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Thread: EGT probe?

  1. #1

    EGT probe?

    Is an EGT probe a good early warning of high cylinder temps or are they too slow and then too late, to be of any value?

  2. #2
    JT jpt7779's Avatar
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    Jul 2008
    Pittsburg, Texas Lake Bob Sandlin
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    EGT probes (thermocouplers) are just another tool to dial your tune in precisely. Reference the photo attached here is a snapshot of a few seconds on a typical run.

    RPM 8873
    lambda actual .828 desired .796
    kpa 206 (15.3 psi)
    EGT cyl 1 1592, cyl 2 1654, cyl 3 1658
    speed 81.3
    max EGT cyl 1 1630, cyl 2 1698, cyl 3 1732

    EGT is a powerful measurement that can tell you how your tune is performing. Advancing the timing from say 32 to 37 decreases EGT temps, but raises knock level! Increasing fuel per cylinder lowers EGT temps and lowers overall lambda (AFR). With the M130 you can add or decrease fuel per cylinder to balance out the temps across all 3 cylinders, which obviously changes overall lambda.

    My first log with EGT clearly showed cylinder #3 150-200 degrees F hotter than cylinder 1 and 2. As you can see now I have all 3 cylinders within 60 degrees F or so.

    Run too lean say .84 lambda and you see the temps get real high above 1700*F. Not a good thing for a long WOT run!

    If you see one cylinder temp not matching up with the others that is telling you something is wrong. Used effectively, you can hopefully prevent something catastrophic from happening.

    I think having them installed and data logging is another great tool. The M130's capabilities in this area is amazing.

  3. #3
    JT jpt7779's Avatar
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    Pittsburg, Texas Lake Bob Sandlin
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    It is also an inexpensive mod compared to other items.

    $340 for the following:

    single channel amplifier (0-5v) with 1 TC (thermocouple)
    dual channel amplifier with 2 TC
    3 quick disconnect connectors

    Simply drill and tap the stock exhaust manifold or a spacer.

    You obviously need an ECU and software that can calibrate, log and display the data.

  4. #4
    GRF + DashPac:) seadoo02xp's Avatar
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    Apr 2005
    They are also a very good indication of a fouled spark plug. You will see an abnormally cool cylinder because of the unburned fuel cooling the probe off.

    I do have a little wrench to throw into the egt theory after watching lambda per cylinder but I'm not gonna comment on that until I do a little more testing. I found cylinder 1 to actually be lean. But i need to make sure .

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