6G Celicas Forums

If I raise boost to 14psi,do you recommend i get colder plugs??

wouldnt be a bad idea going a step or 2 colder if running max boost (17psi just before cutout) all day

14 psi isnt that much over stock, so standard heat plugs should be fine.

a set of KGK BKR7ES for less than 10 bucks is cheap insurance. gap them to about .028 for boost applications.

so basically the stock plugs and fuel system should be fine to let's say 15psi
Won't be running 15 all day though.. Perhaps for only a few minutes every so often

Next in line is a wideband sensor.. So I can monitor wats up with my ratio..

What's our stock heat range? Are there any draw backs of running colder plugs? When not boosting high numbers?

Stock for a GT4 is NGK BKR6EP-8, It's a long life platinum plug with a 0.8mm gap and heat range 6.

An upgrade into the next step colder heat range would be the BKR7EIX which has a 0.8mm gap and a heat range of 7.


From NGK


So if you're taking your car up to 300+WHP, It might be a good idea to get the BKR7EIX, This is what I'm going to be doing.

EIX is the Iridium IX series.

They don't make a laser platinum in the 7 heat range for our engines

if the only mod your doing is raising a few psi your not going to get a truck load more power so based on that alone ide stay stock.

BUT if your planning on further mods down the track...and lets face it who isnt, then going a step colder now wont hurt (if your getting new ones anyway).

To give you an idea im making around 400 awhp and im just using copper, grade 7 heat range plugs. No detonation here. Change them every 5000kms, but at only a couple of $$ each it doesnt matter.

I advise against irridums. They are fine for stock or near stock, but cant/shouldnt be gapped and are expensive to change frequently.

This post has been edited by Cuts_the_Pilot: May 17, 2011 - 11:54 PM

Stuff changing the spark plugs every 5000kms, Iridiums are pre-gapped to stock gap anyways.

Every time you take off/reinstall the W2A IC you shorten the life of atleast 3 hose clamps, you bend 2 water hoses moving it out of the way, and not to mention the damage you do to the rubber throttlebody mouth every time you reclamp it.

When your running decent ammounts of boost and making decent power closing the gaps and frequent changes of plugs are needed regardless if they are $20 irriduims or $3 el cheapo coppers.

Thats why you man up and get a front mount, changing plugs is a 2 minute job.

Im not necessarily saying that he should change his plugs every 5000km, im simply using my own experience as an example to say you dont need to spend your life savings on plugs.

Just FYI i use the stock twin tipped platinum plugs on my Chaser, because its wasted spark ignition. Its my daily and only mildly modified, running different plugs is simply going to be a hinderence.

This post has been edited by Cuts_the_Pilot: May 17, 2011 - 11:59 PM

i have to agree with Cuts on this one. iridiums are no where near as good performance wise. for copper the metal it self is a better conductor but doesnt last as long. iridiums, and platinums last longer but performance suffers. here is a link i found that talks about. take it for what its worth, either way run what you are comfortable with. now the heat range there is no reason to go to anything colder for just 1 or 2 psi. with copper it will transfer less heat just that amount alone will cover you for the couple psi. i say stock heat range just go to the copper plugs and you will be good.

spark plug

You take that article as truth? I'd take that article with a grain of salt. I've had nothing but good results with Iridium & Platinum plugs for years.

Personally I couldn't credit an article that says "Platinum and iridium plugs are more likely to overheat, which causes damage to the plug components and can compromise the delivery of the spark to the engine block." and then later says "However, the overall longevity of these two types of metal is better than copper plugs." and then comes to no conclusion at all and refers you to your own personal mechanic (who's view is going to differ from the next.)

I've kept W2A, I see it as the superior intercooling system in our cars given the mounting arrangements.

"Copper spark plugs are generally considered to have the best performance of any spark plug type"-- this is due to it being a better conductor speaking purely from an electrical standpoint----"This is potentially different from what advertising companies suggest, but the other metals are, unfortunately, not as conductive in general as copper is"

"Platinum and Iridium plugs perform at a lower level than copper spark plugs, because they are less conductive and they tend to overheat"


this is also a problem with running these types of plugs. with increased boost pressures it becomes harder for the ignition system to push the spark across that gap.
Should I gap my Iridium Plugs?
The manufacturers say NO.
This is because most people do not know how to properly gap a spark plug, and the center electrodes on the ultra-fine iridium can easily snap if mishandled. There is no warranty for snapped center electrodes. The manufacturers say an iridium spark plug will run so much better than a traditional plug, even if it is not gapped for that motor, that they would prefer you just leave it rather than risk snapping the center electrode.
Personally, we at ChampionSparkPlugs.com, gap our iridium plugs for our own vehicles (we’re rebels). If you insist on gapping your iridium plug, please refer to Proper Gapping for instruction. ---source

this is why platinum and iridium plugs last longer. they resist this erosion due to being a stronger metal.
The central electrode is usually the one designed to eject the electrons (the cathode) because it is the hottest (normally) part of the plug; it is easier to emit electrons from a hot surface, because of the same physical laws that increase emissions of vapor from hot surfaces (see thermionic emission). In addition, electrons are emitted where the electrical field strength is greatest; this is from wherever the radius of curvature of the surface is smallest, i.e. from a sharp point or edge rather than a flat surface (see corona discharge). It would be easiest to pull electrons from a pointed electrode but a pointed electrode would erode after only a few seconds. Instead, the electrons emit from the sharp edges of the end of the electrode; as these edges erode, the spark becomes weaker and less reliable. --- and yes i know its wiki source

i cant find anything right now that talks about the heat dissipation characteristics of each, but copper is a cooler plug compared to the others of the same heat range. ill keep searching for something on this. honestly in the end run whatever makes oyu happy and what you want to pay for.

based on all the info I've soaked up, I think I', leaning towards copper plugs on my next plug change, but will leave in my orignal plugs, seeing that my rise in boost is only about 1-2psi, I have small mods though, gutted cat and resonator delete, and some intake mods.

I would just put a couple of words regarding my experience with the plugs. For over a year, I left my 2nd gen at pretty much stock boost, about 11psi max. I had the denso iridiums in it and it was fine. When I later turned up boost to 15-16psi, I noticed on long trips @900 plus miles that the car begins to hesistate or buck intermittently whenever I tried to boost. I changed the plugs to NGK copper and have tried the platinum and the problem dissappeared. I thought it was a fluke and went back to iridiums and the problem returned. So I replaced the plugs with platinum again and it dissappeared. This has been my experience. I don't know if anyone else had the same problem. But I think sharing these experiences will help the community gather info and hopefully guide others.

so you had to drive 900 miles to notice a problem?? how soon into the trip did it start?

I drive back and forth to work 11miles each way and not much time to really pay close attention to everything that the car does mostly in traffic. Contrary to long trips and open highway, you notice a lot with more time behind the wheel. That was my experience and I was just sharing. Good luck.