private_user
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Really? Why is it dangerous? Why is it nonsense?
P38 Air suspension
- Thread starter radford19
- Start date
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Really? Why is it dangerous? Why is it nonsense?
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- 18,969
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- Buckinghamshire, UK. ('95 DT)
As you turn, accelerate, brake the weight transfers around the car. The ECU adjusts the bags to compensate. Disabling this makes the car unstable, hence the 35mph max message that comes up on the dash. As long as you're not throwing it about and driving smoothly you can probably get away with it but at one's own risk as it were.
private_user
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@Grrrrrr Thanks for providing some detail about what you think.
Purely as discussion I have to say I don't agree with you. In the P38 EAS ECU I don't believe there is any ACE (Active Cornering Enhancement) or similar per other, generally later, vehicles and as such it won't adjust as you corner, accelerate or brake. It also won't adjust up while it's moving. To this end I don't believe this modification will make it any more unstable than it already is (and, arguably, it could in fact be less risky
Purely as discussion I have to say I don't agree with you. In the P38 EAS ECU I don't believe there is any ACE (Active Cornering Enhancement) or similar per other, generally later, vehicles and as such it won't adjust as you corner, accelerate or brake. It also won't adjust up while it's moving. To this end I don't believe this modification will make it any more unstable than it already is (and, arguably, it could in fact be less risky
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- 58,170
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No they do not, no adjustment is made to ride height whilst driving other than the Motorway > Standard, Standard > Motorway. How it is driven is of no consequence. Once at a ride height it should stay at that height unless there is a leak. The only time any two bags are linked is when the car speed drops below 1 MPH and both front valves open to equalise pressure across the axle. That is why it is so important to have bit readings within two beats side to side at the front. To avoid the apparent dance some complain of as the car comes to rest at lights Etc.
radford19
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I have to say that it did worry me, I am very new to this although having had other vehicles with air/hydraulic/hydropneumatic suspension I do understand it. However, they have all had engine powered pumps/compressors and largely mechanical control valving etc. Having done much research and read the advice given here I am now more understanding.
I think maybe some may have misunderstood my comments. The suspension appears to behave exactly as it should, it is the dashboard lights that seem to tell me lies. Even the LR dealer found it odd that the lights were telling us one thing but that all appeared to be correct.
After a day or two not being used the 'Access', level light would be on and the standard level light would flash indicating it was trying to raise itself. My view was that the compressor was failing to provide enough pressure for the system. Poking around and the compressor kicking in seems to have done the trick. It does not run all the time, just long enough to do what it has to do. It has always driven perfectly fine, went over level crossings as smooth as silk where other cars that I have shake you to bits.
All that appears to have 'gone right' is the lights now work as they should. The previous owner was quite elderly and had it ten years and I just feel that it has either been standing or only very little use recently as it did have a few little issues that seem to have gone with use.
Thank you for your help in this, it re-assures me and assists in my learning curve. I touch wood that it is OK now. If not, at least I have a better understanding and where to go.
shadyadie
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I used to have a P38 and got a lead and disc so I could look at and repair my suspension, they don't cost a fortune, might even still have mine somewhere.
my issue turned out to be one of the sensors was broken, but until I took it off you couldn't tell as it fitted together perfectly when parked up so every-time we looked it was fine , but hit a certain kind of bump in the road and it would move and put the car in limp home suspension mode. Spent hours checking a compressor that was fine and looking for non existent leaks, before I found it .
my issue turned out to be one of the sensors was broken, but until I took it off you couldn't tell as it fitted together perfectly when parked up so every-time we looked it was fine , but hit a certain kind of bump in the road and it would move and put the car in limp home suspension mode. Spent hours checking a compressor that was fine and looking for non existent leaks, before I found it .
Datatek
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If it drops to access in a day, I would bet there is a leak. Neither of mine drop to access in more than a week.
If the airsprings have not been replaced, they WILL be leaking. the design life is 7/8 years, 80K miles.
