Here are my plugs installed around 6000k ago into my rebuild.

http://www.teamfc3s.org/forum/showth...646#post361646

the first is the front chamber trailing
second is the front chamber leading
the last is the rear chamber

#1 looks ok but as you can see the barrel on the plug is clean and the tip is wet...
#2 the tip of the spark plug has actually become rounded what would cause this?
#3 I think these look like typical used plugs ... the barrels are rusty brown and you can tell they are working...

would the plug in the second pic cause the other plug in the chamber not to burn off all the gas causing the tips to be clean and soaked with gas?

and WTF is with the rounded spark plug tip here!?

 

This plug is just plain worn out:

 

thats why its that shape.. thanks, i'll go get a new one right now!

 

This looks like what happens with a leading plug in the trailing hole:

 

The short story:
Leading plugs are a colder heat range so they don't burn up so fast.
Trailing plugs are a hotter heat range so they don't foul.

 

Actually, it's backwards?


-Ted

 

I think I'm right on this:

http://www.ngksparkplugs.com/techinf...000&country=US

 

Yes, the NGK link is correct.
Bigger number = colder heat range
Smaller number = hotter heat range

Isn't this opposite of what you wrote above?

Stock recommendations from Mazda are 7's for leading and 9's for trailing.
9's are colder than 7's.


-Ted

 

I think I had them in the right spots...
guess i'll just have to triple check this time...

 

On page 2 they say you use a colder type plug in hot chamber conditions, and a hot type plug on cooler chamber conditions.
Then they give an example “BP7” as a colder type and “BP5” as a hotter type.
Like you said, the higher number is the colder type.

Here is my confusion.
In the rotary engine, if you reverse the plugs by installing the 7’s in the trailing position & the 9’s in the leading position, the 7’s foul and the 9’s burn out early.
This tells me the trailing location has colder chamber conditions and the leading location has hotter conditions.

Location-----chamber------plug type-------plug number
Leading------hot------------cold---------------BR7EQ (L)
Trailing------cold-----------hot----------------BR9EQ (T)

This implies the smaller number is the colder range plug??

I am contacting NGK for clarification.

My question to them is:
Is the "BR" series an exception to the "smaller number is the hotter plug" guideline?

 

From NGK:
Hello,
This is correct. The hotter the combustion chamber the more heat needs to
be transferred in order to keep plug temperature at the optimum temperature.
A hot spark plug has slow heat transfer and a cooler spark plug has faster
heat transfer. In an engine with high compression the cylinder temperature
is higher. In order to avoid pre-ignition you need to transfer the excess
heat that's why you use a cooler spark plug. In a cooler cylinder you need
to keep the plug temperature at it's optimum temperature. If the spark plug
is too cold it will foul. So a hotter spark plug will have slower heat
transfer causing plug and cylinder temperatures to rise. This will place
plug temperature in it's self cleaning range.

Jon MacQuarrie
Technical Support Specialist
jmacquarrie@ngksparkplugs.com


---So ---I rephrased my question:
So is the smaller heat range number for the hotter or colder type plugs?
The web page says the smaller number is for the hotter type.
My BR7EQ seems to be a colder type than the BR9EQ.

 

They're not...

 

Yup - So says the NGK rep.

>Hello,
>
>The BR7EQ is hotter than the BR9EQ
>
>Jon MacQuarrie
>Technical Support Specialist
>jmacquarrie@ngksparkplugs.com

I am still stuck on how if I put a (colder) trailing BR9EQ in the leading hole, it burns up so quickly.
And, if I put the (supposedly hotter) BR7EQ in the trailing hole, it fouls.

bizarre

 

Is it "BR" or "BUR"?
"BUR" is recommended for our cars.
I've never heard of a "BR" NGK plug...


-Ted

 

looks more like a fouled out P plug. what is the exact part number on this plug?

 

When the plug tips look like they are deteriorating, then its most likely the cause of pre-ignition I believe. Your timing is off.

Correct me if im wrong about this becuase im not to sure.

 

Oops - ya it's BUR7EQ (L) & BUR9EQ (T)

Actually I like BUR7EQP - The platinum leading plugs last about 18,000 miles for me.

 

NGK plugs have the heatranges bvackwards. bur7eq's are HOTTER than bur9eq's.

 

"When the plug tips look like they are deteriorating, then its most likely the cause of pre-ignition I believe. Your timing is off. "


is this true?

 

The leadings will always wear faster than the trailings, cause the leadings fire TWICE as much.



-Ted

 

time to check my timing :P