Which spark plugs

Discussions relating to Turbochargers, Superchargers, Induction, Engine Mods, Exhaust Mods, and other items specifically to make your MX5 or Roadster put out more power.

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poison
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Which spark plugs

Post by poison » Tue Nov 11, 2008 9:02 pm

The recomended plug for my NB8C is a NGK 5, being turbo'd should I go for a hotter 6 plug? The one's in it currently are NGK 6.

Anyone know much about plugs?
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jif
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Which spark plugs

Post by jif » Tue Nov 11, 2008 11:43 pm

the rule of thumb is up a number for an extra hundred hp... so a 6
would seem OK. I have a set of lightly used platinums you can have
... :]

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poison
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Which spark plugs

Post by poison » Wed Nov 12, 2008 9:17 am

Hi Jiff

Thanks, I have a set of Iridium’s, with about 10,000K on them. They were just black from running rich so I thought I’d replace them. What are the benefits of Iridium and Platinum? Just longer life?

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jif
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Which spark plugs

Post by jif » Wed Nov 12, 2008 12:45 pm

they can spark under a wider range of conditions - leaner, richer, and
with less voltage. .. and they last longer and sound cool ;]

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SLYDIT
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Post by SLYDIT » Sun Nov 16, 2008 10:23 am

You'll also need to make sure you get the gap right too as you turn up the boost. Im pretty sure the stock gap for the plugs is 1.1mm and you really want it down around 0.9mm for the turbo application. Have a look through the NGK spec sheets and find the plug that meets these needs. i ended up using a plain old "standard" plug that was one heat range colder and had the 0.9mmgap set at the factory. (cant remember the model number though.)
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jif
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Which spark plugs

Post by jif » Sun Nov 16, 2008 11:01 am

2008/11/16 SLYDIT <horsepower@mx5forum.co.nz>:
You'll also need to make sure you get the gap right too as you turn up the
boost. Im pretty sure the stock gap for the plugs is 1.1mm and you really
want it down around 0.9mm for the turbo application. Have a look through the
oh yeah - that's the other benefit of platinum/iridium plugs... they
can spark across a wider gap (for given conditions) than regular
plugs. I've been running a standard 1.1mm gap on the turbo motor for
~7 yrs now with both standard and Ir/plat plugs, tho if the spark
ever felt weak it would get gapped down too.

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