Hello,

 

The spark plug designed for the 300ZX uses a special design. The spark plug

has a extra long projection with an extended shell.

The purpose of the long projection is to ignite the A/F mixture deeper in

the combustion chamber, allowing fast flame kernel growth as well as good

anti fouling characteristics.

 

Since the PFR6B-11B uses an extended projection, the insulator needs to be

protected from thermal shock. Thermal shock is the heating and cooling of

the insulators firing end. If you look at the PFR6B-11B firing end you'll

notice the insulator is narrow and gets wider the further down in the shell,

like all spark plugs. The insulator tip is hotter than the insulator down

inside the shell. The difference in temperature can cause insulator

breakage. If you notice the PFR6B-11B is a 3/4 thread reach and has a

section past the threads, which has no threads. This section is designed to

prevent thermal shock on the insulator and enables us to reduce ground

electrode length from the weld to the bend. If we didn't use the shell

extension the ground electrode would be very long from the weld to the bend.

This would make the ground electrode prone to failure.

 

We don't list an iridium spark plug due to the fact we don't make this exact

design in iridium. For liability issues we won't list an iridium spark plug

for this application due to it's special design. However by calling or

emailing we can make the recommendation of an iridium spark plug with less

projection, especially in modified applications. Of course the end user

will use at there own risk. In modified applications you don't want as much

projection as a daily driver so performance isn't an issue.

 

You can use the iridium spark plugs BKR series in this application. Again

it will have less projection then the spark plug originally designed for the

vehicle.

 

Jon MacQuarrie

Technical Support Specialist

NGK Spark Plugs

I'm going to change my plugs soon. What are the recomended plugs for the zed running 15.5psi?

Cheers.

NGK PFR6B-11B gapped to .95mm

 

15.5 psi is a little over what the turbos can take 15 or below is the guideline!

I'll be using those plugs next, although I am not sure what is in ther at the mo, they are brand new and I am pretty sure they are the stock ones...

As an NA owner...does the plug choice make such a big difference. ie can we use iridium ones

 

Chris Davies

NGK PFR6B-11B gapped to .95mm

 

15.5 psi is a little over what the turbos can take 15 or below is the guideline!

 

So are these plugs the standard Nissan plugs?

NO, these plugs can only be ordered from America or a british supplier who can import them!

NO, these plugs can only be ordered from America or a british supplier who can import them!

 

Ok, so my next question is do you know any importers of these plugs?

Cheers.