Sparkplug help

[RS13]

So I went to change the plugs today as the Corolla has been running a bit rough lately, Toyodiy gave me the standard electrode plug number K16R-U11 for my particular chassis (and other 1NZFE-powered cars) so bought a set of those.. however as it turns out, my engine has iridium plugs (FK20HR11) in it which are far longer than the K16Rs.



Why such a difference in length? Judging by the blackness/soot on the extra length of the iridium plug, would it be safe to assume that they protrude into the combustion chamber quite far? Not really feeling baller enough to splash out on a set of iridiums for a car we're looking at trading in soon.. has anyone come across this before and would it potentially cause a change in performance if I were to fit the shorter plugs?

[Grrrrrrr!]

The iridiums are just plain wrong.. too long and wrong heat range. Correct iridium would be IK16 or VK16. Stick in the coppers and be done with it.

[RS13]

Yeah, can't help but think that the ground electrode must be pretty close to the piston at TDC! The odd thing is, searching toyodiy the part number for the iridiums comes up for my chassis, however when I go to the parts list for the diagram I'm only getting the part number for the copper plugs? Strange. Denso do list those iridiums as an option for my particular 1NZFE but Toyota doesn't which confuses things further.. Denso also seemed to change to the FK16HR11s from '07 onwards.

Either way, I'll whack the coppers in and see what happens, cheers.

[Grrrrrrr!]

With toyodiy you need to set the date in the url otherwise it defaults to the first year of production.