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Thread: Does Short Pulse width Adder enrich a lean engine?

  1. #1
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    Does Short Pulse width Adder enrich a lean engine?

    Hi All,

    Just trying to tune a supercharged L98 Holden Commodore with an E38 PCM (manual transmission) at the moment. The engine no longer has a MAF sensor as it has been replaced by a MAP sensor so there is no g/s airflow input into the ECM.
    It runs fine on boost but seems to run very lean (17-19:1) between 1000 and 2000rpm and 70-95Kpa MAP (Not on boost) such as when you're trying to take off from a parked position when the engine is at operating temperature. I have tried both methods of increasing the EQ ratio in both the General (gasoline) table and I have also lowered the TPS (Throttle Position Sensor) percentage at which the engine will go in to WOT mode and then uses the power enrichment table (or boost table whichever is richer). The engine goes into open loop with minimal throttle (foot) input now but doesn't seem to use the power enrichment table and still runs lean. Both of these attempts appear to have failed to enrich the fuel mixture. Is there anything that can potentially be inhibiting these changes from taking effect?
    Alternatively, is the short pulse width adder on the fuel injectors a potential solution for this? The current threshold for the minimum pulse width is 4.0ms and there is no correction above 0.9ms. The curent correction is 0.11ms @ 0.9ms. If I added a correction of 0.3ms to the injection pulse widths from 1.2 to 1.6ms and 0.45ms to 1.6 to 2.2ms (where the trouble seems to be according to hp scanner logs), would that increase the amount of fuel going into the engine and stop the car from jerking and backfiring when taking off because it is too lean on low rpms at takeoff?

    The engine idles at around 700rpm with an injection pulse width ranging from 1.0ms to 1.4ms in closed loop though it does seem to run lean even on closed loop with an AFR gauge reading 14.5 to 16:1 ratios on idle as the ECM seems to struggle to maintain 14.7:1 on idle. Short term Fuel trim on idle also ranges from -3% to +12% so that would indicate the engine has a tendency to run lean currently even on idle?

    Any help would be greatly appreciated.

    Thanks in advance guys

  2. #2
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    short pulse adder just helps the injector pulse the amount it should for the shorter pulses, its not a adjustment for fueling only a correction for each injectors characteristics, have u adjusted VE or VVE for fueling preferably using wideband ? there is still a g/s just log dynamic airflow, changing injectors and inputting the data still needs the fueling tables to be adjusted to suit

  3. #3
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    Hi, Thanks for the reply,

    what particular fuelling table are you referring to in hptuners? Can you point me to the particular table please?

    Ones we have looked at are Fuel >> Open Loop/Base >> Gas (Gear) - which determines equivalence ratio when in open loop mode in gear and using gasoline fuel (do these values need to be above or below 1 to enrich the mixture?

    Second table is Fuel >> Power Enrich >> EQratio (gas) - which is an air/fuel ratio multiplier table where values greater than one are rich and values less than one are lean

    Third table is Fuel >> Power Enrich >> EQ ratio vs. MAP which is also an air/fuel multiplier. Engine absolutely pulls when on boost so that table is definitely fine.

    Fourth table is Fuel >> Open Loop/Base >> EQ ratio Min - which determines the minimum equivalence ratio when in open loop mode. (Values greater than 1 are rich I presume).

    I'm assuming tables two and three are multiplying table 4?

    I have added the dynamic airflow into the scanner tool so it will datalog that next time I run it (hopefully tomorrow). How does it calculate this value when in open loop mode with no MAF sensor? Does it use predetermined values or does it calculate it off O2 feedback?

    Cheers for the reply and let us know if you need any more screenshots.

  4. #4
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    all those tables are just multipliers of the VE table for power enrichment , the main fueling is done on the VE table (under airflow, general tab) which sounds like u are using as u mention boost enrich table, VE needs to be populated using a wideband against its error to commanded especially for boost or things could go bad pretty quick, dynamic airflow is calculated from speed density airflow, those 4 tables arnt fueling tables they are just OL eqratio and a minimum, second and third need to be setup for a boosted engine, forth keep as stock, the first keep as stock its just an adjustment of eqratio for OL startups on that table below 1 is leaner and above is richer, dont use those tables for fueling adjustments they control the commanded and the VE table has to be dialed in to equal the commanded, if u havnt got a wideband then u need to get one and see if u can find some videos about the fueling/timing adjustments for boosted, id take it easy till u know its right

  5. #5
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    Hi, ok no worries. We have only changed the boost enrichment multiplier table at the moment - as mentioned the car seems to run fine on boost. We also changed ramp in and out ratio to 2.0

    VE table.png

    Ok, so would you recommend changing the actual values in the table (Normal IMRC open and closed) or would it be easier to populate the TPS multiplier table which multiplies the VE in relation to RPM and TPS?

