J&S Electronics
13925 Parkway Dr. Garden Grove, CA 92843
(714) 534-6975 www.jandssafeguard.com
18)
Boost Retard:
Switch
8
up calibrates the MAP sensor for Boost Retard. The Start knob sets at what boost pressure
the boost retard begins. Fully CCW, the boost retard starts at zero psi. The TP (Test Point) is calibrated in volts per psi. Zero
volts equals zero psi. If you set the voltage to five volts, the boost retard will not start until five psi.
19)
Vacuum Advance: Switch 8
down calibrates the MAP sensor for Vacuum Advance. The start knob sets at what
vacuum the retard will begin. Fully CCW, the retard starts as the vacuum goes below ten inches, which is equivalent to minus
5 psi. If you want the unit to start retarding as the vacuum goes below ten inches, set the voltage on the test point to 0 volts.
If you don
’
t want any vacuum advance, set the knob so the test point reads at least 5.0 volts. Or just turn the Rate knob fully
CCW.
20)
Start knob:
This sets at what manifold pressure (or vacuum) the boost retard activates. Since we want to pre-empt
knock, start the retard a little early. Use the “Start” test point on the front panel to help you set this up. Adjust the knob until
the voltage on the “Start” test point corresponds to the manifold pressure (or vacuum) level you want the retard to begin. For
example, if you don
’
t want boost retard until 5 psi, adjust the “Start” knob so the “Start” test point reads 5v.
21)
Rate knob:
This is used to set the amount of retard per psi of boost. The rate is adjustable from zero degrees fully
CCW, to two degrees per psi fully CW. Use the “Rate” test point on the front panel. For example, for one degree retard per
psi, adjust the “Rate” knob so the “Rate” test piunt reads 1v.
22)
Rev Limits:
These two knobs set the top end and staging rev limits. The corresponding test points are URL for Upper
Rev Limit and LRLfor Lower Rev Limit. The test points are calibrated in volts per thousand RPM. The rev limits can be
changed while the engine is running, but won
’
t take effect until the RPM is momentarily brought below 2500 RPM.
The Staging Limit is activated by connecting12v to pin 8 of the rear connector, labeled “Stg Lim”. Note that pin 1 is the
leftmost pin, looking into the connector from the rear.
When 12v is removed from the “Stg Lim” pin, the top end rev limit is in force.
23)
Nitrous Retard:
This knob sets the amount of retard when the pin on the rear connector labeled “Nit Ret” is
connected to 12v. To set, start the engine, observe timing with a light, apply 12v to the “Nit Ret” pin and adjust the knob until
the desired retard is achieved. Range is zero to twenty degrees.
24)
Cranking Retard:
This knob sets the amount of retard during startup. This is useful on high compression engines
with locked out timing. The unit re-advances quickly, at the rate of one degree per spark event, so you may not be able to
measure it with a timing light. Range is zero to twenty degrees.
25)
Status LED:
The Status LED is located above the jack on the front panel, and pulses with each trigger event. During
cranking, the pulses are slow enough to see, then merge together as the engine comes up to idle speed. The Status LED is
off above 980 RPM. Above 1250 RPM, the LED glows in proportion to the amount of knock retard.
26)
Bargraph Test:
When the key is first turned on, the Staus LED on the front panel should blink for two seconds. If you
have the optional bargraph display, it will count up and back over a two second period. The test can be aborted by moving the
key to start. Some ECU
’
s emit a pulse at power up which will abort the test automatically. If you have one of these, you will
see the first LED on the bargraph blink briefly when the key is turned on.
