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  1. #1
    Join Date
    Dec 2008
    Location
    Exeter
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    130

    Very Hot Ignition Coil

    How hot should the coil get during normal road use on an Sumo 3.5 RV8? The original SD1 coil is triggered by the mag pickup in the Lucas dizzy via an RPI amp. There do not appear to be any problems overall with the running of the car but having burnt my arm a bit on the coil body I wondered. The coil is mounted on a side chassis rail in front of the dizzy where temperatures are just warm not very hot!

    Any thoughts?

    John

  2. #2
    Join Date
    Apr 2004
    Location
    East Leake, Nottinghamshire, England.
    Age
    55
    Posts
    9,511
    What volt coil have you fitted and do you run a ballast resistor ?
    Martin

    351W 416.7 HP and 466.8 ft-lbs

    Running Mega Squirt and Edis 8


  3. #3
    Join Date
    Dec 2008
    Location
    Exeter
    Posts
    130
    Martin,

    The coil is the original SD1 one, I don't know the voltage rating but assumed 12volts, as it was linked to the Lucas C5 module. As there were only 3 wires (+12 volt to module, connection to coil and earth) this was wired instead to the RPI module to get an improved spark. I don't think there was a ballast resistor in this set up. This system has been running for over 10 years/13,000 miles with no problems but I have just noticed how hot the coil has been getting whilst fiddling at the front of the engine!

    John

  4. #4
    Join Date
    May 2004
    Location
    Cowbridge, United Kingdom
    Age
    61
    Posts
    9,916
    It's fairly normal for the coil to get hot over time.
    Just as long as it's not too hot and the right way up of course. ie coil lead uppermost.
    If it's run for ten years it can't be too bad.
    Fitted upside down I've seen all of the cooling oil run out when hot.
    Kev Davies
    South Wales Area Rep. UKCC Membership Secretary
    DAX Mk4, 383 Chevy Stroker, Tremec. SOLD
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    In build- Hawk 289 Sebring

  5. #5
    Join Date
    Dec 2008
    Location
    Exeter
    Posts
    130
    Kev,

    Yes it is the right way up I will soldier on as it certainly seems to run OK. Sometime I will borrow my son's infra red temperature thermometer to see how hot the coil really is out of general curiosity.

    John

  6. #6
    Join Date
    Apr 2004
    Location
    East Leake, Nottinghamshire, England.
    Age
    55
    Posts
    9,511
    Might be an idea to get a spare just in case......
    Martin

    351W 416.7 HP and 466.8 ft-lbs

    Running Mega Squirt and Edis 8


  7. #7
    Join Date
    Aug 2004
    Location
    Christchurch, NZ
    Age
    59
    Posts
    2,311
    Did you leave the ignition switched on whilst working on the car? It is quite normal for a coil to get very hot if you do this.
    Cheers

    Myles D-W

  8. #8
    Join Date
    Dec 2008
    Location
    Exeter
    Posts
    130
    Martin,

    Yes I do have a spare purchased about 10 years ago before I fitted the RPI box. It didn't seem any different compared to the SD1 one when running on the Lucas module so I stayed with the SD1 one. I might try swopping it over to see if the other one gets as hot.

    D-W,

    No the engine wasn't running I had just returned from an 10 mile journey at normal speeds and decided to advance my dizzy about a degree. My recent RR WOT run was originally 17 deg at tickover which was too much ~40 deg at around 3,000 rpm. We moved it back to 12 deg and 35 deg at 3000 which improve things above 2000 but lost torque and BHP below. I believe I am now on 14 deg at tickover which should help low down but not have an impact on the top end.

    As above I will try a coil swap sometime to see if there is any difference.


    John

  9. #9
    Join Date
    Jan 2010
    Location
    Martham, Norfolk
    Age
    64
    Posts
    216
    As others have said above, it is normal for the coil to become hot with the engine running. But what Miles-DW means is that if you switch the ignition on without running the engine, the coil is being charged but is not discharging. This will overheat the coil if left like this for long.
    Henry
    'I tell you, we are here on earth to fart around, and don't let anybody tell you different.' Kurt Vonnegut
    DAX DeDion Chevy 350ci

  10. #10
    Join Date
    Dec 2008
    Location
    Exeter
    Posts
    130
    Sorry I should have been clearer when I said engine not running it also meant ignition turned off as well.

    John

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