SaabCentral Forums banner

1 - 10 of 10 Posts

·
Registered
Joined
·
444 Posts
Discussion Starter · #1 · (Edited)
How'd I use 20 miles worth of gas in a mile and half?

So on Tuesday, after walking a quarter mile in really hot weather, I am sweating when I get to the car. On the SID it says 100 degrees. Whew! I crank up the AC and, because I am low on gas, tune the knob to show me my DTE. It reads 94 miles. I drive off and, after a mile and half, I look up at the SID and it says 73 miles to empty:eek: . Huh? How'd that happen? Does the AC use that much gas? I turn off the AC (didn't want to get stranded now, do I)? and burn all the way to the gas station.
 

·
Registered
Joined
·
9,087 Posts
I find my DTE is much more approximate since I gave her stage 1.
However, a feature I like is when I switch on and DTE is less than 100 kms or 60 miles she tells me.. without my asking.
Also the DTE gets very accurate towards the empty..:lol:
 

·
Registered
Joined
·
413 Posts
DTE uses a calculation to arrive at a an expected range based on the amount of fuel in the tank, current driving style, and calls on ther engine such as running the AC. I have seen similar drops after a cold start (engine cold not cold ambient temperature) and use of the a\c. You may have also noticed, if you have been driving aggressively, the DTE will also drop. If you then start to drive at a steady speed, without excessive use of the throttle, you should notice the DTE start to go up rather than down. At best its an indication of potential range.
 

·
Registered
Joined
·
6,410 Posts
There's obviously some kind of algorithm at work here. Probably calculates a moving average.

The trip computer gets several pieces of data. The float in the fuel tank gives an approximation to remaining volume. The speed and odometer data tell how fast you've been driving and how far you've gone. The fuel injector timing data tells how much fuel you've been using.

All these bits go into a calculation to give DTE. We know the speedometer is at least a 1-2% off. And the trip computer seems to work best when it's reset with every fill-up, so there's some inherent inaccuracy there. The float in the tank is, well... floating, so it moves with the car. And, finally, they never seem to build these things without some "wiggle room." When it reads "D.T.E. 0" you always seem to have some miles left.
 

·
Registered
Joined
·
286 Posts
DavidMorgan said:
I find my DTE is much more approximate since I gave her stage 1.
However, a feature I like is when I switch on and DTE is less than 100 kms or 60 miles she tells me.. without my asking.
Also the DTE gets very accurate towards the empty..:lol:
I ll second that. It is indeed very accurate the last 50 kms. I did not know that around Cote D'Azur you cant pay for fuel with cash after 8pm, the SID scared the hell out of me. Anyway, made it to the hotel and refuelled the next morning.
 

·
Registered
Joined
·
132 Posts
i agree. i have noticed the past two weeks my gas mileage has gone way down because of the 100 plus degree weather here and i am cranking the A/C.
 

·
Registered
Joined
·
1,817 Posts
ctrlz said:
And, finally, they never seem to build these things without some "wiggle room." When it reads "D.T.E. 0" you always seem to have some miles left.

Unless it's mine and it says DTE=30 and the car stops!!! They then say, ah well its only meant to be an indication and refuse to rectify it!

Sorry, thats been building for a while! Rant over.....for now
 

·
Registered
Joined
·
102 Posts
gjdavies said:
Unless it's mine and it says DTE=30 and the car stops!!!
The exact same thing happened to me. Now I consider DTE a course approximation, and refuel as son as it's down to 100 km.
 

·
Registered
Joined
·
297 Posts
THE DTE IS FAIRLY accurrate. I drive this car to 0 all the time, let me tell you, the car is accurate at that point. Sometimes U can get a couple of miles on 0 but not much. I've ran out of gas only 1 ever, lol in mid intersection a block passed gas station right in front of a strip club in the rain. Crazy right, oh and it was the first time I was picking up a girl I met from her job too. Point is when it gets to 0 go get gas ASAP. Or use the saab roadside, we all have it and they give u up to $5 worth of gas, rougly 2 gallons.
 

·
Registered
Joined
·
444 Posts
Discussion Starter · #10 · (Edited)
I've ran out of gas only 1 ever, lol in mid intersection a block passed gas station right in front of a strip club in the rain. Crazy right, oh and it was the first time I was picking up a girl I met from her job too.
LOL. I'd kill to be a fly on the (windshield) as you were explaining your travails to her.:cheesy: :cheesy: :cheesy:
 
1 - 10 of 10 Posts
Top