Ok, so the other day I pulled my plugs to see if any water would come out when I turned the engine over. Nothing came out, so thats good I guess. Anyway, out of curiosity, I pulled all of my plugs out to see if there were any differences between front to rear and leading to trailing, hoping that I wouldnt be burning massive oil on the rear rotor or something. Anyway, heres a pic of my plugs. The plugs are on the table from the left to right as follows: front leading, front trailing, rear leading, rear trailing. In person, the rear leading and trailing plugs look a little lighter in color than the front leading and trailing plugs. I dont know what the colors mean other than this is a HUGE difference than the 85 GSL with the blown oil seal(S) where the plugs that I took out were BLACK. I have read in manuals what the colors are, but I forgot, and I dont have ANY manuals here (not my house and my manual is at my Dads) otherwise I would look cause its the same pictures in any manual. Isint it the lighter it is the more lean its running and the darker the more rich? Also, on the rear leading and trailing there is some "burning" around where the boot sits on the plug. I noticed the wires werent on these plugs as tight as the other two, so I was thinking maybe the spark is kinda burning the plugs? I dont know...I scrubed it off with some steel wool and got the boots on nice and tight this time, so well see if it does it again. Oh, and one other thing before anyone says anything...Im only re-using these until I can get to my Dads where a brand new box of 4 NGKs is waiting for me . So, what do these tell you?

~T.J.

 

I'd say you're a bit lean, I beleive plug colour is supposed to a tan brown, kinda like the one on the far left but a bit darker. The rear trailing plug is scary white. Check these ones out.. (not my plugs)
I'd say most plugs that come out of rexes look like these

A little adjusting later
and they look like this,

 

I'd say your plugs look pretty normal to me. The white porcelin has a nice light brown chocolate color. What kind of driving did you do right before you pulled these plugs? That's real important because the plug color will change depending on it. If you idled it for a few minutes, then I would suggest to richen the fuel mixture a bit because it may be running just a tad lean. If you WOT it then you may wanna experiment with some larger secondary jets. Personally I think these look pretty decent. At this point, if you wanna adjust your air/fuel mixture any better you should use an O2 sensor for low end and an EGT sensor for high end. Spark plug color can only get you so close and these look like they are right in the range.

IMO

 

Do yo have any Hayes manuals..I think they have a spark plug comparison page.Only ou canrealy see how the look.compare if to some plugs in the book.

 

From what I can see, they look normal to a tad lean. Again take the advice from inittab. Need more info. Do you have the RB catalog? Good info on reading rotary plugs in there.
I use a cheap otoscope to look at my plugs. walgreens, like $5. You cant examine plugs properly with the naked eye. You need to see the cement at the junction of the porcelain and the center electrode. I've had plugs that looked good until I looked with the otoscope and found all 4 had cracked porcelain at the center conductor. I stopped using nippondenso plugs after that.

 

It's hard to tell exactly from the picture, but those look too light to me. The plugs out of my car have always been sort of light brown. Not as dark as the ones posted above by Nanaimo, but not nearly as light as yours look in that picture. Personally I don't think I'd be comfortable if my plugs looked like that, but again it's hard to tell with the lighting in the picture - it'd be easier to see in person, and maybe it has something to do with what you were doing before you took them out. But still, those look on the lean side to me.

 

Well, before I pulled them out I was drivng "normally", which includes city driving around 40-50 MPH speedlimits. So when I pull away from a stoplight, I pull away, lol. Also, the car was putting around for a little while (under 30) that day for a little while also. I think theyre too light too, thats why I was trying to figure out what I should do, lol. So maybe Ill play with my carb some more today. Also, a A/F gauge is in the future plans...Thanks guys .

~T.J.

 

there really isnt one answer on "which is best"... it depends on your belief about these engines. first of all, leaner = whiter, richer = darker. we already established that.

Paul Yaw's theory is that these engines make the most hp running real lean... and in doing this the plugs should be almost white. however, mazdacomp says not to do this because it destroys apex seals and wears out the motor (which there probably right). from the factory, these engines were tuned to run rich at high rpm's. so theres different sides to the spark plug issue. most SRX7 guys run the engines lean to make more hp. hurt the engine? maybe (but a road race car is due for a re-build every 1-3 seasons anyway). so theres my 2 cents in this issue.

--eric

 

Looks like your plugs are running a lottle hot and a little lean. Switch to a little bit of a colder burning plug and richen the mixture up just a tad. Or you could just not worrie about it and I guess they look pretty good.

 

Yeah, well I played with my mixture a little, and made it more rich, and there is a difference in power, thats for sure. I leaned it out again, and it felt "right" so Im just running it where it was when that picture was taken.

~T.J.

 

w00t, my plugs are famous.