Hey just wondering what you guys think about this topic. I've heard some people say its stupid to think that the iridiums are better, and some who say they are much better.
On my previous '89 Turbo I had put on the iridiums and honestly the motor did idle much smoother and started up more easily. Don't know if I noticed much of a power gain but it did seem to run a little stronger.
Now on my newer '89 Turbo I went cheap and bought a set of $1.99 a piece spark plugs. It is harder to start (could be others reasons why), and doesn't idle as smooth. Also when accelerating it feels laggy like something is holding it back a little (could be others reasons of course). Let know what you think.
NGK Coppers are the only thing I'll run in my Supra. 3330's (or was it 3033's?) IIRC. Iridiums just cost too much to be justifiable. I think the stock plugs were NGK Plats's, but I don't recall.
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1988 Mk3 Turbo Targa - 17.5psi, 486hp, 494tq.
[img]http://www.**********s.com/supra/rsw_sig_stupidTN.jpg[/img]
Who came up with this 500px wide BS?
Bosh platinums are definitely not worth wasting money for MKIII Supras or 7MGTE motors. Back when my motor was somewhat stock, my car dynoed at 247 on stock turbo and stock boost with the bosch platinums. While the car was STILL on the dyno, we swapped the plugs out with the NGK coppers...and the car fifteen mins later dynoed at 270whp. Bosch plats are garbage for our turbo cars. Autolites which are very inexpensive and can be had at any local WALMART also work great on the 7MGTE.
Turbo and high compression engine don't like small tip plugs (+2, +4). The tip can't conduct heat away fast enough and cause pre-ignition. +4 does work pretty well with A and S series FE engines.
I tried a set of Bosch +4s in my Tacoma. The truck ran like crap. It wouldn't idle right and stumble under acceleration. I figured it had something to do with the fuky plug the 3.4L requires. They fowled somthing awful. I then tried a set in my NA 7m. Same problem. I think the small gap is to blame. There isn't enough room in the plug for the mix to pass through. The 4 prongs nearly completly block the electrode. Now I have gone to a 1JZ in my Supra, and I am wondering how a plug similar to the Tacoma plug would perform. With twin ground electrodes that are long and the large void for the mix to fill and surround the spark on all sides it really is a great design.
The smaller the center electrode is the better the spark is. Denso Iridium uses the smallest center electrode in the world. It is only 0.4mm in diameter. As the spark goes through the plug and tries to jump over to the ground strap much of the energy is in the center electrode. By reducing the C electrode size there is more energy available to jump to the G strap. This is the vreason why people like MSD sell you a better Ignition box to increase the power to make that jump. Thats why you notice a smoother idle when you put the plugs in your car, your motor is burning unburned fuel since the motor at low RPM the motor has what is called valve overlap, this causes pulsation in the intake manifold resulting in poor combustion at idle, the Denso plug is very efficient due to the small C eletrode in this area. If you run a lot of boost w your turbo they work even better in high cylinder pressure, remember as cylinder pressure goes up it is harder for the plug to jump the gap. The small electrode does not suck up the energy of the spark and wants to jump to the G strap rather then stay in plug.
I have had the same Denso Iridium plugs in my car for the last 3 years, still no missing and the car never ran any better. I have them gapped at .034". The ones I use are the Denso IK24s, they are a couple of heat ranges colder than stock.
Regular cheap copper plugs are also great for turbo cars, they just need to be replaced a lot more often.
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Spark Plugs: Iridium vs. others
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