EAS - Harsh Ride - Calibration?

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wammers said:
OK get an air bag with no load applied to it and put 2 psi in. It will be fully extended. Now put a 1/4 ton weight on top of it and see how much air pressure you have to put in it for it to reach the same extended position. If the volume of air is increased the pressure within the bag also has to increase to extend it and carry the load. The higher the suspension is set the more air pressure is in it and the more resistant to compression it is. It is basically a infinatly variable rate spring. If you put 10 psi inside a football 10 inches in diameter and take it 200 feet under water it will be the size of an orange. You would have to inflate it to equal the water pressure at that depth to return it to it's normal size. Hypothetically, say you have 60 psi inside an air bag at standard ride height. If you then load the vehicle, the air pressure within the bag has to be increase to maintain the vehicle at that height. If no pressure was added it would sink as do coil springs. So the more weight that is added to the vehicle for a given height setting the more air pressure is required. That is why when you get out of the car and the suspension is unloaded you hear ticking, that is the valve block releasing air to return the suspension to the selected height setting.
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I agree with the above but the original question reffered to a harsh ride, the vehicles weight doesn't change once its moving apart from the fuel used so the pressure in the airbags/ride height shouldn't change.

The difference in ride heights will be controlled by the EAS, as the weight of the vehicle hasn't changed apart from used fuel, the airbags pressure to support the vehicle weight will not have changed, only the amount of air in the bag.

I'd be looking at suspension bushes and shockers.
 
zzr1200 said:
I agree with the above but the original question reffered to a harsh ride, the vehicles weight doesn't change once its moving apart from the fuel used so the pressure in the airbags/ride height shouldn't change.

The difference in ride heights will be controlled by the EAS, as the weight of the vehicle hasn't changed apart from used fuel, the airbags pressure to support the vehicle weight will not have changed, only the amount of air in the bag.

I'd be looking at suspension bushes and shockers.
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Agreed - and I will - but it's still worth calibrating first given the cost/effort involved. Also the spring rates at different ride heights make calibrating worthwhile (see my previous post - it think we submitted at the same time).

Also I just noticed you're in Hullbridge! Nice and close. If you ever want to calibrate yours, I'll soon have the cable and I'm nearby. :)
 
Valiante said:
Hi guys. I wasn't going to post again until after I received the cable from Datatek, but I see this conversation is carrying on without me so I might as well have some input as it's my thread! :)

@JohnP38 & vougese39
I agree there could be faults with other suspension components causing the harsh ride, however these take more time/money to replace. That's not to say I won't go there, but I'm not going to look at these things first when I can calibrate the ride height for free, give or take a few quid for the serial cable. I'm not "barking up the wrong tree", I'm just focusing on the cheapest/simplest stuff first then I'll work upwards. Also, vouge, a little punctuation and a few line breaks would make your posts easier to read.

@wammers
I appreciate all your advice and whilst most of what you say is accurate (taking a football to high pressure ocean depths would certainly shrink it) - we're not talking about taking the Range Rover diving and altering external atmospheric pressure here. Also your references to weight change in the vehicle requiring greater pressure to maintain height are spot on, but again that's not relevant here - we're not drastically altering the load weight on the springs.

What I don't agree with is that it takes a greater pressure to raise the vehicle, and a lower pressure to drop it. A football or a tyre have a fixed volume, therefore more air means more pressure. Air springs have a variable volume and expand when more air is added, but the external forces acting on them remain the same, therefore the pressure of the air inside remains the same, give or take a few psi during inflation/deflation. What is increased/decreased to change ride height is simply the volume of air.

However, OEM Dunlop air springs have "interesting" variable spring rates and as they increase in size/height the firmer that spring rate becomes. The later Arnott Gen II & III bags don't suffer in this way and have been developed to have the best spring rate at Standard ride height.

So to all:
I fully appreciate and read each and every reply, but until I have the cable and a chance to recalibrate, there's really no use in debating this further. So thanks, and I'll let you know the outcome.
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Simple fact is that if your standard ride height is too high you WILL get a harsher ride. To test your theory out put an air line with a pressure gauge on an air bag line. Blow it up in 5 psi units and note that as you increase the pressure in the system the height changes. As you lower the pressure the height drops.
 
zzr1200 said:
I agree with the above but the original question reffered to a harsh ride, the vehicles weight doesn't change once its moving apart from the fuel used so the pressure in the airbags/ride height shouldn't change.

