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Thread: 36lb or stock LS1 injectors? HC is high...

  1. #21
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    it doesn't have a return style. I've got a Holden VZ SS (5.7 LS1 - 2005 model, where the TB is electronically controlled)

    as I know the FPR is in tank along with the walbro unit. The unit I've got is Walbro 255 ltr/hr high pressure version.

  2. #22
    Joe (Moderator) joecar's Avatar
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    You have a 10 psi variation in rail pressure... I'm not familiar with the Holden fuel pump, does the PCM vary the fuel pump voltage to get pressure changes...?

    If not, and if no manifold reference, then the 10 psi pressure difference is a problem since the PCM can't account for the changes in IFR due to that change.

  3. #23
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    I'm planing to put back the stock fuel pump 194ltr/hr - so you think it is necessary to put a fuel pump larger than the stock one? I mean at what whp should I replace it?

    I've been advised to put 255 walbro but looks like that could be my issue pushing to much at idle and cannot be controlled...

  4. #24
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    also to confirm, is this the right kit for my car? http://www.lingenfelter.com/mm5/merc...egory_Code=C75

  5. #25
    Lifetime Member swingtan's Avatar
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    Just a couple of points on all this....

    1. In CL mode, the trims will keep the final AFR around stoich. which yours are doing. Regardless of fuel pressure issues, the final AFR is being controlled by the NB O2's.
    2. Your LTFT's are pulling up to 10% though, which indicates the commanded fueling is way too rich.
    3. RE: the fuel pressures, the VZ will "prime" the fuel system with a 2 second cycle of the fuel pump, then turn off the pump if the engine is not started. Was the image posted when the pump was running or after it had been powered off? You may want to check the pressure with the pump on to see if it's different.
    4. Your idle spark control is working pretty hard. Large changes in the spark timing will impact exhaust mixtures and that includes the HC levels.


    So, some things that may help....

    • Tune the VE table and then, if using one, tune the MAF. Get the idle mixtures as close as possible to "correct" so the trims are not working so hard.
    • All cammed cars want to "lope" to some degree. Attempting to "correct: this llope can cause other issues so I find it better to just let the lope occur and have minimal corrections. If you look at your log, your engine idle speed varies by about +/- 50RPM, so you would have minimal corrections in this range. Outside of this range is where you want corrections to come in. So it may be an idea to ranp the idle spark corrections in slower at the beginning.
    • You may find that altering injection timing will help with emissions. If you make your INJ timing when hot, closer to the values used when cold, then you may find the emissions are a lot better.


    Simon

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