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- Buckinghamshire, UK. ('95 DT)
Depends on the sensors too. If one sensor is a bit out of expected range (Wammers bitcount comment) and you park on uneven ground where that sensor goes out of expected range it will lower itself overnight trying to level. Pulling the delay timer stops this so if it stays up with the delay timer out then the bags are probably OK. Mine does this when I park in a certain spot. Park elsewhere and no issues.
- Posts
- 18,969
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- Buckinghamshire, UK. ('95 DT)
@Grrrrrr Thanks for providing some detail about what you think.
Purely as discussion I have to say I don't agree with you. In the P38 EAS ECU I don't believe there is any ACE (Active Cornering Enhancement) or similar per other, generally later, vehicles and as such it won't adjust as you corner, accelerate or brake. It also won't adjust up while it's moving. To this end I don't believe this modification will make it any more unstable than it already is (and, arguably, it could in fact be less risky
The picture is a Nanocom trace of my front left bag on a journey. The front right one pretty much tracks it. The blue line is percentage height of target height (i.e. 100% = bang on target); the green line is speed normalised to 1 (max speed = 100% in effect, min spped = 0%) and the orange line is the FL valve filling = 100% or deflating = -100%. You can see when I stamp on the brakes it triggers a fill to balance the front. Similarly, if I really open the taps it vents a bit. You have to be driving fairly hard to trigger it but it does kick in in the right conditions.
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You have a leak or a badly seating corner valve.
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- 18,969
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- Buckinghamshire, UK. ('95 DT)
It is fine. Valve block is only a few years old. Only when you brake very sharply or drive very aggressively. Never tried a trace with the inhibit on. I have one corner sensor that is a little close to the limit of being out of range of the others but it is so rusted solid I am damned if I am touching it!
Datatek
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The sensors are not precision devices, there can be quite a difference in readings when the calibration is correct.It is fine. Valve block is only a few years old. Only when you brake very sharply or drive very aggressively. Never tried a trace with the inhibit on. I have one corner sensor that is a little close to the limit of being out of range of the others but it is so rusted solid I am damned if I am touching it!
private_user
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That's an interesting plot @Grrrrrr but I don't see brake data? I'm not familiar with the Nanocom but is it able to plot (foot)brake, exhaust, inlet, sensor in x 4, and individual corner valves simultaneously?
This was something I was going to do with my development P38 this weekend (my own software) in order to get to the bottom of the original EAS operation, however there'll be no need to publish this if it's already been done - or can be done with existing kit.
FYI the Land Rover SID for the EAS doesn't discuss any ACE (OMG, all these acronyms! or any form of active fore/aft leveling on the move. In my view this is a relatively unsophisticated system by today's standards and the mechanical section wouldn't be capable of handling the sort of work that a more responsive ECU could feed it (with suitable inputs).
I have toyed with the idea of adding an accelerometer/gyro to my development vehicle but for the above reason am not sure it would add any value. It could assist with self-healing (in the event of a faulty wheel sensor for example), something the existing ECU doesn't do as far as I know, but that would seem about it.
This was something I was going to do with my development P38 this weekend (my own software) in order to get to the bottom of the original EAS operation, however there'll be no need to publish this if it's already been done - or can be done with existing kit.
FYI the Land Rover SID for the EAS doesn't discuss any ACE (OMG, all these acronyms!
or any form of active fore/aft leveling on the move. In my view this is a relatively unsophisticated system by today's standards and the mechanical section wouldn't be capable of handling the sort of work that a more responsive ECU could feed it (with suitable inputs).I have toyed with the idea of adding an accelerometer/gyro to my development vehicle but for the above reason am not sure it would add any value. It could assist with self-healing (in the event of a faulty wheel sensor for example), something the existing ECU doesn't do as far as I know, but that would seem about it.
- Posts
- 18,969
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- Buckinghamshire, UK. ('95 DT)
That's an interesting plot @Grrrrrr but I don't see brake data? I'm not familiar with the Nanocom but is it able to plot (foot)brake, exhaust, inlet, sensor in x 4, and individual corner valves simultaneously?
