground.

 

[wuta3]

Who's gonna step up, or are we renaming the site "audi-sort-of-sport" LOL

 

[15Degrees]

Who's gonna step up, or are we renaming the site "audi-sort-of-sport" LOL

It seems where Haldex is concerned no one knows anything ROFL. I have emailed Haldex but they don't bother to reply.

My understanding of Haldex is that it takes all these sensor feeds and sends them to the controller which decides how much to move the valve in and out to give you a % of AWD. Myself and the electronics guy are certain thats ALL the controller does (moves the valve depending on sensed conditions of slip) and in that case our solution above will work fine. The trick is not having the plates engaged fully for slow speed corners or indeed all the time so as not to overly stress them, this is why I want the disengage feature so I can switch it on and off.

Mark.

 

[S3Alex]

It seems where Haldex is concerned no one knows anything ROFL. I have emailed Haldex but they don't bother to reply.

My understanding of Haldex is that it takes all these sensor feeds and sends them to the controller which decides how much to move the valve in and out to give you a % of AWD. Myself and the electronics guy are certain thats ALL the controller does (moves the valve depending on sensed conditions of slip) and in that case our solution above will work fine. The trick is not having the plates engaged fully for slow speed corners or indeed all the time so as not to overly stress them, this is why I want the disengage feature so I can switch it on and off.

Mark.

Hi Mark,

I have to say it's no surprise that Haldex themselves won't give you any help.

Few if any commercial enterprises are willing to let you in on any useful info regarding their products.

I think there is a tendency for overheating or at least wear if slip etc occurs for long periods,as I remember the warnings on the controller on my car re being left in race mode for extended periods.

I don't expect any more from HPA,but did you try emailing them?

 

[s3_sid]

yeah from what you have said above is also my understanding on the system ! i know you can get manual controllers for earlier gens

how ever it will take a lot of learning to get the pressure right as i have read on earlier systems if you run 100% pressure you will burn up the clutch pack and too little can add wear to it ! but thats about all i can help with sorry !

 

[S3Alex]

Yet another long shot.....

Multiple ERC champion Kenneth Hansen used to use Haldex systems on his cars,clearly with some success,but also with a lot of money behind him,so mapping the Haldex and controlling it is obviously something his guys have done,but once more,I'm not sure how they'd go on sharing information,even though he had moved to other systems.

 

[warren_S5]

It's got to be one of the real dark art areas left on the A/S3 platform.

I'd always assumed it was an 'on/off' switch, but as gen 4 has evolved a bit from gen 2 it seems that there is additional scope to send additional power more quickly to the rear wheels. When I first read the post above I wondered whether the solenoid may have been given some float (either way) to reduce the severity of the on/off affects of engaging the haldex in a car that in the main is 2wd, but the more I think about it the less I realise I understand. Be really interested to hear if you can uncover any further info on it.

 

[15Degrees]

It's got to be one of the real dark art areas left on the A/S3 platform.

I'd always assumed it was an 'on/off' switch, but as gen 4 has evolved a bit from gen 2 it seems that there is additional scope to send additional power more quickly to the rear wheels. When I first read the post above I wondered whether the solenoid may have been given some float (either way) to reduce the severity of the on/off affects of engaging the haldex in a car that in the main is 2wd, but the more I think about it the less I realise I understand. Be really interested to hear if you can uncover any further info on it.

Dark Art indeed ha ha. The company I have engaged are way more clever than me on control systems, ecus etc and they are convinced of the following after studying a stripped down system I sent them over and also reading any available PDFs etc.

1. The pressure in the Gen 4 is constant and always readily available, this is what makes it so quick to react. I have this figure in a PDF at home and I think it's about 400 psi but I will check later and post the PDF up for reference.
2. Excess hydraulic pressure is fed back to the accumulator tank by an automatic bypass valve
3. The hydraulic pump spins up when needed to maintain this working pressure so is in a constant ready state
4. The Solenoid valve moves when told to by the controller based on its sensor feeds to instantly direct that available pressure to the clutch pack
5. The amount the valve moves dictates how much pressure goes to the pack and therefore how much AWD you get
6. We assume a fully closed valve = max pressure on pack and max AWD 50F/50R. 50% closed valve = 25% AWD and so on or 75F/25R


That's what we "think" we know so far. The questions above he raised in his email to me are the grey areas on operation on the initial valve position when at rest (open) etc and valve direction of travel.

 

[15Degrees]

It's built It's being posted. Once I get my engine back in this will be going on too. I will let you know how it works and post some pics of the design.

 

[warren_S5]

Nice one, intrigued to see how it goes!

 

[15Degrees]

Nice one, intrigued to see how it goes!

You and me both. It works perfectly on the bench like so.

Dial knob sets the solenoid state from fully open through to fully closed in 5 positions
Switch on switch panel turns on hydraulic pump
Button on my steering wheel moves solenoid to fully open state (disengage AWD)
Press button again and it moves it back to state set on the knob (engage AWD)

Et Voila fully controllable AWD

We will see

 

[15Degrees]

So my little box of tricks arrived and you know what. It works I have sent it back for some fine tuning but essentially it works as planned. next step is testing it out.

