User Manual

THE MAP (MANIFOLD ABSOLUTE /AIR PRESSURE) SENSOR CONNECTOR
he MAP Sensor’s signal to the Timing Computer is through the flat, 3-pin connector.
nstall a 2-
BAR
MAP Sensor, according to its own instructions and plug the Timing
Computer’s male connector into the sensor’s 3-pin female port.
he MAP Sensor reads intake manifold pressure. This makes it possible for the Timing
Computer to adjust to a predetermined timing curve under Vacuum or Boost conditions.
Use an A
CCEL /DFI 2-BAR MAP Sensor, Part# 74776
(No need for a 3-Bar MAP Sensor, even with high boost.)
he MAP Sensor measures pressure. Manifold Absolute Pressure is near 0 BAR at high
acuum, near 1
BAR at wide open throttle, and up to 2 BAR at about 14 PSI of Boost.
Vacuum sensing provides a linear advance of the Base Timing Curve from 0° to full
dvance during high vacuum conditions.
I.E. You have set Maximum vacuum advance
t 10°. At wide open throttle there is little intake manifold vacuum and ignition timing
ollows the
RPM curve. At light load (.5 BAR, about 15 inches of Hg) the Timing Computer
dds 5° (
half the 10° Maximum Timing) to the Base Timing Curve.
Boost retard works the same but in the opposite direction: Suppose you program a Boost
Retard value of 6° at the maximum sensing boost of 1
BAR (about 14 PSI). At 0.5 BAR
about 7 PSI) boost the Timing Computer retards ignition 3° from the Base Timing Curve.
THE SQUARE, 4-PIN, MALE INPUT CONNECTOR
he ACCEL TIMING
COMPUTER
inputs from all kinds of trigger types, except distributor-less,
nd its digital, micro-processor controlled, rev-limiter will be as sensitive as your trigger.
We recommend an
ACCEL Billetech Distributor or ACCEL Crank Trigger. Triggering inputs
re read through the square male connector:
WHITE
wire, or the PURPLE and ORANGE wires.
Your ACCEL+ ignition system should already have this connector in place.
he W
HITE wire’s input is in the form of
Square Wave. It gets this input from
:
• All points ignitions
• Most fuel injections
• Some
HEI modules
he
PURPLE and ORANGE wires get their
nputs from magnetic pickup or crank-
iggered systems
he
PURPLE wire is a positive (+) input
nd the
ORANGE is a negative (–) input.
(See chart for various connections.)
your system uses the WHITE wire you
ust isolate and insulate the
PURPLE
nd ORANGE wires. If your system uses
he
PURPLE and ORANGE wires you must
olate and insulate the
WHITE wire.
*
Older A
CCEL Crank triggers may connect WHITE to PURPLE and BLACK to ORANGE.