The difference in ride heights will be controlled by the EAS, as the weight of the vehicle hasn't changed apart from used fuel, the airbags pressure to support the vehicle weight will not have changed, only the amount of air in the bag.

I'd be looking at suspension bushes and shockers.
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I know the vehicle weight stays the same to all intents and purposes. But the standard ride height is set too HIGH the poster has said this. Therefore the air spring is more resistant to compression than it would be if the height was correct. Therefore a harsher ride.
 
wammers said:
I know the vehicle weight stays the same to all intents and purposes. But the standard ride height is set too HIGH the poster has said this. Therefore the air spring is more resistant to compression than it would be if the height was correct. Therefore a harsher ride.
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Hope this helps
I had this and it was a combination of bushes and ride height and the ride height accounted for most of the harshness
 
wammers said:
Simple fact is that if your standard ride height is too high you WILL get a harsher ride.
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I'm not debating this - I completely agree - but it's down to spring rate, not pressure.

wammers said:
To test your theory out put an air line with a pressure gauge on an air bag line. Blow it up in 5 psi units and note that as you increase the pressure in the system the height changes. As you lower the pressure the height drops.
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I'm not about to do that! :cool: But I'd expect the pressure to equalize once inflation/deflation has completed. It's simple physics (admittedly I only studied it to A level so others will be more knowledgeable) - but don't confuse psi with cm³.
 
Valiante said:
I'm not debating this - I completely agree - but it's down to spring rate, not pressure.


I'm not about to do that! :cool: But I'd expect the pressure to equalize once inflation/deflation has completed. It's simple physics (admittedly I only studied it to A level so others will be more knowledgeable) - but don't confuse psi with cm³.
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You will need around 60 psi to inflate to standard height. Put less than that in and it will not get there. Try it.
 
still think the problem is a compant not a calibration issue.

ok here one range rover classic fitted with arnott gen 2 air bags for the p38a three inch longer bag than original also a greater volume capacity to the original items will it have a smoother or harsher ride?
 
wammers said:
You will need around 60 psi to inflate to standard height. Put less than that in and it will not get there. Try it.
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I think we're talking cross-purposes. Yes you will need pressure to inflate, to overcome the weight of the vehicle. But once inflated, is the pressure in the air springs any different at low vs. standard vs. high? No. Why? Because the car weighs the same at each height.

I'm not going to try it - I don't have the time, inclination, or equipment. :p
 
vougese39 said:
still think the problem is a compant not a calibration issue.

ok here one range rover classic fitted with arnott gen 2 air bags for the p38a three inch longer bag than original also a greater volume capacity to the original items will it have a smoother or harsher ride?
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Vouge, I think you missed my earlier post. If not, you missed my point. I'm not saying it isn't a component. BUT do you think I should leave it riding too high? It should still be correctly calibrated!
 
vougese39 said:
still think the problem is a compant not a calibration issue.

ok here one range rover classic fitted with arnott gen 2 air bags for the p38a three inch longer bag than original also a greater volume capacity to the original items will it have a smoother or harsher ride?
Click to expand...

Really don't know how you can say that. The OP says the ride height is set too high. Because there is more pressure in the system to get it at that setting it will give a slightly harsher ride. Simple as that. There may well be other things but setting it to the correct ride height is the very first step to finding the problem.
 
wammers said:
Really don't know how you can say that. The OP says the ride height is set too high. Because there is more pressure in the system to get it at that setting it will give a slightly harsher ride. Simple as that. There may well be other things but setting it to the correct ride height is the very first step to finding the problem.
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Not much point in me saying anything because I agree absolutely with Wammers. First step get the ride heights right then look at the rest. My bet would be on the shocks, they can do strange things including going stiff, some tyre brands can also produce a harsh ride.
 
You seem to be missing one particularity of these bags: the internal geometry is variable, therefore at different heights you can produce the same force with a different pressure.

