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Tii spark plugs


dmcinfo

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Like others I recommend NGK plugs because the correct Bosch plugs aren't available anymore.  Either BP5ES or BP6ES.  With NGK plugs, the lower number is a hotter plug, so BP5ES is slightly hotter than a BP6ES.  I've been told that the BP5ES is about the same heat range and the old Bosch W8DC which is no longer available.  Likewise, the BP6ES is about the same heat range as the old Bosch W7DC.  With Bosch plugs, the higher numbered plug has the higher heat range (opposite of the NGK numbering system).  I use BP5ES in my '73tii because it runs a little richer and needs the hotter plug.  On my '74tii I use the BP6ES.

You don't really want to use one of the plugs with the built in resistor if you're using the standard resistor boot spark plug wire ends, otherwise you'll be getting a weaker spark.  NGK plugs with the BPR at the beginning of the name means it has a built in resistor.  They'll work, but aren't optimal if you have the resistor boot wires.

 

P1010260_zps0f4ab6dc.jpg

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I ran Bosch plugs for many years in my '02s and other cars...put a new set of Bosch plugs in my V6 Nissan truck before a trip and experienced an inconsistent but annoying misfire all the way to my destination.  The truck had breakerless ignition so I knew the problem wasn't points, cap or rotor.  Bought a set of NGKs and installed 'em at the motel.  Miss disappeared.  

 

Encountered the same problem with Bosch plugs (of the correct heat range) on an 02; NGKs corrected the miss...

 

So now I use NGKs.

 

mike

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  • 6 months later...

With a stock compression ratio and camshaft as long as your ignition system is working correctly Iriduim or even the platinum plugs do nothing but drain your wallet faster. We are not dealing with a super lean mixture in a high compression engine (this is hard for the spark to ignite). We are not running a high voltage long spark ignition system ( this causes a lot of heat right at the tip of the plug) and most of us are not trying to go 50,000 miles on one set of plugs (see above for reasons that modern cars can do that). I have seen a lot of claims about spark plugs increasing power and mileage, not a one of them has ever been proven on a dyno that I have seen. If someone wants to come and strap their car down to our dyno and test spark plugs I'm happy to show you what I have seen over the years.

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With a stock compression ratio and camshaft as long as your ignition system is working correctly Iriduim or even the platinum plugs do nothing but drain your wallet faster. We are not dealing with a super lean mixture in a high compression engine (this is hard for the spark to ignite). ...

 

While I would categorize Sputter as "not entirely stock", I am running a mostly stock ignition system (123ignition, red Bosch coil) and the starting can be a bit sleepy.  Based on the NGK pitch, they claim that the narrow point provides for better spark even at low voltage.  If true, that might be good for cold starting, but I have no experience with that.

 

I did previously have an MSD in the car, which I pulled out mostly for aesthetic reasons (2 smart people told me that I should DEFINITELY use the MSD, and 2 other smart people told me I WOULD BE CRAZY to use the MSD , so aesthetics were the tie breaker).

 

Plug life, extra power, etc., were not my considerations, but having better performance across a range of temps and rich/lean situations appeals to me.  An AFM tells you funny things about what goes on in a tii.

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