Post by Phil Nottingham on Feb 7, 2010 11:39:56 GMT
Have you got the separate one next to the coil or the temp coefficient loom type?
If seperate just connect the 12v side direct to the coil - its best to disconnect and tape up the the other side's connections which is the old coil supply and the solonoid shunt that become live when starter is operated.
If it is the loom type then you must run a new cable to the unfused side of the Ignition Control on the fuse box and tape up the old connection.
Alternatively running on the centre parcel shelf "floor" is the wiring loom and you will see a heat shrink cable joint poking out. The new coil feed can be connected to the 12v end of this (white cable not pink)
Phil - 1964 P5-Coupe PMB***B & P5B-saloon LHO***L & other classic Rovers & Land-Rovers
No I stick with standard .06mm/.025" - have used this sports coil for years with no problem
Newbie here, so hopefully no offence taken.
The purpose of the sports coil is a bigger spark, and so on my old Jag I have opened up the gap to 40 thou to take advantage of this. Leaving the gap as is means little or no gain from the high output coil. In conjunction with electronic ignition and magnecor HT leads all is good.
(Looking to own a P5 again after selling some years ago; currently got a 60's jag.)
Unless your car has a compression ratio that's way over the top, (in excess of 11:1 or more...215psi) it'll make little or no difference apart from the bragging rights. Most normal 12v coils (3 - 3.5 ohms) with a cheap electronic ignition (pertronix clone) and a good set of leads, will easily put out the required voltage to fire the engine without any issues, if your running normal and not super lean air to fuel ratios.
Even at 11:1 compression, a standard points coil (above) will run an LPG fueled V8 without an issue.
NB. Overly big plug gaps just stress the electronics, make the coil run hot and ultimately look for alternate, easier paths to earth. I truly can't see any gain or advantage.
Uhhm, well actually no. Each time the points close and the ignition coil is powered up, it gains 1/2 L I^2 Joules of energy where L is the inductance of the primary and I the asymptotic current flowing in the primary. When the points open this energy is dissipated mostly through the air gap across the spark plug, with some resistive losses in the ignition leads. The amount of energy dissipated is independent of the width of the plug gap and dependent only on the energy stored in the coil.
Why should you not open up the gap? The answer is simple, it take some 3,000V to ionise the air across the spark plug gap and therefore let a current flow if the gap is 020 thou. If you widen the gap to 040 thou it will take twice the voltage ie 6000V. If you then partially insulate the plug with wet petrol, oil etc the voltage required to ionise the air goes up further. If the breakdown voltage of the winding in the coil is lets say 10,000V, then repeated exposure to 6000V + will lead to premature coil failure, short circuiting in the coil and heat generation in the coil.
Is there any benefit to widening the gap? If you produce a bigger volume spark with the same total energy it is clear that you will end up with a lower temperature spark (just bigger). Such a spark may not always be enough to get combustion going under adverse circumstances such as cold starting with the choke out.