vernon

I have had my 1984 928 for 15 years I am going to put sparks plugs in is their any new plugs that will work in my 1984 or should I just go with the ones that came with the car? Thanks Vernon

joejoe

Stay with original.

jeff spahn

Who's new spark plugs again?

OTR18WHEELER

Theirs...

dr bob

A possessive bunch here...

Most RL owners look at the plugs on a regular basis, so they ar out often enough that "longer-life" plugs don't do much beyond draining the wallet. The smaller platinum electrodes are designed to run hotter, supposedly keeping the insulator and tips cleaner but at the same time presenting a 'hot spot' that's a possible cause of other probl;ems. Meanwhile, multiple-electrode pllugs tend to shroud the spark. So the general recommendation is to use the original Bosch copper plugs, and change them every 25-50k depending on how you drive the car.

vernon

dr bob thank you for your help I will put in the Bosch copper plugs.I just turn 165,000 miles an I really enjoy my 928s Thank You Vernon.

ROG100

Only use Bosch WR8DS (we sell for $5.65 each).

danglerb

Bosch WR8DS, silver inside, was the factory plug for some 928's wasn't it?

Amazon.com review suggested it was for racing only, short interval between changes, and long sustained high throttle conditions, not stop and go traffic.

I've bought a few sets in different heat ranges of the standard copper Bosch when I find them on sale, but so far non of the silver.

ROG100

WR8DS or part number 999 170 062 90 used 80 to 84.

kmascotto

So...are you saying I wasted my money...buying these...puppy's
http://www.boschautoparts.com/sparkp...um4.aspx#specs

hacker-pschorr

Yup

There is absolutely no reason to run platinum plugs in a 928 - ever. Unless your #1 goal is not having to change them for 100,000+ miles.

Personally, my #1 goal is making sure the car runs 100%. For that, you want good old copper spark plugs.

kmascotto

Ouch...but very good point. I was hoping for a better burn in these Hemi's

dr bob

Going back to previous note:

Silver and platinum plugs tolerate a higher tip temperature, and are therefore a favorite of engines with wide operating temperature ranges, and/or poor fuel and oil management. You can spec them one stop hotter. WR8DS in silver vs. WR7DC in copper is a good example for th e 928. The 'problem' with hotter plugs is that they are, um, hotter. As you ask more from the engine, combustion temps go up. There's a risk of the hot tip causing pre-ignition in high-load situations.

Multi-electrode plugs are the industry's answer to demands from car manufacturers to supply a plug that will last through the 100k mile emissions warranties required in the US. They don't want to have to change your plugs for you under warranty. Meanwhile, racers have determined that there's extra performance available, with more predictable and even flame travel available from the side of the plug opposite the ground electrode. In race engines, the actual threads in each cylinder are mapped and recorded. Plugs are then indexed and sorted so the open side of the plug faces the center of the chamber in specific target cylinders. So extend that thought, and imagine that you have a plug design that never offers the open side, since the multiple ground electrodes shroud the spark. FWIW, mapping the threads and indexing plugs doesn't buy you as much in a 4-valve head as it does in a 2-valve head.


Conclusion: I pull the plugs at least every couple years, prior to emissions inspections. That way I can get a taste of how even combustion might be. The copper plugs are cheap enough that I can easily justify putting in a new set. The most miles a particular set of plugs might see could be as much as 10k per my use/driving pattern. Usually much less though. So there's really no benefit available from using more expensive platinum, silver, or multi-electrode plugs, except for higher purchase costs and maybe some bragging rights. "Hey, look where I wasted even more money!"


Of course, there are fanatics who believe that because they cost more, they must be better. Maybe they are for somebody, not so much if at all in the well cared for 928.

kmascotto

"Hey, look where I wasted even more money!"....yup that's me!!

The Forgotten On

My 1981 928 came with 4 electrode Bosch platinum plugs in it when I bought it. They seemed new. Should I consider changing them out?