Public Service Announcement: Spark Plug Wires

My car was made in Liberty, OH. It has alot of Made in USA stuff on it.
Including the OEM plug wires made by Prestolite. For my 1999 Civic EX
Coupe (1.6 SOHC), the NGK wires are HE76. I could only find Prestolite
at the dealer. For NGK, I had to go to my local import car part store. I
bought a set of each.

Here I am fiddling with a set of Prestolite and NGK wires for my car.
The engineer in me busted out the multi-meter and started benchmarking.
First of all, the Prestolite looks like it's glued together by monkeys.
Excess glue between terminals and wire, non-clean (powdery white) on
black rubber terminals. The NGK (Made in Japan) looks like it's been
glued much more carefully. Clean, and cool blue in colour.

The BIGGEST kicker is the difference in impedance, Helm manual says
25kOhm MAX when it is time to change the wires:

kOhms: NGK HE76 (Prestolite)
1=6.3 (11.7)
2=5.6 (10.3)
3=4.4 (8.2)
4=3.7 (7.4)

Right off the bat, the Prestolite is almost DOUBLE the NGK's resistance,
and probably half life in comparison as well. Bottom line, don't buy
Prestolite plug wires if NGK makes them for your car. They are priced
similarly, so the Prestolite goes back to the dealer. NGK wires are fo
shizzle ma nizzle!

V.R.

 

| difference in impedance
@ what frequency ?

| kOhms: NGK HE76 (Prestolite)
| 1=6.3 (11.7)
My cables, similar to Magnecor www.magnecor.com/magnecor1/truth.htm
have just 2ohm per ft, I bet your NGK cannot give bigger sparks than mine
( in open air, give bright amber & noisy sparks, fr ordinary size coils fed
by 240v rms 50hz AC current ) : plug gap can be 3mm, yet when engine (
F20A ) rpm is >3000 exhaust noise does not rise fast [ii] torque stays
high. Impossible with less efficient ( incl original Sumitomo ) cables of
240+ ohm/ft, given a small coil.
A similar set on my buddy's 9-97 CRV made torque rise by 15% ( his
estimate, as a QS ), exhaust noise drop by 25-30 % ( my estimate ) !

 

could you repost the previous for non technical readers? TIA

 

Are you sure you were checking resistance instead of impedance? I could only
check for resistance with my meter.
Anyway, 10k of impedance is minor when compared to the impedance of the
airgap inside the distributor. The manufacturers even insert resistance into
the wire, since it's not a big deal with spark quality. Low resistance wires
used in conjunction with a distributor are gimmicks!

 

| could you repost the previous for non technical readers?

I cannot post any diagram ( not allowed by my ISP / this NG ), let alone
explain ( cannot be done without diagrams ) diploma level electrical
engineering.
You can learn ( transformer, dielectric, etc ) fr books in public library,
or just ignore every jargon & buy cables like Magnecor's. New engines
with direct ignition don't even use cables.

 

Then explain why Honda recommends (Helm Manual) replacing the wires if
they reach 25kOhm. While NGK is less than 25% of that service limit,
Prestlite is already at 50%.

PS. Can you define impedance? It IS resistance!

 

Honda's recommendation is related to what it supplied. Deviation of resistance
from standard plug wires Honda supplied means degradation in the wires. If Honda
supplied a different set, it would have a different recommendation for the
deviation.

Impedance is ac resistance and dc resistance. In pure dc circuit, there is no
impedance. In ac circuit, like your spark plug wires, inductance could become
significant. EX, an inductor has 1k ohm of resistance for dc signal, it could have
1 meg of inductance for ac signal. EX1, a spark plug has infinite resistance, yet
could have 3 meg of ac resistance. The impedance is the sum of those 2.

Do a calculation of impedance for the air gap that the spark has to jump inside
the distributor and the spark plug. You'll be surprises that 25k ohm is no
significant.

