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Installation Instructions AUTOTRONIC CONTROLS CORPORATION
1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 (915) 857-5200 FAX (915) 855-9847
Installation Instructions
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Timing Recurve
PN 40622
The Timing Recurve PN 40622 is designed to offer timing advance on vehicles using an
alternate fuel such as Compressed Natural Gas (CNG) or Liquified Petroleum Gas (LPG). The
original petrol or gasoline timing curve is used as a map or reference to generate a new performance
spark timing curve. The Timing Recurve works with your standard factory ignition to reproduce a
curve for CNG or LPG. Plus it retains the original curve for petrol or gasoline.
Application:
The Timing Recurve is designed for ignitions that use breaker points or electronic distributors
to deliver the spark. Vehicles with integrated ignition spark control and fuel injection may experience
a problem when there is no mechanical distributor to readjust the timing set-up. This control will not
work with Distributor-less Ignitions Systems (DIS).
Observe wiring diagrams for best applications.
Features: Unit offers 4, 6 or 8 cylinder calibration. Unit offers CNG, LPG and Petrol Curves. A One-Time timing check and adjustment! Easy 4-wire for installation. Easy to program recurve. (snip wires) One control wire to monitor fuel selection. Two output wires for tachometer monitoring
Overview:
The New Timing Recurve offers two timing advance curves plus it will reproduce the original
petrol or gasoline curves. The gray wire loop connected provides maximum performance on most
CNG vehicles. Snipping the gray wire loop provides a timing curve designed for most LPG vehicles.
The petrol or gasoline curve is selected by applying +12 VDC to the yellow wire. This yellow wire
connects to the gasoline side of the fuel selector switch. Dedicated or single alt-fuel applications
the yellow wire should be grounded. 2
INSTALLATION INSTRUCTIONS
AUTOTRONIC CONTROLS CORPORATION
1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 (915) 857-5200 FAX (915) 855-9847
HOW IS THE ADVANCE CREATED?
The Timing Recurve will electronically delay the factory set timing signal 15 degrees. The user
must mechanically move the distributor timing ahead or advanced 15 degrees. Add 15 degrees to the
original factory gasoline set point. With the 15 degree delay for gasoline, the Recurve can then provide
timing advance for the higher octane LPG/CNG fuel. At idle on LPG fuel, only 10 degrees (CNG fuel,
only 13 degrees) additional advance will appear on your timing device. The other degrees (5 LPG or 2
CNG) of timing are used to compute a smooth, accurate timing for RPM changes. After the (gray wire
loop) fuel timing program is set-up and selected. The fuel selector switch will select the proper timing
program via the yellow wire.
SELECTING CNG OR LPG TIMING CURVE
The Gray Wire Loop determines which advance curve is provided for CNG or LPG.
CNG Timing Curve: Gray Wire Loop attached.
LPG Timing Curve: Cut and insulate gray wire loop.
CYLINDER SELECTION (4, 6, 8)
The Recurve is delivered ready for 8 cylinder engines, that is, with both red and blue wire loops
connected. When installed on a 6 cylinder engine cut the red wire loop. When installed on a 4 cylinder
engine, cut both the red and blue wire loops.
TACHOMETER CONNECTIONS
The new Recurve has two tachometer (tach) outputs available: (T1) White Wire
(T2) White/
Blue Wire. Most of the tachometer which are factory installed will work properly with the
Timing Recurve. If your tach will not work properly, cut the wire to the input of your tach and
install a length of wire to T1 or T2.
T1 Provides a coil kick-back signal which satisfies a large majority of tachs.
T2 Supplies a 14V square wave tach signal.
SECTION II
ESTABLISHING RECURVE TIMING SETTING
To determine vehicle Recurve Timing Setting:
a. Locate and identify the vehicle emissions sticker, generally affixed to the radiator shroud
and observe the factory timing setting.
b. Add 15 degrees to the factory timing setting to determine the Recurve Timing Setting.
Factory Timing Setting
+15 Add
= Recurve Timing Setting (Computed)
Using the timing procedure as outlined on the vehicle emissions sticker, mechanically adjust
or advance the distributor to the computed Recurve Timing Setting.
