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unanswerable question?: phase sensor

Discussion in '348/355' started by pnicholasen, Feb 2, 2013.

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  1. pnicholasen

    pnicholasen Formula 3

    Jan 14, 2011
    1,364
    South of Philly
    Full Name:
    Paul Nicholasen
    #1 pnicholasen, Feb 2, 2013
    Anybody know what the phase sensor does? It's the thing on the rear of the right side intake cam that looks kind of like a weird distributor. There are already 2 crank angle sensors. I presume there are 2 because there's a "heir and a spare". That's already measuring the RPM's and angle of the crank, so what more would the phase sensor have to add? It's relationship to the crank is fixed by the timing belt, so it's not going to vary. I realize it turns 1/2 the speed of the crankshaft, but it's still fixed in it's relationship with the crank. Theories?
     
  2. 97 Spider

    97 Spider Formula 3

    Dec 15, 2012
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    Brian
    #2 97 Spider, Feb 2, 2013
    I'm assuming we are talking about a 355 here. From my understanding the engine has two crank sensors because it is ran like two separate 4 cylinder engines with two ECUs. One sensor for each computer.

    The car uses the cam phase sensor to know when the engine is coming to top dead center on the #1 cylinder and then can better time the ignition and fuel injection. As you said the crank is moving twice as fast, one compression stroke and one exhaust stroke. Without the phase sensor the ECU does not know which is which. The car will run without it, just not as good.
     
  3. Miltonian

    Miltonian F1 Veteran

    Dec 11, 2002
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    Jeff B.
    #3 Miltonian, Feb 2, 2013
    If you are dealing with the phase sensor in your 348 Spider, it is described in detail on pages C5 and C6 of the workshop manual.
     
  4. 355rockit

    355rockit Formula Junior

    Dec 1, 2010
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    San Marcos, CA
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    Vas
    #4 355rockit, Feb 2, 2013
    Last edited by a moderator: Sep 7, 2017
    The 1995 F355 only has one phase sensor located on the right hand side of rhe engine toward the rear of the engine next to the intake. I replaced mine last year due to an error code. I was confused initially because I thought there was supposed to be 2.
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  5. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    9,741
    #5 Mitch Alsup, Feb 2, 2013
    Yes, the crank sensor reads when the cylinder is at TDC. But the ignition system needs to know whether this is the TDC on the exhaust stroke or TDC on the compression stroke. That is what the cam sensor supplies.

    As far as I know the cam sensor is only used in the first couple of rotation of the engine at startup. After that the ignition an remember which rotation the crank is on.
     
  6. pnicholasen

    pnicholasen Formula 3

    Jan 14, 2011
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    Paul Nicholasen
    #6 pnicholasen, Feb 3, 2013
    Thanks for the replies. All that makes sense. That logic would then indicate all cars with electronic engine control have a phase sensor....do they? I don't recall running into one before.
     
  7. bosshog8

    bosshog8 Formula Junior

    Mar 13, 2011
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    Pinelands NJ
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    Demetrius
    #7 bosshog8, Feb 3, 2013
    I'm going with only a distributer-less engine needs or uses a phase sensor.
     
  8. 97 Spider

    97 Spider Formula 3

    Dec 15, 2012
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    #8 97 Spider, Feb 3, 2013
    Yes and no... Any engine with sequential port fuel injection will need it to know the compression stroke timing. You could have an engine with sequential injection and a distributor, but I can't think of one like that off hand.

    Batch fire injection doesn't need one.
     

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