My cranky car

amybang · 10-31-2008, 09:18 AM

I learned last night that when the car wants something, it can be like an annoying little sibling.

First, the recent cold snap we've had has changed the pressure in my tires enough that the low pressure warning has been going off (before the cold weather, I noticed it was sensitive to just a couple PSI). I've had a few really packed days, so I haven't had a chance to top them off yet (plan to do that tomorrow). So the tire light flashed at me constantly.

Then last night, when I was rushing to get somewhere, the gas tank level dropped below that threshold, so then the tire warning was alternating with the refuel warning.

Finally, it was getting dark and the temperature dropped and then the snowflake warning appeared.

I had several stops to make last night before I got to the good gas stations ($2.71 for 93 last night!) and so I had the warning trio several times. And, I did get it down to an estimation of 0 miles left in the tank. When I filled it, I got 13.1 gal into it. Last night was really out of the ordinary - I was running late all over the place and had to park in downtown Boston. I didn't even pass expensive gas stations to put in a gallon to tide me over.

amy!

Juan's1 · 10-31-2008, 09:25 AM

Doesn't really bother me as I view it in a positive light - it shows that the warning systems are working as intended

I've experienced all three warning messages btw, but not all at once.

135iUSN · 10-31-2008, 10:39 AM

it even starts to celebrate Christmas early, just like the stores to LOL

AchtungF80 · 10-31-2008, 10:47 AM

LOL at warning trio gongs.

m_thompson · 10-31-2008, 11:22 AM

Quote:

Originally Posted by amybang

First, the recent cold snap we've had has changed the pressure in my tires enough that the low pressure warning has been going off (before the cold weather, I noticed it was sensitive to just a couple PSI). I've had a few really packed days, so I haven't had a chance to top them off yet (plan to do that tomorrow). So the tire light flashed at me constantly.
amy!

My wife's 328Xi did the same thing yesterday. The tire pressure was down to 28 PSI when cold.

jeremyc74 · 10-31-2008, 12:14 PM

I've had two warnings going at one time, but never 3. Right now I've got low washer fluid.

I'm heading up to the mountains this weekend. I think I'm going to run the car low on fuel, let some air out of the tires, and stay out late enough for the temperature to drop to see if I can get four at one time and claim the gong record!

EarlArlington · 10-31-2008, 12:18 PM

Quote:

Originally Posted by jeremyc74

I've had two warnings going at one time, but never 3. Right now I've got low washer fluid.

I'm heading up to the mountains this weekend. I think I'm going to run the car low on fuel, let some air out of the tires, and stay out late enough for the temperature to drop to see if I can get four at one time and claim the gong record!

lol

Brady1984 · 10-31-2008, 12:21 PM

If you have the tires filled with nitrogen doesn't that cut down on the pressure changes?

lacrosse · 11-01-2008, 04:43 AM

Quote:

Originally Posted by Brady1984

If you have the tires filled with nitrogen doesn't that cut down on the pressure changes?

Sadly that option is only available to Nick Heidfeld and Robert Kubica. Just imagine all the warning gongs they must get!

Justabanana · 11-01-2008, 05:39 AM

Exactly how is a car that's warning systems are operating like they should - cranky?

Where I live, low tire pressure is the n

1 technical problem in a car causing (or constituting in) fatal accidents... so I'd say it's pretty important to keep the pressures at normal levels. If you run out of fuel, it's a huge annoyance and may break components of the injection system. Maybe it's better the car warns you before you have to tow it to the shop? And anyone who lives in cold climates knows how fast the temperature may drop and change driving conditions. No dtc can exeed the laws of physics. A little warning gong is about the smallest annoyance compared to wrecking the car and injuring yourself...

Not to be too much sober-sides here - a laser show like that can be quite hilarious. Especially when you got some friends on board. "I think I'll just walk home, your shiny new car seems to be breaking apart" xD

Artmasterx · 11-01-2008, 08:04 AM

Quote:

Originally Posted by Brady1984

If you have the tires filled with nitrogen doesn't that cut down on the pressure changes?

Not significantly enough to make it worthwhile. Air is 79% nitrogen anyway.

The heat capacity of both O2 and N2 are essentially the same, O2 is actually a bit higher. This means that for a given amount of heat input, the temperature will increase less (in reality they are too close to matter).

By putting in pure N2, you are actually giving a larger concentration gradient for diffusion out of the tire than with pure air. Nitrogen is a smaller and lighter molecule, which is all else is equal means its diffusivity will be less than O2 in air (this may not be true for diffusion through rubber). Diffusivity is a measure of how easily a molecule moves through a medium (air, rubber, metal, whatever).

