Air suspension control program

**Cyclist** · 10th July 2021, 10:26 PM

Three months into D4 ownership I'm still smiling, but also endeavouring to learn this sophisticated machine. I have gleaned what I could from the manual, but I have questions.

I read that if mine is a 'later model' the suspension will drop 20mm if the speed exceeds 100 mph. I don't care whether mine does or does not, and I'm not close to finding out, but how does the system establish 20mm at speed? This relates to a general question: how is the signal from the height sensors processed? Are they in fact used when the car is in motion, when of course the height will not be constant?

I read that opening the crosslink valve(s) "increases wheel articulation and improves ride comfort at low vehicle speeds”. I can see how it might, but what if the vehicle is travelling around the side of a hill? There will be more weight on the downhill side, so if the crosslink valve was open it would tilt further, unless the control program knew that it was on an angle and compensated. Maybe it does that..

I read that if you put a load on the back the level will be maintained. Does this only happen when stationary? Comes back to the general question about how the height sensor data is processed.

Mr Google has not managed to satisfy my curiosity. Any pointers, anyone?

**Graeme** · 11th July 2021, 05:48 AM

Having a read of the suspension section in the workshop manual should be rather enlightening for you, but for starters the system monitors the height sensors almost all the time, although only occasionally while the ignition is off. The levelling while moving is smoothed over approximately 5 seconds but a requested height change commences almost immediately. The system knows when the steering wheel isn't straight ahead and doesn't make height adjustments while cornering. All D3s and D4s will lower 20mm at a sustained 160 kph.

Buy a copy of the WSM from the forum shop.

**Cyclist** · 11th July 2021, 08:53 AM

Originally Posted by Graeme

Having a read of the suspension section in the workshop manual should be rather enlightening for you, but for starters the system monitors the height sensors almost all the time, although only occasionally while the ignition is off. The levelling while moving is smoothed over approximately 5 seconds but a requested height change commences almost immediately. The system knows when the steering wheel isn't straight ahead and doesn't make height adjustments while cornering. All D3s and D4s will lower 20mm at a sustained 160 kph.

Buy a copy of the WSM from the forum shop.

Hi Graeme,
Thanks for your reply. I have the workshop manual, but I didn't find the 5s smoothing reference or anything about monitoring the height sensors. Did I just miss it or have you another reference?

**Graeme** · 11th July 2021, 11:31 AM

Whilst the WSM mentions the longer time interval for when the vehicle is moving, the 5 seconds is from experience. The height sensor monitoring is in the WSM, including the time intervals when heights are checked while the vehicle is asleep.

**DazzaTD5** · 14th July 2021, 09:47 AM

Originally Posted by Graeme

All D3s and D4s will lower 20mm at a sustained 160 kph.

.

Hrmm...
But how does the sustained 160kph alter the state of your drivers licence?

**Tombie** · 14th July 2021, 11:05 AM

Originally Posted by DazzaTD5

Hrmm...
But how does the sustained 160kph alter the state of your drivers licence?

Depends where you choose to do it

It is pretty cool though. Hunkers down and stiffens steering response too which makes it a 3t go kart!

Feels incredibly stable at those speeds.

**mowog** · 23rd July 2021, 11:04 AM

I wonder if you change the speed it will drop at with an IID Bluetooth tool?

**Tombie** · 23rd July 2021, 11:32 AM

Originally Posted by mowog

I wonder if you change the speed it will drop at with an IID Bluetooth tool?

Not that I’ve seen.

Perhaps we should email GAP

**Eric SDV6SE** · 23rd July 2021, 04:16 PM

Can you override "normal" height with X lifter at any speed?

**Tombie** · 23rd July 2021, 05:57 PM

Originally Posted by Eric SDV6SE

Can you override "normal" height with X lifter at any speed?

Yes, and in individual increments of your choice.
Also preset lifts of choice.
Compressor temp monitoring is a bonus.
There’s a few other functions like auto levelling for RTT users or those who sleep in vehicle.
And trailer hitch, which only drops the back. Controlled from a phone app if desired.

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