  6. #6
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    I also changed the Fuel >> Power Enrich >> Throttle >> Hot table to get it to go into open loop with less TPS than what was required (38 and 33 at 1000 and 1500 rpm lowered to 25 each).

  7. #7
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    the VE table is the main fueling (airflow) table for everything all alse is based off that, can u post ur tune up

  8. #8
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    Hi, I haven't change that tune yet so it's still stock E38 LS2 engine. What is the difference between when the intake manifold runner is opened vs the table for when the intake runner is closed? That doesn't have anything to do with open or closed loop does it? so which table do I use?
    I've attached a picture of the stock VE table when the intake manifold runner is open.

    stock VE table.png

    Thanks again for your assistance.

  9. #9
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    just change both table so they are the same if u make any changes, its to do with manifolds with runner adjustments best to just keep both the same

  10. #10
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    Awesome, thank you very much, worked a treat this afternoon. Car is running mint (mostly) across the range following a few changes.

    The car does seem to be turning off when the coolant temperature reaches 100 degrees celcius though. Do you know where this feature is in hptuners and how do I increase to 105 (if it is a text box) or disable it if it is a enabled system?

  11. #11
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    not sure there isnt anything i can thing of that would cause that on purpose would have to see tune to see if anything stands out

  12. #12
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    Hi, so latest update, tuning in VE table has worked very well, only issue is it only goes up to a maximum of 175kpa MAP in both the VE table and Boost EQ ratio multiplier. Is there a way to increase this table to say 200kpa in the ECM? It is running that much boost according to scanner tool and when it goes over 175kpa, it doesn't run too well obviously because it doesn't have a lot of information to work with. Or is this a limitation with the ECM?

    cheers

  13. #13
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    ve should go to 255kpa if your map sensor does, just change the column values to suit ur peak, click on the "manifold absolute pressure" at the top if the table

  14. #14
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    Hi, it lets me add to these values i.e. I can add 5 to 175kpa and make it 180 but how do I add a new column for 180,185,190,195,200kpa MAP pressures? If I can't do that, do I have to utilise the existing columns and make it so they go up in values of 10 i.e. 140,150,160,170,180,190,200 kpa?
    map range.jpg7

  15. #15
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    yes u can't add more columns u have to adjust the ones that are there so if u change any u will have to keep the right cell values in them and populate the ones u need to

  16. #16
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    ok cool, I will change those column values then. So, where has it been deriving information from to run at 200kpa MAP currently?
    Is it using values from lower MAP cells to continue on a similar value or is it simply using no information at all? It still seems to run just not that well.

  17. #17
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    Is the VE initial correction factor the table that is used for start up? The engine seems to get a large amount of fuel on start up and needs to be throttled up to keep the engine from stalling? I have enriched the VE table across the range. Do I need to reduce that initial correction factor multiplier table value as well? Also, it still seems to be cutting fuel when the coolant temperature reaches 100 degrees celcius? Is there a safe guard hidden in the tune for this?

  18. #18
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    Also, where is the table to change timing advance in relation to MAP and RPM? Just having some timing issues with too much advance on boost around 200kpa - seem to be around 25 degree timing - should be 15. Also, the knock retard table in the scan tool doesn't seem to be populated with anything. Is it possible that Knock retard has been turned off?

  19. #19
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    Just did another run with the vehicle and captured it on the scanner tool. It has more timing then the Spark table says it should have (using the base high octane table minus any correction tables e.g.coolant temperature).high boost timing.png

    It does have a stock spark table and correction table. Camshafts have been changed though. They are a bit more aggressive than stock but not over the top.

  20. #20
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    timing is only to cyl airmass, i wouldnt be doing anything to that without a wideband, your iats are too high, spark is too high look at all the multiplier tables, cant see anything without a tune file