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HOWTO: Speed Density via MAP Sensor (Traditional VE map)


Roland@pcmtec
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As part of our custom operating system we have several features available which can be selected as part of the 5 credit "Standard Custom OS".

One of these features is the "Speed Density via Map Sensor" which replaces the intake camshaft Y-Axis on the speed density tables with map pressure.

For cars with locked camshafts this converts the speed density system to a traditional style VE table which allows for non linear airflow characteristics which are typical with large camshafts.

For the layman this means you can easily fudge the fueling at low map pressures where you may be experiencing oscillation and reversion in the intake.

Please note, this is ONLY possible with locked camshafts. If you are running VCT and you use this system and the camshaft goes into a full advance/full retard position due to a failure your fueling will be roughly 10-15% rich or lean as the VE has changed and the speed density system can no longer account for it. If you are using VCT stoppers to limit the range of motion this system may still work acceptably. This system also works for the 5.4 V8s with no VCT

To enable this feature you require the workshop edition and a 5 credit "Standard Custom OS".

First open the custom operating system wizard.

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Press Next

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Now you can enable any other Custom OS features you would like which are discussed in other guides.

Press "Check License and Proceed" This will charge you 5 credits total for the vehicle (2 extra on top of the existing 3 credits).

On the next page select "Speed Density via MAP Sensor" and press Next

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You will now see a summary where you can press "Finish".

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Now all of your speed density tables will have the intake camshaft angle replaced with map pressure. In the example below we have increased the resolution of the table as well which is useful for large camshaft engines spinning to 7250+ rpm.

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To tune this map we recommend datalogging the intake camshaft position (even though the camshafts are locked). In this example the intake camshaft was found to be measuring ~10 degrees. As the car was already running fairly acceptably at WOT it is recommended to copy the row from the old tune at 10 degrees to every row.

As can be seen in the original file we have selected the row. Right clicked "copy" or Ctrl + C

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Then we opened the new file and pasted this row into the entire table. This must be done for the map slope tables and the map intercept at zero tables which can be seen below. Ensure you manually enter the new rpm columns if you have also changed the resolution.

Map Slope

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Map Intercept

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Once you have done this to both the Slope of MAP and Map Intercept at Zero tables perform a WOT dyno run and you should observe identical load in the datalogger and identical fueling on your AFR plot as before the change. Once you are confident that the engine is running exactly the same as before you can start "fudging" the low kPa points of the tune where the large camshafts are causing reversion/oscillation and erratic fueling to achieve better drivability.

Normally you must tune both the map intercept and the map slope tables. With this patch you can now tune just the map slope table which makes the process much easier.

Happy datalogging!

Update:

For more information on how the factory speed density system works (required for VCT) please read this guide:

 

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