Leyland Car Owners - Coil position in the P76

Mick Clarke wrote:
: Date: 02/08/04

: I have a question for the members of the mailing group......someone told me that if you move the coil on the V8 to a position very close to the distributor..ie: on a bracket at the front of the valley cover.....this will provide benefits in spark and even a smother running engine, by virtue of the short length of wiring from the coil to the distributor.

: What are the thoughts on this and peoples opinion on whether there would be benefits in moving the coil?

Tassy Grosdanis reponded:

: Electrical/Electronic systems are not my strong point, but in theory this would make sense.

: Ohms Law can be defined by the following two equations or relationships:

: R= V/I, where
: R = Resistance (Ohms)
: V = Voltage (Volts)
: I = Current (Amps)

: Therefore resistance increases, current is reduced. Resistance decreases, current increases.

: R= p x (L/A), where
: R = Resistance (Ohms)
: p = Resistivity of the material (Ohms)
: L = Length of conductor (metres)
: A = Cross-sectional area (square metres)

: In this instance with respect to the coil lead, p and A are fixed, thus the longer the lead the higher the resistance. Therefore to answer your question the shorter the lead the lower the resistance within this circuit thus providing more current to the distributor. Obviously if you do not want to decrease the length of the coil lead, increasing the cross-sectional area of the lead will provide the same affect, hence thicker spark plug leads.

: Again, Electrical/Electronic systems are not my strong point, but as the theory above shows this would make sense. All you can do is try it and see if the difference is quantifiable in your mind by test driving the car after the change. Obviously, proper measuring devices would give you a definitive answer.

: David responded:
: Date: Sun, 8 Feb 2004

: electrical theory is that a short lead is better.the coil has a voltage potential and the lead,plug and rotor air gap absorb that potential leaving some to jump the plug gap and run the engine.

: But it is combustion theory that is more important. The spark is a heat source to ignite the stuff in the cyl. the gap, the temp and the time are important.

: My old leyland put out about 8-12 000 volts on a good day.less as revs increase and it takes more to do the job under higher engine load. So by the time you add in leads cap/rotor and plugs not much left.

: Modern cars are running 25-40 000+ volts "potential" then they use hi-resistance leads and plugs to increase the time that the plug heats the fuel.

: Conclusion.
: Is the coil better under the air cleaner, if it gets hot and covered in oil/dirt then no its not.

Leyland P76 Owners 2005

Technical Information

Coil position with respect to Distributor

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