[ROVERNET - UK] P6 -SD1 spark plug gap?

Paul Smith Paul.Smith at auroraenergy.com.au
Wed Jan 17 21:33:40 GMT 2007


There are 2 main types of electronic ignition, TAI and Capacitor Discharge Ignition.
Personally I like CDI but they are out of favour currently.
I think Pertronix are a Hall Effect or inductive sensor triggering a TAI.  I have points triggering a TAI.
On a normal (Kettering) ignition, the points take 3 to 4 amps (more on Jags, don't kow why) which runs through the coil primary.  The coil is a step up transformer.  When the points open breaking the current (fairly quickly, there is arcing) the spike change induces a high voltage in the secondary - the HT side which goes to the spark plugs.   If you get 15kv it will produce an ok spark at the plug.
However it gets trickier...
As the revs rise, the time for the primary current to establish itself (recover) once the points close can mean it never reaches the 3A, so the secondary voltage falls.  This happens with V8s easily, since there is half the time of a 4 for each cylinder fire.  
Soooo the solution is to extend the dwell time - the time that the points are closed establishing that current.  This can be achieved mechanically by 2 sets of points, so that one close shortly after the other opens.  A TAI does it electronically, by switching a transistor to reestablish primary coil current.  The other solution is a better coil - they have higher permeability ferrite in them, I don't know more.
This also removes arcing (and thus lots of wear) from the points since they now handle 0.3A or so.
The next step (a la Pertronix) is to replace the points with a non contact trigger, a magnet of some form.  This elimminates the need to adjust at regular intervals.

PVS

-----Original Message-----
From: rovernet-bounces at lyris.ccdata.com
[mailto:rovernet-bounces at lyris.ccdata.com]On Behalf Of geffandjulie
Sent: Thursday, 18 January 2007 4:50 am
To: rovernet at lyris.ccdata.com
Subject: Re: [ROVERNET - UK] P6 -SD1 spark plug gap?


What is a transistor-assisted ignition?  That's a new term. I think I 
understand electronic ignition, and the Pertronix system, but...
----- Original Message ----- 
From: "Paul Smith" <Paul.Smith at auroraenergy.com.au>
To: <rovernet at lyris.ccdata.com>
Sent: Tuesday, January 16, 2007 1:28 PM
Subject: RE: [ROVERNET - UK] P6 -SD1 spark plug gap?


P6B used ballasted coil.
Yes, any coil should do the job, I usually get one off a Jap car, they last 
and work well.
Right at the moment I have the Lucas on my P6B, it is working fine, and I 
added a Transistor Assisted Ignition to improve voltage.  Can take pictures 
and show wiring.

PVS

-----Original Message-----
From: rovernet-bounces at lyris.ccdata.com
[mailto:rovernet-bounces at lyris.ccdata.com]On Behalf Of geffandjulie
Sent: Wednesday, 17 January 2007 5:03 am
To: rovernet at lyris.ccdata.com
Subject: Re: [ROVERNET - UK] P6 -SD1 spark plug gap?


Thanks. Can I try a higher voltage coil? And does it need to be ballasted? I
am showing my ignorance!
----- Original Message ----- 
From: "Paul Smith" <Paul.Smith at auroraenergy.com.au>
To: <rovernet at lyris.ccdata.com>
Sent: Monday, January 15, 2007 7:39 PM
Subject: RE: [ROVERNET - UK] P6 -SD1 spark plug gap?


Yep.
The max gap is determined by the coil voltage (not so great with Lucas
standard), the min gap by what makes the mixture burn and the plug not foul.
Try .025.

PVS

-----Original Message-----
From: rovernet-bounces at lyris.ccdata.com
[mailto:rovernet-bounces at lyris.ccdata.com]On Behalf Of geffandjulie
Sent: Tuesday, 16 January 2007 2:19 pm
To: Rovernet05
Subject: [ROVERNET - UK] P6 -SD1 spark plug gap?


I have SD-1 heads on my P6. Based on advice, I have installed the correct
SD-1 plugs, NGK BP6ES. However, I set the gap to .030" vs. the .025 book
figure for the Champion N92YC.   It has a standard Lucas distributor and
coil. It starts but runs rough.
***Is the gap too wide?***
Thanks in advance.
Geff and Julie McCarthy
AvMedSafe
503-241-8468


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