I am looking into replacing my STI JDM 2005 plugs with Denso Iridium. Can any one tell me the OEM plug and the Denso replacement number. My engine is the EJ207. I was told the IKH22 would be the preferred choice as my engine is modded and running around 20 lbs boost.

Thanks for the input

 

Iridium plugs are, allegedly, really good conductors, so the electrode can be made smaller/thinner, therefore exposing the spark more openly to the air-fuel mixture, for more complete ignition/combustion

That said, I'd stick with the widely used NGK PFR7B gapped to 0.65mm.

 

Thanks jaz8968. I had Denso IK20 in my previous MY00 and they ran very well having to be changed every 30,000 km.

Is the NGK PFR7B the OEM for the JDM 2005 STi or for another model?

 

Not quite sure EXACTLY the make/model of plug that Subaru fits at factory, but the NGK PFR6B are the equivalent to OEM i.e. the heatrange of '6' is the same, AFAIK

The '6' is the plug 'down' from the '7' i.e. it runs hotter than the 7. That's why, if you have a modded car, the colder 7 is a good choice, as it manages the higher cylinder heat/pressures better, and helps with keeping possible detonation at bay.

 

I was thinking about upgrading to the iridium plugs. But them I heard they over sparked on hard acceleration, and under certain circumstances, caused the engine to shut down (fail safe) which would suck!!

Wondering if anyone had these plugs work 100% and what are the benefits, ie BHP?

 

Any other ideas out there

 

No massive benefit other than they last a bit longer. I don't think it's conductivity, it's that iridium is verra, verra hard and can be made smaller without the tip dropping off.

Just don't put those bloody 4 electrode things in. You might as well wrap tinfoil around the plug.

Final point - people stick expensive plugs in then go "Wow, I can feel the difference!". Yeah, you would have felt the same difference if you'd just put some OE ones in too though.

Have a nice day

 

Ah right.


Totally!

Also a handy <ahem> tip is to make a mark on the ceramic insulation (using a black marker) the position that corresponds in line with the open side of the cathode/electrode. That way, then when you screw the plugs in, you can fine position them so that this open area is facing the inlet valves and centred between them. In theory, this should aid igniton of the A/F mixture (it certainly shouldn't make it worse lol).


Yeah, very much the Placebo effect lol.