Glossary; Banks Engine Air Density System Overview - banks iDash 1.8 DataMonster Owner's Manual

SECTION: 15

GLOSSARY

15.1 Banks Engine Air Density System Overview

Horsepower is directly dependent on the number of oxygen molecules available for
combustion. Simply put, the more oxygen your engine has, the more fuel it can combust
resulting in greater horsepower. Boost pressure has been the go to performance
measurement to predict horsepower changes because it directly affects the amount of
oxygen available to the engine. However, it is only part of the story and leaves out the
temperature effects on oxygen content, which is a critical element that can greatly alter your
engine's horsepower.
So if Boost isn't the best performance indicator, what is? Air Density is the most direct
measurement of oxygen molecules being used by your engine for combustion. Unlike looking
at Boost pressure, it accounts for the effect that temperature plays on oxygen content of
the air. Density is defined as lbs. mass of air per ft³ of volume. We display this parameter as
lbs./1000ft³ which scales it to an easier to read range of typically 0-300.
Because the air density changes based on pressure, temperature and humidity, the power
output of your engine will also change based on your current ambient conditions. The Society
of Automotive Engineers (SAE) has defined a set of ambient conditions that all engines
must be corrected to when measuring Horsepower. SAE J1349, which is the most common
correction factor, uses an ambient pressure of 14.4 psia, an ambient temperature of 77°F and
a relative humidity of 0%, resulting with an ambient air density of 72.2 lbs./1000 ft³. Another
common density standard is SAE J607 which has an ambient air density of 76.4 lbs./1000ft³.
Manifold Air Density (MAD) is calculated just like AAD except it uses the Manifold Absolute
Pressure and Manifold Air Temperature data. This reading represents the mass of oxygen per
unit volume available in the manifold.
Boost Air Density (BAD) is another useful measurement which is calculated as:
BAD = MAD – AAD
It is the additional Density available in the manifold greater than the current ambient
conditions and is a more insightful performance measurement then simply using Boost
pressure.
Note: U.S. Patent 7,254,477 B1 U.S. Patent 7,593,808 B2 apply to this product.
70
97654 v.7