Fundamentals
Multec 3.5 Fuel Injector Application Manual
2-4
Delphi Energy and Chassis Systems
Revision: 11/05-1
Since the A/F will vary depending on the makeup of hydrocarbons in the
gasoline, a more appropriate method for referencing A/F is to use a
normalized value. In this way, we can refer to stoichiometric A/F as equal
to 1, regardless of the makeup of the gasoline. Two such terms are
commonly used:
•
Lambda (
λ
), where
λ
= (A/F actual) / (A/F stoichiometric). This is also
referred to as the excess air ratio.
• λ
> 1.00 for lean mixtures
• λ
< 1.00 for rich mixtures
•
Equivalence Ratio (
φ
), where
φ
= (F/A actual) / (F/A stoichiometric)
• φ
< 1.00 for lean mixtures
• φ
> 1.00 for rich mixtures
Fuel Type
Stoichiometric Air /Fuel
Ratio
Typical Unleaded
Gasoline
14.5 (Range 14.2 – 14.8)
10% Ethanol Blend
13.9
24% Ethanol Blend
13.3
85% Ethanol Blend*
9.95
15% MTBE Blend
14.1
100% Ethanol*
9.0
*Non-standard fuels requiring special fuel rail and injector
components.
Table 2-1 - Stoichiometry of Alternate Fuel Blends
2.2.1.2 Stoichiometric
“Ideal” Combustion Mixtures
Complete or “ideal” combustion produces by-products of carbon dioxide
(CO
2
), nitrogen (N
2
) and water (H
2
O). However, ideal combustion does
not occur in an actual engine. The chemical equilibrium required is often
difficult to achieve. Transient operating conditions, combustion chamber