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Best Spark Plugs?

67K views 113 replies 41 participants last post by  Beef6  
#1 ·
If the objective is to make power ;) what is the best spark plug ?

I've always run Denso copper plugs. I'll be perfectly honest and admit that I don't even know if they're colder than stock. I've just developed the habit of going into Autozone and asking for "copper plugs for a 1993 3000gt turbo" every couple thousand miles.

Now that I've worked out most of the kinks in my set-up though, I wouldn't mind experimenting with better plugs.

The obvious answer is the Denso Iridium plugs (IK27), but I'd like to know some opinions from people that have tried a variety of plugs. As far as I know, Matt Monett runs NGK Coppers.

Thoughts? (Sorry if this topic has been discussed to death in the past)
 
#4 ·
altough they are very expensive i must admit the irdiums definitley out perform any plugs and i have ran the ngk coppers :D
 
#5 ·
I'm a big fan of the coppers.. but haven't tried the iridium's for myself yet. Dave ^^ clearly had better results with iridium than coppers.. we ran with less knock and more timing.

on my car with copper NGK's I was able to allow a bit more timing/boost when I got to the 7 range but 8's and 9's didn't seem to make any difference even though they are cooler.
 
#7 ·
NGK copper baby!
 
#8 ·
It comes down to this... Would my car be able to make more power (more boost / more timing on race gas without knock) with iridium plugs? I realize they're expensive, but spending money is just part of going faster, right?? :)
 
#9 ·
AdamVR4 said:
It comes down to this... Would my car be able to make more power (more boost / more timing on race gas without knock) with iridium plugs? I realize they're expensive, but spending money is just part of going faster, right?? :)

u will make more power on race gas and if it has enough octane u can turn up the timing ,speaking from experience as for the iridiums i personally believe they out perform the coppers from my results but the coppers are definitley more economical to the wallet ,,i have ran the IKR24 AND THE 27'S
 
#10 ·
Vr4twinturbo92 said:
u will make more power on race gas and if it has enough octane u can turn up the timing ,speaking from experience as for the iridiums i personally believe they out perform the coppers from my results but the coppers are definitley more economical to the wallet ,,i have ran the IKR24 AND THE 27'S
Believe ME, I KNOW you can make more power on race gas by advancing the timing and raising the boost... What I want to know is if IRIDIUM plugs would allow me to raise the boost and timing even MORE.

I'm running 22.5 PSI and about 31* of timing (at redline) on a mix of 93 and C16... I'm getting about 6 counts of knock at the worst. If I didn't change anything but the spark plugs, would IRIDIUM plugs allow me to run say... 24 PSI and 33* of timing with the same (or less) knock?
 
#11 ·
well i dont know for sure if that would be true or not me and mellon did some logs and mine definitly has less knock with the iridiums
 
#12 ·
I've been using the NGK BCPR-7ES copper plugs for quite a while. Just had them out today, and they look perfect. If you are trying to make more power and reduce knock, go with -8 or -9, although they will foul easier if you run them rich.

I also had the Iridiums - but they were IK22 so they really didn't seem to change anything either way. I'd probably run IK24 if I picked those again.
 
#16 ·
I can't imagine how you could make more power with irridiums than with copper, the only difference is irridum/platinum lasts longer. Copper is actually the best conductor, although I doubt that makes any drastic difference in performance. I use BCP7ES.
 
#17 ·
NGK copper here.
i use bkr7es (recessed electrode) ... standard FI/nitrous/import plug.

I wouldn't run iridiums in a high high high hp car. you know why ? because they have a needle point looking tip. Sure that tip is good for electron injection, but what do we know about hot spots ? are you sure you want to run that much boost and that much timing with something that looks like a needle inside your combustion chamber.

NGK copper. Cheap, effective, while still not resembling something as fine as a needle and so britle that you can't eve gap it (they break).

I dunno maybe there are some high hp guys running Iridium. But i'd stick with the ngk coppers.

-nuke
 
#19 ·
AdamVR4 said:
If the objective is to make power ;) what is the best spark plug ?

