spark plugs do matter

I'm happy with my $1.94 (for two) Autolite 3924's

Trojan Horse said:

The irridium plugs are made from a super tough alloy that can withstand a lot more heat. The center electrode thereforem, is considerably smaller and able to provide a better spark than standard or platinum plugs............... At least that is what I learned from researching them. I have not bought any yet because of the high price, but I do plan on trying a set of the NGK as they are considerably cheaper. Around $6, I think.

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That could have a factor. A sharper hotter spark. A/C Delco's, NKG's, and I guess Denso uses the type that makes a point at the electrode. I have heard one of the "hp tricks" is to grind the electrode and center electrode to a point to increase the intencity of the spark. I know that A/C's and NKG's are great plugs. I might try a set next time. It's just that I am not having any problems with old Autolite 25's. The important thing is the material, and how it conducts electrisity. Platnum is only good for long life, and that Bosch + stuff makes no sence.

From Denso's website; they seem to be playing down any 'hp increase' and pointing to long term reliability. Of course the first q/a in the FAQ speaks of the source of iridium being an asteroid that hit earth millions of years ago forming the Gulf of Mexico and killing all the dinosaurs, so it's hard for me to take some of this seriously. I believe they named it incorrectly in any event - should've been called "Unobtainium" for the price they're charging. AutoZone online wants $13 A PIECE for them - including tax here in TN, that's $115 for a set of plugs whose main benefit seems to be that they'll last longer. I'm no economist, but I believe I can replace my Autolite or Motorcraft plugs a little more often and still come out ahead.

"Q. What kind of performance will I get from this plug?
A. Generally, you do not purchase spark plugs for performance enhancement. While DENSO Iridium Power spark plugs have contributed to numerous accomplishments through dyno-testing and actual use, their true benefit lies in their efficiency, durability, and improved firing power. Serious tuners modify their vehicles by increasing boost through turbo-chargers, super-chargers, and Nitrous. They are also known to add high-energy ignition systems, tinker with timing, adjust fuel mixture ratios, and increase horsepower through other means. Putting these kinds of demands on their engine increases the need for an efficient, durable spark plug that can handle these kind of harsh environments. That’s where DENSO Iridium Power can make a major difference."

From NGK:

"Iridium is a precious, silver-white metal and one of the densest materials found on earth. The natural properties of Iridium offered NGK the opportunity to create one of the world's finest spark plugs. The result are spark plugs that require less voltage to spark, burns fuel more efficiently, sparks at leaner air/fuel mixtures, and delivers higher horsepower and better gas mileage.

Iridium IX Spark Plugs are the most technologically advanced high performance plugs available. Featuring a 0.6 mm iridium center electrode tip, they offer superior ignitability without sacrificing durability. The tapered ground electrode increases flame kernel expansion, while the superior heat range design is ideally suited to the demands of high performance environments. Specially designed to meet the needs of serious enthusiasts, Iridium IX Spark Plugs offer outstanding acceleration, high fuel efficiency and long life. When you demand the most from your engine, rely on the proven performance of NGK Iridium IX Spark Plugs."


From I forgot where?:

10 Horsepower From Sparkplugs?
"The following article is in response to several customers’ questions regarding the performance claims of Split Fire spark plugs and others like them.
To help you understand the answer we're about to give, you need to understand what happens during a normal combustion event.
When the voltage from the ignition system finds its way to a spark plug, an electrostatic charge builds between the center and ground electrodes. When this charge becomes intense enough, current starts flowing through the air/fuel mix that's situated in the gap between the two electrodes. Current flow always generates heat, and it's this heat that ignites the air/fuel mix and begins the combustion process.

It's important to realize that the voltage required to jump the gap and cause the start of the combustion event is much higher than the voltage needed to sustain it. On a typical stock 302, about 10 kV is needed to bridge the gap, while only a few hundred volts is required to keep the gap lit up and burning. When cylinder pressures are dramatically increased, through supercharging, turbo charging, high compression, high revving, or nitrous, the voltage needed to bridge the gap is much greater. This is when a high quality aftermarket ignition is needed and will help produce more power.

