Posts: 13
Joined: Mon Jan 08, 2018 10:25 am

Re: 33 Years of BMW...

Fri May 25, 2018 1:41 pm

Anyone else have nitrogen in their tires? Mine does and it started warning us the tires were low. I am a real big DIY type so I invested in a tank of my own, initial investment with the nitrogen specific regulator and tank deposit was about $240. Now I never have to go to the dealership to top off and that time saved makes it more than worth it in my book.


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Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: 33 Years of BMW...

Fri May 25, 2018 2:28 pm

Jims5543 wrote:Anyone else have nitrogen in their tires?
Yeah, those of us who don't want to waste money on 100% nitrogen have 78% nitrogen in our tires (i.e., air). Pure nitrogen has only one advantage over air: the nitrogen molecule is slightly larger than the oxygen molecule so it diffuses through the tire's rubber and porous alloy wheels a little bit more slowly. Because air is only 21% oxygen, this affect is usually unmeasurable.

The pressure of all gases changes with temperature to exactly the same degree, so inflation pressure in a tire filled with dry nitrogen changes by the same amount when the tire's temperature changes as does a tire filled with dry air. However, most, but not all, compressed air, can contain water vapor because it wasn't dried when it was compressed. Water vapor can condense when a tire cools which would cause the inflation pressure to drop more than a tire filled with any dry gas, including nitrogen or air, or any liquid water in a tire could vaporize when a tire warms which would cause its inflation pressure to increase more than a tire filled with any dry gas.

Nitrogen might make sense in tires used in competitive racing where inflation pressures might need to be carefully controlled and matched. But in a street vehicle, the small advantages of dry nitrogen don't justify its cost.

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

Posts: 110
Joined: Wed Apr 16, 2014 3:04 pm

Re: 33 Years of BMW...

Sat May 26, 2018 10:46 am

The only advantage I can see to 100% (or close to it) Nitrogen gas is it is not reactive like oxygen is. TPMS sensors probably prefer it for this reason, although they should be sealed to prevent corrosion.

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Joined: Sat Mar 28, 2015 8:02 pm

Re: 33 Years of BMW...

Thu Jun 28, 2018 11:55 am

Yes, I have been using N2 for years in my tires. I probably wouldn't though if I couldn't get it for free at work. We have a N2 generator.

Posts: 13
Joined: Mon Jan 08, 2018 10:25 am

Re: 33 Years of BMW...

Wed Oct 24, 2018 7:20 pm

We are now at 42K miles and have not owned it a year yet. IIRC we had 26K miles on it at purchase so we are close to putting 20K miles on it in a year. We have not had a single issue with it.

We recently drove it 130 miles one way for a long weekend. We left home with 1/2 tank of gas and 100% battery 90% of our drive would be highway. I activated the REX at 75% battery, and drove to empty, then stopped to fill at a rest area.

Once we pulled out of the rest area we were at 68% battery and I forgot to turn on the REX, I noticed at 48%, I turned it on and finished the drive in to our destination using the 2.3 gallons of gas. We used about 3 gallons of gas and 60% battery traveling 135 miles driving at 75 MPH the entire way.

Our destination hotel had a charger on site so we were able to charge it back up.

Trip home was a different route, we left hotel with no gas and 100% battery. We stopped 10 miles in and topped off gas tank, at this point we were nearing our 75% battery. We switched on the REX and drove a solid 100 miles at 70 MPH before stopping for gas.

We topped off and then were on back roads for the last 40 miles of our trip, we used 1/4 of a tank of gas and still had 60% battery upon arrival home.

Our conclusion is yes, you can drive on the highway, this car is much happier being on back roads traveling at 50 MPH or so. Once we got off the highway the REX kept up and used little gas.

My wife is still commuting 100 miles plus a day. She drives 25 miles back and forth in the morning then repeats in the afternoon. MWF it is put on a stage 2 charger between commutes, T - Th she uses the REX.

We are having random issues with the gas cap, like one out of every 5 tanks of gas gives us an issue. Otherwise, no issues.

We just had a brake service completed, the dealership left the dipstick slightly out of its seat causing about 1/2 quart of oil to puke out and make a mess. This triggered a check engine light as we appeared to be a quart low.

I pulled the engine cover, cleaned up as much as I could and added 1/2+ a quart back in. The check engine light shit back off, after a test drive and cycling the car off and back on.

I think I am going to sell the 1982 318i, I need to free up some room for another project. If anyone is interested PM me here or email me at my screen name @ gmail

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