MSD 2950 Installation

Atomic LS EFI

DANGER

Master Kit LS2/LS3, PN 2950

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Thank you for selecting the Atomic LS EFI System! MSD’s Atomic EFI systems are designed with
two major goals; to simplify EFI and deliver better overall performance from your engine. Simplicity
is achieved through wired-less technology to ease installation plus the Atomic is simple to program
with no PC required! Performance is delivered through advanced control of the fuel and ignition, just
as you’d expect from MSD.

Parts Included:

2 – Integrated Fuel/ECU Rail Assemblies
1 - Power Module
1 - Handheld Monitor
1 - Wideband O2 Sensor, Bung and Plug
2 - MAP Sensor Adapter Harnesses
2 - Camshaft Sensor Harnesses, 1x and 4x
2 - Crankshaft Harnesses, 24x and 58x
4 - Injector Harnesses
1 - IAT Sensor and Grommet

Parts Required, Not Included:

• Injector O-Rings

• Fuel System: Fuel Pump, Regulator, Line

• LS1 and LS6 Installation Kit - PN 2955

For use with Master Kit PN 2950. Provides the

correct brackets and EV-1 injector connectors
for the early car intake manifolds identified by
a 3-bolt throttle body.

• Thread Sealer for Intake Bolts

Not legal for use on pollution controlled vehicles: The MSD Atomic LS EFI system is not CARB
approved for use on emission controlled vehicles. This system is designed to control the EFI and
ignition on LS based engines being retro-fit into older vehicles that do not require emission controls.

1 - TPS Sensor Harness
2 - 90° -6 AN fittings
4 - -6 AN fittings
1 - 18" High Pressure Fuel Hose
4 - Installation Brackets
4 - Intake Manifold Bolts
8 - Injector Retainers
8 - 8/32" Socket Head Cap Screws
1 - 4G Micro SD Card

modifications must be carried out by a qualified automotive technician. Installation of fuel system
parts requires handling of gasoline. Ensure that work is performed in a well ventilated area with an
approved fire extinguisher nearby. Extinguish all open flames, prohibit smoking and eliminate all
sources of ignition in the area of the vehicle before beginning the installation.

When working with fuel systems, eye goggles and other safety apparel should be worn to protect
against debris and sprayed gasoline. The finished work must be thoroughly checked to ensure
there are no fuel leaks.

MSD •  WWW.ATOMICEFI.COM  •  (915)  855-7123  •  FAX  (915)  857-3344

WARNING

Installation of this product requires detailed knowledge of automotive systems
and repair procedures. Installation of fuel system parts and any fuel tank

2 INSTALLATION INSTRUCTIONS

CAPABILITIES

The Atomic LS EFI system is designed to fit OE intake manifolds, as well as some aftermarket intakes.
The Atomic EFI is a self-tuning fuel system that continuously adjusts after the basic configuration is
complete. There is no laptop programming. Based on the engine descriptors you input, the Atomic
will automatically create a base fuel map to get the engine running. Once running, the self learning
system will optimize those maps resulting in the best performance possible. If you change altitude,
outside temperature, or other factors the Atomic will adjust accordingly, on the fly. This ensures that
your engine will produce excellent driveability at all times, even if you drive from the sunny coast to
the cold mountains.

The Atomic LS fuel injection system is capable of running the fuel and ignition system of most LS engines.
The system incorporates OE style connectors to use with the factory sensors on the engine. The only
external sensor required to add is the supplied Wide-Band Oxygen sensor.

There are four main components of the Atomic LS system; the driver’s side and passenger side integrated
fuel rails, the Power Module and the Handheld Monitor. The ECU of the system is divided onto the fuel
rail assemblies and communicate to each other, as well as the Power Module, through MSD’s proprietary
CAN-Bus technology.

Crankshaft Trigger Wheel ID: It is important to know what crankshaft
trigger wheel your engine is fit with. There are two; early engines used a
24-tooth wheel and later model engines use a 58-tooth wheel. These can
be identified by removing the crank sensor (located behind the starter)
and looking inside the engine (see photo at the right).

Fuel/ECU Rails: The unique fuel rails of the Atomic LS EFI system also
incorporate the ECU of the system. The two banks receive power from the
Power Module and communicate to the system through MSD’s CAN-Bus
network. To install the rails to the intake manifold, the covers will need to be

24x 58x

removed (which is outlined in the instructions).

