Electronic ignition

[TR Rob]

Thinking of converting my Lucas 25D to electronic ignition to reduce maintenance etc.

 I thought I would remove my existing distributors base plate with points, condenser and wiring and replace it with a new base plate with the electronic module fitted.

The reasoning being, in the case of the electronic unit failing I could revert back to the original set up at the roadside.

I am reasonably competent with mechanics , but was wondering if people on here with more experience than me on these cars, think this is a good idea.

I don’t want to start carrying spare distributors or rebuilding at the roadside ….any comments ?

[Lebro]

Gets my vote, I have a standard distributor, refurbished by "The Distributor Doctor" & fitted with Pertronix electronic module. I carry a spare module in the glove box in case of problems, but don't expect to need it any day soon. (wish I hadn't said that !)  Much easier to swap to another module, than fiddle about fitting points on the side of the road.

Bob

[RobH]

A number of people have done that Rob and it seems to work for them.  

I do wonder at the 'reduced maintenance' though.  Given the low annual mileage that most members manage, checking the points gap once a year when the car comes out of winter hibernation is hardly onerous.

Even if you fit electronic ignition you will still need to lubricate the dizzy spindle from time to time with a few drops of oil after removing the rotor arm.

Edited November 6, 2023 by RobH

[james christie]

+1 to Lebro's contribution. I have exactly the same setup  - including the spare unit in the glovebox - thanks to the pessimists contributions to the fora. 
The only time it failed was entirely my own fault. Not bad over 20 years or so.

james

[RogerH]

38 minutes ago, TR Rob said:

Thinking of converting my Lucas 25D to electronic ignition to reduce maintenance etc.

 I thought I would remove my existing distributors base plate with points, condenser and wiring and replace it with a new base plate with the electronic module fitted.

The reasoning being, in the case of the electronic unit failing I could revert back to the original set up at the roadside.

I am reasonably competent with mechanics , but was wondering if people on here with more experience than me on these cars, think this is a good idea.

I don’t want to start carrying spare distributors or rebuilding at the roadside ….any comments ?

Hi Ron,

I have the Luminition module in my 4A Dizzy. It works well and have never adjusted it since 1998.

However I do about 15,000 miles/year.

BUT!!!  I do have a fear, as I spend most of my time in the fast lane of the motorway when on it - it could fail

The electronic units die instantly or quicker. Whereas the CB's slowly fad into oblivion.

 

Roger

[AndyR100]

I’ve used Pertronix, Lumenition, Powerspark and 123Ignition on different cars - the only failure of the unit itself has been with the PMA of the Lumenition (Optronic).

just for balance, I have also had condensers fail  

….. Andy

[Chris Glasbey]

My TR3A has the 123 ignition .....fitted now for over 20 years ....no problems yet ?!  

Chris.

[ianc]

Piranha/Newtronic fitted in 1993 - 30 years is a pretty good test. 

Adjustments made to timing when petrol changed from leaded, to LRP (awful stuff - made car difficult to start) and now to cope with introduction of ethanol (I try to use E5, which may actually be E-zero at Esso stations).

It's fit and forget as far as I am concerned, but I do carry a spare Piranha kit in the boot.

Ian Cornish

[Ian Vincent]

I have a Pertronix set up in a distributor that was overhauled by the DD.  Works for me, it’s fit and forget. 

Rgds Ian

[Chris Glasbey]

Which is also why I have forgotten when I fitted the 123 .....it may be 25 yrs +

Chris

[Cleo's Dad]

I replaced the Dizzy complete with a Powerspark electronic version. Very reasonable, simple to fit and noticed the difference in performance straight away.

Clive

[iain]

Rebuilt dizzy from DD, spare base plate carried in the car…never used.

Not convinced by the electronic solution. I seem to read more issues on the forum for electronic ignition than for standard items…..or maybe I’m selective in my reading:-)

 

[RobH]

39 minutes ago, Cleo's Dad said:

noticed the difference in performance straight away.

 

Classic sign of a worn distributor, with the electronic system masking the effects.  There should be no discernable difference in performance if the standard system was in good order. 

[Z320]

Hi,

I use a Pertonix Ignitor 1 unit after my Powerspark unit failed.

I caused this myself because I let the ignition switched on while the engine was not running.

This simple units don’t like this….

The distributor is not „refreshed“ because I see no need.

It is in good condition and no point are constantly tumbling the shaft anymore.

The electronic unit switches off the coil faster than points, this causes stronger sparks.

With points I used a reliable Bosch condenser from a Fiat (?) and had no worries.

Ciao, Marco 

[RobH]

1 hour ago, Z320 said:

The electronic unit switches off the coil faster than points, this causes stronger sparks.

Er - not sure about that Marco.

Faster switching may in theory result in higher voltage if there was nothing connected to the coil, but in practice the voltage reached is limited to the breakdown voltage of the spark gap which is rather less than the coil can provide.  The total spark energy is not related to switching speed either, but only to the magnetic saturation of the coil core which is limited by the dwell time achieved at high revs.

  For a standard system there is practically no difference, in normal driving, in the spark between electronic and points systems provided the distributor is in good condition.  The electronic system may possibly have an edge at high revs on a 6 cylinder engine, if it controls dwell better. 

 

[Z320]

Hi Rob,

sorry me, I simplyfied the issue, I learned this:

With "faster" I mean the immediately 100% interrupted current, producing higher ignition voltage.

While with points the condenser indeed reduces the spark (and current) on the points, but can not aviod it 100%.

This not wanted current via the points reduces the ignition voltage.

With a faulty condenser the spark (and current) on the points increases - and the ignition voltage drops.

