half of its reading from the MAP sensor and half from the TPS. If the TPS read 1 Volt and the MAP sensor
read 3 Volts, the modified MAP Value would be 2 Volts for this setup.
The Blend Percentage can be changed as a function of RPM. Typically, the Blend Percentage
should be highest at low RPM’s and lowest (usually zero) at higher RPM’s. Typical 4-, 6-, and 8-cylinder
street-based engines with individual throttles respond well when the TPS voltage is tapered to zero by
4000rpm. Around the idle speed (0-2000RPM), the Blend Percentage is typically kept constant somewhere
between 45% and 75%. See
Figure D.4. 6
for a typical Blend Percentage curve.
The
TPS Voltage
is simply the current Throttle Position Sensor voltage reading. This can be
observed from the engine monitor screen when the engine is running. Similarly, the
MAP Sensor Voltage
is the current MAP sensor reading that is observed with the engine running. This is the unmodified MAP
sensor voltage.
The
TPS Offset
is a number that is added to the TPS reading in the Modified MAP Value
calculation. This number causes the actual TPS voltage to be increased slightly when it goes into the Blend
routine. This is useful for placing the Modified MAP Value at the desired point. Generally, this parameter
is used when the TPS output is not at the desired point. In practice, if an engine needs more fuel, the TPS
Offset should be increased. If it needs less fuel the TPS Offset should be decreased. TPS Offset is not used
for anything other than the TPS/Blend calculation (i.e. it will not be displayed as the TPS voltage on the
monitor screen).
The four variables all come together in the following equation:
Modified MAP Value
= [Blend Percentage x (TPS V TPS Offset Voltage)]
+ [(100 – Blend Percentage) x MAP Voltage]
Keep in mind that the Modified MAP Value is used in place of the actual MAP sensor reading when
TPS/MAP Blend is being used. As a result, the pulse width equation from before now becomes:
Pulse Width = [(Modified MAP Voltage
÷
5)
×
TOG
×
(VE “Absolute” %
÷
100)]
+
IOT
Typical TPS/MAP Blend Curve
0
10
20
30
40
50
60
70
0
1000
2000
3000
4000
5000
Engine RPM
Blend Percentage
Figure D.4. 6:
A typical TPS/MAP Blend curve.
Take some time to learn how to use the TPS/MAP blend function. Getting a radically-cammed
engine to idle nicely is very easy once you have mastered this feature.
______________________________________________________________________________________
TECgt Manual Version 2.0
- Page 66 -
©2008 Electromotive, Inc.