Tec3r Manual Version 1.11
- Page 29 -
©2017 Electromotive, Inc.
If you are not able to get an engine to idle with the VE Table settings, it may be time to use
TPS/MAP Blend. Blend is useful when the low-rpm pulsewidths are too high, and the VE Table adjustments
are at their maximum negative allowance.
B.6. Using TPS/MAP Blend
It is necessary to first read the theory of operation for TPS/MAP Blend in
Section D.4.e
of this
manual. The relevant terminology for the Blend function is defined in that section.
When an engine needs blend, it is usually best to enter the same Blend Percentage Values around the
idle RPM. That is, if an engine’s idle speed is 800rpm, set all Blend Percentages to the same value from
1000 rpm and below. This will keep the Blend routine from moving around with small idle RPM changes.
As a starting point, set the Blend Percentage Value at 60% for all RPMs around and below the idle
speed. At around 200 rpm above the idle speed, the Blend Percentage can be brought down smoothly to zero
at around 2000-5000 rpm. The more radical the engine, the higher the RPM point for zero Blend Percentage.
Optionally, the Blend Percentage can be set to a fixed level at all RPMs. This would effectively
make the system use the TPS reading as part of the load calculation
all the time
. Taking this to the extreme,
if the Blend Percentage was set to 100%, the load calculation would be
entirely TPS-based
. This is generally
not a good tuning method, since throttle position is not a very ideal load indicator.
The Blend function should be thought of as two things: a MAP sensor filter and a pulse width
modifier. When the MAP sensor reading is unsteady, but the engine is running at roughly the right pulse
width, the TPS/MAP Blend can be used to smooth out the MAP sensor reading, and therefore smooth out the
pulse width fluctuation. To accomplish this, enter a small amount of Blend Percentage (25-50%) near the
idle point. Raise the TPS Offset Voltage to increase the pulse width to the desired level. Lower the TPS
Offset Voltage if the engine is running too rich. The pulse width should stabilize once the proper settings are
established.
B.7. Tuning for Cold Engines and Cold Weather
When an engine is cold, or when the intake air is cold, it will require additional fuel. To add this fuel,
the TEC uses coolant temperature enrichments that are activated as functions of cranking, normal running,
and accelerating. These enrichments are best tuned after an engine has been tuned when warm. Tuning the
cold enrichments before an engine has been tuned when warmed-up can be misleading.
To begin with, the most important coolant temperature (CLT)-based enrichment would be the Warm-
Up Enrichment. This enrichment adds a fixed percentage to the pulse width calculations as a function of
engine temperature. If an engine is tuned at 90C coolant temperature, the Warm-Up Enrichment should be
zeroed at 90C. At temperatures below 90C, the enrichment should ramp upward.
Starting a cold engine can also require an additional amount of fuel over and above that which is
necessary on a warm engine.
SE-0 and ASE-0
from the Starting Enrichment section can be increased to
provide these enrichments as a function of engine temperature.
The Warm-Up Enrichment can be tuned by starting an engine when cold, and waiting for the 20
second enrichments to turn off (simply wait for 20 seconds after the engine has started). Add the required
Warm-Up Enrichment at the current coolant temperature to achieve a smooth idle. Smooth out the curve
from the current operating point to zero at 90C. For example, if the engine is at 30C and needs 40%
enrichment, ramp the enrichment from 40% at 30C to 0% at 90C. For temperatures below 30C, back-track
the slope of the enrichment curve upward (i.e. continue the line that was established between 30C and 90C).
See the figure in
Section D.4.g
for a typical Warm-Up Enrichment curve.
Cold weather operation lowers air intake temperature. Colder intake temperatures mean that the
incoming air is denser than usual, and will require MORE FUEL to burn at the same air-fuel ratio. As
mentioned in
Section D.4.h
, the density of air increases drastically with decreased temperature. The plot in
Section D.4.h
shows the Manifold Air Temperature Fuel Enrichment that would be required for various inlet