®

Each bank has OEM connectors that plug into the injectors, coils and specific
sensors of the engine. Each bank has a ground wire that must be connected to the

LS

CONTROLLER

block. The fuel line inlets of the rail accept -6 AN and -8 AN fittings and internally
are equivalent to a -8 line (-6 AN fittings are supplied.)

Power Module: The Power Module of the Atomic LS is the communication hub of
the system and provides the high current fuel pump circuit and other input/outputs
for optional features. The unit has two ports for the MSD CAN system as well as
a wiring harness. There are connections for the WB02, the Handheld Monitor as

POWER MODULE

well as power and communication to the integrated fuel rails.

Programming: The Atomic EFI is a self-tuning fuel system that continuously adjusts after the basic
configuration is complete. There is no laptop programming. Based on the engine descriptors you input, the
Atomic will automatically create a base fuel map to get the engine running. Once running, the self- learning
system will continuously adjust those maps to obtain the desired air/fuel ratio. This feature ensures that
your engine will have the right fuel mixture at all times, no matter where you are driving.

Intake Manifolds: The Atomic LS EFI system is designed to fit most OE intake manifolds, as well as some
aftermarket intakes. There are different mounting brackets available for several of the key intake manifolds.
MSD offers two Installation Kits that are supplied with different injector connects and fuel rail brackets for
manifolds such as the LS1 or truck. They are described in the ‘Not Included’ list of parts above.

Fuel System: The Atomic LS system can be used with return or returnless EFI system. Review the Fuel
System Information section starting on page 3 for detailed information.

MSD •  WWW.ATOMICEFI.COM  •  (915)  855-7123  •  FAX  (915)  857-3344

INSTALLATION INSTRUCTIONS 3

Wide-Band 02 Sensor: A Wide-Band 02 sensor is supplied in the Atomic LS Master Kit. This sensor is
responsible for constantly monitoring the exhaust gases and relaying that information to the ECU where
adjustments are constantly made to the fuel delivery in order to meet the air/fuel targets. Only one sensor
is required. Page 5 outlines the sensor installation.

Crank Sensor: The LS engine platform has used two different crank position sensors through the years.
There is a 24-tooth wheel or a 58-tooth wheel on the crankshaft. The sensor has always been located
behind the starter. The 24-tooth sensor has a black connector whereas the 58-tooth sensor has a gray
connector. The Master Kits are supplied with connectors for both the 24x and 58x trigger sensors.

Cam Sensor: The Cam Sensor of LS engines has changed throughout the years. Not only it’s location,
but its wiring as well. Early models have the cam sensor located at the back of the block near the deck
surface. During 2005, as a running change, the location changed to the front of the block between the cam
and crankshaft. The Atomic LS system can function with both designs.

Throttle Body and Sensors: The Atomic LS requires a mechanically operated throttle body. In the future
Throttle by Wire applications will be covered. The Atomic has all of the OE connections for the throttle
body including Throttle Position (TPS) and Idle Air Control Solenoid (IAC).

Intake Air Temperature (IAT) Sensor: This sensor is supplied and it is recommended to install it in the
air intake duct before the throttle body. A 3/4" hole is required for the sensor.

Rev Limiter: There are two settings for a rev limiter; one through fuel, one through ignition. There is an
optional 2-Step Rev Limiter that can be used on the starting line for a low rpm limit. This is temporarily
activated through the Dark Blue wire of the Power Module to produce consistent launch rpm.

Power Adders: The Atomic LS system can accept wet nitrous systems and boost through a turbo or
supercharger. For nitrous, there is a program that allows you to set a target air/fuel ratio when the nitrous
is activated as well as an selection to set a timing retard. For boosted applications there is a target air/fuel
ratio setting for times of boost pressure. See the advanced settings on pages 15-16.

FUEL SYSTEM REQUIREMENTS

The Atomic LS fuel injection system requires a high pressure fuel pump system. The fuel system is
not supplied due the large variety of applications incorporating the LS engine platform. Depending on
your engine combination, the Atomic LS requires a minimum of 58-62 psi to operate. When selecting
a pump, regulator and lines, be sure each component is designed to perform at high pressure. MSD
offers fuel pumps, hose and accessories to complete your installation. Following are some guidelines
in helping set up a fuel system for your Atomic as well as components available separately from MSD.

• The Atomic is capable of operating with a return or returnless style system. For best results with

either system, MSD strongly recommends an in-tank pump. Installing the fuel pump in the tank
results in quieter operation, less chance of cavitation and a reduction in pump temperature.

