The Porsche Story

[steve-on-mark]

Originally Posted by FlyingScot

Agreed they can be irritating. But you should be able to set the tire pressure monitors to whatever pressure you'd like so that they're only warning you when you need a bit more air. This is a good thing, especially since modern tires do not show out ward signs of low pressure until they are super low. Full disclosure--mine have been flashing at me for a week, I really need to add some air. Damn things

Tire pressure monitoring systems were mandated by the federal government...wasn't the manufacturer's idea to add them. The properties of air change with temperature...1 pound of air pressure for every 10 degree temperature change. If you set your tires pressures on a 60 degree day, when the temps drop to 20, the tire pressure goes down 4 pounds, and sometimes it's enough to turn the light on. This is why some places advertise nitrogen filling of tires...it has different properties and pressure stays the same. I advise people to set their tire pressure a little high in the colder months...the pressure will still drop, but not low enough to make the tpms light come on. Some manufacturers also disable the ability to turn off traction control systems ( Honda for one ) whenever the tpms light is on. That's a pain when you need to get some wheel speed in the snow...when I keep a 12volt inflator in my trunk...just in case I need to inflate..while on my way to the lake!

[jeffk]

Here's a consideration. The tailgate is probably tied into the cars locking system. Most cars starting out locked, when unlocked with the FOB (it will NOT happen if you use the unlock buttons in the car), will, if no one opens a door in a period of time, relock themselves.

If they open the tailgate with the FOB, and do not open any other door, the locking system might decide that, in a minute, it should relock the car, INCLUDING closing the tailgate.

The issue about systems like this is that the programmer of the cars electronics must anticipate EVERY possible situation and build a proper response. In sophisticated programming environments, engineers grab various, predesigned software modules without fully understanding exactly HOW those modules work, in detail. An example in this case. Suppose a general locking software module for a CAR is extended by the engineer. He ADDS on the ability to deal with the tailgate, opening and closing it. But buried in the original module is the timeout relock feature. In the original CAR application, all that happens is the doors relock. No big deal. In the SUV, it ALSO closes the tailgate, a physical, possibly dangerous action. The software designer did not add this functionality when he added the tailgate capability. It was buried in the original code which he did not build and did not think about. If the previous designer of the CAR code was good, he documented this but minor features might not be documented. Then the new programmer needs to read the existing documentation. Maybe he does or doesn't and again, a minor function like this could be overlooked.

Confirmation tests for this would be:

1. When the problem does happen, is the SUV always locked when they open the tailgate with the FOB? A likely scenario is coming back from shopping and putting packages away.

2. With the car locked, unlock it with the FOB, open a door, and open the tailgate with the FOB. Does the automatic close ever happen?

The funny thing is, the software is trying to be "helpful" by a one touch, close all the doors and lock the car. It becomes a problem when the auto relock is triggered. Unintended consequences because the passenger doors can't be automatically closed. The tailgate is a similar, but not EXACTLY the same kind of door. The locking button on the FOB is a similar but not EXACTLY the same locking mechanism as the buttons in the car because only the FOB triggers the auto relock. The software needs to recognize and manage all these subtleties and the programmer needs to anticipate them all.

[Hillcountry]

Originally Posted by steve-on-mark

Tire pressure monitoring systems were mandated by the federal government...wasn't the manufacturer's idea to add them. The properties of air change with temperature...1 pound of air pressure for every 10 degree temperature change. If you set your tires pressures on a 60 degree day, when the temps drop to 20, the tire pressure goes down 4 pounds, and sometimes it's enough to turn the light on. This is why some places advertise nitrogen filling of tires...it has different properties and pressure stays the same. I advise people to set their tire pressure a little high in the colder months...the pressure will still drop, but not low enough to make the tpms light come on. Some manufacturers also disable the ability to turn off traction control systems ( Honda for one ) whenever the tpms light is on. That's a pain when you need to get some wheel speed in the snow...when I keep a 12volt inflator in my trunk...just in case I need to inflate..while on my way to the lake!

That’s what I did when my pressure light came on recently. I set my pressure higher than normal (only one tire was the culprit). I’m due for new tires in December and will check out the prices for the nitrogen fill. Thanks for the info!

[TheTimeTraveler]

Originally Posted by Hillcountry

That’s what I did when my pressure light came on recently. I set my pressure higher than normal (only one tire was the culprit). I’m due for new tires in December and will check out the prices for the nitrogen fill. Thanks for the info!

If you buy your tires from Costco not only will you save money, but all they use is nitrogen to fill the tires!

Unfortunately their only store in New Hampshire is in Nashua, but the savings are well worth it. Their warranty is excellent also (road hazards included).

[fatlazyless]

Too much automobile technology here:

You are better off driving a manual transmission with a clutch pedal, and using a $15 floor style bicycle pump w/ air gauge to maintain the tire air pressure. It takes about 40 pumps to raise a car tire up from 25 to 30-psi, and pumping it manually gives you a much better appreciation on tire traction than an inflation system.

Tapping the inflated tire tread hard with a hammer is also a good test for tire inflation without using a gauge and is easier to do in the rain or in the dark.

And, a manual transmission gives it a better grip on the snow.

[Descant]

@JeffK
Great explanation of the development process.
I always recall the axiom the "No human can build a machine so smart that some other human will be able to operate it improperly.