94
Double
electrode plug
Needle and sphere
Plate and plate
Plate and needle
Regular Plug
Plug
Spark voltage
Low
High
Electrode
model
Ground
Center
Double electrode plug
Small cooling effect
Large cooling effect
I drive a GT-R tuned to 850HP. Would it be
okay to install 0.4mm dia. Iridium Power
series plugs?
The DENSO Iridium Series have the world's thinnest 0.4mm iridium
center electrodes, but because the durability of the iridium alloy
developed by DENSO is higher that even platinum, which has in the
past been said to be the most durable, it can be said that it's the best
plug for tuned engines. Specifically, it has the following advantages:
[1] Iridium alloy has a melting point and hardness above that of platinum, even
turbo, with its high combustion temperature, can be used with confidence.
Also, even when used with powerful ignition systems such as MSD and
MDI, these plugs are even more reliable than platinum racing plugs.
[2] The issue for high boost engines is that misfiring that occurs at high
revolutions. The fine electrodes of the Iridium series require a lower
voltage, allowing the energy generated by the coil to be sparked
without losses. It can be said the 0.4mm dia. DENSO Iridium
Power series are a strong ally of tuned high-boost turbo systems.
What is the optimum heat range for a tuned
up Golf4 GTI 1.8L Turbo?
(Tuning: Turbine Changed, High Volume Injector Installed,
and ROM Adjusted to give an output of 200PS from 150PS.)
It's difficult to give a heat range based on going from 150PS to 200PS
alone, and it's best if you judge the condition of your current plugs and
judge for yourself, but as a general rule, for boost pressures between
1.0 and 1.2kg/cm2, an IK24 should be sufficient. During the winter, #22
should improve starting and low speed feel. The heat range is different
depending on how the engine has been tuned and how it's used; using
an increase in heat range of 1 or 2 as a starting point, decide on a heat
range, always looking at the condition of your current plugs.
I have Rover Mini AT ('90). Since changing to
Iridium Power, the idling rotation in neutral went
up 400rpm from the previous plugs (1000rpm
before the change, 1400rpm since). Before the
c h a n g e , g o i n g f r o m n e u t r a l t o d r i v e w a s
550rpm, but now it goes below 550rpm and
stalls. The revolutions increase smoothly and
acceleration is good during driving. Why is this?
Frequently for older vehicles, the ignition system has
degraded, and it is sometimes not possible to see the full
effect of Iridium Power. In this case, the spark gap should
be adjusted from 1.1mm to 0.8mm. Also, in the VK series,
there is the VK20Y plug where the gap has been preset to
0.8mm.
Can I replace my double, triple, or quadruple
electrode plugs to Iridium Power or Iridium Tough?
This is possible. The reason: because of the 0.4mm center electrode
in Iridium Power and Iridium Tough plugs, they have a lower spark
voltage compared to double, triple, and quadruple electrode plugs.
Please refer to the Standard Resistor Model Quick Chart.
■
Spark Voltage
The thinner the electrode is, the stronger the electrical field is. Because
the electrical field affects spark voltage, a thinner electrode lowers spark
voltage. If each type of electrode shape is modeled as shown below,
Iridium Tough has a lower voltage than double electrode plugs.
■
Ignitability
The more the contact area between the flame kernel and the electrode is
minimized, the smaller the cooling action from the electrodes and the better
ignitability is. Because of the 0.4mm center electrode, the contact area between
the flame kernel and the electrode is small, resulting in excellent ignitability.
Can an Iridium Power be installed on
an RX-7(SA22C Turbo Model)?
In the rotary engines in some old Mazda's on the T
(Trailing) side there is a plug, the terminal nut for which
must be removed. In others, the removal of the T side plug
terminal nut is necessary as in the Cosmo (HB22S).
DENSO has Iridium Racing plugs for rotary engines, with a
variety of heat ranges from #27 to #35. Iridium Racing
Plugs for Rotary Engines come standard with terminal
nuts.
How is the compatibility with trial vehicles.
The "IW series" is well suited for most trial vehicles. Though these
vehicles frequently use a low heat range, the heat ranges available for
Iridium Power starts with IW16, so choose one that matches the type of
driving you do. Better accelerator response and torque can be expected
with Iridium Power, which has excellent ignitability. Recently, the space
to install plugs in trial vehicles has shrunk, and there is a demand for
miniature plugs. In these cases try the IK types. However, the space
between the plug cord and the insulator will require waterproofing.