 

| Do a calculation of impedance for the air gap that the spark has to jump inside
| the distributor and the spark plug.
Pls show us how to do this.

| You'll be surprises that 25k ohm is no significant.
Nonsense, you have no experience of high efficiency cables [ii] forgot
voltage division is in proportion to resistance loads : the higher is ( carbon-
core ) cables' resistance, the more of the high voltage sent from distributor
will be used to travel through cables, i.e. the lower will be the voltage (
fewer amperes too ) available across plug gaps, this would be why if honda
prescribes cables' resistance of <25k ohm.

| > Can you define impedance?
sum of resistance & reactances ( inductive / capacitive )

 

I have an electrical engineering degree along with 4 years of experience in
the trenches and I had trouble making heads and tails of what you wrote. I
think the main issue is your English. Besides, I doubt you can
realistically expect someone to truly learn about impedance from library
science books. What the original poster was asking for is a simplification
that makes it clear what you were trying to say. If everything can be
summed up by "just buy Magnecor wires", why even write anything else?

To address the original post, either set of wires will work adequately
according to Honda's specifications. I think plug wires are one of those
things that represents such a relatively small cost that the seemingly
higher construction quality of the NGK plugs justifies any price difference
there may be. As for the measurement, it should be done at DC per the shop
manual. 25kOhms is the DC resistance, and the actual impedance may be
higher/lower depending on the dominant frequency of the spark delivered
(which is not just the RPM divided by 1/2 the number of cylinders, certainly
no where near 50Hz).

Lee Cao

 

Impedance is a measurement made up of a resistance value and a
frequency-dependant inductance/reactance value. What you are measuring at
DC is the resistance value. Impedance at frequencies other than zero also
includes the inductance/reactance value.

So strictly speaking, impedance is not the same thing as resistance,
especially in the case of spark plug wires.

Lee Cao

 

The resistivity of air is about 20,000,000,000,000 ohms-meter. Assuming
that the air gap is a 1mm cube, that's 20,000,000,000 ohms.

This is ludicrous. We are not talking about a DC where you can plug in Ohms
law and start touting the benefits of low impedance wire. A car's ignition
system is a high frequency inductive circuit. I have no will to do a
detailed analysis, but 25kOhm is of no significance compared to the
resistance of the 1mm spark plug air gap. The resistance built into the
spark plug wire is their to slow the slew rate of the spark delivery as a
means to limit electro-magnetic induction noises that may be detrimental to
the vehicle electrical system.

Lee Cao

 

Sure Lee, but did you factor in the effect of the electric clock and
the absence of the o-ring on the distributor cap????

 

| Assuming that the air gap is a 1mm cube, that's 20,000,000,000 ohms.
Not when sparks jump across this gap. Per "Electrical Technology" 6th
edition paragraph 5.28, composed by Edward Hughes ( fellow of Heriot
-Watt University, Edinburgh, Scotland ) revised by Ian McKenzie Smith
( head of dept of electrical engineering, Stow College, Glasgow ),
published by ELBS ( Longman, UK ) in 1987 : -
"If the p.d. between the opposite sides of a sheet of solid insulating
material is increased beyond a certain value, the material breaks down.
Usually this results in a tiny hole or puncture through the dielectric so
that the latter is then useless as an insulator." In this paragraph's table,
ordinary air of 1mm gap breaks down @ just 4.46 kv.

| We are not talking about a DC where you can plug in Ohms law
Voltage division applies identically over resistance / reactance loads,
in DC / AC circuits, see above book's example # 8.5 .

| 25kOhm is of no significance compared to the
| resistance of the 1mm spark plug air gap.
When air is compressed by 9.6, & is hot, resistance must be just a
fraction of original amount. Nevertheless, hardly any resistance exists
when a dielectric breaks down.

| The resistance built into the
| spark plug wire is their to slow the slew rate of the spark delivery as a
| means to limit electro-magnetic induction noises
www.magnecor.com/magnecor1/truth.htm

 

| 25kOhms is the DC resistance, and the actual impedance may be
| higher/lower depending on the dominant frequency of the spark

Impossible ; impedance cannot be < resistance, @ any frequency,
in a series circuit.