Parts Included In This Kit
1 - Timing Recurve Unit
1 - Lug, Male Insul. Connector
6 - Heat Shrink Caps
4 - Female Wire Splice
4 - Pan Phil Steel Screws
1 - Instructions
4 - Beaded Wire Ties
1 - Lug, Female Insul. Connector
1 - 0.250" Ring Lug
1 - Female Lug Loose INSTALLATION INSTRUCTIONS
3
AUTOTRONIC CONTROLS CORPORATION
1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 (915) 857-5200 FAX (915) 855-9847
NOTE: Most Fords will require a clockwise direction.
NOTE: Most GMs will require the distributor to rotate in a counter clockwise
Direction.
TIMING: SET-UP & ADJUSTMENTS
1
st
Start the engine and observe timing at idle on gasoline (without recurve
connected), using a timing light.
2
nd
Locate and remove vacuum advance hose on distributor.
3
rd
Speed up the engine and verify that the factory mechanical timing advance
is operational by observing the timing increase.
4
th
With the engine at 1500 RPM, alternately connect and disconnect the
vacuum advance hose using the timing light to verify the vacuum
advance is in good working order by observing the timing
increase/decrease.
5
th
Observe gasoline factory timing setting with vacuum hose removed.
6
th
Example Check:
Factory timing setting
0 degrees
Add recurve requirement
15 degrees
Recurve timing set point
15 degrees at idle
7
th
Now, with recurve timing determined and verified, stop engine. Loosen
distributor lock-down bolt at point where distributor will move with slight
resistance.
8
th
Start engine and adjust distributor to 15 degrees (or your required
adjustment) at idle and secure distributor, lock-down bolt. The timing is
now set.
9
th
Stop the engine and connect the distributor vacuum advance hose and
the Timing Recurve Unit. See operational testing for further timing
readings proceed to section III wiring the unit.
NOTICE: Upon connecting this recurve, the factory timing will reduce 15 degrees.
Observed by the timing light that the factory gasoline timing curve is reproduced when
on gasoline. On alternate fuels the timing delay is reduced at a lesser amount, thus
providing timing advance; advance more than the standard factory gasoline curve. At idle
and above idle is the new alt. fuel curve.
SECTION III
WIRING THE UNIT
To ensure proper and permanent electrical connections, all wire taps and splices must be
soldered and sealed, using a rosin core solder and heat shrink. Do not mount components
or wires near the exhaust manifold, or any moving parts.
OBSERVE THE ATTACHED DRAWING and Steps 1 6 to install the timing recurve.
When completed use operational testing Section IV to verify installation.
STEP 1 POWER TO THE UNIT +12VDC
Attach the pink wire to the ignition key on/off +12VDC. Test the coil (+) side for
+12VDC or another power source.
STEP 2 GROUNDING THE UNIT
Attach the black wire to a clean engine or frame grounding point.
STEP 3 COIL (-) RPM AND TIMING CONTROL WIRE
Attach the brown wire to the ignition coil (-) wire, verify that the brown & black wires
are correctly placed. 4
INSTALLATION INSTRUCTIONS
AUTOTRONIC CONTROLS CORPORATION
1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 (915) 857-5200 FAX (915) 855-9847
STEP 4 TIMING CURVE SELECTOR WIRE
The yellow wire monitors the fuel selector switch and determines which timing curve
to provide. Attach the yellow wire to the gasoline (petrol) side of the selector switch.
Gasoline Curve: +12VDC on yellow wire.
CNG or LPG Curve: 0VDC on yellow wire.
STEP 5 SELECTING CNG OR LPG TIMING CURVE
The gray wire loop determines which advance curve is provided for CNG or LPG.
CNG Timing Curve: Gray wire loop attached.
LPG Timing Curve: Cut and insulate gray wire loop.
STEP 6 OPTIONAL TACHOMETER WIRE CONNECTION
Vehicles with a tachometer or governor may require a special signal for correct
operation. Rev-up engine to verify above device is functional. If tach or governor
requires the T1 white wire or T2 white/blue wire, cut and relocate the OEM input wire
and reconnect it to this special signal. Insulate the old OEM input wire.
SECTION IV
OPERATIONAL TESTING
NOTE: The following test procedure must be performed using either
conventional gasoline or alternate fuel. Do not alternate between fuels while
conducting this test.
1. Determine that all installation instructions have been completed in accordance with
Autotronic Controls Corporations outlined directive.
2. Disconnect vacuum advance hose on distributor and the Recurves YELLOW
wire from the fuel selector switch add a