I was on Mazdatrix today looking for spark plugs for my 86 NA and i noticed that they were selling leading and trailing plugs. Now i know which plug leads and which plug trails, my question is what is the difference in the two plugs?

 

leading are top ones, they ignite, trailing are bottom ones, the burn the remaining un burnt fuel. You need 2 of each.

 

While I'm not sure what metals they are made of, I noticed my OEM NGKs were varying in color. I'm assuming one sset is copper while the others are platinum. I may be wrong, but it's just something I noticed. Also, have you seen the price for Denso Iridiums? $35 PER PLUG!!! Ouch!

 

Trailing is a hotter plug.

 

thanks guys all cleared up now

 

Maybe I'm going crazy, but I'm almost certain that the leading plugs are the lower plugs.

 

Thats what I thought, leading lower plugs trailing top plugs. Also, (noob question) will using all trailing plugs be beneficial?

 

I'm a noob and I've got my flame-retardant (or is it just retarted ) suit on so here goes...wouldn't the leading plugs be on top since it has to ignite the fuel first then the trailing plug on bottom to clean up the leftover fuel? Or does the rotor rotate counter-clock wise (when looking from the front of the car)?

 

yea good point actually. I was always unsure on which was which too.

 

When you are in front of the car, the rotors turn clock wise.

Just picture it in your head, the exhaust is on the left side.

If it was counter clock wise, the rotor would go to intake, then exhaust and then ignition.

Doesn't make any sense.

 

Even more so, the rotor would suck in from the exhaust and blow through the intake.

...and ignite air. lol

 

trailing is on top

 

Wait!!! you mean to tell me that air dosent enter through my exhaust and then burn in the combustion chamber and then get pushed out throught the intake!?!?!

J/k yea that would make an even better point......the blind leading the blind..............the newbs leading the newbs..........scary world out there........ =)

 

the leading is on the bottom and the trailing is on top. the reason why they call it "leading" is because that spark makes the rotor turn "clockwise" (as F.C.3S mentioned) as it should so the exhaust gases pass through the exhaust port (sorta leads the rotor if you will..). if the leading was on top it'll turn the other way. the trailing plug fires second to finish combusting the uncombusted fuel. if you look at your housings in the car you should be able to see the "T" mark on top and the "L" on the bottom. also if you've seen a disassembled engine, look at the inside part of the housing and you'll notice that the bottom hole is bigger than the top. that means that the bottom (leading) hole gives out more spark than the top (trailing) one. ahh....sleepy time. hope this helps

 

Time for some rotary edumacation. Click, watch and learn...

http://www.rotaryengineillustrated.c...quicktime.html

Watch the other animations while you're there. Being able to visualise what's happening inside your engine will make your rotary life much easier.

 

Sweet holy hell...

Leading = Lower
Trailing = Top

L1 = Leading, front rotor
T1 = Trailing front rotor

It's bloody marked on the housings!

 

lol that was funny, good shyt aaron

 

Doh!

Yeah just checked the FSM and the trailing is at the top. Consider this noob skud.

 

Half right. Yes, the leading (bottom) spark plug hole is larger than the trailing (higher) hole but this is to balance internal pressure, not provide a greater spark.