george44

Hi guys, trying to find out what is the correct spark plug for my car ('79 911 SC Targa Euro model engine code 930/03); when I bought the car it had Bosch W 7 DC and this is what's in the engine now and it runs very well. Owner's manual and catalog at auto parts store says it should be W 8 DC; Bosch catalog at http://www.bosch.com.au/content/lang...senger_(2).pdf says it should be WR 3 CC (with WR 7 DC being the correct plug for the 3.2 Carrera). Most likely I would not have posted, as I said the engine runs beautifully, but had a plug quit and replaced with a WR 7 DS (S for silver electrode), engine runs very well (but I won't leave it like this, 5 plugs of one kind and one different). Second question, is there a gizmo you can use to determine what plug is not working for ex. by attaching to the plug cables one by one? I did not feel like pulling all the plugs out to see which one is faulty and pulled the connectors one by one, got a few jolts. no big deal but not exactly pleasant either, would gladly skip next time if I have a choice. Thank you all,

George

theiceman

george I would stick with the 7s or 8's mine are 7's and is a 78, i am not sure what difference the eurospec one makes. maybe some other guys driving Euro ones could pipe in.

theiceman

if you go with the 8's a might have a brand new set you can have them for what I payed for em 3.00 a plug. The guy shipped me 8's instead of 7's for my car.. not worth returning for 20.00

Peter Zimmermann

Euro '78/79 cars are set up for W5DCs (USA models call for W8DCs). Depending on your gasoline quality going to a slightly hotter plug (W6DC) is probably OK, but I don't think that I'd push my own car to W7s.

To do an easy diagnosis, with the engine off, loosen one bank of plug connectors, but leave them in an almost-installed position (use light pressure to get the connector on the end of each plug, but not so far that it clicks into place) . Start the engine, and use an insulated plug wire pliers (see Mac, SnapOn, Sears, etc.) to lift each connector in turn away from its plug. This will tell you quickly if a plug isn't firing. Shut off the engine, push the first three connectors back on, loosen the three on the other bank, and repeat.

theiceman

Great tip Pete ...

george44

Thank you Clive and thank you Pete, I will do that if it ever happens again (check them one bank at a time). There should not be differences in the Euro to US spec cars of this period ('78/'79) but I know there are few, one of them being the different gear ratios in the gearbox. But the engine should be standard, same everywhere. But seems it's not really. Pete, to answer your question, I use Sunoco 94, it's the highest octane gasoline you can buy at the pump in Canada. Had the car since 2000 and it's had the same plugs, W7 DC, can't say I noticed anything wrong, as I said engine runs beautifully. I never tracked the car and I don't intend to, I'l go occasionally to 6,000 or close to 7,000 on accelerating but that's about it. I know a hotter plug is not good as it's not very good to use one that's too cold either. Had the car to an independent Porsche mechanic, he looked at the plugs and did not make any comment. I'm a bit confused now, you say W 5 DC, Bosch says WR 3 CC and the US cars have W 8 DC. But this engine was supposed to be the same all over the world, same compression ratio and same power output so frankly I'm sorry but I'm afraid I'm missing something, it does not make sense to me.

Peter Zimmermann

You're correct, the hotter plug used in USA delivery cars must have been somehow tied to emissions, or the factory decided that they would be OK with the hotter plug as long as the cars weren't going to be run on the Autobahn at high speeds - maybe a little of both!

theiceman

Hey George I checked and I have all 8's. different no,enclature surrounding it. From my air cooled motorcycle days I always ran the coldest possible plugs that would not foul. I can't imagine the 911 is too different.
i would say go with the 7's or 8's, i would not go to 5's personally ..

genripper

FWIW the Porsche parts catalog disc lists W3CC p/n 999 170 162 90 as the spark plug for all ROW 911 SC's. The owner's manual for my 81 ROW Targa lists W4C1.

Peter Zimmermann

genripper: Everything changed in '80 when the factory raised compression from 8.5:1 to 9.3:1 and introduced Lambda. RoW '80/81 cars required a W4C1 (W260T2) cold plug, while USA '80/81 SCs called for the W5D (W225T30). The W5D evolved into a W5DC, which then became the WR5DC. W3CC plugs are very cold, the "3" heat range is more appropriate for Turbos, which use W3DPOs.

genripper

Pete, just passing along what's current in the parts catalog. I'm guessing a W4C1 has turned into W4CC. The ROW cars had an air pump but no catalytic converter or O2 sensor, so maybe that's the reason for cooler plugs than US spec. The last letter refers to the core material, C=copper, P=platinum, S=?, Bosch's racing plug is a W4CS. I'm speculating 1=copper before platinum plugs were available.

Peter Zimmermann

...and remember, some Euro (RoW) markets were still using leaded fuel with a whopping 98 RON octane rating! The factory, from '78-81, made many different versions of the SC, with changes to achieve sales dependent on emissions, noise restrictions, etc. I don't know how they did it, but they did, and many different engines even ended up with similar specs. In '78 alone six versions were made: 930/03, 930/13, 930/04, 930/05, 930/15 and 930/06 - all 6 had the same hp/torque and compression ratio, all had smog pumps, four were fitted with catalyst, and three had exhaust gas recirculation.

genripper

My head is spinning, I have to go lay down now.

theiceman

was any of this in English ? :-)