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308 spark plugs types and recommandations

Discussion in 'Technical Q&A' started by adesalos, Jan 13, 2004.

  1. adesalos

    adesalos Karting

    Mar 19, 2003
    233
    Texas
    I read several different threasds about 308 spark plugs. However, I don't get too much concensus:
    Some people use NGK BP6ES, or NGK BPR7EIX.
    What's the difference between the 2? Do they need adjustment to fit correctly in the 308?
    What is the added value of iridium type?
    Why people would change from the Champion of Bosch used OEM?
    Do the recommandations differ if carb or injected car?
     
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  3. Mike328

    Mike328 F1 Rookie
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    Oct 19, 2002
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    Didn't somebody recently recommend NGK BP5ES for older (carb) 308s in a recent Forza article? Tony Palladino was his name.

    That's what I run...

    Here's a thread where John Miles cites this article:
    http://www.ferrarichat.com/discus/messages/256120/199708.html

    In that thread I was running BP7s, then switched to BP6s, and then finally to BP5s which is what I've settled on...

    This may all change with the elctromotive HPX ignition I'm about to install, though.
     
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
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    "What's the difference between the 2?"

    The BP6ES is a non-resistor, standard 2mm diameter center electrode plug, heat range = 6 (which is a reasonable choice for a US street F).

    The BPR7EIX is a resistor, small (<1mm) center electrode plug, heat range = 7 (which is a little colder heat range -- and if you're lucky enough to be hitting extended high RPM runs frequently, would be a good choice).

    "Do they need adjustment to fit correctly in the 308?"

    Both have the proper mechanical shape/spark position to fit 308-2V heads.

    "What is the added value of iridium type?"

    The "value" of the iridium electrode is that it can be made smaller and run at a higher temperature because it has a higher melting temperature (which helps keep it clean and prevent fouling).

    "Why people would change from the Champion of Bosch used OEM?"

    Three points I would make here:

    1. NGK is quality supplier that is equivalent to (or better than) Champion and Bosch (so you can always cross-reference the stock Champion or Bosch to a stock equivalent NGK)

    2. IME, the standard ignition, carbed-cars can benefit most from these exotic electrode (palladium/platinum/iridium) type plugs (which weren't available then)

    3. Although the brands didn't change, F went from standard electrode plugs to exotic electrode plugs circa 328 or testarossa.


    Do the recommandations differ if carb or injected car?

    I think the 1st distinction here should be standard ignition vs electronic ignition and then carb vs injected being the second factor. I.e.:

    electronic ignition + injected = Plug type matters least (although interestingly, all F of this configuration spec an exotic plug)
    electronic ignition + carb = Plug type probably not critical
    standard ignition + injected (not really any cars like this)
    standard ignition + carbs = Most potential benefit from exotic electrode plugs

    Would I pay $15 each for an Iridium plug -- NO, but for $5 each it's a reasonable investment compared to the labor to install -- JMOs.
     
  5. adesalos

    adesalos Karting

    Mar 19, 2003
    233
    Texas
    So based on this thread I conclude that in normal conditions (i.e. at sea level or so), and in a carb/double distributors 308, I should buy:
    BPR5EIX
     
  6. Steve Magnusson

    Steve Magnusson F1 World Champ
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  8. ham308

    ham308 Formula Junior

    Nov 3, 2003
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    The R in BPR... means resistor type plugs, which I don't think you need if you've got the plug extenders and resistance leads. The extenders on mine are about 2 kOhm each and the leads around 1 kOhm. You can get BP6's, BP7's etc without the resistance.

    Or am I mistaken?? :)
     
  9. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Your thinking is OK, but they don't make every possible combination -- I've never seen a non-resistor EIX NGK in the BP series (e.g., BP6EIX) offered; whereas, in the ES style NGK both BP and BPR are more available as you noted.
     
  10. adesalos

    adesalos Karting

    Mar 19, 2003
    233
    Texas
    You have also the choice between: BPR6EIX and BPR6EIX-11. (see clubplug.com)

    What is the differences?
     
  11. BigTex

    BigTex Seven Time F1 World Champ
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    Dec 6, 2002
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    NGK BP5ES. In stock engine. HTH

    Keep a spare set in the trunk.
     
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  13. yelcab

    yelcab F1 World Champ
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    Nov 29, 2001
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    BPR5ES, no complaints.
     
  14. 4re gt4

    4re gt4 Formula 3

    Apr 23, 2002
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    I got over 10,000 miles out of my last set of BP6ES. They looked really sooty when I pulled them out tho. Probably too much town driving.
     
  15. adesalos

    adesalos Karting

    Mar 19, 2003
    233
    Texas
    Since I want to place an order today, I need this info ASAP.
    Based on the comments from 91TR supported by my mechanic, and looking at the cost adder, I decided to go iridium.
    The question is what difference "-11" designation make?
     
  16. Steve Magnusson

    Steve Magnusson F1 World Champ
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    The "-11" suffix indicates that the nominal electrode gap has been set to .044" -- not a huge deal to overcome, but a more conventional electrode gap for your 308GTB might be .024"~.027"~.030" (depending on ignition type). See, for example:

    http://www.brfoundation.com/RX-7/plugs.htm

    although that particular NGK code table pre-dates the availability of the "IX" construction.

    And the price per plug?
     
  17. BigTex

    BigTex Seven Time F1 World Champ
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    Dec 6, 2002
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    .027 is the gap in the older 308s, as well.
     
  18. Mike328

    Mike328 F1 Rookie
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    Yes, for stock ignition. When I just put in a new set of NGK BP5ES plugs last week, I found they were all gapped to approx .035, so I had to bend 'em all down a bit (easy to do by you or your mechanic).

    --Mike
     

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