[SOLVED] 300ce spark plugs

Discussion in 'Engine' started by anfieldassasin, Sep 30, 2016.

  1. anfieldassasin

    anfieldassasin Hardcore MB Enthusiast

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    Guys what's the difference between HR8DC and HR8DC+ plugs?

    I just bought an 88 300ce which calls for the hr8dc plugs but all I can find are the + variant??
     
  2. hotrodder

    hotrodder Hardcore MB Enthusiast

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    The + stands for 'super plus technology' in Bosch plug marketing speak. In English it means the copper core of centre electrode is a 'better' copper yttrium alloy. No changes to any important bits of the plug spec, they're denoted by the rest of the code... H is the plug body (dia, thread, seat type), R = resistor, 8 = heat range and DC calls out reach length and electrode type

    Curious where the HR8DC recommendation came from as they are resistor plugs and the ignition system is designed around non-resistor plugs as the suppresion resistors are in the connectors on the ends of the HT leads

    http://www.w124performance.com/service/w124CD1/Program/Engine/103/15-1031.pdf lists the various origional plug specs for Beru, Bosch and Champion brands, i'm guessing HR8DC / HR8DC+ is the closest Bosch plug that's available today?

    Personally i'd go with whatever NGK plug cross references (probably BP6EFS or BP5EFS)* or just buy 'em from a main dealer, there's not gonna be much in it price wise and they're probably sell you Beru plugs in disguise (little MB star logo on them)?

    * NGK plugs often have a wider heat range so depending where you look/who you ask either or both of them may cross reference to any of the origional plug specs
     
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  3. stwat

    stwat Hardcore MB Enthusiast

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    You need none resister plugs.
     
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  4. 190

    190 Hardcore MB Enthusiast

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    Bosch have stopped making non resistor plugs. It's an issue with old BMW motorcycles like mine that have points ignition and already have resistors in the caps. Resistor plugs will work but a little spark energy will be lost. The most realistic way to look at it is even though they'll seem to work OK, resistor plugs remove some of the safety margin and a fouled plug will fail to spark sooner than a non resistor plug.

    NGK plugs are the answer.
     
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  5. whirsk

    whirsk Active Member

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    Hi folks
    I was able to source the correct plugs for local merc dealer.
    It appears merc still have them in stock in Germany.

    Sent from my SM-G920F using Tapatalk
     
  6. OP
    OP
    anfieldassasin

    anfieldassasin Hardcore MB Enthusiast

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    Hi yes I know non resistor plugs are called for failed to realize the R stood for resistor. I must have misread the slam panel will check again tmrw and feedback. I recall for my 230ce I got the h7dco so these must be h8dco.

    Want work up the 300ce odly UT feels more sluggish than my 230ce. It is though so much smoother than the 230ce

    If I can get h8dco plugs would still recommend the ngk non res plugs over them?
     
  7. 190

    190 Hardcore MB Enthusiast

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    I doubt it matters much either way but there are rumours that Bosch quality has gone down hill and that the plugs are no longer made in Germany. I suspect the only place you will find non resistor Bosch plugs is from MB.

    NGK have been considered top of the pile for ordinary plugs for as long as I can remember so they are always a safe bet. There are other good plugs, I also use Nippon Denso but they are perhaps less easy to come by.
     
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  8. optimusprime

    optimusprime Hardcore MB Enthusiast

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    I found that Bosch recomend the multi electrode plugs .So i sent for a set only to find they were resistor type plugs in the end so i ad to remove them . So best to get the right plugs none resistor type.
     
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  9. OP
    OP
    anfieldassasin

    anfieldassasin Hardcore MB Enthusiast

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    So was at dealer today picking up odd bits like the interior 0.4w bulbs, asked about spark plugs he had a set of 6 in stock. Borought them out, they were in the merc box opened them. Up and Bosch plugs were inside the non resistor ones marked h8dco! £3.50 each

    Of your in Essex I've been using mercedes on Southend arterial Road for some time now and they excellent in service dept. Always helpful and when ever I ask for. Discount they always work. Something out for me no matter how small!
     
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