Porsche 928 S 1984 Owner's Manual page 31

Tachometer
The transistorized tachometer operates on
the pulse count principle and shows engine
speed in revolutions per minute (rpm).
The red mark at the end of the scale indicates
the maximum permissible engine rpm. Before
reaching this area, the next higher gear should
be selected. Earlier shifting saves fuel.
Shift to the next lower gear when the engine
rpm drops below 1500 rpm.
CASIS
Computer Assisted Shift Indicator System
(Manual Transmission only)
A computer continually evaluates vehicle data,
such as driving speed, engine rpm, engine
load and engine temperature.
When the CASIS arrow in the tachometer
lights up, it means the engine could operate
more economically. The light indicates that
you can increase fuel efficiency by shifting in-
to a higher gear. The CASIS light will go out
when a higher gear has been engaged, when
taking your foot off the gas pedal or when ac-
celerating at a higher rate. In fifth gear the
CASIS light is inoperative.
During maximum acceleration, the CASIS ar-
row light will only light up at a point where en-
gine rpm is such that improved acceleration
can be obtained by shifting into the next higher
gear. This means the CASIS arrow does not
indicate any set shift point, but that the com-
puter calculated shift points depend on the
way you drive. The arrow will light up at the
lowest speed range when cruising, and the
highest speed range when accelerating with
wide open throttle.
How to use CASIS
Drive your Porsche shifting as you normally
would.
As soon as the engine reaches uneconomical
load range, the CASIS light will remind you to
shift into the next higher gear to keep the en-
gine at the same performance level but with
lower fuel consumption.
You will get used to CASIS quickly and as a
result operate your Porsche with the CASIS
arrow light coming on only now and then.
WARNING
Use CASIS to your best advantage but re-
member that traffic, road and weather con-
ditions must always have priority when
shifting gears or changing speeds.
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