There are more complex issues at hand too (because of the increased pressure), but I can't imagine any that would give nitrogen a significant benefit over just air in a normal car.

amybang · 11-03-2008, 08:54 AM

Quote:

Originally Posted by Justabanana

Exactly how is a car that's warning systems are operating like they should - cranky?

Well, my post was sort of tongue in cheek. But.

It's "cranky" because I noticed the warning the first time it happened, was aware of the problem, and had a plan for fixing it. At least it doesn't keep chiming, but actually, having the two symbols (gas and tire) flash back and forth on the dash is, IMHO, a worse safety hazard -- it's in my peripheral vision and so I keep getting distracted each time it changes. There's no way to acknowledge the them and make them go away for a while.

And, unless one tire has a visible problem having one or two (or 4 of them) be down 1-2 PSI is not a safety hazard IMHO. Which is all that warning is telling me.

Quote:

Originally Posted by Justabanana

Not to be too much sober-sides here - a laser show like that can be quite hilarious. Especially when you got some friends on board. "I think I'll just walk home, your shiny new car seems to be breaking apart" xD

It's a sound and light show!

amy!

amybang · 11-03-2008, 08:55 AM

Quote:

Originally Posted by jeremyc74

I've had two warnings going at one time, but never 3. Right now I've got low washer fluid.

I'm heading up to the mountains this weekend. I think I'm going to run the car low on fuel, let some air out of the tires, and stay out late enough for the temperature to drop to see if I can get four at one time and claim the gong record!

Uh-oh! No way! You do that, and I'll have to put my laptop on the passenger seat to get the seatbelt warning to go off!

amy!

EspressoBoy · 11-03-2008, 09:17 AM

Quote:

Originally Posted by Brady1984

If you have the tires filled with nitrogen doesn't that cut down on the pressure changes?

It should, so I was told... a few local shops here offer it for $10 per tire... will remove air, and put in nitrogen, then replace the cap with a green one. I didn't ask them about the cap, plastic or metal... LOL

EspressoBoy

JME · 11-03-2008, 09:28 AM

Quote:

Originally Posted by Artmasterx

Not significantly enough to make it worthwhile. Air is 79% nitrogen anyway.

The heat capacity of both O2 and N2 are essentially the same, O2 is actually a bit higher. This means that for a given amount of heat input, the temperature will increase less (in reality they are too close to matter).

By putting in pure N2, you are actually giving a larger concentration gradient for diffusion out of the tire than with pure air. Nitrogen is a smaller and lighter molecule, which is all else is equal means its diffusivity will be less than O2 in air (this may not be true for diffusion through rubber). Diffusivity is a measure of how easily a molecule moves through a medium (air, rubber, metal, whatever).

There are more complex issues at hand too (because of the increased pressure), but I can't imagine any that would give nitrogen a significant benefit over just air in a normal car.

Apparently it is the water content in the air that creates all the funkiness with pressure variations. That's just what I've heard, and it kinda makes sense.

m7ammed · 11-03-2008, 09:42 AM

Perillie tire shop over here in Saudi offers N2 for tires , according to them it would be constant over different temperatures, and something about it not leaking from the tire overtime like normal air does, I guess they are taling about molecules penetrating rubber .

jeremyc74 · 11-03-2008, 08:57 PM

Quote:

Originally Posted by amybang

Uh-oh! No way! You do that, and I'll have to put my laptop on the passenger seat to get the seatbelt warning to go off!

amy!

I could have beaten that this weekend. On top of everything else I needed a quart of oil. :biggrin:

jeremyc74 · 11-03-2008, 09:01 PM

Quote:

Originally Posted by EspressoBoy

It should, so I was told... a few local shops here offer it for $10 per tire... will remove air, and put in nitrogen, then replace the cap with a green one. I didn't ask them about the cap, plastic or metal... LOL

EspressoBoy

The nitrogen fills are marketing BS when it comes to street cars. The difference in pressure changes are going to be measured in tenths (maybe even hundreths) of a PSI.

There are a ton of articles about this floating around the internet, with the exact calculations based on various humidity in the compressed air.

A shop using a decent air compressor system is going to have a dryer on the line to get rid of moisture anyway. The nitrogen is just another way for them to make money off people who don't know any better. Your $10 basically buys you a green cap that means nothing.

