Auto Meter 4378 User Manual

2650-1143-00

Rev. A

INSTALLATION INSTRUCTIONS

21/16" WIDE BAND AIR/FUEL RATIO MONITOR

®

Installation

1. Disconnect the negative (-) battery cable.

2. Gauge can be mounted in a 21⁄16” dia. hole
with brackets supplied. Gauge can also be
mounted in Auto Meter Mounting Cup, or in
Auto Meter Gauge Works Pods.

3. Wire gauge as shown.

WARNING

Sender Will Get Very Hot During Operation.

Red Wire(Power):
Connect to a fused and switched 12V positive source

that is turned on and off with the ignition switch. Place
a 3 amp automotive fuse (available commercially) in

line with this connection to protect your gauge. It is
recommended that vehicles without alternators connect
this wire to a separate switch or direct to the vehicle’s
master cutoff switch. (See Sensor Heating Element Section)

Black Wire(Ground):

Connect to good engine ground.

Brown Wire(Optional Peak/Recall & Warning WOT Switch):

Connect to Wide Open Throttle Switch. Required for
Peak Recall Functionality.

Blue Wire (Optional Data Logger Signal Output):

Connect to signal input(+) or Engine Management System

or Data Acquisition unit.

Blue/Black Wire (Optional Data Logger Signal Ground):
Connect to signal input(-) on Engine Management system

or Data Acquisition Unit.

Data Logger Output

Blue

Blue/Black

Carb or

Throttle Body

Wide Open Throttle Switch

(for WOT peak function)

Black

Brown

Throttle Cable

Red

Fuse

12V Ignition Switch

Good

Engine Ground

Connect Data Acquisition Unit and Air/Fuel
Ratio Monitor to a common grounding point

Mounting Sensor

The heated oxygen sensor comes with a stainless steel weld-in bung,
plug, and wiring harness with a weather pack connector. The oxygen
sensor should be installed as close to the cylinder head as is reasonably
possible so that the sensor reaches operating temperature quickly. If
long tube headers are used, the oxygen sensor should be installed in
the collector. If cast iron manifold(s) or shorty headers are used, install
the sensor in the pipe just below the manifold. In multi-bank applications
mounting in the left or right side is acceptable. Turbocharged applications
should have sensor installed 4-5" after turbo on the down pipe.

Auto Meter recommends welding supplied
stainless steel bung with a TIG welder.

1. The exhaust pipe in front of the sensor should not contain any pockets, projections, protrusions, edges, flex-tubes etc. to avoid
accumulation of condensation. A downwards slope of the pipe is recommended. If the exhaust pipe is parallel to the ground, the
sensor must be installed in the top half of the pipe to avoid damage to due to condensation

2. Tightening torque: 30-44 ft Ibs.

3. Avoid excessive heating of the sensor cable. Route sensor cable away from exhaust pipe.

4. The maximum temperature of the sensor on the outside of the exhaust fitting should not exceed 900o F.

The Air / Fuel Ratio Monitor can be used with the following fuels.

Fuels

Unleaded Gasoline

Methanol

Ethanol

LPG (Propane)

CNG

NOTE: OK for use with Nitrous Oxide.

NOTE: Stoichiometric Air / Fuel Ratio is the chemically correct

ratio where theoretically all of the oxygen and all of the
fuel are consumed. The mixture is neither rich or lean.

Stoichiometric Air / Fuel Ratio

14.7:1

15.5:1

17.2:1

6.4:1

9.0:1

Operation Guide

This product has many features that can be adjusted for your specific application. Use the MODE (-) and SELECT (+) buttons to navigate
menu options, confirm selections, and fine tune options to your needs.

Acronyms:

A list of acronyms and abbreviations are defined below in order to help you more clearly understand the menu operations, functions, and
components available on your Auto Meter Wideband Air/Fuel gauge:

BGD – Bar Graph Display. This is the curved, multi-color, LED radial display used to indicate how “Rich” or “Lean” the current Air Fuel or
Lambda reading is relative to your Stoichiometric point with respect to your upper and lower range tolerances.

SSD – Seven Segment Display. This is the digital numeric display that indicates your current Air Fuel or Lambda reading. This display is
also used to help you navigate and make changes to your settings.

AFR – Air / Fuel Ratio. This is shown as a numeric value on the SSD, characterized by only having a single decimal place (i.e. 14.7). This
value is also visually represented on the BGD, indicating whether the value is “Rich” or “Lean” of the selected Stoiciometric value and rela­tive to the upper and lower range tolerances. AFR, as the name implies, represents the ratio of Air to Fuel being mixed and consumed, in
real time, by the engine / vehicle upon which this instrument has been installed.

ʎ Lamda, is an alternate way of expressing AFR, assuming that the stoichiometric point selected equals one and readings “rich” or “lean”
will be expressed as values above or below one, characterized by a value displayed with two decimal places, (i.e. 1.00). The gauge can
display data in either AFR or Lambda as needed by the user.

Real-Time Mode:

Real-Time mode is the default mode of operation for this product. When Real-Time mode is active, the instrument will display the current
air/fuel ratio in either AFR or Lambda.

To toggle between AFR and Lambda display types, press the SELECT(+) button. Remember that AFR values have a single decimal place
(i.e. 14.7), and that Lambda values have two decimal places (i.e. 1.00).