Iridium Spark Plugs

[mikewags]

What are your thoughts on Iridium Spark Plugs? I was originally going to put them in my Z months back (was told they improve performance) but ended up going with the NGK Stock Plugs.

Would iridium plugs make much of a difference?

[doradox]

What are your thoughts on Iridium Spark Plugs? I was originally going to put them in my Z months back (was told they improve performance) but ended up going with the NGK Stock Plugs.

Would iridium plugs make much of a difference?

They were stock in my wife's car. I replaced the plugs with Bosch Platinums around 65,000 miles. At about 110,000 I put OEM spec iridiums back in and other than a slightly smoother idle, which could be explained just by the fact that the plugs were new, there was no discernible difference. Of course this was on a late model V8 so this may be irrelevant to a Z motor.

Steve

[hls30.com]

The only difference Iridium will make in your Z is lightening your wallet!

You made the best choice and you were horribly misinformed-unless the performance the recommender was talking about was emptying your wallet quickly. In 25 years of realworld testing, and trying everything out there, nothing beats the proper NGK plug in a well-maintained L series engine.

Will

Edited September 18, 2008 by hls30.com

[mikewags]

The guy who told me was a mechanic that worked on classic cars...maybe he buys a bit much into the hype of certain products.

Thanks for the insight guys!

[sblake01]

For those of us who have tried just about everyting out there, like myself, regardless of what any 'expert' may tell you, Will nailed it:

......nothing beats the proper NGK plug in a well-maintained L series engine.

[doradox]

Iridiums can be an advantage in vehicles that have difficult to replace plugs. The extended change interval can offset the initial cost if you value your time at all. Of course, since it takes about 2 minutes to change plugs on an L6, there's no value to that.

Steve

[Carl Beck]

The longer change interval is mostly if not entirely due to the HEI ignition and significantly wider plug gap's in modern cars. Also due to the use of computer controls metering out all but exact air/fuel ratio's for every combustion stroke using lead free fuels.

Spark plugs rarely "wear out" or "burn up" in an L6 - normally they become carbon fouled. In which case all you need to do is clean them. Most people, not having a high quality spark plug cleaning machine - wind up simply replacing them.

The el cheapo spark plug cleaners (aka Harbor Freight) are worthless. The A/C and Champion Spark Plug Cleaners from decades ago will make dirty/fouled plugs look and perform like new. Clean them up and run a file across the tip of the electrodes... and put them back in...

FWIW,

Carl B.

[doradox]

The longer change interval is mostly if not entirely due to the HEI ignition and significantly wider plug gap's in modern cars. Also due to the use of computer controls metering out all but exact air/fuel ratio's for every combustion stroke using lead free fuels.

Spark plugs rarely "wear out" or "burn up" in an L6 - normally they become carbon fouled. In which case all you need to do is clean them. Most people, not having a high quality spark plug cleaning machine - wind up simply replacing them.

The el cheapo spark plug cleaners (aka Harbor Freight) are worthless. The A/C and Champion Spark Plug Cleaners from decades ago will make dirty/fouled plugs look and perform like new. Clean them up and run a file across the tip of the electrodes... and put them back in...

FWIW,

Carl B.

Yes, lead free, exact metering, elimination of rotor and cap, in some cases even wires, AND spark plugs that don’t wear. I’ve seen ground electrodes virtually gone on cars way overdue for a tune up. The ignitions would be pumping out over 20,000 volts at idle and they still ran fine. Everything upstream would be fried. If your plug gap stays consistent everything else lasts longer. Iridium plugs just last longer and I see that as the key to long ignition life. By long I mean 60-100K miles. Kind of pointless in a car that needs points, condenser, cap and rotor serviced at best every 10-15K and is so easy to R&R plugs.

Larger gaps? 350Z is .043 in. Toyota Tundra .031. Chevy Suburban .040. Not really significantly larger. Now by modern if you meant the 1980’s….

Steve

[John Coffey]

The initial impetus for longer life plugs was California's requirement of a smog equipment warranty of 50,000 miles concurrent with the BAR '90 legislation. This eliminated the "tune-up" part exemption under previous CA emission warranty rules. Manufacturers didn't want to replace the spark plugs twice under this warranty. It also took away a significant chunk of dealer service revenue.

Under the standard Datsun 10-15K service interval almost any spark plug will function well. Based on Dyno testing done way back when by Javier at JG Engine Dynamics, Champion projector tip spark plugs developed the most power in an ITS built 2.4L L6. Granted, the power differences were minor and only of interest to racers.

[MikeW]

Based on Dyno testing

That's the only credible way to evaluate claims of a performance boost by miracle products. Whether it's Slick 50 or Seafoam or anything else I'd believe it if the dyno results can back it up.