EGT gauge.

Discussion in 'Engine' started by Dieselman, Nov 26, 2008.

  1. Dieselman

    Dieselman Banned

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    I've been meaning to fit an EGT gauge for a while just to see what the temperatures are in standard trim.

    Also as my car doesn't have a fuel computer I thought it would be good to use as an indication of how much load the engine was under so would indicate how much fuel is being used, much like a vacuum gauge does on a petrol engine.

    First the probe needs to be installed poking into the exhaust manifold so...
    Manifold and turbo need to come off.
    Note the nice swept shape of the manifold, this gives good gas flow.

    [​IMG]

    Part the turbo and manifold.
    Note the turbo intake aperture is larger than the manifold exit aperture. This restricts and disturbs the airflow into the turbo.

    [​IMG]

    Having decided on a suitable place drill and tap the manifold and fit the thermocouple ferrule.
    This will project through slightly so grind the excess back.
    Whilst at it I decided to create a bell mouth for the gasses leaving the manifold for better gas flow into the turbo.

    [​IMG]


    Install the thermocouple about 1/3rd-1/2 way into the gas stream.

    [​IMG]

    Thread the cable through to the passenger cabin and connect to the gauge.

    I've only been able to do this temporarily for now as the cable is too short, so I've ordered some.

    [​IMG]

    Having taken it for a drive I can say it works brilliantly and is sensitive enough to detect such engine loads as switching the lights or vent fan on...and especially putting the gearbox in gear or turning on the air-con..

    Idling sees temps of about 108c tonight, but 140c earlier when fully warm, and maxxed out up a steep hill gives ~715c and a 777c momentary peak...

    No room for adding extra fuel there..
     
  2. tuikku

    tuikku Hardcore MB Enthusiast

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    What kind of weather you have there.
    Here are "full" winter already... and snowing.
    10-20cm more new snow this night.



    In warm day, it is very easy to get there 100c more.
    Throttle position is very important.
    More power -> more heat.
     
    Last edited: Nov 27, 2008
  3. maddog

    maddog Hardcore MB Enthusiast

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    Most people i know fit them in the downpipe after the turbo this may be easier if you dont have a pre cat there
     
  4. Uberwagon

    Uberwagon Hardcore MB Enthusiast

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    Just before the turbo will be the highest temp so this is where the probe should be fitted.

    Dave!
     
  5. BTB 500

    BTB 500 MB Club Veteran

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    That's a really useful mod.

    I like the gas flowing work too, probably offsets the very slight additional restriction from the probe!
     
  6. maddog

    maddog Hardcore MB Enthusiast

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    Actually the highest temp would be close to the exhaust port , this is where race cars have their egt sensors

    Stuck out in the flow right before the turbo is driven is not where i would put any obstruction , after the energy from the gasses have been used seems a much more suitable place to put the sensor especially if the whole point is to determine how much fuel is being used not exactly running things on the ragged edge on a standard engine
     
  7. Uberwagon

    Uberwagon Hardcore MB Enthusiast

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    That is not because they are the highest temperatures, but because they want to know how well each cylinder is working.

    Dave!
     
  8. tuikku

    tuikku Hardcore MB Enthusiast

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    Yes !

    I have been measured that way also.
    That is exactly how happens.
    "Working stroke" is only every second stroke.
    So, sensor get cooler by waiting the second working stroke.
    And, ... there are differences between cylinders.
     
  9. OP
    OP
    Dieselman

    Dieselman Banned

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    The downstream temp is inaccurate and will be at least 200c lower than upstream so isn't a good guide.

    If I wanted to monitor each cylinder for power balance I would put a probe in each manifold tube but that was overkill for this application.

    Although it doesn't appear so, the probe is set back in the manifold exit and is actually at the widest point of the tube so shouldn't create much restriction to flow.

    As far as running on the ragged edge, the max temp was 770c which is plenty high enough. I wouldn't add any more fuel without increasing air flow first.
    A better intercooler, higher flow turbo, freeflow exhaust, etc will reduce EGT temps, more fuel will increase them.
     
    Last edited: Nov 27, 2008
  10. OP
    OP
    Dieselman

    Dieselman Banned

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    It was about 5c yesterday, today is 10c....:bannana:

    It was your posts that prompted me to get on and install a gauge. Thanks..
     
    Last edited: Nov 27, 2008
  11. lynall

    lynall Hardcore MB Enthusiast

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    If its a k series thermocouple loads on e -bay so you can measure intercooler before and after std and modified, coolant temp in fact anything some of the figures were interesting especially the supposed super duper intercooler:eek:
    Even measuring the air temp in the air box and watching it go up 30 deg as a/con switched on as all that lovely red hot air went everywhere.



    Lynall
     
  12. tuikku

    tuikku Hardcore MB Enthusiast

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    I have measured also intake temperatures, and -pressures, and vacuum before charger.
    Thats why I have in my car as big intercooler as it is possible to fit.

    [​IMG]


    Moore boost gives lower exhaust temps, but is bad for fuel economy.
    And if you donĀ“t have enough big cooler, intake temps peaks.
    MB,s stock coolers are poor.
    Bigger charger gives more air at same boost pressure, and is good for economy (and power :rolleyes:).
     
  13. paul_f

    paul_f Hardcore MB Enthusiast

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    What intercooler did you fit?
     
  14. tuikku

    tuikku Hardcore MB Enthusiast

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    It is custom made.
     
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