Is this wrong, please?

Ciao, Marco

 

 

[RobH]

Not really Marco but perhaps a bit too simplified.  

When the primary current is interrupted, the collapse of the magnetic field in the coil core produces a secondary voltage which is proportional to :-

 the flux density, (primary ampere-turns during the dwell period) B

the length of the winding in the magnetic field  l

and the speed with which the fields collapses v.      ( e=Blv )  

As you say, if the electronic system can cut off more quickly than the points can open (with the condenser across them) , the secondary HT voltage will be higher - or rather it would be if there was nothing to limit it.  In practice apart from an extremely short initial spike which carries no current, the plug gap breaks down and 'clamps' the discharge at a lower voltage, rather less than the theoretical peak. The discharge voltage is then held fairly constant until the coil runs out of energy. Of course this discharge voltage will depend on how wide the plug gap is set. 

The amount of energy that flows in the plug gap (and hence the spark temperature) is not determined by the emf but by the amount of magnetic energy stored in the coil.  At high engine revs when the dwell time is short, the HT voltage tails off  because there is less time for the coil primary current to reach its maximum  ( B becomes smaller). This is more critical for a 6 cylinder engine than for a 4-pot.

The wider the plug gap is set, the higher the breakdown voltage and spark current will be, but the shorter time it will last and at extremes the HT may not reach a sufficient voltage to fire the plugs properly.  It is often said that electronic ignition can be used with a wider plug gap because there is more 'headroom' when things get marginal. 

All this means that if you install electronic ignition and don't change anything else, the engine will perform in more-or-less the same way as it did with points.  It may be that if you change the coil for a more energetic type and widen the plug gaps as well to make use of the extra energy, there will be some benefit at high revs. 

[Z320]

Hi Rob,

thank you for this explanation.

As I sometimes stated I should be more critical with what I‘ve been told.

I think I will make a practical test with points and electronic ignition next year to see my own.

I should have done this before….

Ciao, Marco 

from the www.Pertronix.com website, extremely simplified:

PRODUCT INFO

Delivers twice the voltage to the spark plugs, increasing horsepower, fuel economy, and spark plug life.

 

Edited November 24, 2023 by Z320

[John McCormack]

15 hours ago, RobH said:

Classic sign of a worn distributor, with the electronic system masking the effects.  There should be no discernable difference in performance if the standard system was in good order. 

Yep. Maybe a better idle if there is slight wear in the shaft bushes which affects the points gap at idle but will be hidden by the electronic ignition.

[Z320]

Looking on the timing mark on the pulley with my ignition lamp,

I see the mark "jumping" with points back and forth because the spring of the points makes the shaft tumble.

While the electronic ignition doesn't do this at all - and the position of the mark is very "quiet".

[RobH]

It was gone midnight when I posted the above and I see I have omitted some detail - apologies

The spark-plug waveform looks something like this:

The initial spike is the voltage required to break down the gas in the spark plug gap.  The voltage required to do this depends on many factors including  the gap width, the pressure in the cylinder, the temperature of the gas and the fuel mixture ratio so it will vary quite a bit.  Typically the peak will be in the order of 10kV and the flatter discharge region following will be 3 to 4 kV.  At normal road speeds the average ignition coil can produce well  in excess of 20kV so if everything is working properly, the system has no trouble in reaching these voltages irrespective of whether the trigger is points or electronics.  

At very high engine speed, however,  things get more marginal and the maximum coil voltage begins to drop, because the coil primary has little time to 'charge' during the dwell . It is possible that ultimately the coil voltage drops so low that it cannot break down the gap reliably and misfire is the result.  (Setting the points gap too wide will make this effect worse of course).

This can be overcome by using a coil with higher initial voltage capability so it still has some voltage in hand at top revs, allowing wider plug gaps to be used.  Electronic ignition may also help here by better control of the dwell time and eliminating the jitter inevitable with a mechanical system at high speed.  If it can switch faster it will also increase the highest voltage that the coil can produce, so again counteracting the droop. 

 

 

 

Edited November 24, 2023 by RobH

[RobH]

4 minutes ago, Z320 said:

I see the mark "jumping" with points back and forth because the spring of the points makes the shaft tumble.

This may not be points-bounce, it could be wobble in the distributor shaft due to bearing wear - which is why electronic ignition can seem to make a car run more smoothly by eliminating the effects of wear.   

[Z320]

Yes,

it is the spring of the points pressing 4 times each turn against the distributor shaft,

making the shaft tumble. 

Edited November 24, 2023 by Z320

[stuart]

14 hours ago, RobH said:

Er - not sure about that Marco.

Faster switching may in theory result in higher voltage if there was nothing connected to the coil, but in practice the voltage reached is limited to the breakdown voltage of the spark gap which is rather less than the coil can provide.  The total spark energy is not related to switching speed either, but only to the magnetic saturation of the coil core which is limited by the dwell time achieved at high revs.

  For a standard system there is practically no difference, in normal driving, in the spark between electronic and points systems provided the distributor is in good condition.  The electronic system may possibly have an edge at high revs on a 6 cylinder engine, if it controls dwell better. 

 

Classic demonstration on a 6cylinder was what we found racing Jaguars back in the Seventies, the only readily available electronic ignition back then was the Sparkrite units that sat clipped onto the side of the coil, they had a switch on the side to bypass the unit so you could easily see how much higher you could rev the engine and the difference at high revs was the ability to get another 1000 RPM

Stuart.

[Ian Vincent]

I'm impressed you can remember the seventies Stuart, I find everything from that era is a bit hazy.