Spark Plug references.

[dL_RL]

NGK BKR6ES *STOCK heat range* <-- STOCK Plug

NGK BKR6E "V-Power" *STOCK heat range*

NGK BKR6EGP Platinum Plug *STOCK heat range*
NGK PFR6T-10G "Laser" Platinum *STOCK heat range*

NGK BKR6EIX Iridium *STOCK heat range*


Autolite 3922 Copper Plug *One Range Colder*

NGK BK7RE Copper Plug *One Range Colder*

NGK BKR7E Iridium Plug *One Range Colder*
NGK BKR8E Iridium Plug *Two Ranges Colder*
NGK BKR9E Iridium Plug *Three Ranges Colder*

Denso Iridium IK24 *Two Ranges Colder*
Denso Iridium IK27 *Three Ranges Colder*


Stock Gap is 0.45"
PSi-Fi Pulley Kit Recommendation gap is 0.28"
Intense-Racing GM-MAF-T/42.5lbs Injectors/2.8" Pulley Gap recommendations is 0.45"
South Florida Pulley Headquarters suggested NGK BK7RE gap is 0.35"

For those of you running 2.8" or below. TWO RANGES COLDER IS RECOMMENDED.

The one stage is just not cutting it, well for me atleast here in California.

For those of you that want to go balls to the walls like Jmc007 with the 2.6" Pulley. Do yourself a favor and go with the 3 ranges colder plug.

I personally am a NGK guy, i've had a bad experience with Denso (but I know they are a great plug).

I used the Autolites for like a day and hated them. Car felt like shit..

Anyone with anymore information to add, please do so..

[jmc007]

Good post ! I didn't install my 3 step colder Denso Iridium #IK27 plugs yet, but in a couple of days they will !

Here is some correction about your post :

NGK Iridium plugs (0.6 mm electrode) are in fact BKR6EIX, BKR7EIX, BKR8EIX and BKR9EIX. They are "like" the Denso Iridium Power #IK20, IK22, IK24 and IK27 (0.4 mm super small electrode).

[jmc007]

Originally Posted by dL_RL

Copper is way more conductive. I would use copper, you just have to change them a lot more often.

FYI Denso Iridium Power spark plugs are COPPER core electrode with an Iridium tip. The tip itself have a very small effect on plug ability to extract heat form the engine. But the smaller it his, the easier the voltage goes through.

silverss for a 3" pulley you could use some NGK V-Power BKR7E (one range colder) or Denso Iridium #IK24 (two range colder). Iridium plugs ignite the air fuel mixture fastly, resulting in a hotter spark.

[jmc007]

As said earlier, Iridium plugs ignite the air fuel mixture fastly, resulting in a hotter spark. But hotter spark and faster spark can also means faster knock retard if the timing advance isn't optimised ...

[jmc007]

Originally Posted by jmc007

As said earlier, Iridium plugs ignite the air fuel mixture fastly, resulting in a hotter spark. But hotter spark and faster spark can also means faster knock retard if the timing advance isn't optimised ...

I installed the Denso Iridium IK27 (three range colder than stock), but there was a LOT of knock with them. As expected earlier, since the electrode is so small and take less voltage to spark, they seem to spark either stronger or sooner, giving some knock (the timing being not optimised). I went back to NGK V-Power BKR7E.

[jmc007]

I found that my knock was caused too by the fact that I scaled down the MAF signal, which cause the PCM to think it's less loaded than it really is, so it runs too much timing advance.

[dL_RL]

Jmc007, do you know of any two stage colder copper plugs?

[jmc007]

I try to found some cheap ones but with no success. I think NGK makes some race ones, but they aren't cheap.

Like suggested by spark plugs manufacturers, a good rule of thumb is one range colder for every roughly 75 more HP.

I don't think we really need two step colder one, since most of the knock is caused by the 91 octane gas and the timing setting.

[jmc007]

About the plug gap, I tried 0.030" on my Denso IK20 (same heat range than stock), but the knock wasn't better or worst.

Again, the knock at mid RPM's is mainly caused by the un-optimised timing, not the spark plugs. The knock at higher boost (15+ PSI) is probably caused by the timing AND the 91 octane gas.

[jmc007]

Originally Posted by jmc007

I installed the Denso Iridium IK27 (three range colder than stock), but there was a LOT of knock with them. As expected earlier, since the electrode is so small and take less voltage to spark, they seem to spark either stronger or sooner, giving some knock (the timing being not optimised). I went back to NGK V-Power BKR7E.

Update : I install back my Denso IK27 and I gap them today to 0.026" (tight) , since I run 21 PSI of boost with the 2.6" pulley. Knock retard is way less than when they were gapped to 0.035".

DL_RL I suggest you to try your BKR8EIX gapped to 0.026" (gapped tight with a feeler gauge) not 0.028" or 0.032" or 0.035".

DL_RL since you (and me) run 91 octane gas, it support merely at least 2 or 3 degress less timing than 93 octane gas.

For your information, each single more PSI of boost need at least one full point more of octane (some says it can take up to 4 points of octane for every PSI of boost !).

It's normal to see some knock retard when running high boost (17 or more PSI) on 91 octane gas.