I always read on the .org that when you throw on an SC (or reach X horsepower), one should run one step colder plugs. I listened to you guys and did that on my '96 (I can't say I noticed a difference one way or the other). As I transfer the SC to my '99, I am contemplating just using stock plugs (NGK platinum). I have spoken with several local shops and they advised me to run stock plugs. Questions:

1.) What exactly is the tecnical reason behind going one-step colder?

2.) Do you guys really/strongly think I should use one-step colder? (or am I o.k. with stock?)

3.) Spark plug gap?

Thanks guys.

- Josh

 

1) Sparkplug tips are designed to absorb some of the heat in the C.C. and transfers it to the cylinder head so that it can maintains an "optimum" temperature to avoid carbon build up. Assumption is that EGT temperatures will go up, so if the sparkplug can't transfer enough heat away to the cylinder head at a certain rate, the sparkplug tip may reach a high enough temperature to cause preignition.

2) I say 1 step colder but as long as you don't have the above problem, use the "hottest" plug you can.

3) Similar to above... as long as your ignition can "light up" the plug... there's no need to reduce the gap... larger is better (in general).

 

To further expound on gap, the reason people decrease gap as they make more power is that cylinder pressures are higher, and it becomes harder for the spark to bridge the gap, thus they reduce it.

 

I don't know how you'd know if you have pre-ignition before the engine goes boom. My thinking is that colder plugs are cheap insurance, the only downside being possible fouling. So clean them.

 

Mike, I LOVE the picture!!!

 

i regapped mine. you can really notice the increase in power with properly gapped plugs. I didnt go colder because I had just put brand new platinums in. workin like a charm with 8psi, lets see how they handle the 2.87 pulley.

 

So would you say that under low boost conditions the stock plats would work fine? Did you make the gap smaller than stock?

 

much smaller but you'll get adicted to the boost.

 

Do you remember what you gapped them to? If i remember right stock is somewhere around 0.044"

 

i think mine was 38 or 32

 

I recall from somewhere that platnum plugs aren't the best choice. 2nd best choice is copper ngk and 1st are the iridiums. I currently use 2 step colder coppers.

 

yeah, but this was done 3 months before i decided to boost.

call me a cheap bastard, i dont care.

 

0.44 is correct for the stock gap and no you dont need colder plugs for stock s/c set up. stillen and jwt told me it wasnt needed just a saftey option just in case. i ran stock plat plugs for several yrs with s/c and nitrous set up with no ill effects. funny enough i did detonate while using copper one step colder plugs for the first time last year. if you buy the plugs for the car they come pre- gapped already.

 

but that doesnt mean that they didn't get knocked around, and "regapped" during shipping, its always a good idea to double check

 

I gapped mine 1 step colder NGK coppers to .34 or right in that area... 10psi with stock injectors. I think it runs good. What do you guys think of that gap, too much?
I also went years on the factory plugs with s/c and no problems.

 

so what should be appropriate for running with the 3.125 or even the 2.87 pulley and all other bolt-on's? I know if you go with the JWT S/C chip, the timing is very conservative so "pining" or pre-ignition/detonation is not so much a worry...which is why I might consider staying with the NGK copper but no colder...I have 2 step colder coppers laying around but am wondering whether to throw those in or not...haven't had any "pinging/detonation" as of yet or as I can tell, but I always run chevron premium with techron so demote the possibility of carbon buildup and hence detonation...I do live in socal...and it hasn't been a very hot day yet...so I don't know if with the stock heat ranged plugs I will detonate or not...but I hear the copper plugs are naturally slightly colder (as a charateristic of the element) than the platinums even with the same heat range rating...we shall see what happens in the summer! also is a .36 or .34 gap optimal with the 3.125 or 2.87 setup....? what do most of you use from 320-350whp?

 

i believe .034 is the proper gapping for our boostin applications. I know that everyone's setup is different, but we do not see enourmous amounts of boosting power (except maybe a handful: neal, hal, mardi, etc.)

 

but I believe those crazy guys are the ones running .034 gaps....so I would think that those of us that are running that on a S/C'ed application with 320-350whp would be kinda overkill....do you think .036 or .038 would be okay for my applications then (which is what I have it at right now)....

but I still wonder if my 2 step colder coppers are necessary as a lot of you guys are running the stock heat range plugs in your boosted applications just fine...which goes to the old wives tale that not only are coppers colder by nature, but japanese cars require plugs that are generally colder than german car plugs...which is sorta why people with bosch spec plugs have trouble on our engines sometimes...

 

well im running 0.38 and the car idles and runs well and like you said for only 350 hp anything else would be overkill. i do think 0.34 is a bit low unless your over 400hp

 

i was running really lean, so we gapped them accordingly.

 

maxboogie, what heat range are you running as well?

 

I had mine gapped at .36 and I swear I was experiencing hesitation at red line in 1st. NGK copper 1 step colder. Since I have changed them out with the new gap of .34 which I had before .36 with no hesitations in 1st I have changed my alt fixed small oil leak dripping on alt and have aquired a bad clutch so can't tell you the difference yet.

With .36 all of my plugs looked really good (dark brownish) but I was also n/a for 2 months with the blower rebuild........

 

I wish I knew the max hp you can run with the largest corresponding gap so that the spark won't blow out...I know the rule is reduce gap by .004 for every 50hp added (but does that mean crank or wheel?)

as far as heat range goes, I live in socal so the intake charge might be higher in the summer months which equates to higher combustion temps and a possibility for pre-ignition...although the JWT S/C program does run very conservative timing which would decrease the likely hood of detonation induced pre-ignition, I better switch to 2 step colder when I move to the 2.87 pulley or keep my 1 step colder for my 3.125 right now...just to be on the safe side...

 

Hey, man, just following instructions!

 

Just wanted to share this. My 03 Max (bone stock) with 60,000 miles started to ping at this mileage only at 2000rpm under load, e.g. climbing slopes or after the auto changes to 2nd and 3rd gear. I only use 91 octane gas. When it starts to ping, the power of the engine drops. I changed the stock plugs(ngk plfr5a-11) and replaced them with an equivalent one step colder plug (Denso Iridium IKH20). The VQ35 beast has returned after doing this change. No more pinging at all and full power. My fuel mileage has improved and top speed.

 

Hmmmmmmmmmmmm 2 year bump FTMFL lol

 

Try 3 years..... OMG
Ok im done here.....












lol

 

i went to one step colder and noticed that the car would be alot smoother on hte top end.....used to get alot of "popping" on top end b4 i had one step colder