This was something I was going to do with my development P38 this weekend (my own software) in order to get to the bottom of the original EAS operation, however there'll be no need to publish this if it's already been done - or can be done with existing kit.
FYI the Land Rover SID for the EAS doesn't discuss any ACE (OMG, all these acronyms!
I have toyed with the idea of adding an accelerometer/gyro to my development vehicle but for the above reason am not sure it would add any value. It could assist with self-healing (in the event of a faulty wheel sensor for example), something the existing ECU doesn't do as far as I know, but that would seem about it.
It doesn't have ACE, Wammers is quite correct. But, if you throw the car around enough to push the sensor outside its expected range the EAS attempts to compensate. So heavy braking or similar will trigger it.
The Nanocom is somewhat simple. I think it uses an Aduino or similar inside. The sample rate is quite slow at about 1 second intervals on the logging. What the EAS itself works with I don't know. @Datatek and @pwood999 know way more about this sort of thing.
The Nanocom live trace records the following:
Front Left TARGET HEIGHTS 0-255
Front Right TARGET HEIGHTS 0-255
Rear Left TARGET HEIGHTS 0-255
Rear Right TARGET HEIGHTS 0-255
ACTUAL HEIGHTS 0-255
ACTUAL HEIGHTS 0-255
ACTUAL HEIGHTS 0-255
ACTUAL HEIGHTS 0-255
Ride state LOW/STANDARD/HIGH
Front Left actual height (again!) 0-255
Front Right actual height (again!) 0-255
Rear Left actual height (again!) 0-255
Rear Right actual height (again!) 0-255
Front Left VALVES STATUS CLOSE/OPEN
Front Right VALVES STATUS CLOSE/OPEN
Rear Left VALVES STATUS CLOSE/OPEN
Rear Right VALVES STATUS CLOSE/OPEN
Compressor ON/OFF
Exhaust valve CLOSE/OPEN
Inlet valve CLOSE/OPEN
Inhibit switch ON/OFF
Park/handbrake ON/OFF
Footbrake switch ON/OFF
Door/disable CLOSE/OPEN
Thermal switch NORMAL/???!
Pressure switch CLOSE/OPEN
Lower switch CLOSE/OPEN
Raise switch CLOSE/OPEN
Battery (V) 0.00-255.00?
Road speed(mph) 0-255?
Road speed(Kmh) 0-255?
Engine speed 0-255?
Ride state (again) LOW/STANDARD/HIGH
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Each height setting has an upper and lower bit count limit, under normal driving conditions with the bit count set correctly and height set correctly, those upper and lower limits should never be exceeded..
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- Buckinghamshire, UK. ('95 DT)
You'd be amazed how fast it an go round a roundabout for such a heavy car with live axles!
private_user
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Thanks guys, that's useful detail.
1sps is probably sufficient for most purposes, and if it can log all of that simultaneously then I expect someone will have done what I was going to do, so there's perhaps little point in me doing it.
I was mumbling to myself over reducing the sample rate down to 10sps from the 50 or so I was going to use mind you, so perhaps I'll have a mess around anyway just for the hell of it; I suppose it could be useful if I wanted a better look at absolute min/max sensor levels. It may also be that the sensors have sufficient resolution to determine individual wheel balance if one sampled them at a reasonable rate...
I need to remind myself that this is just a car mind you, and there are other things to do this weekend.
1sps is probably sufficient for most purposes, and if it can log all of that simultaneously then I expect someone will have done what I was going to do, so there's perhaps little point in me doing it.
I was mumbling to myself over reducing the sample rate down to 10sps from the 50 or so I was going to use mind you, so perhaps I'll have a mess around anyway just for the hell of it; I suppose it could be useful if I wanted a better look at absolute min/max sensor levels. It may also be that the sensors have sufficient resolution to determine individual wheel balance if one sampled them at a reasonable rate...
I need to remind myself that this is just a car mind you, and there are other things to do this weekend.
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- Preston Lancs.
Yes and that is why with the extra pressure being exerted on one front wheel air can be squeezed past the corner valve. That is the reason the pressure is equalised when the car comes to a halt.