Trying to put this in simple terms, the weight of the vehicle is counteracted by the force that is a result of the internal pressure x area of effect. When the spring changes its size, the area of effect changes, thus allowing for the resulting force to stay the same (the area lowers as the bag increases in height/volume). If you look at the Arnott Gen III bags, these offer a softer spring at High and a harsher spring at Highway position. This is achieved by a different geometry of the bag's internal "piston".

(As you may have noticed from my writing and location, I'm not a native english speaker, so bear with me :) )
 
mcapinha said:
You seem to be missing one particularity of these bags: the internal geometry is variable, therefore at different heights you can produce the same force with a different pressure.

Trying to put this in simple terms, the weight of the vehicle is counteracted by the force that is a result of the internal pressure x area of effect. When the spring changes its size, the area of effect changes, thus allowing for the resulting force to stay the same (the area lowers as the bag increases in height/volume). If you look at the Arnott Gen III bags, these offer a softer spring at High and a harsher spring at Highway position. This is achieved by a different geometry of the bag's internal "piston".

(As you may have noticed from my writing and location, I'm not a native english speaker, so bear with me :) )
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But the standard airbags supposedly give a softer spring rate at normal height becoming harder as they extend. At a given height, the applied air pressure remains constant and the air in the bag compresses according to the movement imposed and the design of the piston. :) Thus if the ride height is too high, air pressure and piston design will both conspire to make the ride harsh. Gen 3's are effectively falling rate if what you say is correct, an effect produced by the piston design.
 
Valiante said:
Vouge, I think you missed my earlier post. If not, you missed my point. I'm not saying it isn't a component. BUT do you think I should leave it riding too high? It should still be correctly calibrated!
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To be honest i for one don't give a **** anymore. You ask for advice get it then ignore it. Do what you want.:mad::mad::mad:
 
Valiante said:
Also I just noticed you're in Hullbridge! Nice and close. If you ever want to calibrate yours, I'll soon have the cable and I'm nearby. :)
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I already have the lead and software, and have spent a couple hours adjusting the heights on mine and still could spend more time getting it right.

But I want to fit new height sensors before I try again.
 
I've been doing a bit of research on the Arnott site where it gives the spring rates for Gen 2 & 3. For Gen 2 (much like the standard), the rates quoted are:
Motorway - 129 lb/in
Normal - 155 lb/in
High - 175 lb/in
The same page also shows the loading against pressure. The more pressure, the more loading. The effective pressure is quoted as between 10psi and 100psi i.e. virtually empty to absolutely full with max load applied to it.
In other words, as Wammers says, the higher you go, the stiffer the springs become.
 
Ok another view
If you did not have the equipment to calibrate the eas or the software what would you be looking at?
Springs, bushes,shocks, ball joints not the electronics as with most things looking at the electronics is not the be all in the case of problems the obvious is always the first port of call
The eas system will work perfectly well with a small part of ecu calibration corruption which is what you have here but with the other possible faults I would ideally start with the obvious then when happy then recalibrate
 
Derek Ward said:
I've been doing a bit of research on the Arnott site where it gives the spring rates for Gen 2 & 3. For Gen 2 (much like the standard), the rates quoted are:
Motorway - 129 lb/in
Normal - 155 lb/in
High - 175 lb/in
The same page also shows the loading against pressure. The more pressure, the more loading. The effective pressure is quoted as between 10psi and 100psi i.e. virtually empty to absolutely full with max load applied to it.
In other words, as Wammers says, the higher you go, the stiffer the springs become.
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As i said suspension set too high, too much pressure, harsh ride. It really ****es me off when people ask for advice, then when given it start arguing the toss. If they are so bloody smart why ask.
 
Warmers spitting your toys does not endear to helping others!
As I have already said I have been tuning and developing the eas system for over 13 years and in that time even with a badly calibrated system a harsh ride ie rarely contributed to the calibration issue!
Having all the computer technology and testers most of the time means going for the tester over actualy looking at the mechanical components which is a coman problem I come up against I get emails on phone calls from people seeking help because they have used tester to read ecu and think all the faults are the problem but as you are aware the fault is the effect not the cause
 
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