When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
So I ordered new spark plugs and coils for my 60k service and began installing. Not too difficult, but I did realize the plugs that I am installing are materially different than the ones I'm pulling out; notably the reach (the threaded part of the plug) is much longer (see picture).
I've done 3 plugs and started the car once (idles great, at least) before I realized that they are different. Not sure why they are different, but before proceeding I wanted to see how bad this is, if at all.
So there's my dumb question - my spark plugs (that I thought worked on my 955 Turbo) are different lengths and I'm having a hard time understanding why my pistons didn't blow them out when I started the car
in sum, they should work, potentially offer better mpg, maybe some butt dyno benefits, at the cost of potentially running into pinging.
Not sure if anyone has any thoughts, would be helpful as long plug vs short plug is a totally new concept to me, but given this car has now officially been turned over to my wife, better mpgs I won't complain about as long as it doesn't ping under high acceleration/towing (neither done anymore).
What plug did you use?
Edit- just saw your recent post.
Personally, I wouldn't run with a longer plug but since you've already started the engine and it didn't blow up, you can be the Ginny P!G and let us how it works out. Since initially the plug didn't make contact, my next concern would be the flame pattern being different than designed and the long term effects on the piston head, cylinders, and valves.
I can understand experimenting and going up or down one heat range...but to use a drastically different spark plug, especially in a modern engine, is flat out crazy imo.
I'm also guessing a large portion of threads are going to be exposed to the combustion chamber causing hot spots and rock hard carbon buildup on them. When it comes time to pull those plugs out again, how do you think that will turn out?
I pulled them all out and put the old ones back in. I'm somewhat surprised that the 2008 (957) takes these plugs but the 955 doesn't. I'm just not informed at all about spark plugs (DFI doesn't mean anything to me) so I'll be sending them back to get the right ones.
Upside is i I can do cayenne spark plugs once the covers are off in about 2 minutes
Good call. Pat yourself on the back for stopping to think about the plug difference. Just wait and buy the right plugs. Eat the cost of the wrong plugs if you can't return them. Those 957 plugs may work just fine but you'e facing a potential $15000 or more loss if they cause a problem.
Yup; big believer in doing things right. I didn't even notice the difference in length until I had installed 3 plugs and had set the 4th by the old ones to notice the difference!
No way I would use a longer plug. Fortunately there was no piston to plug contact. For all the reasons above, especially exposed threads I would not do it. Good thing you caught it.
Yup, though in doing some research it does intrigue me some the idea of a longer plug, assuming you aren't in the pistons way - I can see more complete combustion as a natural outgrowth; though the difficulty in removing due to carbon/corroded threads sounds like it might be real (though I assume that the threads will wear with everything else and might not be as hard to pull out as you think. Anyway, per Lupo's Rec I bought the NGK's for about $10/plug and two new air filters to get that done while I'm in there...
There's a big difference between heat ranges due to slightly different insulator lengths WITHIN THE PLUG and installing a completely wrong spark plug with a different THREAD REACH.
40% of those threads are going to be in the combustion chamber. They're going to be heat glazed and baked with carbon (in a turbo engine no less). When you go to back them out, you'll either snap the plug or strip the aluminum threads right out of the head. In the end, you'll be paying someone to install a set of good used heads.
That's just one issue...
The heat range is going to be so far off, it's going to be in a different universe. Look at the photo you posted, there's a good 40% more plug length and God only knows what kind of insulator difference!
You now have a big object protruding into the combustion chamber completely changing the volume and flow characteristics. Does that seem like it might be a good thing?
Pinging? Sure, the knock sensors will try to compensate...to a point. Timing will drop back, performance will drop but still probably not enough to keep from burning a hole in pistons.
If it were a good idea that had any benefits, why didn't Porsche use that plug to begin with? Your CTT cost well over $100K...using advice written by ricer kids on a Mazda forum probably isn't the best idea.
I had exactly the same thoughts as George in Indiana. If this works to improve the engine somehow - why didn't Porsche do it? Well - because it doesn't. OP - wherever you got the idea that it might just improve the performance - stop listening to them. They're idiots.
And you can install new plugs in 2 minutes? Per cylinder or the whole 8? Does that include torqueing them properly?
02-11-2018, 02:28 AM
Possibly stoopid question: Spark Plugs
