feature be turned OFF. TPS changes, on the other hand, force an additional amount of fuel to be added to
the cylinders. It is recommended that most applications turn the TPS Acceleration Enrichments ON.
Typically, the duration of the required fuel addition is around one second. For this reason, there is a
set of enrichment parameters devoted solely to One Second Acceleration Enrichments. Additionally, lower
coolant temperatures will often require more enrichment. Consequently, a temperature-based one-second
enrichment is included.
What if an engine required an acceleration enrichment that was either longer or shorter than one
second? This is where the Variable Time Acceleration Enrichments come into play. If an engine only
needs 0.50 seconds of acceleration enrichment, simply set ACE-4 to be 0.50 seconds. The One Second
Enrichments could then be turned off completely. The Variable Time Enrichments also have the ability to
decay from the full enrichment value to zero enrichment as a function of the time defined in ACE-4.
To find the proper enrichment settings for an engine, it is best to start with proper TOG/UAP and
IOT/POT numbers. Then, the VE Table should be tuned at as many points as possible under steady-state
conditions. Once these conditions have been met, turn the TPS-Based Acceleration Enrichments ON. It is
recommended that ACE-4 and ACE-5 be used for most engines once they are fully warmed-up. Start out
with values of 50% for ACE-5 and 1 second for ACE-4. If the engine hesitates right after the throttle
position changes, increase ACE-5. If it hesitates a short amount of time after the throttle position is
changed, increase ACE-4. If the engine does not hesitate at all, decrease ACE-5 in 5% increments until the
engine stumbles under acceleration, then increase ACE-5 by 5-10%.
ACE-8 and 9 generally are not necessary for an engine that has a properly tuned VE Table.
However, if the engine is going lean during Acceleration Mode and all other acceleration enrichment, it
may be a good idea to add a small amount to ACE-8 (start with 0.5ms). ACE-9 should normally not need
to exceed 2 seconds on a tuned engine.
B.5. Adjusting the VE Table
OK, OK, now you are ready to jump into that big table with all the numbers to fine-tune your
engine. Be forewarned, however, that most engines (even throttle-per-cylinder setups) can run quite well
with the VE Table zeroed out (as long as the engine is not overly radical). If you start making drastic
adjustments to the VE Table, there is likely something amiss in your IOT and/or TOG/UAP settings.
Radically cammed, high-rpm engines may require some substantial VE Table adjustments, though.
When making changes to the VE Table, it is a good idea to watch the injector pulsewidths on the
bottom of the screen. If these values fall below about 1.4ms, your injectors are too big.
Begin the VE Table adjustment procedure by viewing the VE cells in which the engine is running
(by using the cell highlight feature). This will show you where the engine is operating at a given instant,
and will enable you to correct the appropriate cells. Try to operate the engine in a specific portion of the
VE Table when tuning. This will allow you to fine-tune individual sections of the table to get an overall
view of the corrections that need to be made.
For naturally aspirated (NA) engines, the TOG calculation that is made by the Tuning Wizard can
be thought of as the necessary pulse width when the engine is at 100% volumetric efficiency. In reality,
most NA engines will not operate at 100% volumetric efficiency unless they have a fairly radical camshaft
and high compression.
Turbocharged and supercharged engines will operate at well over 100% volumetric efficiency. The
calculated TOG number from the Tuning Wizard is scaled to make the specified boost peak the 100% load
number. Therefore, boosted engines should enter the peak boost (plus 10kPa) that they intend to run as the
highest point on the MAP scale in the VE Table. As an example, if an engine is to run up to 150kPa
(absolute pressure), the peak MAP value in the VE Table should be 160 kPa.
The volumetric efficiency peak will coincide with the torque peak. When an engine is not at the
torque peak, the volumetric efficiency is decreased. Typically, but not always, this goes hand-in-hand with
a decreased fuel requirement when below the torque peak. Fuel requirements generally increase or stay
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TECgt Manual Version 2.0
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©2008 Electromotive, Inc.
