Spark plug upgrading?

ok so searching around on ebay i came across some Denso Iridium spark plugs. The add says you will gain 6-10 HP. Is this possible to do just with plugs? Heres the link http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=2478485112&category=33693

i have heard that they will add about 5 hp, but i have a friend that bought some for his srt-4 and he said they he couldnt feel any difference at all. i dont know if that was just his car or not.

Sounds like a sales gimmic to me. Be objective: What does a spark plug do? It allows a spark to jump the gap...period. These spark plugs are guaranteed for how much?....250,000 miles? Really? I suppose that you could clean the fouling off the plugs every 15,000 miles or so, but you can do that to a regular $1 spark plug too. And how was their testing done? Did they remove a completely fouled set of spark plugs, put their's on and then claim a 5 hp increase? That wouldn't surprise me, and they wouldn't be lying either.

People believe what they want to believe in. Look at those magnets which are clamped to a fuel line...supposed to give better fuel burning. The magnitism is supposed to polarize the fuel, or something like that. Hell, the fuel line is already polarized just sitting in the magnetic field of this planet! Well, if the magnet doesn't work on your fuel line you can always put it on your wrist to cure your arthritic condition, impotence, motion sickness, headaches, or whatever else you believe in.

Going back 100 years, such salesmen were "snake oil" salesmen. Apparently they never died-out.

All increasements in power from the plugs are usually within the accuracy of the dyno, in other words there are no power benefits that you will notice (unless the plugs don't work for your engine, then you will see a drop in power).

Iridium plugs do however last longer, much longer.

Sounds like a sales gimmic to me. Be objective: What does a spark plug do? It allows a spark to jump the gap...period. These spark plugs are guaranteed for how much?....250,000 miles? Really? I suppose that you could clean the fouling off the plugs every 15,000 miles or so, but you can do that to a regular $1 spark plug too. And how was their testing done? Did they remove a completely fouled set of spark plugs, put their's on and then claim a 5 hp increase? That wouldn't surprise me, and they wouldn't be lying either.

People believe what they want to believe in. Look at those magnets which are clamped to a fuel line...supposed to give better fuel burning. The magnitism is supposed to polarize the fuel, or something like that. Hell, the fuel line is already polarized just sitting in the magnetic field of this planet! Well, if the magnet doesn't work on your fuel line you can always put it on your wrist to cure your arthritic condition, impotence, motion sickness, headaches, or whatever else you believe in.

Going back 100 years, such salesmen were "snake oil" salesmen. Apparently they never died-out.

:1:

Since Iridium is consumed at a much slower rate than typical electrode material, the electrodes can be made thinner which increases spark intensity. That is why you see so many electrode materials, like platinum, copper, nickle, and iridium, the objective is to find a material that is more slowly consumed by combustion so the electrode can be thinned.

Will you gain any power?...probably not
Are they better?...yes.

I think any power "gained" would just be power recovered from using old spark plugs. Thus, in reality, it was not really gained, it just enabled the engine to run at its optimal efficiency.

Well, with a hotter spark, there is the potential for better combustion. Now, whether or not that will actually happen in a given engine is another story...

As SaabJohan said, 5 hp is within the dyno's margin for error, so it's hardly compelling evidence. I wouldn't call Denso a snake oil peddler, but I wouldn't count on the stated gains, either. If you want more power, index your plugs. That'll do you at least as much good as switching to iridium plugs.

The main advantage of iridium plugs is life. They'll last you a good, long time.

BTW, never trust the seat-of-the-pants dyno for less than a 20 hp gain. The placebo effect is amazingly powerful.