52
Tell me about the firing performance of
the
.
Use of a ultra-fine 0.4 mm diameter iridium center electrode
and a tapered cut and a U-groove in the ground electrode
has enabled us to achieve previously unparalleled firing
performance in the
.
Q
11
A
Ordinarily, the leaner the air mix the more difficult the firing.
The greater the ignitability limits, that is the leaner the air mix in which a
plug can spark, the better firing performance a plug is said to have.
The following graph shows some examples of ignitability limits (*) for various
spark plugs.
Test engine: 1600 cc, 4-valve, 4-cylinder
Good
10
0.6
0.8
1.0
1. 2
1.4
1.6
11
12
13
14
15
16
17
18
(mm)
Ignitability Limits
︵ Air/Fuel
︶
spark plug gap
(Lean)
(Rich)
Normal plug
（
φ
2.5）
Platinum plug
（
φ
1.1）
（φ 0.4）
Compared to normal spark plugs, with a spark gap of 0.8mm, the Ignitability
limits is better by 2.5.
*: Ignitability limits (Air/Fuel);
1)Lean limits to be able to fire
2)As this figure is getting higher, it will become easier to fire.
(The above is analyzed in DENSO.)
