Points ignition vs electronic

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Truckedup
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Points ignition vs electronic

Post by Truckedup » Thu May 17, 2018 7:29 am

I have several vintage Triumph race bikes...I use modern electronic ignition ,not points or magnetos...There's always discussion with bike guys about the advantages of electronics over points..The old bikes are two cylinder with two sets of points and two coils..Two separate ignition systems so to speak. The dwell time for each coil is about 140 degrees.These engine rev to 7000 -7500 rpm...I mentioned that points V8's had only 36 degrees dwell with dual points and one coil to fire 8 cylinders at 7000 rpm..They say an electronic ignition can by it self, make more power than points for a moderately tuned engine....
Let's say you have a modified 350 Chevy with the usual stuff to make about 375-400 HP using a modern electronic ignition, MSD or whatever you use. Suppose you install a well sorted dual points distributor...Do you think the engine can still make the same power ? Obviously the electronic ignition is more accurate but does an increase in spark energy make a difference for this type of engine?
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Re: Points ignition vs electronic

Post by Walter R. Malik » Thu May 17, 2018 9:40 am

Truckedup wrote:
Thu May 17, 2018 7:29 am
I have several vintage Triumph race bikes...I use modern electronic ignition ,not points or magnetos...There's always discussion with bike guys about the advantages of electronics over points..The old bikes are two cylinder with two sets of points and two coils..Two separate ignition systems so to speak. The dwell time for each coil is about 140 degrees.These engine rev to 7000 -7500 rpm...I mentioned that points V8's had only 36 degrees dwell with dual points and one coil to fire 8 cylinders at 7000 rpm..They say an electronic ignition can by it self, make more power than points for a moderately tuned engine....
Let's say you have a modified 350 Chevy with the usual stuff to make about 375-400 HP using a modern electronic ignition, MSD or whatever you use. Suppose you install a well sorted dual points distributor...Do you think the engine can still make the same power ? Obviously the electronic ignition is more accurate but does an increase in spark energy make a difference for this type of engine?
Points can float and give incorrect timing.
Magnetic fields and light triggers, don't.
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Re: Points ignition vs electronic

Post by JohnP » Thu May 17, 2018 9:50 am

Yes, an electronic ignition can have much more spark energy than points.

For an inductive ignition, the points are replaced by a transistor, which can handle much more current than points.

Points require a ballast resistor or high resistance coil to limit the current, to protect them from burnout.

The energy stored in the coil increases with the square of the current in the primary:

Energy = 1/2 inductance times the square of the current

For points, let's say we have a coil with a 3 ohm primary.

With 13.7v battery, max current at spark time with 45° dwell could be 13.7/3 = 4.56A.

For transistor ignition, subtract about 1.5v because the transistor has some resistance, so you have maybe 12.2v to work with.

But now you can use a 0.5 ohm coil, giving you a max of 24.4 amps if you didn't control dwell or limit the current. But we have dwell control and current limiting, so let's say we limit the current to 7 amps.

So, the increase in current from 4.56 to 7 Amps is 1.535 times.

1.535 x 1.535 = 2.356 more spark energy.
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Re: Points ignition vs electronic

Post by FC-Pilot » Thu May 17, 2018 11:13 am

Truckedup wrote:
Thu May 17, 2018 7:29 am
I have several vintage Triumph race bikes...I use modern electronic ignition ,not points or magnetos...There's always discussion with bike guys about the advantages of electronics over points..The old bikes are two cylinder with two sets of points and two coils..Two separate ignition systems so to speak. The dwell time for each coil is about 140 degrees.These engine rev to 7000 -7500 rpm...I mentioned that points V8's had only 36 degrees dwell with dual points and one coil to fire 8 cylinders at 7000 rpm..They say an electronic ignition can by it self, make more power than points for a moderately tuned engine....
Let's say you have a modified 350 Chevy with the usual stuff to make about 375-400 HP using a modern electronic ignition, MSD or whatever you use. Suppose you install a well sorted dual points distributor...Do you think the engine can still make the same power ? Obviously the electronic ignition is more accurate but does an increase in spark energy make a difference for this type of engine?
This is a great question. I have heard it said that if you have enough "spark" to light the cylinder that the right time that "more" does not make more power. I guess the real question is on your hypothetical 350, even if there is a hotter spark, do you see in in the HP numbers. If I get a chance one of these days that would be fun to test on the dyno just to give fact to the theory. Although I am sure someone on here has done it.

