I'm dropping the guts out of my 97 C2 in a few weeks to do an RS LWF/clutch and I'm taking advantage of the situation and changing plugs the "easy" way.

I've already ordered a set of Iridium plugs based upon prior favorable experiences with them. In fact, my other 2 cars have been running these for some time now. Both cars have direct ignition, however, unlike the 993's cap/rotor setup.

I was very impressed with the performance of the Iridium plugs the first time I tried them. I hadn't really expected much, other than a longer useable life. After all, I change plugs often enough that I usually feel guilty about throwing away what appear to be perfectly good plugs (so now I have a fairly large collection of very good used plugs), but these seemed to make an immediate improvement in smoothness and throttle response. I've used Denso Iridiums ever since.

So if I'm so convinced, why am I asking for input on this issue? It's all TheOtherEric's fault, really. I ran a search and came across just a few posts on this topic and one of his really got me worried. Apparently his GF's car had one self destruct in the combustion chamber, which is something I would like to try and avoid.

So. Any other horror stories out there, or was this an isolated incident?

 

If your engine is stock, use the factory recommended plugs. Porsche recommends them for a reason, since the engine is designed to work with them. Contrary to popular belief, "upgraded" spark plugs do not increase performance on a stock engine, no matter what the car is. On modern cars, the engine is a fine-tuned piece from the factory, especially a Porsche, and all those flashy aftermarket plugs/wires are designed for one purpose: to extract money from your wallet. Only when you start seriously modifying an engine (IE turbocharging, changing compression ratio, etc) do they make a difference. Your car will probably run worse w/ the iridiums, but even at the very best it'll run about the same but you'll be wasting money on more expensive plugs for no reason.

---

Chris Andropoulos
Schneider Autohaus
Santa Barbara, CA

 

Perfect advice from Chris A. Nothing else needed to say, IMO. Now, how about those Splitfires?

BTW, whatever happened to the rather strong Splitfire marketing campaign??

 

The stock plugs are really an antifouling design with the three ground straps. I run NGK Iridium in my race engine (because they are less expensive than the Denso version) On the dyno I have found that with a good ignition system you can open the plug gap and reduce ignition timing and make slightly more power. However, I agree that with a stock engine you aren't likely to see much of a performance advantage. They do run fine in a stock engine and the fine wire technology makes it easier for the spark to jump the gap. The NGK Irridium are the same price as the stock plug and I run them in the stock engines.

 

Good info Geoffry thanks.

---Chris A.

 

Part number?
The NGK site shows a three electrode ( carbon steel?) BCPR7ET for the NA cars, and a two electrode '6' heat range plug for the turbo; however, no link to their Iridium iX series.

 

I run an NGK BCPR7EIX. If you want a larger plug gap then the BCPR7EIX-11 is what I use. I've had both in a stock engine.

 

Thanks!

 

Lol, sorry to cause such consternation. But seeing my (now) wife pull an Iridium out of her car with a missing tip made me decide to stay away from them and to stick with factory recommendations. I suppose one could make excuses like it was an isolated incident or her car is a tuned bi-turbo or whatever, but I'm just reporting what I saw. Overall I think Chris A's advice is good.

 

Thank you to everyone for their input.
Like I said, I had already ordered the denso Iridiums based on previous favorable experience with them, after which I just decided to run a search here to see what others thought.

I don't think these things are based upon the same sort of marketing gimmickery that brought us the infamous Splitfires. The reasoning behind the use of platinum or iridium in this sort of application is sound. If it allows a slightly larger gap and/or provides a longer usable life, all the better, since plug changes are no joke on these cars.

As far as the argument that the manufacturer, Porsche or otherwise, specifies a particular fluid, tire, brake pad or plug - I think cost plays a very large part in this equation. If everything were perfect from the OEM, we wouldn't spend so much time and money swapping out so many different OEM parts for more expensive, durable or better performing pieces. The "G50/G64 Transmission Clutch Shaft Fix-It Kit" comes to mind.

I agree with Geoffrey:
I hope TheOtherEric's experience was a fluke. I've been using these since they were introduced and never had a problem (many, many plugs) and they appear to be made of pretty good stuff. My hope is not so much a performance increase as it is to maximize the useful/optimal life of the ignition system. Since 993's are still based on rotors and caps, I expect that as these parts wear and more energy is expended to jump those gaps, that more efficient plugs will still permit a good spark and be less likely to foul. Hey, at least we don't have to deal with points...

Thanks again.