The Split Fire plug's main claim to fame is that it produces a shower of sparks throughout the combustion event, which results in more complete burning of the air/fuel mix. Result: Better fuel economy, more power and lower emissions. In our book, that isn't possible, because once the gap is hit with the initial jolt of electricity to start combustion, the voltage level drops off sharply and is far too low to add any significant benefits.
Last Fall during a dyno session with a fairly mild 5.0 (328 hp @ 4650 / 363 ft lbs. @ 3950) we spent more than 16 pulls trying several different trick plugs, including Split Fires. None of them showed any miracles, there was no more than a 1.5 hp difference and it wasn't a consistent difference (meaning on 2 of the Split Fire pulls there was no difference at all).
The only plug that showed a significant improvement was a prototype Delco Racing Plug that used a unique 4 grove channel around the center electrode as a ground electrode. And by significant difference, I mean it gained 4.5 hp and 5 ft lbs. peak. I suspect the reason it made this increase was the lack of shrouding sometimes caused by the ground electrode in the chamber.
Bear in mind that the electrostatic charge needed to ionize the air/fuel mix is at its strongest when there are sharp, distinct edges on the plug's center electrode. Over time, these edges round off through normal wear. When we change plugs for a customer during a routine tune-up, in effect we restore those sharp edges, thereby lowering the voltage required to fire the plug. The results are more complete combustion, lower emissions and greater fuel economy."

I have underlined the portions that "may" make Iridium plugs work a little better than standard plugs. Everyone will have to make their own decision about whether they are worth the extra expense.

Here's the part of your post that I think is most enlightening -- "Last Fall during a dyno session with a fairly mild 5.0 (328 hp @ 4650 / 363 ft lbs. @ 3950) we spent more than 16 pulls trying several different trick plugs, including Split Fires. None of them showed any miracles, there was no more than a 1.5 hp difference and it wasn't a consistent difference (meaning on 2 of the Split Fire pulls there was no difference at all)."

Even the 4HP from the Delco's is well within the range of variability from pull to pull on a typical dyno -- meaning you could simply shut the car down, change nothing at all, make another pull and have a run that showed 4HP more.

I believe that the 'gains' attributed to plugs like the Iridiums and Split Fire plugs are more a function of those company's marketing departments than anything else. My rationale for this is simple - you don't see professional racers knocking themselves out to run only Iridium or SplitFire plugs. If there were significant, consistent HP to be gained, the racers would all run them. They don't. From what I've seen, only those that have sponsorship from those companies run them. Kind of like Slick 50.

I'll spend my $100 elsewhere. And I'm sure others may chose differently. It's a great country that way!

Save the 100$ cause the "10hp" you could gain will not be felt in the pants, spend the money maybe on a few items to restore the look.."remember its better to look good than to feel good"..lol

In my professional shop experience, I've never seen these plugs to do anything but cause problems, or at best, make no difference at all. I've seen cars with plat's that just couldn't be made to run right until they came out, and cars with Splitfire's that were downright scary. One of the first things we did to make cars that are running like crap immediately run better is to take out whatever trick plug of the month the customer put in, and replace it with whatever the factory specified. Almost across the board, this always made an improvement and never even once did it make things worse. On Fords, that means Motorcrafts or Autolites... and I've seen Mustangs with 5,6,700 HP and more running just fine on plain old Autolites. Some applications call for a colder plug. How convenient! They make those too, same price. Anyone who can talk you into paying more than $2 a piece for a spark plug should be selling mobile homes in Florida.

If there were significant, consistent HP to be gained, the racers would all run them. They don't.

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At least someone hit it on the head

StangLou - they usually just say that I'VE been hit on the head....

Not sure this has much to do with anything but one big difference between newer Toyotas and older Fords is that the Toyotas now have coils for each two cylinders. The coil actually sits right on top of the spark plug, which sounds to me like it has much less resistance as it fires the plug.

Michael Yount said:

StangLou - they usually just say that I'VE been hit on the head....

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Or that you've just hit me upside the head

"...should be selling mobile homes in Florida...."

LOL bear - funny! In fact, many homes in FL have been particularly 'mobile' over the last couple of months. You and I both need to smack each other occasionally to 'reboot the sytem'.

RydeOn - the Explorers and Mountaineers with the 5.0 have the direct-fire distributorless ignitions too from 96-2000. Doesn't seem to make too much difference one way or the other.

Michael Yount said:

LOL bear - funny! In fact, many homes in FL have been particularly 'mobile' over the last couple of months.

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Yeah, my old one was "if you believe that, can I interest you in some Florida swampland?" but right now, I think you'd have to be pretty talented to sell a trailer down there. Hell, I sold Kirby dirt suckers for awhile, and I still won't pay more than $2 for a sparkplug...

I'd do a Crane Fireball myself, but then, that is what I did...

Then I did the Performance Distributors "Screamin Demon" coil. Now that's a hotcan!

I bet if you put an iridium plug in that Kirby vacuum it would really suck.

It can suck an iridium plug right through a 2x6 wall as it is Best vac out there- I was just too young at the time to go into someone's house and tell them they needed a thousand dollar dirt sucker. I've got one myself though, it's awsome. I won't use anything else.

We've been known to hijack threads too. Give 'em an inch...