Cvlinder Head Temperature gauge

Discussion in 'Mech Tech' started by redgaz, Nov 28, 2019.

  1. So did I
    I’m a true believer in using your senses
    Ears eyes and smell

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  2. Looking at gauges is common sense – when you hear the rattle, see the smoke and smell the burnt oil it’s too late.
    Mark Darby likes this.
  3. I've got some bluetooth barbecue probes to try, cheap as chips going to give them a go on the engine break in see how various points compare.. if their any good they might stay on as a long term test

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  4. Keep us informed :thumbsup:
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  5. :D:thumbsup: Tell me about it. :rolleyes::(
    Last edited: Nov 30, 2019 at 4:15 PM
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  6. I do drive all my cars/ vans 'with respect', i call it 'mechanical sympathy'.
    But.....all the respect in the world can't prevent unforeseen mechanical. electrical component failure or an unnoticed plastic bag getting sucked into your air intakes and so forth.
  7. I agree!
    More often than not , and in some cases , regardless of the signs portrayed by the gauges the damage has already occurred.
    Sometimes incidents happen through not fault of our own , it’s just bad luck.
    I prefer not to drive with the radio on because I’m constantly listening and assessing how she’s running ....... am I paranoid

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  8. [

    Yes it... enjoy it,.. worry less , the journey is part of the fun if not most of it, destinations are all pretty much the same your parked up enjoying the day (journey includes the restorations too).. if it breaks fix it ..repeat
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    Last edited: Nov 30, 2019 at 6:38 PM
  9. I think there is some paranoia sets in. With being air cooled and not having the water jacket to insulate Some of the noises.
    They do sound clanky compared with quiet modern day motors. I think you have to keep telling yourself this and not worry too much :rolleyes:
    paul2590 likes this.
  10. Your spot on there ! :thumbsup:
  11. The EMPI/Autolinea heads have a tapped boss high up on the head fairly near the exhaust, but still in the bulk of the cylinder head metal. Some way from the chamber..

    Its where VW put a sensor for the Mexican Fuel Injection system to richen the mixture as it gets hotter..

    I think the problem with measuring at the exhaust studs is that you are beginning to more measure exhaust gas temperature rather than head metal temperature.

    In the end you are trying to find whether the aluminium is reaching danger point near the spark plugs and valve seats : the spark plug base is closest to where heads crack, and thats why on the T4 with the space around the spark plugs, its the best location for the sensor. And that cracks can form at 150 -170 deg C ..

    I expect next best would be to drill a 2mm hole a couple of mm deep near the spark plug hole and epoxy a bead thermistor into that hole...
    Last edited: Nov 30, 2019 at 7:46 PM
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  12. I think my heads maybe Autolinea, i'd have to check, could that tapped boss be got at though ?.
  13. Mine are AMC type 4 but the boss mentioned is in roughly the same place. Quite a bit cooler there than at the spark plug, roughly 20C
    I know because I used to have the sensor under the plug. I just add +20C on what the gauge tells me now.
    redgaz likes this.
  14. I use some stainless thermocouple probes which are a bit long so I ended up cutting holes in the tinware above them to get the wires through.
    Also on my home made setup (STM32 microcontroller with ADCs in the engine bay with a serial data link to dash mounted multifunction displays) it doesnt like any part of the sensor or its shielded cable to be touching the engine block electrically - Would have been better with bead thermocouples with the fibre glass cable insulation.
    The thing that gets me is that the new engine CHTs measured at that boss are now lower or the same as the oil temperature. With all ancilliaries the same everything is 10 (oil) or 20 (CHT) degrees cooler. I think its mostly that the finish on the EMPI heads is so much cleaner (less flash, and more metal conducting heat to the fins/meat for porting than the original VW 040 heads)

    Please note that this post is an endorsement of EMPI products.
    Last edited: Dec 3, 2019 at 7:06 AM
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