Chuck Schreiber

Going through the GTS over the last year mechanically and replacing things little by little.

One of my to do's were the Spark Plugs on her as I've got no records on any "tuneup". (only scheduled maintenance like oil changes, etc, and major service like rack, timing belt, etc.) So I went to Rogers and he suggested the Bosch 3 Prong (in the Porsche Box). He let me know that it may cut down a little on the pinging and also increase power over what I guessed might be in there.

Installed them today and all I can say is Holy S@@T!!
I didn't think plugs could make that much difference. The ones I pulled (I'll get some pics) did not look too bad, but looked pretty old. They were single prong Bosch and were all uniform in color. I immediatly could tell the car idled noticeably smoother and quieter. Stepping on the loud peddle, I could tell a difference. Rapped up faster and roared!! The old ones must have been toast!!!

Next stop to the garage with the lights out. Going to check if the wires are toast. (Fireworks show??) If so, I'll do the wires, caps and rotors.
BTW, When I did The fuel pumps it eliminated quite a bit of the pinging at high RPM, the plugs seemed to have cured what was left. We'll see as I drive it a bit more.

Seems I found some HP that should have been there in the first place??

joejoe

Strange but familiar story. I was giving my '84 944 a tune up (new car to me) and tried to get correct plugs for it from autozone. They were special order so I went with suggested cross reference replacement. Car ran for 1 day then would not idle or hardly start. Pulled plugs, and found they were fuel soaked and not firing. Called 944 guys in Florida and got a set of correct plugs $8 each. Installed and car would not even start! Same problem fuel soaked. Decided to run old plugs that came with car...the bosch 3 prong. Runs perfect.

Marine Blue

Nice Chuck. Great feeling getting a great return on very little money spent. Also shows that these cars respond really well to maintenance and when you do something new to them you realize "so this is how it is suppose to feel"

Are these plugs an improvement for all 928's or strictly the GTS?

I'm due for plugs this spring so I'm curious what everyone is using and what is best.

Dean_Fuller

Nice Chuck!
Whats the price per plug??? I replaced the plug wires on my 89 S4 a few months ago. The car would at time go into "limp home mode" and run like a lawn mower......PLUG WIRES were the cause! Hard to believe they could cause that much havoc.

Randy V

Can you provide the part number for the plugs?

Rog - what is your price? I think I'm overdue on this.

ew928

Bosch WR7DTC??? from my vague memory from ages ago.
T for triple.
C for copper.
Not sure if 7 is a good heat range. Hear of the SC crowd liking the cooler 6 plugs.

Did I guess right?

Jim M.

Chuck, If you had single prong plugs in there then they were the wrong plugs. All GTS's came with the three prong plugs from the factory. I ran the four prong Bosch plugs on the 89GT, but so far I'm staying with stock on the GTS.

On both cars, new plugs always made the idle better and starting easier. My ***-o-meter never could tell a difference in performance, but I tend to over-maintain the 928's so I doubt I was loosing much performance.

hacker-pschorr

Sounds right - I still use the single electrode, makes it easier to play with plug gap.

Heat range 7 is stock, I do not see any reason why a stock GTS would have any issues with a 6. Worst case scenario is fouling, they are cheap enough I would try the 6.

Marine Blue

So is the consensus that three prong is better than one across the board on all sharks or just the GTS?

hacker-pschorr

In theory when brand new, a triple prong should not performe any different than an equal speck single prong.

Down the road as the spark plug ages and the side electrode starts to wear or full of carbon, the riple plug has two more "fresh" points to pick from.

It's tricky to gap a triple or even a double, which is the main reason why I do not use them.

Stole this from some spark plug FAQ:

Mike Frye

Great info.

I've also read on here that the WR7DC plugs in copper work better than platinum ones in the 928, but I can't seem to remember why that was. Anyone?

ew928

Only way I can see of "gapping' the triples would be a round crimper type device that moves the 3 electrode arms in in equal amounts whilst centered on the central electrode node.

I always thought the rounded triangular central electrode on a worn triple plug was pretty cool.
I'm easily amused.

hacker-pschorr

The only advantage platinum has is longevity since it's much harder than copper, it doesn't wear down as fast. A quad electrode platinum can go 100,000 miles.
I’ve “fixed” some friends cars by installing cheap old copper plugs after they “upgraded” to platinum or iridium plugs. Not just older cars either, my friends VW GTI 1.8 Turbo had a bad misfire with iridium plugs.

Mike Frye

So was the misfire caused by the platinum or iridium or the fact that it's hard to get exact gapping on the multi-prong plugs? Is the issue the material it's made from or the way it's setup? I personally wouldn't want to leave a set of plugs in there for more than a year or two no matter what they're made of. I like to take a peek in there and also do a compression check every few seasons and copper plugs are cheap enough to replace on that schedule.

hacker-pschorr

I'm not 100% sure, this might have something to do with it:

This is interesting:

http://www.se-r.net/engine/platinum_copper_ngk.html