I've always run Denso copper plugs. I'll be perfectly honest and admit that I don't even know if they're colder than stock. I've just developed the habit of going into Autozone and asking for "copper plugs for a 1993 3000gt turbo" every couple thousand miles.

Now that I've worked out most of the kinks in my set-up though, I wouldn't mind experimenting with better plugs.

The obvious answer is the Denso Iridium plugs (IK27), but I'd like to know some opinions from people that have tried a variety of plugs. As far as I know, Matt Monett runs NGK Coppers.

Thoughts? (Sorry if this topic has been discussed to death in the past)
Denso irridium IK27s all day every day
there is no substitute.
If on a budget,,,,ngkr 3330
 
#20 ·
Vr4twinturbo92 said:
well i dont know for sure if that would be true or not me and mellon did some logs and mine definitly has less knock with the iridiums
yep, we had to pull his base timing several degree to keep knock at bay when we ran the NGK 9's vs the Iridium 27's he had in there previously. I can't explain it but that's the facts
 
#21 ·
mjannusch said:
I've been using the NGK BCPR-7ES copper plugs for quite a while. Just had them out today, and they look perfect. If you are trying to make more power and reduce knock, go with -8 or -9, although they will foul easier if you run them rich..
Matt,

What do you think about the non resistor plugs? I tried a set of the non-resistor 9's and really didn't notice a difference... but just given that the resistor is gone... the spark should be hotter, right?

I think they also come pregapped at .28.
 
#22 ·
Perhaps I should adjust the question slightly.

Will spark plugs that operate at different 'heat ranges' affect power output? Would I be able to create more power running COLDER plugs? Is a colder burn a better burn? Is a hotter burn a better burn? Somebody clue me in.

Oh, if one more person says "NGK Copper" with absolutely no evidence to support their opinion, I'm gonna give up on 3Si forever. I'm sick of reading useless posts on this forum. Either be productive or STFU. Rant over.
 
#23 ·
It has to do with pre-igniting... if you get a colder plug... you get less chance of the plug pre-igniting from the heat created from the engine. But that's about it. So if you make huge jumps in HP... you generally want to go with a colder plug. But you won't 'get' more HP by runnin colder plugs.
 
#24 ·
In theory yes colder plugs will carry more heat from the combustion chamber into the head which will help suppress knock. There are absolutely no negatives to running the coldest plug possible unless you go so extreme that it fouls.

I used to run stock plats back in the day. Then I switched to coppers when everybody else did. Then I melted a copper while racing at an IDRC event. Kinda shot the day in the butt when I was firing on 5 cylinders at WOT. So I switched to IK24's which (for all intensive purposes) should never melt. I noticed they were REALLY white about halfway down the center electrode porcelin. So I switched to IK27's. They were about as good of a heat range as you can ever expect to see. Check out this pic. I figured what the hell...I'll try IK31's. Without changing fuel from the IK27 pic the IK31's fouled in like 50-75 miles. They were completely black all the way over the center electrode. So those were a bust.

The two reasons I like the IK27's are that they can put up with a butt load of heat and I KNOW they're the perfect heat range for my car.

Oh...BTW. IQ27's are actually closer to stock and should work better with the stock wires. The bottom of the plug is the same as an IK27 except the area that the wire boots snap into is Japanese standard length...IK27's are ISO standard. From now on I'll be ordering IQ27's. Oh...and if you shop around you should be able to get a set of 6 iridiums for $67 shipped.
 
#25 ·
NGK COPPERS FOOO! ;)

http://auto.howstuffworks.com/ignition-system2.htm

************
The carmaker will select the right temperature plug for each car. Some cars with high-performance engines naturally generate more heat, so they need colder plugs. If the spark plug gets too hot, it could ignite the fuel before the spark fires; so it is important to stick with the right type of plug for your car.
************
 
#26 ·
With 99% of the cars on the road manufacturers purposely go really hot on the plugs and sacrifice knock overhead to make sure they stay clean even under the worst fueling conditions. You could probably drive around with 660's and no fuel computer with the stock plugs and they'd never foul. :rolleyes: