From: TJQuill [tjquill@juno.com] Sent: Sunday, November 26, 2000 7:35 PM To: 928 Subject: [928] Re: Bosch + 4 spark plugs Best $50 I've spent so far on mine was for the +4's - starts easier, idles smoother, better power. The plugs I took out (Bosch Supers) looked brand new, but there was a noticable difference immediately. -----Original Message----- From: Wally Plumley [mailto:wplumley@bellsouth.net] Sent: Wednesday, January 31, 2001 9:06 AM To: Preston; 928 owners club Subject: Re: [928OC Public] spark plug change? At 10:36 PM 1/30/01, Preston wrote: > I purchased a tune up kit from 928 specialists for my my 86.5. Good move! ;-) > For plugs I >chose the bosch +4 and I am in the process of removing the old plugs. I >have the spark plug tool from the hatch. Is there any easy technique for >either removal or installation. Not on an '85 or '86. > I am afraid of stripping the threads during >installation because of the odd angle of attack. Any other special tools >that would be helpful? The factory tool works well, as will a standard spark plug socket and extension. I would suggest taping the socket to the extension. You just have to use care in starting the plug into the threads in the cylinder head. You are screwing hard steel threads (on a cheap spark plug) into soft aluminum threads (in a very expensive cylinder head) - if you get the plug cross-threaded, guess which one is ruined. One way to help avoid problems is to know how far the plug should screw in by hand, and never putting the handle on the tool (or the ratchet on the extension) until you have screwed the plug in until the gasket touches. > Also on the left side and attached to the air >intake manifold and right above the access to the plugs on the left side >there is a rubber hose. I loosened the series of clamps(4 or 5) along the >hose and tried to disassemble, but there is a metal fitting in the center. >What is this? I have not taken apart as yet, but would help in accessing the >plugs on this side. There are two lines in this area. I can't tell what your line is. One is the vacuum line from the booster venturi attached to the intake that runs to the vacuum brake booster. You can take this one loose, but if you do, be careful with the old, fragile plastic fittings on each end. This line does not normally have a metal fitting in the middle. The other line is the power steering pressure line, which does have a metal fitting in the center, but is not normally retained by clamps. It is normally crimped onto metal fittings, as it is a very high pressure line. I would not take it loose. > Also, is some type of anti sieze compound recommended >for the threads? Some people swear that you must have anti-seize on the plugs, some people swear that this just gums up the threads and cuts heat transfer. If you do use anti-seize, never, never use any anti-seize or grease on aluminum that contains graphite. I normally don't use anti-seize on the plugs. Wally Plumley 928 Specialists From: Rodkey, John [JRodkey@genphysics.com] Sent: Wednesday, January 31, 2001 9:30 AM To: 'Wally Plumley'; Preston; 928 owners club Subject: RE: [928OC Public] spark plug change? Thought I'd add a smidgeon to Wally's usual thorough response: The biggest reason people experience seizing and thread damage is due to working on hot aluminum heads. You should not replace plugs on a warmed engine. Using anti-seize is one of those debatable subjects. As Wally stated, graphite based material is a no-no. Permatex ant-seize (the silvery stuff) might have graphite in there, but it's also got aluminum particles. Aluminum based anti-seize is also a no-no. I've used a copper based material with great success. JP Rodkey 79 Euro From: Stadter, Jim [jstadter@logicon.com] Sent: Thursday, August 16, 2001 1:03 PM To: 928 Subject: [928] RE: 4 prong Bosch > Has anybody used the 4 prong Bosch plugs on their car yet? > What have you experienced? Any pro's or con's to speak about? > I am thinking about installing them. Is it worth it? Here's one for the con's list. This is from a friend who is an electrical engineer and a car enthusiast. He had just sent it to me last week. -- Jim Stadter '83 928 S 5-speed (U.S. spec) 59K miles '88 928 S4 5-speed 112K miles Hill Country Region PCA (Austin) -- > > A couple years ago I tried a set of Bosch Platinum+4 in the > Legend. At first I couldn't tell any difference in > power/mileage compared to the regular Bosch Platinum's that > I've used in all cars I work on since the mid 80's when they > first came out. Recently the Legend has been stalling and > hesitating occasionally. I replaced