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Thread: Sigma Engine - Questions About MAP Sensors

  1. #11
    Join Date
    Jan 2006
    Location
    Seattle-ish
    Posts
    1,450

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    I'm not sure how the Sigma is set up in the 310. An ECU can be setup to use a MAP sensor as you indicate, and what I referenced earlier with air density within the intake. However, if you are running a Throttle Position Sensor, which many people do, you can then use a MAP sensor as a barometric sensor to identify the ambient air density -- i.e. altitude. The ECU then compares this reading to sea level and adjusts the fueling table based on a look up table. This is helpful if you tour and go through mountain passes -- or if you live in the mountains and head down to the seashore. I B Sevener is using the MAP sensor (or at least the pictured MAP sensor) in that capacity. If it were determining the air density within the intake to establish A/F based on amount of air passing through the throttle, then the vacuum port would need to be attached to the intake.

    -John
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

  2. #12
    Join Date
    Apr 2019
    Location
    Little Rock, Arkansas
    Posts
    25

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    Thanks

  3. #13
    Join Date
    Jan 2006
    Location
    Seattle-ish
    Posts
    1,450

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    Just did a little digging and it appears the 310 uses the stock Ford intake with a MAF sensor, so it looks like the MAP is definitely intended as a barometric sensor.

    -John
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

  4. #14
    Join Date
    Mar 2017
    Location
    Western New York, USA
    Posts
    12

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    I was not at the shop today so I asked one of the "helpers" to shoot pictures. He got pictures but not the MAP. I'll get more Saturday. If you want any special pictures email me rick@timemachinesauto.com as my files are too large to post without reworking them.

  5. #15
    Join Date
    Apr 2019
    Location
    Little Rock, Arkansas
    Posts
    25

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    This morning I heard from Josh at Rocky Mountain Caterham re: the MAP sensor.

    " Hi Dave,

    Just got the official word back from Caterham on the Sigma MAP sensor:


    "The map sensor on the current 310 is designed to be left open to atmospheric pressure. This means that the corresponding opening on the inlet manifold should therefore be blanked off with a rubber bung. Regarding the ECU calibration, you are correct in your thinking, as the sigma ECU mapping is TPS based."


    So, confirmed. Looks like hooking up the vacuum line basically just makes for a more complicated bung!


    Josh "

    There you have it, the definitive word.

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