10-31-2008, 09:18 AM	#1
amybang ... and Orca too! 29 Rep 845 Posts Drives: 128i Convertible (AW/CR) Join Date: Apr 2008 Location: Belmont, MA iTrader: (0)	My cranky car I learned last night that when the car wants something, it can be like an annoying little sibling. First, the recent cold snap we've had has changed the pressure in my tires enough that the low pressure warning has been going off (before the cold weather, I noticed it was sensitive to just a couple PSI). I've had a few really packed days, so I haven't had a chance to top them off yet (plan to do that tomorrow). So the tire light flashed at me constantly. Then last night, when I was rushing to get somewhere, the gas tank level dropped below that threshold, so then the tire warning was alternating with the refuel warning. Finally, it was getting dark and the temperature dropped and then the snowflake warning appeared. I had several stops to make last night before I got to the good gas stations ($2.71 for 93 last night!) and so I had the warning trio several times. And, I did get it down to an estimation of 0 miles left in the tank. When I filled it, I got 13.1 gal into it. Last night was really out of the ordinary - I was running late all over the place and had to park in downtown Boston. I didn't even pass expensive gas stations to put in a gallon to tide me over. amy!
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10-31-2008, 09:25 AM	#2
Juan's1 Senior Member 0 Rep 8 Posts Drives: 2008 SGM E82 Join Date: Aug 2008 Location: NW Indiana iTrader: (0)	Doesn't really bother me as I view it in a positive light - it shows that the warning systems are working as intended I've experienced all three warning messages btw, but not all at once.
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10-31-2008, 10:39 AM	#3
135iUSN 19 X5 1998 M Roadster 64 Rep 1,503 Posts Drives: 135i Alpine White / Terra Join Date: Sep 2008 Location: SW Florida iTrader: (1) Garage List 1998 BMW M Roadster [0.00] 2009 135i [0.00]	it even starts to celebrate Christmas early, just like the stores to LOL __________________ '09 135i Dinan In BMW heaven 09.28.2022 - Stage 2/Alpine White w/Terracotta /High Gloss Black Trim/ZCW/ZPP/ZSP w/313's /CA/PDC/Steptronic/
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10-31-2008, 10:47 AM	#4
AchtungF80 Brigadier General 276 Rep 3,465 Posts Drives: 997.2 GT3, '17 G30 Join Date: Apr 2006 Location: NJ iTrader: (2) Garage List 2008 135is [9.50] 2010 Cooper S [10.00] 1991 318is [10.00]	LOL at warning trio gongs. __________________ ig: 0verrev
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10-31-2008, 12:14 PM	#6
jeremyc74 Banned 76 Rep 5,970 Posts Drives: '08 135i Montego/Terra Join Date: Feb 2008 Location: Evansville, IN iTrader: (0)	I've had two warnings going at one time, but never 3. Right now I've got low washer fluid. I'm heading up to the mountains this weekend. I think I'm going to run the car low on fuel, let some air out of the tires, and stay out late enough for the temperature to drop to see if I can get four at one time and claim the gong record!
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10-31-2008, 12:21 PM	#8
Brady1984 Lieutenant 186 Rep 413 Posts Drives: 2015 M3 Join Date: Sep 2008 Location: Oklahoma iTrader: (0)	If you have the tires filled with nitrogen doesn't that cut down on the pressure changes? __________________ "Most things I worry about never happen anyway" -Tom Petty
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11-01-2008, 05:39 AM	#10
Justabanana Enlisted Member 0 Rep 30 Posts Drives: 123d ///M-Sport Join Date: Jun 2008 Location: Periferia iTrader: (0)	Exactly how is a car that's warning systems are operating like they should - cranky? Where I live, low tire pressure is the n 1 technical problem in a car causing (or constituting in) fatal accidents... so I'd say it's pretty important to keep the pressures at normal levels. If you run out of fuel, it's a huge annoyance and may break components of the injection system. Maybe it's better the car warns you before you have to tow it to the shop? And anyone who lives in cold climates knows how fast the temperature may drop and change driving conditions. No dtc can exeed the laws of physics. A little warning gong is about the smallest annoyance compared to wrecking the car and injuring yourself... Not to be too much sober-sides here - a laser show like that can be quite hilarious. Especially when you got some friends on board. "I think I'll just walk home, your shiny new car seems to be breaking apart" xD __________________ 123d ///M-Sport Coupé (& e21 318) Alpine White: Because originality is overrated.
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11-03-2008, 09:42 AM	#16
m7ammed Captain 210 Rep 959 Posts Drives: 2019 M2 Competition Join Date: Nov 2008 Location: Saudi Arabia iTrader: (0)	Perillie tire shop over here in Saudi offers N2 for tires , according to them it would be constant over different temperatures, and something about it not leaking from the tire overtime like normal air does, I guess they are taling about molecules penetrating rubber .
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