EnigmaWmn

I think we need for a third person to chime in, so that I'd know who's right/wrong here.

Comrade, буду болеть за вас, but let the right man be right

Slow Guy

How have you managed to survive RLOT all these years?

mcbit

Spasibo bolshoe Chushka, we've established that the diameter doesen't change so a 5" cylinder 10" long has a volume of 196 in3 and a 5" cylinder 14" long has a volume of 275 in3, doesn't really stretch the intellect too far.

ArneeA

You're assuming that the cylinder (air bag) is rigid, which is incorrect.

The folds in the bottom part of the air bag allows it to extend and retract.

Porsche didn't invent something new here, I hate to break it to you.

ArneeA

Air bag isn't rigid, therefore, it contains the same volume (to some degree, since the bag will also expand slightly at max pressure) depending on ride height. When pressure increases, the bag inflates and height increases.

Anyway, that's all folks. Believe it or not. Engineer or not so engineer.

EnigmaWmn

911SLOW

The Cayenne features a closed air suspension system with a compressor, solenoid block with integrated pressure sensor and a pressure accumulator. To raise the vehicle, air is pumped into the spring units by the electric compressor. When lowering the vehicle, the excess air is not released to the outside, but is fed back into the 5.2-litre pressure accumulator by the compressor.

Raising
The air springs on the front and rear axles are filled separately in order to raise the vehicle. Air is pumped out of the accumulator by the compressor and is routed to the air springs via pipes and valves. Change-over valve 1 and the corresponding airspring change-over valves (e.g. USV) are switched for this purpose.


Lowering
The air springs on the front and rear axles are switched separately in order to lower the vehicle. Air is pumped out of the air spring by the compressor via change-over valve 1. The air is routed through the air drier and change-over valve 2 into the accumulator. This circuit design means that any moisture is repeatedly eliminated from the system.

ltc

I believe the Panamera uses a slightly different implementation

ArneeA

Thanks, John, this is my point. It's the "basic" concept of a pneumatic suspension system - not just Porsche's. I've described the above in my prior post as well.

My point is ride height is controlled by pressure changes, which is what I've described multiple posts prior also. This is again consistent with what is in your post.

EnigmaWmn

My grandma has one of these (NSFW):

mudman2

sorry my brain is fried

Nice watch

mcbit

I'm not assuming its rigid so its not incorrect.

I don't believe anyone mentioned Porsche inventing air suspension

Wrong.

Nothing I disagree with here! The pressure sensor has little to do with the self levelling method which I described, it along with a bunch of accelerometers assist in the dynamic operation of the adaptive suspension. Other than that dosen't disagree with anything I've said to date.


Another little question for you to ponder over, how does an airspring achieve its progressive spring rate without changing volume? .......Beats me

Until now I hadn't actually researched anything I'd written as it all seemed pretty obvious, but since you wouldn't believe me I did a little research and wonder if you will now believe Firestone. Below a couple of extracts from the Firstone design guide for the particular type of spring (rolling bellows) we have, for the main part, been discussing.

The full PDF can be found here

The first pic shows that for the recommended operating range between heights of 20 and 16 inches the following statements are true:

1. At a given pressure the load rating is constant
2. In shortening the spring from 20" to 16" the volume decreases from 1351.3 in3 to 1058.06 in3

The second pic shows that:

1. The spring rate is higher at a higher pressure.
2. For any given pressure, the spring rate is highest at the lowest ride height.

This is the basic principle of most air springs fitted to cars.