let me start off by saying, I'm not expecting any special performance boosts from spark plugs. I am confused why platinum plugs are not good for my m103 engine. I have used the Bosch 4+ plugs in my engine for about 10K miles.( I purchased these plugs before I knew they were bad) they haven't eroded the electrodes or caused any side effects. why are they no good in my engine. if someone could clarify this for me I would be grateful.
thanks,
Adam

I believe the consesus is that the platinum plugs CAN leave platinum deposits in the engine which isn't good for it. I don't know if that means it will put platinum deposits in, but it can do it if the conditions for it to happen are met.

I also think essentially that the copper plugs do just as good of a job as the platinum ones.

I'm not a tech, but I'm more than willing to follow the advice of my fellow members here.

Alon

Dang, I knew I should've saved that link today. I was just reading something about that from a OEM parts specialist from NGK. He was talking about that and other things in detail about the spark plugs for BMW and MB. What I could understand was that they use a sophisticated design to make sure the plugs last 100,000miles, not 60,000 without (Pt, Ir) precious metals.. The electrode is much bigger than a platinum plug also and lasts longer, due to the design. It gets complicated explaining 3 different cooling passages to cool the plug, duh, duh, duh... Sorry, wish I could explain it better, but I kind of skimmed thru the article, b/c it was too long. Look up under your search engine either Bosch spark plugs or Bosch heat. I used those keywords, I think. The article focuses on BMW stock plugs, but it pretty much applies to MBs also.

The biggest problem with platinum plugs is the small center electrode which makes a thinner spark. This effects idle quality.

I have seen a few posts on this subject in the past that elude to the platinum plugs breaking and destroying motors. I don't know anything about that though.

Before I found Mshop, I ran a set of platinums in my M103 probably 80,000 miles or so. I'm a little ashamed to admit that publicly, but the truth is the truth. I do have better idle quality now with a set of Bosch copper cores set at .038.

Good luck,

This topic has been discussed MANY time before! Did you use the search function in the upper right corner of the Shop Forum? If not, give it a try and search for the word "platinum". You will learn a lot about why you do not want to use these plugs in a car not specifically designed for them.

HERE is one example post where WDurrance explains the primary reason for not using platinums.

Does anybody index their plugs?

No offense to anyone who believes in this, but I think indexing spark plugs is a bunch of BS. The fuel will ignite no matter where the negative electrode of the spark plug is.

JRBrown and Harrym.
 

JR, I have indexed my spark plugs ever since I could buy the spacing shimms. I've witnessed dyno test using plugs installed as seated and indexed plugs. There is an increase at flywheel HP using the same running conditions. For the street machine you won't realise the change; but I try to do every little trick I can to help my old tub to do better. Consider the small investment and hardly any labor. And it gets you closer to your machine.

HarryM. how can I question your opinion about a subject you feel so strong. You know, the negative electrode igniting the fuel/air mixture. Go ahead and discount the little ole "Flame Curtain".

Happy Trails Beep Beep from Houston.

Donald
just old fashion

Donald
 

I'll concede that indexing the plugs will make a difference at Indianapolis 500, but on a street car I'm skeptical.

Well you might want to explain what indexing is. :) I sure am curious as hell about it now. hehehe

Alon

just a guess...
 

but it sounds like having all of the electrodes point in one particular direction. Question is, which direction? :D
I am thinking towards the direction of the valves, with the "back" of it towards the closest wall. I am sure I'll find out here shortly! :D

Larry, You spot on.

Harry, it doesn't hurt to consider/respect alternative views.

My cars are a hobby. Will indexing eeek out a weeeee bit more performance/hp/gas mileage? Probably. How much? I don't know. Noticable? Not with my equipment or "seat of the pants" feel. Certainly nothing equivelant to a first class tune-up, higher compressions pistons, different cams, timeing etc.

There is a body of work out there, that has looked at indexing. The item that caught my eye was how complete the total burn appeared to be as compared to the flame curtain effect. I don't have the info/data anymore and it's a mute point for me. Indexers are very inexpensive.

I do like Donald's observation, "closer to your machine". It's a hobby and a passion. Not emotional and I try to not squash others ideas or thoughts.

Cheers all.

GREAT BOARD!!!!!

Platinum plugs bad??? no, but?
 

The real issue is this: under very light load conditions (like idle, cold slow driving, etc.) the platinum plugs can foul because the electrode just does not get hot enough to keep from forming carbon deposits. During combustion, there are lots of carbon 'free radicals' around hunting for cold surfaces on which to collect. (lots means enough to leave a film that conducts electricity) Does no harm on heads and pistons because they warm up and burn off. BUT on the spark plug electrode, it CAN cause a partial or complete misfire, causing a rough idle and high emissions.

It depends on how you drive. A periodic 'Italian tune up' at high enough loads to get things hot in there helps keep the plugs clean and free from fouling.

Slow trips, frequent cold starts, no higher speed running to burn soot off plugs will cause them to foul.

To All
 

You fellas just took all of the moxy out of me. I was going to write a multi-paragraph speel on Spark Plug Indexing and you fellas in two or three sentences said it. Aim the open part of the electrode toward the INTAKE valve. Strike a match at the source.
Oh Pooh!
Happy Trails Beep Beep from Houston.
Donald, the indexed one.

KEBOWERS
 

I always supected the Italians were radical but I never would have in a thousand and one years they were free. I use copper cored plugs because Jacobs Engineering who manufactured my ignition system told me to.(they are cheap too). I have a plug board holding two sets of six plugs. Both are the same brand and heat range. The difference in these two and the set in the engine is the air gap. I am continuiously trying to find the best gap. The engine set is at 0.054 inches and indexed. What Joy to be a professional tinkerer.
Happy Trails Beep Beep from Houston
Donald, what's next?