______________________________________________________________________________________
Coolant Enrichment Curve
0
10
20
30
40
50
60
70
-40
-20
0
20
40
60
80
100
120
140
Coolant temperature, C
TECgt Manual Version 2.0
- Page 69 -
©2008 Electromotive, Inc.
Oxygen Sensor Voltage Outputs
0
0.2
0.4
0.6
0.8
1
0.7
0.8
0.9
1.0
1.1
1.2
1.3
Lambda
EGO Voltage
Cold
Sensor
Hot
Figure D.4. 7:
Typical oxygen
sensor voltage variation with
exhaust temperature.
D.4.g. Warm-Up Enrichments (Coolant Temperature-Based)
Since engines need more fuel when the block, valves, cylinder head, and intake manifold are cold, a
coolant temperature-based enrichment curve is included in the software. The coolant temperature
enrichment serves the same function as the choke plate on a carburetor. This parameter has the ability to
provide different fuel enrichments for different coolant temperatures. If the engine is operating
substantially above the thermostat value, the coolant temperature enrichment can be used to add fuel to help
cool down the engine.
If a cold engine is running rough (misfiring), but not blowing black smoke from the exhaust, the
coolant temperature enrichment likely needs to be increased. If a cold engine is blowing black smoke out
the exhaust, the coolant temperature enrichments should be decreased at the problem temperature.
Figure
D.4. 8
is a fairly typical coolant enrichment curve.
When the warm-up enrichment is in effect, its percentage of enrichment adds directly to the VE
“Absolute” correction. Therefore, if the VE Absolute is 90% at a given point, and the coolant enrichment
was 20%, the effective VE Absolute correction would be 110%. Fittingly, the pulse width equation must
be modified to reflect this enrichment. It now becomes:
Pulse Width = [(MAP Voltage
÷
5)
×
TOG
×
{(VE “Absolute” % + CLT)
÷
100}]
+
IOT
The same calculation method is used for both the EGO and MAT enrichments, which are outlined
in subsequent sections.
Figure D.4. 8:
A
typical coolant
enrichment curve.