worf928

Yup. $7.28 each last time they ordered them from Porsche. Unknown if they are available from Porsche or what the current price actually is.

cobalt

Thats not so bad I recall the old platinum plugs for my SC were $12 ea back in 1983.

heinrich

I can't yet say about the 5.4-litre engine, but for other Porsches I've owned:

6-cylinder 2-valve: Use 2-prong WRDC copper
6-cylinder 4-valve: haven't owned
4-cylinder 2-valve: Use 2-prong WRDC copper
4-cylinder 4-valve: Use 4-prong platinum
8-cylinder 2-valve: Use 2-prong WRDC copper
8-cylinder 4-valve: Use 4-prong platinum

I have seen 2-prong platinum and I do not like the apparent carbon buildup on them ... so I would not use them. Surprisingly ALL platinum plugs appear to have significant carbon on the 2-valves ... so I would not use them there. I have in the past both on 944 and 928 replaced Platinum +4 with WRDC copper and found MUCH cleaner burn.

cobalt

Yes but these were not used from the factory the 4 electrode platinum plugs only came out about ten years ago. I have tried the 4 electrode plugs on other cars and found performance to drop and I noticed some pinging and when going back to the original copper plugs the pinging went away. I do recall my guy saying no to the 4 electrode plug on the GTS that he experienced nothing but problems and felt the factory plugs were best. IIRC i believe he said it had something to do with the Beru connectors resistance vs the amount of voltage needed for each specific plug but don't hold me to it.

heinrich

Anthony, let me put it this way: I use ONLY WRDC copper on ALL my cars

ROG100

PET calls up 999 170 189 90 WR 7DTC and they are single electrode.
Do you have a Pt Number and I will see what I can get?

worf928

Roger, the "T" strands for triple electrode (at least in the Bosch terminology). See

https://rennlist.com/forums/showpost...6&postcount=91

for more info and link to the Bosch lexicon.

Bill Ball

Yes, that's what Jim Morton confirmed for me.

Bill Ball

Further information from the owner this morning....

- Both fuel pumps & fuel filter replaced within the last 2 months (<1000 mi)
- Fuel injectors rebuilt < 1000 mi
- Oil consumption: 1qt/800 mi avg, 1qt/500 mi spirited driving. Jim Morton says he gets similar results.
- Pinging worse and some heavy knocking with GT EPROM

So, several of the other solutions have been tried. The oil consumption is different from what I stated, but I wouldn't call it better. Jeez, do all GTS owners put up with this?? Egad!

So, if the later pistons have drain holes (??), then this is a combo of looser forged pistons and rings +/- some ring wear versus valve stem seals. We'll see if a leakdown reveals anything.

BTW, I see the controversy over plug types with strong votes both ways. In my S4 I've had both 4-prong platinums and the single electrode coppers at various times and couldn't tell any difference whatsoever.

cobalt

Nope I haven't kept records but I usually need 1 quart added per oil change which is done between 2000 and 2500 miles or once a year whichever comes first. Better than most Porsche's I have owned.

worf928

Bill, do you have any good temperature measurements from this one yet?

Also,
- is the pinging at tip-in (only)? Or at part-throttle under load? Or something else?
- did the Diag tools give the car a clean bill of health? (You reported failed idle adaptation, but no reports on other stuff e.g. Idle/WOT, NTC-II, knock sensors, tank vent, ECU faults, etc.)

Jim bailey - 928 International

I went out for lunch with a customer last week he drove his GTS and as he pulled away from a stop it was pinging pretty hard...it also uses too much oil.

Bill Ball

It pings under a variety of conditions.

The diagnostic shows no error codes and idle/WOT operating correctly. The owner now reminds me that on one test we got faulty O2 sensor a while back after the water injection was done. O2 could be fouled, but there were no error codes yesterday. We'll run all the test again.

It does fail the idle adaptation in an odd way (racing idle) and I haven't had a chance to inquire with John Speake and Theo about that. The ISV moves and responds to power, but we squirted some WD40 down the hose to it anyway.

Bill Ball

JB: That's encouraging. I guess you hope for relatively simple solutions like Roger and several others have found. Most of those have been explored with this car already. If it is oil coking, as I suspect is at least part of the problem here, the solution doesn't look to be very easy at all.

928ntslow

I'm very surprised you guys would recommend using a hotter plug on a car that is pinging.

Bill, this may be a long shot, but can't hurt. Throw a quart of RISLONE in the engine. I would expect you are familiar with this stuff. It truly is one of the best products out there for cleaning up the inside of an engine and restoring power.