Altimeter?

[NatersXJ6]

Does anyone else wish their Jeep had an altimeter?

It seems like they must read the air pressure somewhere for engine management. How hard could it be to calculate altitude?

Just pondering...

 

[Zeep]

My Garmin has one!

 

[Geek]

My jeep's head unit (430) has one in the nav and my cel phone has one.

I believe they both do it by gps triangulation.


.mobile

 

[Hopeless Diamond]

The 430N Nav systems in the JK jeeps do have an altimeter reading, the Kenwood in my truck does too. Both use Garmin for their mapping. It's not real accurate though, I always compare when I go over marked highway passes and it's usually pretty close, even exact, but down at sea-level, it could be up to 100+ feet off.

 

[Mass_Mopar]

 

[Geek]

Here is a free iphone app i just downloaded. It is currently off by 39 feet.

.mobile

 

[jscherb]

I find that my Garmin is usually with about 10 feet of the signs at mountain passes, sometimes it's off a bit more at sea level. Below sea level it was within a couple of feet a few weeks ago in Death Valley...

 

[tarditi]

GPS + Phone makes it not terribly important... like an inclinometer. Would be fun if they had them like the old troopers or monteros, but not really a missed item.

 

[codesertrat]

Yes, the engine ECU does read barometric pressure, although I don't remember the units Chrysler shows when reading OBDII. I know I've read it with my laptop, and I assume that scangauge could as well.

While it varies by weather, standard atmospheric pressure at sea level is considered to be 29.9" Hg or 14.7 psi. Atmospheric pressure drops by about 1" Hg/1000ft elevation or 0.5 psi / 1000ft. So at 6000ft elevation, atmospheric pressure is approx 23.9" Hg or 11.7 psi. These are common calculations used I have used when tuning industrial natural gas powered engines (where it is important to calculate engine load based on absolute intake manifold pressure), and also the altimeter in an airplane.

 

[verdesardog]

Barometric pressure is not a good way to measure altitude as it changes with the weather. For it to be accurate it needs to be calibrated daily to match local air pressure. GPS altitude is more accurate but not as accurate as location since the gps only uses two satellites to determine altitude.

 

[codesertrat]

The simple "rule of thumb" method I gave is accurate within a couple percent up to 10,000 ft, regardless of weather fluctuations (approx 1 or 2 % up or down from the 29.92" Hg standard). Keep in mind that the weather report always "corrects" barometric pressure for sea level, regardless of whether you are in Galveston, TX or Leadville, CO.