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Custom OS Basics - Obsolete


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Obsolete: Please see the new documentation here

Old post below:

PCMTec Custom OS includes the following features:

  1. TMAP Switch
  2. Table Input change
  3. Table Resize
  4. Dual Map / Flex Fuel 

With more features to come. I will go over what each feature provides and a little insight on how it works to help you iunderstand what can be done.

TMAP Switch:

Many tuners are experiencing issues with the current 4/3.5 bar Bosch TMAP sensors. Basically the problem is that they generally only read down to about 35 Kpa whereas the factory 2.5 bar sensor will read down to about 12Kpa. Usual symptoms are the car will stall coming up to a round about or stop, wont do decel fuel cut properly and have poor high vacuum drive ability. 

To work around this issue PCMTec allows you to use the factory TMAP sensor and at a certain point switch over to using the boost sensor as the MAP reading. You only need to purchase the 4bar Boost sensor and you have full MAP reading from 12Kpa to about 407Kpa allowing for factory drive-ability and full boost control. The way this works is you configure it here:


 This shows that the Editor has configured to use the Boost sensor when the TMAP voltage reading exceeds the configured voltage (auF100000 = 2.15V). So when the TMAP voltage goes over 2.15 V (close to 100Kpa but those mathematically inclined can use the TMAP Slope and Offset to calculate the actual reading).  You can enable/disable this function with the TMAP_Switch drop down.

Table Input change

This provides the ability to do functions like Gear/Speed Based boost control. GUI control of this function will be released with 0.74 expected mid September. 

Table Input Change works by selecting the new axis that you want to use on a table and it automatically updates the code to put this new axis on all the tables the axis is referenced on and then alters the input for all those tables to use the new axis input. As an Example of this is putting gear based boost control on the Turbo tables. Select the new axis as being the Y axis off the Driver Demand Filter (Gear) and apply it to the Desired Boost Y axis. The Editor will automatically update all tables that use the original Boost Y axis (Intake Air temp) and apply the input change to all the tables accesses. The end result looks like:


Table Resize

Table resize allows you to increase the number of breakpoints on a table or the list of tables that use the same axis. It can be used to increase a normal Axis table as well as you might have seen from the previous screen shot where the gear axis for the driver demand filter only goes to gear 5 normally so we used this function to extend it range to include 6th Gear. Most commonly used to increase resolution on spark and speed density tables.  Here is an example of increased resolution used on the Borderline Knock table:


A future release will allow for changing a 1D table to 2D if the demand exists. Possible use of this is to extend the turbo TPS multiplier in early BFs to a 2D like table in the later. calibrations (77DA for example).

Dual Map / Flex Fuel 

Flex Fuel is a subset function of Dual Maps. The basic concept is you select a set of tables you want to do Dual Map on (you can resize them first if you wish) and you select a blend table to use on these tables and you click Enable Dual Map. This will generate the code to allow the tables to be mirrored and allow switching based on the blend table you selected. There are 3 default blend tables provided. One each for Boost, Fuel and Spark. Basically you select the set of tables to use, say the Spark, blend table on and the Editor will automatically generate the code and tables to provide this function. Repeat for Boost and Fuel.

Next you configure the inputs that drive if this is a switch like function or a Flex like function. The switch or Flex function is controlled by this table:


This example shows a configured Flex configuration. Given a set of voltage inputs on the rear O2 sensor then the desired ratio  Alcohol is calculated based on a fictitious sensor.

To configure it for a switch where the voltage with the switch off is < 0.5 Volts you would have this configuration:



These are the basic concepts for understanding what is happening with Custom OSes. In the next write up we will describe in detail configuring these Dual Map and Flex tables.

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FYI if you enable the TMAP switch over logic and you are seeing a "Trans Trunc" torque reduction despite the vehicle being a manual and torque reductions turned off the following will resolve it.

In the use case we had the user was pegging the standard tmap at 23psi with a 4 bar boost sensor. They had enabled the tmap switchover logic however they were seeing the trans truc feather the throttle at high boost.

The solution is to set the TMAP max volts ( auF0044 ) to 6v. This stops the FMEM limiting action kicking in when the TMAP sensor saturates. This is safe to do as with the tmap switchover logic the boost sensor output replaces that of the TMAP.

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  • Roland@pcmtec changed the title to Custom OS Basics - Obsolete

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