plug leads 308 / resistor or not ? | FerrariChat
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plug leads 308 / resistor or not ?

Discussion in 'Technical Q&A' started by Martin308GTB, Jan 11, 2006.

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  1. Martin308GTB

    Martin308GTB F1 Rookie

    Jan 22, 2003
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    Martin N.
    #1 Martin308GTB, Jan 11, 2006
    Hello from Germany,

    on another thread someone states, that for the later electronic ignition on the carbed 308, induction wound ( resistor ) plug leads are mandatory.
    But though asked, he doesn't tell me why.
    Now I have two faulty plug leads on my 308 and would like to opt for the more reliable copper cables without resistance together with the stock 2 kOhms plug extensions.
    Can anyone tell me, if resistorless leads are possible to use on the electronic ignition cars, and if not, why.


    Best Regards and thank you in advance

    Martin
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    #2 Steve Magnusson, Jan 11, 2006
    IIRC, if the impedance of the secondary path (wire+extender+plug) gets too low, this can be stressful on the output transistors of an electronic ignition that are supplying the current into the coil primary (although I don't recall whether it was an induced over-voltage condition or a direct over-current condition that might damage the transistors).
     
  3. Martin308GTB

    Martin308GTB F1 Rookie

    Jan 22, 2003
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    #3 Martin308GTB, Jan 12, 2006
    Thanks. Completely confused I phoned with a specialist at Bosch Automotive this morning.
    Due to his explanations resistorless copper core leads CAN be used on the 308 transistor ignition. Together with the 2kOhms resistor plug extensions ( the stock red ones no. 116 613 ) this setup would be absolutely o.k.
    No damages to be expected and sufficient suppression.

    Best Regards from Germany

    Martin
     
  4. ferrarifixer

    ferrarifixer F1 Veteran
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    #4 ferrarifixer, Jan 12, 2006
    Hi Martin, sorry for not replying, your query got badly filed by me.

    The induction wound resisted leads suppress the interferance from the higher output of the electronic system.

    Sure, your car will run fine with either, but your radio, phone and neighbours TV will possibly get static noise.

    They also reduce the tendency to cross fire or short to ground... like maurice had trouble with recently.
     
  5. Martin308GTB

    Martin308GTB F1 Rookie

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    #5 Martin308GTB, Jan 12, 2006
    Hi Phil,

    thanks for this clarification. Bosch says, that the 2 kOhms extensions are sufficient for interferences suppression of the ignition system. I will simply try it.
    On my Alfa for instance I run the ignition systems with copper core leads and only 1 kOhms plug caps and a resistor rotor.
    Only when I replace that rotor with a resistorless version I can hear slight noises in my car radio ( a contemporary simple Blaupunkt from the late 70s, absolutely no noises with any modern radios ). And nothing on my TV or home radios. Also no interferences in my mobile phone, not even when using it inside the car while the engine is running. What's, btw, not permitted in Germany.

    Best Regards from Germany

    Martin
     
  6. Martin308GTB

    Martin308GTB F1 Rookie

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    #6 Martin308GTB, Jan 23, 2006
    Phil you were correct. I tried the copper core leads and HAVE noises in my radio. Since there's no chance for suppression on the distributor end I will now restore my old Cavis leads with new SAE-plug ends and contact needles.
    The distributor side still looks as new.

    Thanks once more; I didn't want to believe, and now I paid for an unsuitable copper core HT lead set.

    Best Regards from Germany

    Martin
     
  7. ferrarifixer

    ferrarifixer F1 Veteran
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    #7 ferrarifixer, Jan 23, 2006
    No problem Martin. There should be a small capacitor on the feed to the coils to reduce as much interference as possible. I can't remember the value though.

    The WSM might have it?
     

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