WAS: Bosch +4's on the 4.7 NOW: Platinum theory

From: Sevrence, Sean (S.J.) (ssevrenc@visteon.com)
Date: Wed Mar 20 2002 - 15:20:35 EST


Hey Guys and Gals!

With all the talk about the coil-on-plug design, I asked the "platinum vs.
non-platinum" question to one of the spark plug manufacturers. I did some
work with this company in the past, so I sent the question to the engineers,
not the help desk. Here is the response I got after their internal
discussions....

My question to them:
Referring to platinum plugs, does it take more energy to fire a plug with
platinum than without it?

What this question is stemming from is my new truck has the 4.7L which has
the coil-on-plugs design. People are saying that the platinum plugs do not
work well with this design. Do these comments hold water?

"The dealer was saying that the platinum's don't burn the fuel very cleanly
or all the way."

Their response:
Okay, just got back from talking to the experts, the word is that platinum
gives up it's free electrons with far less ease than does the steel alloy in
most regular center wires so the required voltage may be anywhere from 1-2
KV higher in platinum designs. Under most circumstances*, the consumer
doesn't notice this or the fact that after, say 15,000 miles, a regular
center wire spark plug begins to approach this same required voltage which
continues to increase until the engine starts to miss due to gap growth and
wear. The platinum spark plug on the other hand has the advantage that once
this point is reached, it remains virtually the same for at least 80,000
miles, more on double platinum designs.

  With regard to the remark 'Under most circumstances*' what I need to
clarify is that we have seen that the coil-on-plug design simply doesn't
deliver the 'same punch' as would a regular distributor coil as there are
inherently fewer coil windings. Also, as the coil-on-plug concept is still
relatively new, warranty returns seem to infer that coil-on-plug is a
'work-in-progress' where more time is still needed to perfect a more robust
or efficient design. Therefore where any coil-on-plug unit is the least bit
marginal in this 'delivery of power', under load, it may miss
using a platinum spark plug where a new standard plug might still fire under
the same circumstances. That cylinder will eventually mis-fire sooner than
the rest of the cylinders once the regular center wire spark plug begins to
wear and increase the required voltage. To compensate for this and still
get the longevity of platinum you might consider going to a fine wire
design, i.e. 'rivet' where one exists, as the finer tip reduces the required
voltage by focusing the
energy, that is available, at the tip and by the fact that the tip itself
runs hotter making it easier for platinum to give up it's free electrons to
jump the gap.

  In summation, in warranty returns we have seen, both the platinum spark
plug AND the coil-on-plug unit are replaced simultaneously as both may be
seen as suspect. So the comment 'that the platinum's don't burn the fuel
very cleanly or all the way' may have more to do with the delivery of power
for a spark than in use of platinum on the business end of the center wire.

-----

My comment: Initially, the standard, non-platinum plugs have an easier time
firing than the platinum plugs. After 15k or so, the platinum's have an
advantage as the non-platinum plugs require more voltage due to the every
increasing gap (unless we remove them and re-gap the plugs). Looks like I
need to gap my plugs this weekend ;^P

Sean
'92 RC Sport 3.9L 5spd - 256,000mi!
'01 CC SLT+ 4.7L 5spd 3.92 LSD Mobil-1 - 38,300mi!
http://www.twistedbits.net/WWWProfile/dakota/DnuuSncssJujU



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