For cars with ITBs, or extreme cams the Manifold Air Pressure (MAP) cannot be relied upon to give a good signal - the resolution is poor and the pressures fluctate wildly. So its common practice to run setups like this as AlphaN where the Throttle Postion Sensor (TPS) is used instead of the MAP sensor, this gives very sharp throttle response and smooth running.
AlphaN is a pain to setup, so for this reason VEMS ecus tend to be supplied using Speed Density MAP sensor to make starting the car and initial tests easier. So once you have everything setup and the car idling you can change to AlphaN using the following steps:
(Remember to save your configuration before you start so that you can return to working settings).
In MegaTune select Alpha-N/Speed-density blending:
And you will get the following screen on early releases
Of this screen on the later releases
for
max RPM for Alpha-N (rpm) enter 25500
and
min RPM for Speed Density (rpm) entere 25500
If you have
MAP(load) multiplication ensure that it is set to
DisabledOnce you've set these values take a look at the main screen - you will see that the MAP gauge reads 0.0 kPa.
Press the throttle down and MAP will rise to 255 as Throttle Position goes from 0 to 100%.
If you do not get the full range on the TPS then you will need to check the TPS calibration.
Now we need to change the Maps go to:
Settings->VE Table and fill the kPa settings with the following values starting from the bottom cell:
0, 2, 5, 12, 23, 35, 53, 75, 115, 165, 225, 255Make sure that you burn the change to VEMS by using
File->Burn To ECU In the VE Table window.
To help you keep the car running (as ITBs tend to have terrible IACV control) its not a bad idea to put a "kick" up in the Ignition advance down at the lowest Load and RPM cell. In
Settings->Spark Table Put a value of about 30 down on 0kPa and the lowest RPM cell.
When your engine goes to stall it will get a sudden advance which will catch the stall and cause the engine to rev.
Once your VEMS is better calibrated it is possible to remove the Ignition Kick, and use the Ignition based advance which gives a similar function but is better controlled.
