New set of Denso Iridium Spark Plugs ...
 

Hello -

During the end-of-year holidays I was having a lot of crummy tanks. Part of this was due to the cold weather, and part of this was due to unpredictable XMas traffic. But after the holidays, something didn't feel right. For about 70K miles I have had Denso Iridium spark plugs installed, and I have been happy with them. As one of my XMas presents (for my car), I got a new set of Densos. Here is an old/new comparison of the tips of the Densos :

http://ecomodder.com/forum/attachmen...1&d=1233203447

The old tip has lost maybe 24% of it's height from the white ceramic base.

Here are the specs on these plugs :

http://ecomodder.com/forum/attachmen...1&d=1233203447

At the same I changed my plugs, I did other things to the car :

- New set of Denso Iridium Spark Plugs
- Synthetic oil change, Union 76 10W/30 (mechanic normally has dyno oil, but had synthetic on hand)
- "Piston Soak" to clean carbon off of pistons
- Switch to 91 Octane
- Adding Redline Fuel Injector cleaner
- 49 PSI in tires (was in low 40s due to laziness)
- Hotter drier weather
- Better traffic

With all these variables going on, my last 7 tanks have gone well :

http://ecomodder.com/forum/attachmen...1&d=1233203447

But, because I made so many changes, it's hard to know what made the difference.

In any case, I'm happy, :)

CarloSW2

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Hey man...

I used to install upgraded plugs (Bosch +4, Beretta GTZ Quad-4, specifically and other cars) but didn't really notice a huge difference in performance and economy.

The trick is to compare this particular brand of plug vs. new stock plugs. You also mentioned 91-octane. Is that new as well? I did the same with the higher IATs, coolant temps, and advanced timing. I had a pretty big bump with those three and new wires. Don't forget Seafoam!

Long story short, it's hard to tell if the design of the plugs made the difference or any other variable. Nevertheless, it improved!

-Rick

Rick and CarloSW2,
I like Iridium plugs in a small engine - several im my experience have gone 150k+ miles before needing change.
Plus, if I'm correct, won't larger gap size help FE to a small extent at low RPM?

By piston soak, are you referring to a SeaFoam treatment?

Kudos on the improvement, especially in January.

my truck ing. system is too strong for iridums, i have tried 2 sets and get abou 20-30k out of them till the tip is gone. then the truck starts missing. u dont know how funy it was pulling into autozone and buying cheapie plugs and changing them in 5 minutes in there lot in front of the door, so i could continue on my road trip/

but looks like a decent improvement for you.

RH77 -

The 91 Octane is new because gas is cheap for now. If it keeps creeping up in price, I will lower the octane. My mechanic didn't use Seafoam per se, but it looked like the same thing, with lots of white smoke coming out of the exhaust during the cleaning out process.

I'm not on a "Saturn-service-department" schedule anymore, so I think this qualifies as a partial tune-up. I think there is a throttle-body cleaning and EGR cleaning in my car's near future.

CarloSW2

gascort -

Yes, I have heard at least 100K miles on other forums, but I was happy with how they performed and wanted to yank the old ones to see if they had degraded. They definitely lost some of their tip. I can keep them lying around as a set of backup plugs.

The larger gap + low RPM is a great question, I just don't know. I am sure someone will pipe-up with an answer.

My mechanic was cagey with me. I watched him pour liquids in through the spark plug hole. He made me turn the engine over multiple times without the plugs to work it in. Then he ran the car parked in neutral while the exhaust cleared out from at first a white smoke to normal. He also air-blasted debris (loosened carbon?) out of each piston through the spark plug hole.

CarloSW2

taco -

The saturnfans website swears by the OEM copper NGKs, or the performance copper NGKs. I got into the iridiums because they were for being sold on a Saturn performance website. From my POV, they have been very reliable, so I will stick with them.

CarloSW2

I'll have to admit, I'm running 91-octane because it's cheaper too :o

I still get a bit of pinging at around 6000 RPM / WOT. It's a rare event, but there's an up-hill onramp around here that requires a 2nd gear windout to merge.

I have found that the hotter the engine runs, the better the FE. Advanced timing, blocked rad, 200-210F coolant temps, and 100F+ IATs are a perfect storm for city driving.

Regarding the piston soak -- this actually saved an overheated '93 Chevy K2500 350 V-8. It was nearly seized, but the Seafoam soak saved it.

Plugs -- Hmm. This could be debated. Gap, indexing, temperature and electrode(s) material all play a part in FE. Honestly, I'll have to look up what I did with gap -- perhaps wider. I think I went with the NGK's last tune-up. The wires crapped-out early -- I should've saved the receipt for a free refill.

Curious about the EGR cleanse. I'm sure 140K miles have built-up enough carbon to choke things off a bit in my ride.

Stay warm in SoCal :p

-Rick

I use ngk v power or denso u groove usually.
Yeah I like the idea of 100k on a set

Hello -

It looks like I got some vindication quicker than I had planned :

Trip: home to work - 2009/01/30 - 61.4 MPG
This is my "milk-run" where I make most of my MPG hay. If I keep the car in good running shape, it should give me some good runs in spring and summer.

CarloSW2