[Harvey]

I know there's a lot of different feelings on which spark plug performs in the 968 best (mine's 1994 if that makes any difference) but the three-prong jobbers in there now definitely need replacing. Also, the distributer cap and rotor look to be getting their share of flame. The car runs great but it's obvious that the plugs are up for a change and the others...well...they may be pretty pricey to change out right now so I might just clean them.



I had platinum tri-prong plugs (new) for my 928 when I first got it and had a mechanic do some work for me that was over my head. He saw the plugs and said that my car would run better with stock plugs. Always wondered about that. Has anyone actually noticed any difference or is it mostly hype?



Suggestions?



Thanks,



Harvey

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[flash]

many of us are now running the NGK iridium plug with great satisfaction - much better than the bosch, platinum or otherwise - there are a couple of other new multi-tip plugs there though that some guys have tried and liked



www.sparkplugs.com

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[ds968]

I also have NGK iridium, but I see more and more ads for Brisk plugs for sports cars... claiming around 5 hp gains ( which seems to be way to high to be credible, but then again, compared to what type of plug ? - if they test a car using the cheapest plug on the market and then use the top of the line Brisk plug may be that 5 hp difference is attainable, but I wonder how they compare to anything else that is of same quality..)



Here's their site, btw



http://www.briskusa.com

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[ds968]

went to the testing link on their website and looked at the first one which compared NGK copper plugs with their Brisk.



yup, as I thought, apples and oranges.

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[BigL2U]

A friend of mine races his Acura and he's a big fan of Nology Silver plugs and Nology Hot wire.



I wasn't sure if such a big spark would cause premature detenation in the 968. Any thoghts or experience with these Nology products?



Nology Products

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[Cloud9...68]

The topic of spark plugs hasn't come up in awhile, so I was wondering what the general feeling on them is these days (other than that the car tends to run much better with them than without them, for you wise guys out there <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" /> ). NGK Iridium's seem to be a popular choice. My engine has 105,000 miles on it, an increasing proportion being on the track, so I'm looking for a plug that performs best under stressful, high rpm conditions. It's been a good five years, and about 25,000 miles, since the plugs were replaced, so they're probably due. I also want to use the spark plug replacement as an excuse to do a compression test (for which I'm about to open a new thread, if I can't find one that covers my question). Thanks.

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[PorscheG96]

Best spark plugs? Properly spec'd new ones every year or two. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[Cloud9...68]

Well, it's been a good five years for me, including many hours of very hard track time, so I guess I'm just a tad overdue... Torqueing spark plugs into this car's cylinder head gives me the willies, so I do it as infrequently as possible. I will use the opportunity to do a compression test, however, as my motor has over 105K miles on it now.

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[flash]

frequency of change is relative - my car sits a lot, so i tend to varnish plugs pretty quickly - i change them when i change my oil - no, i don't "need" to, but they are cheap enough, and since i don't drive the car for anything but fun, i want every last bit of performance



which reminds me that i need to order more

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[banditsc]

[quote name='flash' post='64752' date='Dec 28 2008, 12:26 AM']frequency of change is relative - my car sits a lot, so i tend to varnish plugs pretty quickly - i change them when i change my oil - no, i don't "need" to, but they are cheap enough, and since i don't drive the car for anything but fun, i want every last bit of performance



which reminds me that i need to order more[/quote]



Perhaps you could start selling sets of your old ones in the classifieds here...

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[Cloud9...68]

[quote name='flash' post='64752' date='Dec 27 2008, 11:26 PM']frequency of change is relative - my car sits a lot, so i tend to varnish plugs pretty quickly - i change them when i change my oil - no, i don't "need" to, but they are cheap enough, and since i don't drive the car for anything but fun, i want every last bit of performance



which reminds me that i need to order more[/quote]

Are you still using NGK Iridiums? If so, which part number? Thanks.

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[flash]

yes - can't ever remember the number though - lol - i am going to have to look it up myself again - i think maybe i have an old set around here i can go from

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[Cloud9...68]

[quote name='flash' post='64758' date='Dec 28 2008, 09:44 AM']yes - can't ever remember the number though - lol - i am going to have to look it up myself again - i think maybe i have an old set around here i can go from[/quote]

OK, no problem - I'm sure I can find it on NGK's web site.

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[xrad]

All these plugs are nice, but I really think the biggest difference is made by my Crane multispark HI-6 CD digital unit......

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[Ryan]

How is it that many of todays new cars don't get new plugs for 100,000 miles?

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[flash]

better fuel and ignition controls maintain more consistent conditions, thereby lengthening the lifespan of the plug - however, most plugs are long overdue in the real world at 100k, and generally poop out about 70k - still, that's a heck of a long time - i remember having to change the plugs in the mgb about every 3k



i'm sure i could get a lot more out of the plugs i run now, but i also tend to think that they don't perform as well as new when they old either - a fresh set always seems to perk it up

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[DayDreamer]

I remember a thread several years ago on another site that spoke about using shims on the plugs to get all the spark gaps to point in the same direction (I think down) to get a more consistant burn pattern. Claimed about 5hp. Does anyone remember that?

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[flash]

it's called "indexing" - on a 2 valve head, this can be beneficial - on a 4 valve shaped head, i'm not so sure about any gains

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[xrad]

It's called 'indexing' the plugs to create a more uniform burn pattern. With a single ground electrode, the electrode generally should point to the center of the combustion chamber(of course you have to find out where the true compression center is, not just the physical center!!) and possibly towards the exhaust valve. It depends on the configuration of the combustion chamber in question and how to get the best flame front propagation at speed. Usually, you will have to try several different positions to find the best location, if there is one. Multi electrode plugs could not be used to 'index' because the spark will take path of least resistance which may not be where you want.

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[Cloud9...68]

OK, I went to NGK's web site, and their top of the line spark plug is the Iridium IX. It's a little pricey for a spark plug at $7.83 each on sparkplugs.com, but considering the hard track use my car gets, and the fact that plugs aren't something I tend to replace very often, the price is no big deal. Does anybody have ay experience with these particular plugs? Thanks.



Next, it's going to be a new cap and rotor, followed in short order by connecting rod bearings, and, depending on what the compression test shows, a cylinder head "freshening" at RS Barn.

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