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Flex fuel configuration guide

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Firstly read the file from your PCM. This will get the current OS and maps, plus VIN and model details.

Use the the Read/Write vehicle icon to open the Flash Toolbox



Save afterwards say as HACCKD5_readPCM.tec



If the vehicle is not licenced, then use Licence Vehicle to licence the file. Then start the Custom OS wizard


Custom OS Wizard


This starts the wizard. If you have a previous custom OS in the vehicle you will need to press previous 3x to return to the main screen and start over. 


If you have a Mk1 FG you will need to upgrade to the HAEE Operating System. Please see this guide for more details 


Click Next

Dual Tune Flex Sensor

For a Dual Tune using the Flex Sensor, select 'Via Flex Sensor'


Select the flex kit you are using


This can be configured later

If you are using a Pirotta plug and play kit select the kit you have purchased (Zeitronix or Innovate), you can modify this calibration later by editing the Pirotta Performance Flex kit table curve. This can be accessed via the navigator tree after the Custom OS has been created


If you are using a custom flex fuel converter kit use the Voltage Conversion table for sensor/switch table. This can also be used with an on/off switch to toggle between E85 and 98. 


You now have the option to increase the table sizes inside Custom OS, typically this would be left stock. For this example we will use stock spark and speed density table sizes 


Next you can add extra tables to the base tables for ethanol flex blending


For example if we adding auF2433 to adjust the MBT spark by coolant temperature, we can tick and then add to Blend Ramp for Spark by pressing the -> button next to the Spark Blend Ramp. If you make a mistake and need to remove a table you can press the <- arrow to remove it. You can also use Ctrl + A or Shift + Click to select then press the space bar to select. 


For E85 cold start it is recommended to add the following tables to the fuel blend ramp. 


Any scalars selected like LTFT will be used later by the Flex Fuel Multi Tune Ethanol switch point. It doesn't matter which blend category you add them to as they will not be interpolated. These scalars will instead be selected when the ethanol content is above the value in the "Flex Fuel Multi Tune Ethanol switch point" scalar. By default this is set to E42.5 


Once you have added any extra tables on top of the default tables, press 'Check licence and Proceed'. Full credit pricing is detailed on the start page of the custom OS wizard. When you have finished creating the custom OS you can add up the total credits spent via help -> view licenses and summing the credits for the vehicles VIN. 


Then provide a new file name to save as. For example: HACCKD5_readPCM_Stock_CustomOS.tec

For this example we will use default options (using the Pirotta Performance Flex fuel kit)


Final confirmation


After the configuration window is finished, you can later enable various custom operating system features in the Custom Operating System configuration list. You can also edit these by revisiting the custom operating system wizard which you can run as many times as you'd like. 


Each section (Fuel, Spark, Boost etc) has a blend ramp between 0% Ethanol (98 octane) and 85% Ethanol (E85) 
An example of the below: 

Note: You need to experimentally determine these blend ramps

These ramps must be determined on a dyno with knock monitoring equipment. It is not safe to assume these values. Typically you would not want to start adding timing until you see at least E20, you will also find some engines can take full timing by ~E70.



To see the tables that the blend ramp affects, scroll further down in the view:


The actual tables fuel fuel, spark, VCT, boost etc you can modify are located under Custom OS Table for Flex Fuel and Multi Tune


Next start your tune 98 octane, and work with the first set of tables listed under "Tune 1 Base Tune or 98", afterwards drain the tank, fill with E85 and work with the second set of tables under "Tune 1 Base Tune for E85". If you have enabled a multi tune, be sure that you have selected tune 1 via the cruise control buttons until the base tune is completed. 


Other tables

Ethanol Conversion to Stoich 

Used for closed loop operation to adjust the stoichometric ratio depending on the level of E85. This would not typically be adjusted, the only time it would be recommended to use non standard values is when you are utilising an existing E85 tune that used a different stoichiometric value. 


Scalars switch point

This scalar specifies the ethanol percentage when switching over from 98 octane operation to E85 operation for scalars 
These will be switched between 98 and E85 based on the below configurable switch point: 


These will be switched between 98 and E85 based on the below configurable switch point:



Multi Tune with Flex

A multi tune with flex fuel allows you to build two sets of 4 tunes. One for 98 and one for E85, eg a typical setup would be low boost/high boost/boost by gear. Then the flex fuel sensor will interpolate between the two sets of 4 tunes depending on ethanol content. 
This is setup similar to the above flex fuel setup, with the following changes: 

In the wizard, select Multi Tune:


Then select Flex fuel sensor from the drop down


Then the kits lookup table you are using


Continue selecting if you want expanded maps (or not)

Then select the tables you wish to use for Flex and proceed with adding to Custom OS


After you have finished, you can view which multi tune maps are used for each blending table by clicking on the blended ramp parameter and then viewing the tables they are blended from and to:


Logging Ethanol

Add the 'PM' (Normalised value of percentage of alcohol) to the logging list to view ethanol content in the logs


if the PM (Ethanol Content) does not match the ethanol content on the gauge or tank you will need to recalibrate the analog input. To do this fill the tank in 10 steps from E0 to E85 making note of the real ethanol content and the sensor voltage. Once complete you can update the voltage table (either the pirotta or custom voltage input depending on which option was selected earlier). 
Depending on which vehicle you can log the analog input via the following items. 

Ego Voltage B1S2 (bank 1 sensor 2) : EGO RAW B1D

ID: MID80545  (VEGO[0][1])

Ego Voltage B2S2 (bank 2 sensor 2) EGO RAW B2D 

ID: MID80547 (VEGO[1][1])

Note: if you used the opposite rear o2 sensor, then B1S2 (EGO RAW B1D)

FLEX ALC% to monitor Flex percentage (can view as absolute or % values)

ID: MID69386

BA I6 
IAP_VOLTS (boost sensor voltage) 






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