Recommended air/fuel ratio chart – Mallory Ignition ACCEL Engine Analyzer Series Wideband Oxygen Sensor 77062_77062n_77062s_77063 User Manual

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Recommended Air/Fuel Ratio Chart

The following chart may be used as a guideline for baseline tuning of your engine.
The values specified in this chart should provide reasonably safe starting points when

beginning an engine calibration. Once you have tuned your engine to run at or near
these values, you can experiment to see how small changes in fueling impact power,

economy, and drivability.

If you have any questions or concerns about these values or how your combination

will work with these values, you should consult your engine builder or a professional
tuner before you begin. Such factors as fuel octane rating, air temperature, ignition

timing, exhaust configuration, cam profile, compression ratio, and combustion
chamber design all have an impact on the “ideal” air/fuel ratio for your application.

This chart should be considered a guideline ONLY. In addition to air/fuel ratio
information, you should monitor engine temperature, listen for spark knock, and

read the spark plugs to determine a fuel setting that is safe and appropriate.

Suggested A/F Ratios

Engine Type

Idle

Cruise

WOT

Stock - little or no modification

to engine, 87 octane gasoline

14.7:1 14.7:1 12.5:1

Street/Strip engine – naturally

aspirated, performance

camshaft and exhaust, 10.0-

11.0 compression, premium

pump gasoline

14.2:1 14.0:1 12.8:1

Race engine – naturally

aspirated, high lift/duration

cam, 12:1 or higher

compression, high-flow heads

and exhaust, high octane

racing fuel

13.5:1 13.5:1 13.0:1

Turbocharged/supercharged –

stock or mild performance, 6

to 8 psi boost, premium pump

gasoline

14.2:1 13.8:1 12.3:1

Turbocharged/supercharged –

street/strip performance, 10

to 15 psi boost, intercooler,

pump gas with octane booster

or race gas mix

14.0:1 14.0:1 12.0:1

Turbocharged/supercharged –

race configuration, 20-30 psi

boost, intercooled, high octane

race fuel

13.0:1 13.0:1 11.5:1

Turbocharged/supercharged –

race configuration, 20-30 psi

boost, NON-INTERCOOLED,

high octane race fuel

13.0:1 13.0:1 11.0:1