• When running a returnless fuel system (Pulse Width Modulated) the fuel pump must be mounted

in the tank. It is recommended to use an MSD Atomic Fuel Pump, PN 2925 or PN 2926.

• MSD supplies -6 AN Push-Lock style ttings for the fuel rails. These ttings must be used with MSD's

high pressure EFI hose. Refer to page 9 for installation.

• If mounting the pump in the tank is not an option, install the pump as close as possible to the tank.

Within 2-feet of sending unit is recommended.

• Do not use hard line when plumbing the fuel system. When using a PWM fuel system, pulsations

and harmonics could cause unstable fuel pressure resulting in pump cavitation or poor engine
performance.

MSD •  WWW.ATOMICEFI.COM  •  (915)  855-7123  •  FAX  (915)  857-3344

4 INSTALLATION INSTRUCTIONS

, MOUNT

FUEL RAIL

(UNDER COVER)

-6 90° FITTING SUPPLIED

FUEL RAIL

FUEL RAIL

(UNDER COVER)

(UNDER COVER)

NOTE: IF RUNNING A RETURNLESS
FUEL SYSTEM, THE PUMP MUST
BE MOUNTED IN THE TANK.

MSD ADJUSTABLE

REGULATOR

FUEL

FILTER

FUEL TANK

FUEL

PUMP

IT IS RECOMMENDED TO MOUNT
THE FUEL PUMP IN THE TANK
WHENEVER POSSIBLE. IF IT MUST
BE MOUNTED EXTERNALLY
THE PUMP WITHIN 2-FEET OF THE
FUEL TANK SENDING UNIT.

Figure 1 Atomic LS Return Fuel System.

In-Tank Pumps
The MSD Atomic Fuel Pump (not supplied) can be used in the tank however it would require a sock, or
filter element, on the pickup side. It is important to note that the wiring used to run the pump will need
to meet requirements to be submersed in fuel. When wiring an in-tank pump, it is recommended to
use a wire that conforms to SAE specifications J1128 and J378. This wiring features a Thermoplastic
insulated wiring with polyvinyl chloride insulation for protection against gasoline, oil, and more.
In addition, different fuel line will be required internally if the pump is to be mounted in the tank. Fuel
line that meets SAE 30R10 specifications MUST be used. Failure to do so will cause severe damage
to your engine and/or fuel system.

WARNING: Improper installation or use of fuel system components can cause severe damage your

engine and/or fuel system that will not be covered by the manufacturer’s warranty.

Atomic Fuel Pump, PN 2925: This pump features 3/8” inlet and outlet. The pump will support

approximately 525 hp and is approved for in-tank use (no wiring or in-tank mounting hardware/
pickup element are supplied).

Fuel Pump Kit, PN 2920: This Kit is supplied with MSD’s PWM Fuel Pump, a pre and post-filter, 15-ft

of 3/8 fuel injection line and mounting hardware.

Fuel System Return Kit, PN 2922: If you plan on running a return line with your Atomic LS, this kit

provides another 15-ft of 3/8” injection line, an MSD Regulator and two push-lock fittings.

High Horsepower Fuel Kit, PN 2921: This pump will support the power demands of engines up to 650

horsepower. The pump features 3/8” inlet and outlet. The pump will support approximately 650
hp and is approved for in-tank use (no wiring or in-tank mounting hardware/sock are supplied).

WARNING: MSD’s Push-Lock fittings are designed for use with the MSD fuel hose only. Do not use

the MSD fuel hose with other fittings. Do not use MSD Push-Lock fittings with other
fuel hose. Compatibility issues may cause fuel leaks.

MSD •  WWW.ATOMICEFI.COM  •  (915)  855-7123  •  FAX  (915)  857-3344

INSTALLATION INSTRUCTIONS 5

WIDE BAND OXYGEN SENSOR INSTALLATION

The MSD Atomic EFI system requires a single Wide Band

02 SENSOR

Oxygen Sensor (WBO2) for operation. MSD suggests that
the bung for this sensor be installed prior to starting any
other part of the conversion process. By having the WBO2
in place first, there is a reduced chance of the vehicle
being immobilized for an extended time. The bung for
the WBO2 provided by MSD has a plug included so that

POSITION
AT LEAST
10°

the vehicle can be driven between the time of exhaust
modification and installing the rest of the Atomic system,
if needed.

