Hydractive ECU re-map?

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isisalar
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Hydractive ECU re-map?

Post by isisalar »

Was in the local mot station getting one of the centerless alloys re balanced. They've recently started a engine re mapping service, for £300. I declined their kind offer but with the massive improvement since the E-crofting diode mod, to the suspension, the thought occurred to me that possibly a suspension ecu could be re mapped too.
Has anyone done this, is it possible?
A proper comfort/sport option would be lovely.
Cheers
Paul
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Mandrake
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Re: Hydractive ECU re-map?

Post by Mandrake »

I'm not aware of any remapping options available for the Hydractive 2 system.

The problem with any sort of remap is that unlike the more advanced system on the C6 (and C5 X7 ?) which have fully variable damping per wheel, there are only two states it can be in - "hard" and "soft" for all four wheels. Everything the ECU does is all about deciding when it should be hard and when it should be soft based on various sensor inputs.

Front and rear also always switch together between hard and soft, even though the hardware could in principle allow independent switching of front and rear with a software change. (They're controlled by different output drivers in the ECU and can independently detect faults with the two electrovalves) There's a good reason front and rear switch together though - safety. If you had the front in soft mode and rear in hard mode when cornering on the limit you could induce dangerous over-steer, likewise if the front was hard and the rear soft that can induce on limit understeer. The Hydractive 2 training manual explicitly calls out the fact that front and rear must switch together within a few milliseconds, although it doesn't specify why.

Because you only have hard and soft to choose from at any moment there is inherently a compromise between comfort and handling... a good example is that when you accelerate from a standstill unless you ease off the throttle the suspension will instantly switch to hard when you punch the throttle and stay there for 3 seconds to minimise squat in the rear suspension. As junctions tend to be riddled with potholes this means you crash your way over these potholes each time you accelerate from a junction, and the front suspension also switches to hard even though only the back suspension needs to be hard to resist squat.

I actually ran my previous Xantia with the throttle potentiometer unplugged for a couple of months to see how it would behave - the system would still switch to hard mode as normal during cornering, (steering wheel sensor) emergency braking, (road speed sensor) and in response to sudden rises/dips in the road, (front anti-roll bar movement sensor) but would not respond to the throttle being poked - so would stay in soft mode when accelerating from a stand still and also stay in soft mode when pressing and releasing the throttle when driving in a straight line. This gave a very obvious increase in ride comfort, especially when moving off from a potholed junction.

So the single easiest "mod" you could do to improve ride comfort without hindering handling significantly would be to unplug the throttle sensor. It's the potentiometer that is mounted up behind the accelerator pedal arm with a finger that hooks over the arm - there is a connector about half way up the back of the accelerator pedal arm that you can unplug. It's a wee bit fiddly to reach and release but not impossible. A fault code will be logged but the system will otherwise continue as normal as its a non-critical input, and the fault code will go away when you reconnect it.

The drawback to doing this is you soon learn why they implemented this sensor - acceleration squat! :twisted: Without it the rear suspension will tend to squat right down under hard acceleration in a somewhat comical way that is reminiscent of Citroen's of old... even my 2 litre petrol Xantia squatted right down under acceleration with this mod, I hate to think what my V6 would do :twisted: (I might try it for a laugh) If you primarily want comfort and aren't in the habit of flooring the accelerator all the time then it may be an acceptable compromise though - you still get the safety of the stiff damping should you start chucking it around corners or braking hard, but a significantly improved ride during more casual driving...
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
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