PI : DI Ratio Discussion

[thambu19]

Any idea why you didnt go 100% DI at low speed WOT? This is where the DI really comes into play for knock relief

[thambu19]

If you are running boost and if you have not adjusted the Cam timings to account for boost yet then it might be better to run full DI in those areas. If you still have the huge valve overlap of the NA tune in the scavenging region then with PFI you will be shortcircuiting a lot of fuel into exhaust and engine might actually run lean. If you have already changed the timings to cut down overlap then ignore this

[KoolBRZ]

Originally Posted by thambu19

Any idea why you didnt go 100% DI at low speed WOT? This is where the DI really comes into play for knock relief

The wrx's only have DI and they can't run as much timing as we can because they don't have PI for knock prevention.

[thambu19]

Originally Posted by KoolBRZ

The wrx's only have DI and they can't run as much timing as we can because they don't have PI for knock prevention.

WRX is a boosted engine running at higher torque outputs so cannot be compared to our engine. Boosted engines also use a lot more turbulence and hence do not need as much spark advance to get the same combustion. In short we cannot compare the two.

[Kodename47]

Originally Posted by KoolBRZ

The wrx's only have DI and they can't run as much timing as we can because they don't have PI for knock prevention.

DI gives better knock relief, not PI.

[KoolBRZ]

Originally Posted by thambu19

Any idea why you didnt go 100% DI at low speed WOT? This is where the DI really comes into play for knock relief

I'll try it and compare these two versions of the PI tables. As you can see, from 1.0 Load on up and 2200 rpms and up till 5200 it is 100% DI. I'll try the two tunes with this as the only change and let you know how it works. Having an AT is great for engine tuning because every change has a much more dramatic effect, but when it isn't running right it sucks the joy right out of driving.

[KoolBRZ]

The zero PI at WOT tune, (28) runs better at WOT. Definitely. So I need to use full DI sometimes for performance reasons. Now to find out when and where.

[KoolBRZ]

Hey @thambu19 and @Kodename47. Tell me what you think about the next table I'm trying. Old vs new. A lot more DI and less PI. I've changed the thresholds back to the stock settings.

[thambu19]

Originally Posted by ztan

Def for above A01G:

    <table name="PI_Ratio_Thresholds" storageaddress="10C70C" />
    <table name="PI_Ratio_RPM_Threshold" storageaddress="10C71C" />
    <table name="PI_Ratio_Load_Threshold" storageaddress="10C720" />
    
    <table type="2D" name="PI_Ratio_Thresholds" category="Fueling - Injector Ratio" storagetype="float" endian="little" sizey="2" userlevel="4">
      <scaling units="PI Ratio %" expression="x*100" to_byte="x/100" format="0.0" fineincrement="5" coarseincrement="10" />
      <table type="Static Y Axis" name="" sizey="2">
              <data>PI Ratio 0% under</data>
              <data>PI Ratio 100% above</data>
       </table>
      <description>If PI Ratio RPM and Load Thresholds are not exceeded, PI Ratio is set to 0% if this value is not exceeded</description>
    </table>
    <table type="2D" name="PI_Ratio_RPM_Threshold" category="Fueling - Injector Ratio" storagetype="float" endian="little" sizey="1" userlevel="4">
      <scaling units="Engine Speed RPM" expression="x" to_byte="x" format="#" fineincrement="250" coarseincrement="1000" />
      <table type="Static Y Axis" name="" sizey="1">
              <data>PI Ratio thresholds not applied above</data>
       </table>
      <description>If this RPM threshold is exceeded, PI Ratio full on and full off thresholds are not applied</description>
    </table>
    <table type="2D" name="PI_Ratio_Load_Threshold" category="Fueling - Injector Ratio" storagetype="float" endian="little" sizey="1" userlevel="4">
      <scaling units="Load g/rev" expression="x" to_byte="x" format="0.0" fineincrement=".05" coarseincrement=".2" />
      <table type="Static Y Axis" name="" sizey="1">
              <data>PI Ratio thresholds not applied above</data>
       </table>
      <description>If this Load threshold is exceeded, PI Ratio full on and full off thresholds are not applied</description>
    </table>

I am a noob when it comes to xmls. So to enable this definition what am I supposed to do? Take the regular RR def file and copy this code and paste it into the RR code? Anywhere in the code will do? Do I have to be mindful of what ECU id I have?

[ztan]

Originally Posted by thambu19

I am a noob when it comes to xmls. So to enable this definition what am I supposed to do? Take the regular RR def file and copy this code and paste it into the RR code? Anywhere in the code will do? Do I have to be mindful of what ECU id I have?

Yes, copy and paste. Most of us keep addresses pointers all together and the table defs lower down in the text file.

ECU Calibration ID is critical - if you don't have the right one in, you could be altering calibration data or code happily at random before bricking your ECU. There is also an issue with OFT calibrations all being based on the latest they are using despite naming them with a stock ID calibration. Before you alter anything with your def file, click on a lot of tables and make sure they are all sane.

Kodename47 has pulled addresses for some different ECU calibration IDs. If they don't match yours, let us know which ECU ID you need.

[thambu19]

Thanks mate!

[KoolBRZ]

I just got back from the beach. Tried 2 tunes on the way out, weak power, 28 mpg. made a new tune while I was there, good power, good AT shifting in "D" mode, mpg went from 28 to 31 as we went down the coast from 20 mph to 60 mph. Power was just about a perfect match with the transmission. Refilled in Salem and drove 75 mph north, which usually gets about 30 mpg, this time got 33. PI was off at 75 mph, (2600 rpms) with loads from .5 to .7, but back on with loads up to .8 or .9. See pic below, 36 is the tune I ran today, 37 is the one I'm trying out tomorrow. Will it get better mpg with PI on at 75 mph? Or does it get better mpg with PI off at cruising speed?

[thambu19]

Sorry not sure what to say. You could be getting more mileage because pi burns faster than di ' same effect advancing spark until knock

Sent from my HTC One_M8 using Tapatalk

[thambu19]

Originally Posted by KoolBRZ

I just got back from the beach. Tried 2 tunes on the way out, weak power, 28 mpg. made a new tune while I was there, good power, good AT shifting in "D" mode, mpg went from 28 to 31 as we went down the coast from 20 mph to 60 mph. Power was just about a perfect match with the transmission. Refilled in Salem and drove 75 mph north, which usually gets about 30 mpg, this time got 33. PI was off at 75 mph, (2600 rpms) with loads from .5 to .7, but back on with loads up to .8 or .9. See pic below, 36 is the tune I ran today, 37 is the one I'm trying out tomorrow. Will it get better mpg with PI on at 75 mph? Or does it get better mpg with PI off at cruising speed?

When you get a chance can you try something like this? At WOT I have gone 100% DI. This means you need to a degree or so more spark there to use the full potential. If you do not then it will feel sluggish compared to stock calibration.