 

[warren_S5]

Great news. Were the differences significant or subtle, and if significant what was the greatest characteristic of improvement in the drive/handling? Intrigued.

What have you asked them to fine tune?

 

[15Degrees]

ha ha not ran it on the car yet.

I asked them to do the following

Move the dial pot from the unit to be external
Make the dial pot a ratchet style
Fine tune the dial pot travel as it had some free at the end of the movement
Move the arm and switch leds to external

I want to mount the dial pot on my switch panel next to the haldex pump switch
I want the armed and switch leds on my dash so i can see them.

It's awesome though as with it armed I can move the dial pot and see the pin inside the valve moving back and forwards, awesome and then when i pressed the button it clicked to fully open and then pressed again it went back to where i had left it on the diel pot. If I disarm it the valve fully opens and current stops to it. All in all im impressed. I am getting Mik to make a nice housing for it based on the original but nicer looking as I only need wires to go to the two valve pins now.

 

[Muzza80]

Subscribed!!

 

[15Degrees]

When I get it back and the housing made Ill take a load of pics of the whole thing and then some vids of it in the race car. I shall also update my build thread as I have done LOADS of work on the car!! Some of which

New engine build blueprinted with JE pistons
New 06a oil filter plate with 1.8t hosuing
Massive air cooled oil cooler
Ally fuel rail
Syco fuel reg
New catch tank system
Twin fans on rad
Electric water pump
Uprated 06a oil pump
Fluidamper
Helix race ally clutch kit
New black seat
New schroth harness
Front splitter with custom subframe mounts
New ally expansion tank with turbo water feed (hot turbo water does not go back to block but to tank)

 

[warren_S5]

When I get it back and the housing made Ill take a load of pics of the whole thing and then some vids of it in the race car. I shall also update my build thread as I have done LOADS of work on the car!! Some of which

New engine build blueprinted with JE pistons
New 06a oil filter plate with 1.8t hosuing
Massive air cooled oil cooler
Ally fuel rail
Syco fuel reg
New catch tank system
Twin fans on rad
Electric water pump
Uprated 06a oil pump
Fluidamper
Helix race ally clutch kit
New black seat
New schroth harness
Front splitter with custom subframe mounts
New ally expansion tank with turbo water feed (hot turbo water does not go back to block but to tank)

Wow, love hardcore builds, too much plug and play these days. Look forward to it.

 

[veeeight]

Having played with a Haldex unit on the bench recently (Gen 4) - with no pressure/no power at the pump, there is an inherent "drag" from the clutches (looking at the measuring blocks on VCDS in the car, around 10%). Some people call this permanent engagement, but having thoroughly examined this unit for a few hours, it's not active engagement, just drag.

This is just friction of the plates, with a little fluid viscosity. You may wish to account for this in your setup! But I think its insignificant, especially as there is no clamping pressure present, definitely not enough engagement to even call it 90/10 when it matters in real world situations.

 

[15Degrees]

Cheers for that insight.

The bit we have not been able to work out is in real life with all sensors attached does the controller vary the valve position like it does on my manual control. From full open to full closed there is only about 2mm of travel so there is not much movement to play with.

We are assuming it does work like this otherwise you either have full on (valve closed, full pressure on pack) or full off (valve open no pressure, apart from the drag you mention on the pack)

 

[15Degrees]

Wow, love hardcore builds, too much plug and play these days. Look forward to it.

All in my build thread Warren which is soon to be updated with all the new bits.

 

[A3SBQ]

Have you seen this?
Haldexsteuerung Beschreibung
They are doing a lot of options to set.

May I asks what your solution cost?

 

[15Degrees]

Have you seen this?
Haldexsteuerung Beschreibung
They are doing a lot of options to set.

May I asks what your solution cost?

None of the Haldex controllers are any good for me buddy because I am running none of the sensors they need to work and also a race ECU too. This is why we had to develop a race solution from scratch.

Ill let you know when ive finished paying for it It's ongoing.

 

[A3SBQ]

Ahh I see.
Yes please inform us on your solution. Have been thinking of this for a long time too.

By the way. How is your build going on? Haven't read any lately!

 

[tom2001s3]

Any more to this? Interesting read..

 

[15Degrees]

Hiya

Update coming soon with pictures but full update will have to wait till I get the new engine in.

Cheers
mark.

 

[15Degrees]

Essentially I now have

1. A ally box of tricks with a custom board inside it for the controller
2. Another ally box on top of my main switch panel with a red and green light on it and a dial knob with ten positions
3. A load of wires
4. A custom box to hold the valve at the rear in the Haldex
5. A button

The box of tricks connects to the power and also to the valve at the back with two wires. I set the amount of rear diff on the dial knob with ten being max and 1 being zero. The button engages and disengages it. So if its set at say 5 and engaged the green light will be on and ill have the valve at roughly half travel (partially closed). If I press the button again the green light goes off and the valve moves to the fully open position.

Now! This works on the bench perfectly but when we fitted it the red power light was flashing and it didn't work! Poo. I think the valve is shorting somehow through the custom housing I had made so we need to investigate that next and I need to take a load of pictures for you guys