The WBO2 can be installed in downstream of either

EXHAUST
COLLECTOR

Figure 2 WBO2 Sensor Location.

exhaust bank. The sensor connects to the Power Module,
so install the sensor on the bank closest to where you
plan to mount the Module. The bung should be installed by a qualified exhaust technician and pressure
tested. Proper installation of the oxygen sensor is critical to the performance of the Atomic EFI. Improper
installation could lead to engine damage.

1. Locate the ideal spot to install the WBO2.
a. This location should be 2-4 inches after the exhaust collector. The sensor must be more than

18 inches forward of the exhaust tip. For applications where short or open headers are used,
install the WBO2 in the primary tube of the rear cylinder at least 8 inches away from the exhaust
port. The Atomic will not work on “Zoomie” style headers.

b. The WBO2 sensor should be at least 10˚ above horizontal to allow condensation runoff. Without

this angle the sensor is significantly more likely to sustain water damage (Figure 2).
c. Never place a WBO2 on the outside of a bend.
d. The WBO2 must be mounted in the exhaust prior to any catalytic converter, if applicable.

2. Drill a 7/8” hole in the exhaust where the WBO2 will go.

3. Weld in the supplied bung. Ensure the weld goes completely around the bung and is air tight.

4. Insert supplied plug in bung. Never run the vehicle with a WBO2 installed but not powered; it will
damage the sensor.

5. When completing the Atomic EFI installation, remove the plug and insert the WBO2 for use. MSD
suggests using a small amount of anti-seize on the threads.

Note: The Atomic EFI is extremely sensitive to air leaks in the exhaust system. Any air leak between

the engine and the WBO2 will cause the Atomic to have false readings, which can lead to poor
engine performance, misfires, and an inability to properly auto-tune. Extended running of the
Atomic EFI with an exhaust leak can result in detonation and severe engine damage. Improper
installation of the oxygen sensor, and any damage that may result from such an installation, is
not covered by the manufacturer’s warranty.

MSD •  WWW.ATOMICEFI.COM  •  (915)  855-7123  •  FAX  (915)  857-3344

6 INSTALLATION INSTRUCTIONS

INSTALLING THE INTEGRATED FUEL/ECU RAILS

The integrated fuel/ECU rails are supplied with the covers installed. The rails are designed to install to OEM
intake manifolds and many aftermarket designs. To prepare the rails for installation, locate the four intake
manifold bolts supplied with the Atomic LS Master Kit, as well as the four mounting brackets.

It is important to note at this point, that you have the correct injectors for your application as well as O-ring
seals and the injector retainers. These components are not supplied in the master kit.

WARNING: Care must be used when installing the fuel injectors and rail assemblies.

COVER

COVER

FUEL RAILFUEL RAIL

DISENGAGE
FROM FUEL
RAIL

LIFT COVER UP

FUEL RAILFUEL RAIL

LIFT THIS SIDE OF
COVER ENOUGH TO
CLEAR FUEL RAIL

COVER

FUEL RAILFUEL RAIL

PUSH COVER

Figure 3 Removing Fuel Rail Covers.

The following steps will guide you
through the installation of the two fuel
rail assemblies.

1. The fuel rails are supplied with
the covers in place. Remove the
covers to prepare and install the

REAR

BRACKET

rail assemblies (Figure 3). Also,
determine which rail is which by
reviewing the sensor connectors
and location as shown in Figure 9
on page 8.

9 3 2 6 7

2. Figure 4 shows the location for the fuel
rail brackets. Remove the hardware
from the intake manifold and install

REAR FRONT

the brackets as shown using the
supplied longer intake bolts. Use
GM 1245383 thread sealant or
equivalent on the intake manifold

8

5 1 4 10

bolts. Note that the passenger rear
bracket requires a spacer (supplied)
as shown in Figure 4. Torque the new
intake bolts to 89 in-lbs.
NOTE: If installing the intake manifold

for the first time follow the

NOTE: THE PASSENGER

SIDE REAR MOUNT
REQUIRES THE
SUPPLIED SPACER.

torque sequence in Figure

4. Torque in steps; 44 in-lbs
first, followed by 89 in-lbs.
It is recommended to hold

MUST USE THREAD SEALANT

TORQUE SEQUENCE
STEP 1 - 44 LBS/INCH
STEP 2 - 89 LBS/INCH

a straight edge against the
brackets to ensure alignment
while torquing.

MSD •  WWW.ATOMICEFI.COM  •  (915)  855-7123  •  FAX  (915)  857-3344

Figure 4 Fuel Rail Bracket Locations.