VIRTUAL VOLUMETRIC EFFICIENCY

Rather than a traditional VE table, certain GM vehicles use something called "VE coefficients" for volumetric efficiency. If you are tuning such a vehicle, you can use the Virtual Volumetric Efficiency Table Editor window to unpack the VE coefficient data and edit it in a format similar to a conventional VE table.

To access this window, select Edit > Virtual Volumetric Efficiency in the menu bar.

EDITING VIRTUAL VE TABLES

A brief summary of the procedure for modifying a virtual VE table can be found below. See the HP Tuners Live Training session on Speed Density Tuning for details.

NOTE: If you have changed the fuel injectors, it is critical that you have accurate data for the new injectors entered under Engine > General > Injector Control. If the injectors are not accurately described here, your VE table configuration will not be correct.

1.

If the engine also has a MAF sensor, it is necessary to temporarily force the engine to use speed-density mode in order to gather the data necessary for VE table calibration. See Forcing Speed-Density Mode on a GM Vehicle.

2.

Use the VE Mode and Camshaft Angle controls to select a version of the VE table to configure.

3.

Configure the data in the VE table using the same methods you would use for a conventional VE table.

4.

When you have a version of the table data that you want to flash to the vehicle, click Calculate Coefficients to update the VE Coefficients tables based on your modifications.

5.

Flash the revised tune file to the vehicle.

6.

In VCM Scanner, create a log containing fuel trim data at various rpms.

7.

Use the observed fuel trim data to determine what changes to the virtual VE table (if any) are needed. If further changes are needed, return to step 3 and make further modifications.

8.

If the vehicle has a MAF sensor, restore MAF sensor operation by reversing the changes made in step 1.

VE MODE

Some vehicles have a (runner control) switch in the intake manifold that can be open or closed. It is possible to configure a separate VE table for each position of the switch.

On vehicles that support Displacement on Demand (DoD), an alternate version of each table can be configured for use when cylinders have been deactivated.

Use this dropdown menu to select the version of the VE table to configure.

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Manifold Switch Closed

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Manifold Switch Closed (DoD)

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Manifold Switch Open (DoD)

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Manifold Switch Open

Vehicles that do not have an intake manifold runner control switch use only the Manifold Switch Open version(s) of the table.

Vehicles that do not support DoD use only the non-DoD versions of the table.

CAMSHAFT ANGLES

On VVT vehicles, a separate VE table can be configured for each CAM angle combination. Select a combination of intake and exhaust cam angles to configure the VE table used for that combination.

On fixed cam (non-VVT) vehicles, these can be left at 0.