the distributor > cap/rotor since they were very worn (60K miles), and adjusted > the idle since it was also low (surprisingly you can adjust > the idle speed even though it is ECU controlled, since they > want the engine auilary air control valave to stay in the > middle of it's range). The stalling stopped but it still > hesistated. > > The Platinum+4 had 30K miles on them so I decided to replace > them also. It solved the problem, and I believe the problem > is due to the four electrodes for the plug design. The > center insulator was a nice tan color, but there were alot of > deposit on top of the insulator near the platinum center > electrode. I think the 4 side electrodes block too much of > the center top of the insulator not getting enough heat in > there to burn off the deposits. The deposits are probably > causing a short spark versus a long spark from the platinum. > > My $0.02 worth is too avoid the Platinum+4 and sticke to the > regular Bosch Platinum. > From: Dr. Bob [dr.bobf@worldnet.att.net] Sent: Thursday, September 27, 2001 9:03 AM To: 928 Subject: [928] re: Bosch 4-prong Spark Plugs Shark chums: Just a reminder (second-hand now from Bosch...) that the four-prong "Plus Four" plugs are intended only to provide the extended life necessary with new-car manufacturers' desire for that no-tune-up period and the extended emissions warranties necessary on new car in some states like California. (Big Sentence...) In a well-tuned clean-running 928 equipped with electronic engine management, they should last longer than single-electrode platinums. Remember that, in a clean-running engine, the definition of plug wear is only the erosion of the corners of the electrode, so more electrode area slows down the specific erosion on any one electrode. The race-motor guys will talk some about alignment of the plug electrode to expose the spark to the intake charge. This is not so much an issue on the 32V cars as on the 16V models, but is worth a few horses when done correctly. Obviously, the four-prong plug has no open side, instead the only clear path to the charge is directly out the end of the plug, in the gaps between the ends of the ground electrodes. Does this affect horsepower? I have no data to support an answer. Some users have claimed that their cars run better with the four-prongs than with the regular platinums, and that may be true especially if the comparison platinums have some miles on them. I think I saw some dyno data (maybe here on Rennlist) that supports some small increase with the plus-fours, but the difference was so small as to be negligible, in the noise variation among several dyno passes. Keith W. points out that his mechanic doesn't like them because they don't last very long. I submit that most independent Porsche shops do a predominance of their business in 911 cars. I know from experience that most 911's, especially the early cars with carbs and even the early einspritzen models, are very sensitive to plug quality. The temp variations in the air-cooled cars means that the plugs that are hot enough to avoid low-load fouling and misfiring are often too hot for sustained high-speed high-load use. Platinum and silver plugs are the basic solution for those cars, but even with them there still needs to be a clear path across the electrode gaps to allow the incoming charge to wash the plug. The four-prong Bosch plugs don't allow that flow to keep the gaps clear, and would therefore be a poor choice. All that said-- I put a set of plus-fours in my '89 S4 auto, stock except for Autothority chipset, and have no complaints. These replaced a set of Bosch copper (the original plugs from the factory) at about 50k, and have run perfectly for about 5k since. Keeping in mind through all this that the originals still ran fine, looked fine when removed, and probably could stand another 50k of my gentle driving without a problem. I suspect that these new plugs might get replaced in a couple years when the prophylactic (look it up in the dictionary before you make any rude comments...) timing belt procedure is done at about 70k. Belt will be at 45k but five years old then. The distributors will be off so new parts and wires will be installed then. Will the plugs really need to be replaced? I doubt it. Were they the best choice for this car? Probably not, but I did it anyway. I find myself spending on stuff for the 928 that doesn't necessarily make perfect sense, like the chipset upgrade. But it is a toy, and spending on the original purchase probably didn't make perfect sense either, but I did it anyway. dr bob