Originally Posted by Basher
A little more digging reveals that this is a trick for the 02-05 HEMI's, and then in 06-newer they have the coils firing the same cylinder.
As stated above, it is an emissions thing, where the 'crossover' wire is firing on an exhaust stroke.
Thanks for humoring me on this. If you want to know more about it, Google 'Taylor Shorty Wires'
Well....I did some serious digging..LOL..which started with the Goggle search as recommended, and discovered that there are Dyno results posted that show a degrade in performance
with the shorty cables, which under the circumstances is no surprise.
From it's inception, the 5.7L Hemi has fired 2 cylinders at the same time, which results in both plugs in each cylinder firing at the same time on the compression cycle, and on the top of the exhaust cycle as a 'wasted spark'.
Each cylinder has one plug fired by the coil on top of it, and the other plug fired by the coil on the compliment cylinder that is one engine revolution out of phase with it. In the case of #1 cylinder, the compliment is #6 cylinder.
Here is description from the 2003 Ram service manual. Specifically page 8I-22.
The ignition system is controlled by the Powertrain
Control Module (PCM) on all engines.
A “wasted spark” system is used on the 5.7L
engine combining paired, or dual-firing coils, and 2
spark plugs per cylinder. The coils and spark plugs
are connected with paired, secondary high-voltage
Each cylinder is equipped with 1 dual-output coil.
Meaning one coil mounts directly over one of the
dual spark plugs for 1 high-voltage output. A second
high-voltage output is supplied directly from the
same coil (using a plug cable) to one of the dual
spark plugs on a corresponding (paired) cylinder on
the opposite cylinder bank.
Each coil fires 2 spark plugs simultaneously on
each of the cylinder banks (one cylinder on compression
stroke and one cylinder on exhaust stroke).
EXAMPLE : When the #1 cylinder is on compression
stroke and ready for spark, the #1 coil will fire one of
the dual spark plugs on the #1 cylinder (directly
below the coil). The other dual spark plug on the #1
cylinder will be fired by the #6 coil. At the same
time, the #1 coil will fire a “wasted spark” to one of
the dual spark plugs at the #6 cylinder as coil #6 also
fires a “wasted spark” to one of the dual spark plugs
at the #6 cylinder.
The firing order is paired at cylinders 1/6, 2/3, 4/7,
5/8. Basic cylinder firing order is 1–8–4–3–6–5–7–2.
Battery voltage is supplied to all of the ignition
coils positive terminals from the ASD relay. If the
PCM does not see a signal from the crankshaft and
camshaft sensors (indicating the ignition key is ON
but the engine is not running), it will shut down the
Base ignition timing is not adjustable on the
5.7L V-8 engine. By controlling the coil ground circuits,
the PCM is able to set the base timing and
adjust the ignition timing advance. This is done to
meet changing engine operating conditions.
The PCM adjusts ignition timing based on inputs it
² The engine coolant temperature sensor
² The crankshaft position sensor (engine speed)
² The camshaft position sensor (crankshaft position)
² The manifold absolute pressure (MAP) sensor
² The throttle position sensor
² Transmission gear selection
Based on this description, and I have the same description from some of the newer model years, the fact that the shorty wires actually reduce engine performance is completely understandable.
Basically, the shorty wires are strictly for cosmetic purposes.
So if a small reduction in performance is acceptable in an effort to make things look better, then the shorty cables appear to be an attractive mod, but if you are more about performance than what the spark plug wires look like under the hood, then the shorty's are not for you.