674 Datasheet, PDF (1/4 Pages) Littelfuse – Axial Lead and Cartridge Fuses - Ceramic Body

OPERATING INSTRUCTIONS
FORM #1492 (REV. B) 9/00
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HYFIRE^® VIIC CONTROL UNIT
PART NO. 674
RPM Switch:
NOTE: This feature is not available on the HYFIRE^® 667C. The built-
in RPM switch can either turn an electrical load off or on at a selected
RPM. See below for more detail.
NC This is the RPM switch (mode 7) relay contact that is normally
closed. In other words, as long as you haven’t reached the point
where the RPM switch is active, this contact remains connected to
the “common” or “C” terminal. You would use this connection if, for
example, you wanted to turn something OFF (such as a nitrous
system) when you reached the RPM switch point. See example 1.
C
This is the common terminal for the RPM switch (mode 7) relay in
the main unit. It is connected to the RPM switch, where it will switch
the accessory connected to the “NC” terminal OFF, and the acces-
sory connected to the “NO” terminal ON when the RPM switch
value is reached. The “C” terminal can be used to switch either to
power or ground.
NO This is the RPM switch (mode 7) relay contact that is normally
open. In other words, as long as you haven’t reached the point
where the RPM switch is active, this contact isn’t connected to the
“C” contact. You would use this contact to turn something ON (such
as a shift light or an air shifter) at a specific RPM. See example 2
and example 3.
RPM Limiters:
The HYFIRE^® 667C has three built-in RPM limiters. Each one has a range of
1000 to 12,800 RPM in 50 RPM steps. On the main display, there is a decimal
point on the mode digit. When that decimal point is lit up, the RPM limit is
increased by 50 RPM.
RPM1 (Mode 1)This is the RPM limit that is always active if you haven’t
selected any other RPM limit.
RPM2 (Mode 2) This is an auxiliary RPM limiter that is activated when you
apply 12 volts to the “RPM2” terminal on the top-side connector.
This could be a burnout limiter. When selected, it overrides RPM 1
(the main engine protection RPM limiter). See example 4.
RPM3 (Mode 3) This is the other auxiliary RPM limiter. It also is activated
by 12 volts on the “RPM3” terminal on the top-side connector, and
overrides both RPM2 and RPM1. Use this limit as a staging (start-
ing line) RPM limiter. See example 5.
High Speed Timing Retards:
RET1, RET2, RET3 (Modes 4, 5, 6) These are all high-speed timing retard
functions that are activated by 12 volts on the appropriate top-side connector
terminal. Each higher stage overrides the lower stages, which means that
you set each stage for exactly the amount of retard you want, rather than
adding up each stage to get the actual retard. See example 6.
NOTE: When you apply 12 volts to RPM2, RPM3, RET1, RET2, or
RET3 the display will switch to show that function. If you have both
an auxiliary RPM limit AND a retard selected, the display will show
the retard value.
See the accompanying illustrations for some examples of how to use the RPM
limiters, the RPM switch, and the timing retard functions.
Push this button to change the mode.
FIGURE 1
Push either of these buttons to change
the value of the mode.
NOTE: If any button is held down for more
than 1/2 second, the displayed value will
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change automatically.
1