NGK BUR7EQP & BUR9EQP. The Difference.

[Tiger_kpt]

Just a quick question.
 
Normally people use BUR9EQP\'s all around the engines as leading and trailing.
 
But some use two BUR9EQP\'s with two BUR7EQP\'s.
 
I have two of each to install ASAP.
 
I know that the two top plug ports on the engine are the trailing plugs. The lower two are leading.
 
But in the case of using two 7\'s and two 9\'s instead of four 9\'s... which plugs do the 7\'s act as? Leading? Or trailing?
 
And are 7\'s hotter or cooler than 9\'s? And what are the advantages of using them?
 
Thanks in advance.

[Crazy Eddie]

Hopefully someone can confirm this the bottom 2 plugs are the leading and where you would place the 7\'s in.

The 7\'s are a hotter plug than the 9\'s and so the benefit of having them in the leading is that there is more chance of igniting and so less chance of flooding.

For example I recently changed mine to 9\'s all round and have had a couple of problems with flooding therefore I am now going to replace the leading (bottom 2) with the 7\'s.
http://www.mazdarotaryclub.com/forums/showthread.php?t=264
Have a look at this thread.
HTH
Eddie

[Tiger_kpt]

I\'m SURE that bottom plugs (nearest the ground) are the leading.
 
So, 7\'s are hotter, and therefore the leading replacements to the regular 9\'s all round. Think that\'s answered the question. Thanks.
 
Good link by the way. Missed that.

[Fish]

Yes bottom plugs are the leading and in original trim the 7\'s would be there. Due to most cars being modified in some way, shape or form they wouldnt really be needed.

Running 9\'s leading and trailing shouldnt be an issue.

Fish

[RobbieRX-7]

It tells you on the engine block by the holes which are leading and trailing Either L or T

[pdtaylor18]

quite right but how does it affect the sparking if its been modified. I have an apexi and its running richer than before more as a safeguard so surely the hottter spark plug will ignite better when it has too and make for a more reliable start. I have just ordered a set of 7\'s from the States as mine are 9\'s all round and just fancied tinkering to see if its any better. might suit one engine different from the other dependant on age and mods.

[Ricco_04]

I\'m going to stick 7\'s & 9\'s in mine.  I use the car every day and with the hotter 7\'s in I have never (finger\'s crossed) flodded my engine in 3 years.