i orderd a set of NGK IX iridium LFR7AIX part#2309 , and i know their same as stock except 1 step colder and i was wondering if it would change my afrs in any way?

my mods are godspeed downpipe, hks ti carbon catback, utec stage 2 and mbc

bump 11

....how could they????

i dont know it was a question someone told me they did cause its colder..

.....afaik, colder heatrange of the plug deals with the plugs ability to transfer more heat out of the combustion chamber, into the head......if that can change air or fuel in some way, I'd like to know about it, too......

Plugs set up properly for a more complete burn would cause more fuel and more air to combust in one felled swoop. I'd figure the ratio would stay the same though. The outcome of the same AFR would be different / hopefully better. A spark plug won't choose to burn more air or fuel independantly of the other. Just thinking out loud here.

....a colder plug could be tuned for and its characteristics(if, indeed, beneficial for the app) thus making a different AF(a bit leaner, most likely) more advantagous....

Since there's a thread on this let me throw in my noobie question. Would old/fouled plugs be a reason for not being able to run as much timing up top as other motors/similar setups??

Old thread revival...

I was wondering the same thing. I've been running rich lately and don't know why. I've taken off the IC and looked for leaks, but can't find anything. A bud and I were thinking that an imcomplete burn from an old plug could cause the AFRs to be skewed.

They could change resultant AFR (ie what we see in widebands) but won't change the actual AFR. This is why dyno tuning is so important...you can see the torque changes for a given AFR.

A bud and I were thinking that an imcomplete burn from an old plug could cause the AFRs to be skewed.An AFR sensor would report a very lean AFR if the engine misfires because it would be responding to all the oxygen which failed to combust.

hmm, well my AFR gauge has been reading rich. Still trying to find out why.