When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I hate to break it to you but that's too cold. You need to move.
I agree! Last night with the wind chill it was -45C (air temp was -32C). So, of my climate, I think Porsche could do a bit more work on the seal design.
Same with the heating system. My heater produces very good heat with the engine at 90C, but the problem is, on my 20 minute commute home, after the car has been sitting for 8 hours at work, it is barely at 70C by the time I arrive home, so I get luke warm air on the drive. Our 2018 Honda mini van's engine heats up quicker. It's only half bad though; my house has a 2 car heated garage which I keep at 13C (55F) so the drive to work is toasty.
Is this seals leaking or simply air molecules getting closer to each other as temperature drops? As above poster says, it might be just basic physics and it becomes more pronounced in very cold temperatures.
Is this seals leaking or simply air molecules getting closer to each other as temperature drops? As above poster says, it might be just basic physics and it becomes more pronounced in very cold temperatures.
I think it may be a little of both. 1) Rubber seals don’t work well in extreme cold. Remember Space Shuttle Challenger disaster? That was attributed to the rubber O-rings leaking due to cold temperatures. 2) Gas laws also play a large part. Here’s an excerpt from an article:
Temperature is a major parameter for air ride. Air density and pressure can vary widely due to temperature. This is called Charles’s Law.
If a driver with an air ride suspension drives their vehicle home from work with an outside temperature of 32ºF, and the brakes also heat the air in the bladders, the air’s volume in the bladder expands. If the driver parks the car overnight and wakes up to a 10ºF morning, the air inside the bladder will have contracted and there will be less volume and pressure to support the vehicle. When he walks outside, the car will be riding lower.
Some systems will wake up to retrim the vehicle at predetermined intervals with the air in the reservoir. But, air temperature also impacts the reservoir. As the temperature decreases, the amount of air [pressure] in the reservoir also decreases. This means there is less air [pressure] to trim the vehicle.
I think it may be a little of both. 1) Rubber seals don’t work well in extreme cold. Remember Space Shuttle Challenger disaster? That was attributed to the rubber O-rings leaking due to cold temperatures. 2) Gas laws also play a large part. Here’s an excerpt from an article:
Temperature is a major parameter for air ride. Air density and pressure can vary widely due to temperature. This is called Charles’s Law.
If a driver with an air ride suspension drives their vehicle home from work with an outside temperature of 32ºF, and the brakes also heat the air in the bladders, the air’s volume in the bladder expands. If the driver parks the car overnight and wakes up to a 10ºF morning, the air inside the bladder will have contracted and there will be less volume and pressure to support the vehicle. When he walks outside, the car will be riding lower.
Some systems will wake up to retrim the vehicle at predetermined intervals with the air in the reservoir. But, air temperature also impacts the reservoir. As the temperature decreases, the amount of air [pressure] in the reservoir also decreases. This means there is less air [pressure] to trim the vehicle.
^^^ That’s a good point, kayjh. Those theories don’t account for that. Hmm . . .
The service guy said something about the front end being set up differently than the rear end but I call bs on that. I suspect there is a valve on the branch going to the rear of the car that is leaking. If you have a parts diagram it would be interesting to know. In any event, it only drops in very cold weather. I’ve seen units on the dealers lot do the same.
The service guy said something about the front end being set up differently than the rear end but I call bs on that. I suspect there is a valve on the branch going to the rear of the car that is leaking. If you have a parts diagram it would be interesting to know. In any event, it only drops in very cold weather. I’ve seen units on the dealers lot do the same.
Your service guy might be onto something. Check out the difference in gas volume between the front and rear air springs (highlighted in red). The front has an integral damper, whereas the rear spring has an external damper.
Note the purple O-ring on each of the solenoids. This is one of the locations where an air leak might occur.
Thinking out loud here, but all else being equal, the larger volume will be more affected by temperature drops. Do you think that might account for the difference?
Your service guy might be onto something. Check out the difference in gas volume between the front and rear air springs (highlighted in red). The front has an integral damper, whereas the rear spring has an external damper.
Note the purple O-ring on each of the solenoids. This is one of the locations where an air leak might occur.
Thinking out loud here, but all else being equal, the larger volume will be more affected by temperature drops. Do you think that might account for the difference?
I think it is possible but both rear sides of the car drop at the exact same rate which is what has me wondering if there is a central valve that is a "gate keeper" of air going to the rear axle? Otherwise, there might be a difference in heights to the right and left side. On the other hand, does the system allow for higher/lower pressures on each wheel to combat roll in turns? In that case, a central valve wouldn't make sense and your speculation might - assuming the double valve seals in each air spring lose air at the same rate (at least when the air springs are new, like mine are.)
I couldn’t find a pneumatic diagram for the 9YO. Here’s the best diagram I can find. The system appears to have two valve blocks and two controllers.
It shows the air compressor with integrated valve block and controller located in the rear. The accumulator is located in the middle, and additional controller and valve block located up front; presumably to control the front air springs.
I found some more good info about the air suspension in a technical bulletin addressing drooping struts. It included a very good diagram of the system.
As it turns out, the system only has one valve block but has two accumulators. The nominal pressures are higher than I had thought.
Front Struts: 90 psi
Rear Struts: 73 psi
Accumulators: 250 psi (!)
@kayjh To your question in previous post: Does the system allow for higher/lower pressures on each wheel to combat roll in turns? Yes, I believe it does. Here’s what Porsche says about the air suspension:
“If strong pitching or rolling motion occurs, the system immediately switches to a higher spring rate for additional stabilization.”
In the diagram below, check out Body and Wheel Acceleration Sensors (#’s 1,4,9, and 15). These would tell the control unit (10) to stiffen the appropriate springs — front during braking and rear during acceleration. Likewise, for rolling motion during turns.
02-04-2022, 01:06 PM
