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  1. 01-20-2023, 07:34 AM #1
    BartdeBruijn
    BartdeBruijn is offline
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    Aug 2012
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    Question on MFI tuning on own build MFI test bench

    Hi!
    After finishing the full restoration of my ‘69 911T she is performing beautifuly ! Now a few years later I decided to build a more powerful engine and keep the matching number engine as it is.
    Slowly I am collecting parts for this new engine. It should run with this fantastic MFI. I have restored the whole MFI setup. Bored throttle bodies removing the wear and added one size bigger valves. After that I restored the whole MFI pump, great piece of mechanical engineering.
    With a lot of information from the forum
    Jonny042 - Project heavy metal
    Jeffc280sl - Open heart surgery
    356RS [Mark Jung]
    And many others!
    I managed to restore the pump and build my calibration setup. Bringing it to Eisenbrand Renn & Motorsport is easy but only half the fun, right!?

    So that as a short introduction, I ran into some issues that I do not really know how to resolve.
    1)
    In picture one [Bosch datasheet], rack movement at pre adjustment, I managed to get the following vallues for the rack.
    Angle rpm rack
    Max - 2000 - 7.02 (should be 7.00)
    0 - 400 - 4.46 (should be 4.45)
    8.3 - 800 - 4.25 (should be 4.25)
    29.5 - 2000 - 4.73 (should be 4.75)

    Now when I move forward to the next set of tests the Full load vallues,
    Angle rpm rack
    Max - 700 - 7.00 (should be 6.25)
    Max - 900 - 6.83 (should be 6.75)
    Max - 2000 - 7.01 (should be 7.00)
    Max - 3000 - - - - (should be 7.3)

    The full load vallues should be corrected via the rack head screw[as per Bosch data sheet], right?
    Question 1: If so, I will alter also the value(s) obtained in the first table as the first line adjustment is through the rack head screw and that is the one I have to use to correct the second table. So feels like chasing my tail!

    For now I am using a diesel calibration fluid that is odorless and not flammable (like petrol or white spirit) Only thing is that diesel (like) fluids have a slight higher viscosity.
    Question 2: Does anyone has an idea on the effect of this difference on the quantities I am measuring/adjusting now?

    Thanks a lot,
    Bart
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    Last edited by BartdeBruijn; 01-21-2023 at 01:14 AM.
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