^
Same here.
I had an 87 Audi CS5000 (turbo, 5-speed stick,small engine, two locking differentials) with one of those engine parameter real-time readouts on it and I consistently got about 31-32 MPG in winter and other long-term cool spells versus about 28+ in warmer weather. So it wasn't just gasoline tailoring for the seasons, and it wasn't gas brand, and it wasn't my driving habits, and it wasn't relative altitude between destinations. I would vary my route depending on traffic conditions (I stayed off I-70 and used side streets if there was a jam-up) and the story was the same. I "kicked" the turbo only when necessary.
That always puzzled me, because as someone mentioned, the computer should have adjusted for maximum mileage --although according to the manual, it took about ten miles for it to adjust to your driving habits, as opposed to instantaneous driving condition changes.
Unless it had something to do with warm versus cold air interacting with the turbocharger... even though I avoided "using" it, it was still in the manifold intake circuit and still doing some compression. I noticed the questioner in the article did not mention a turbocharger.
On the topic of instant fuel mileage calculators, my Buick has one. It also has a gizmo that tells you how many miles left you have on your current tank of fuel. We typically stay in City for the most part, where the Buick gets about 16mpg. One time we went on a short trip up north, and the range estimator said our remaining range was 270 miles when we left and it steadily increased the whole time we were on our trip until it said 340 miles when we got to our destination. We should go on long trips more often; it's like getting free gas!
I too used to reset the computer just at the top of a long hill just to get a 199 MPG reading and an enormously long miles-to-go readout.
Fiddlin' with the instrumentation...
As a side note, I suspect the "Boost Pressure" readout on the turbo of my Audi would have made a fine weather barometer if it had a couple of more digits on it. After the engine cooled down and the manifold pressure had come to ambient, it would read 0.8 Bar at this altitude when you first turned on the ignition. At higher altitudes it would kind of flicker between 0.7 and 0.8. All of which was consistent with the local absolute air pressure.
In shutting the engine down at idle (throttle valve closed) and turning the ignition back on, you could see the manifold pressure leak back up from .2 or .3 Bar to a normal reading.
(Absolute ambient air pressure at my altitude is about 635 mmHg, which is 635/760 = 0.83 Bar. Call it 12.3 psia as opposed to the 14.7 psia at sea level.)
Terry, 230RN