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Re: Points ignition vs electronic

Post by lefty o » Thu May 17, 2018 12:57 pm

in a perfect set up etc, the best points can do is to start wearing the second the distributor starts to turn.

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Re: Points ignition vs electronic

Post by JohnP » Thu May 17, 2018 1:09 pm

Yes, as the rubbing block on the points wear, the dwell increases. Then there is the pitting and transfer of metal from one contact to the other.

The HEI is fine for this application.
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Re: Points ignition vs electronic

Post by Truckedup » Thu May 17, 2018 1:26 pm

FC-Pilot wrote:
Thu May 17, 2018 11:13 am


This is a great question. I have heard it said that if you have enough "spark" to light the cylinder that the right time that "more" does not make more power. I guess the real question is on your hypothetical 350, even if there is a hotter spark, do you see in in the HP numbers. If I get a chance one of these days that would be fun to test on the dyno just to give fact to the theory. Although I am sure someone on here has done it.

Paul
You answered my question =D> If you replaced the distributor in the hypothetical 400 HP 350.. .Lets say a properly curved high performance HEI with a similarly curved quality dual points distributor...Would there be any difference in power ??? Yes, points go out of adjustment but lets just say before that happens...
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Re: Points ignition vs electronic

Post by DrillDawg » Thu May 17, 2018 1:55 pm

Wire your bike up using a electronic pickup, two aftermarket coils and aftermarket Harley Davidson computer control box with adjustable timing curves and start retard, use a 16 volt battery to the coil. If points make more power than that, more power to ya.
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Re: Points ignition vs electronic

Post by Truckedup » Thu May 17, 2018 2:23 pm

DrillDawg wrote:
Thu May 17, 2018 1:55 pm
Wire your bike up using a electronic pickup, two aftermarket coils and aftermarket Harley Davidson computer control box with adjustable timing curves and start retard, use a 16 volt battery to the coil. If points make more power than that, more power to ya.
I use Pazon electronic ignitions with dwell control ,a low resistance dual outlet coil ,12 volt battery total loss electric...Engine makes 1.6 HP per cubic inch..
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Re: Points ignition vs electronic

Post by DrillDawg » Thu May 17, 2018 2:40 pm

At the rear wheel?
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Re: Points ignition vs electronic

Post by mk e » Thu May 17, 2018 3:17 pm

When I saw the tread title I thought I'd been transported back in time 30 years to when point were still used on performance engines ;)
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Re: Points ignition vs electronic

Post by Truckedup » Thu May 17, 2018 3:35 pm

DrillDawg wrote:
Thu May 17, 2018 2:40 pm
At the rear wheel?
55 at the rear wheel on a Superflow dyno, about 62 at the flywheel...
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Re: Points ignition vs electronic

Post by FC-Pilot » Thu May 17, 2018 3:52 pm

A car I watched race, and later raced against for many years ran a dual points distributor. He was deadly consistent and the car was very reliable. The only issue I remember ever seeing in years of racing was a rotor broke and blew up the cap. I asked him one day about changing his ignition setup. He said why? I run consistent and win races. that is what I am out here to do. I could not argue it. When other guys were loosing races to loosing "boxes" and electrical issues he just kept going rounds. He may have been able to go a little faster, but I could not deny his wins.

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Re: Points ignition vs electronic

Post by benno318 » Thu May 17, 2018 5:18 pm

i do work for several different one-make circuit race series, one is still mandated to run points only (love how they always say its to keep costs down, yet many racers in this series have been there well over ten years and spent more on points than if they were electronic) we have no problem with points really.

one of the other classes was the same, but they changed the rules to allow a pertronix ignitor conversion. these little 1600cc cars are a good test as they are a fixed (quite low) compression ratio, control camshaft, alloy head engine. they rev to about 7000. comp works out to be approx 8.5:1 so pretty much everyone runs a locked distributor - good for a comparison as distributor curves dont come into the equation.

the cars i have seen on the chassis dyno make 80 to 83rwhp. one car i was involved with had points, we dyno'd it, next time we saw it he had put on the ignitor, and no change whatsoever to the power - either at peak, or the whole curve. i THINK he had changed the coil to suit but i cannot be 100% sure - so maybe that is why no improvement was seen. over the years all of the electronic conversion reports have been to replace poorly maintained points setups, in which case of course there will be a massive power and driveability gain.

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Re: Points ignition vs electronic

Post by kirkwoodken » Thu May 17, 2018 5:42 pm

Grumpy used a Corvette F.I. dual point in his early "Toys" cars and won many races. Don't know what others were using. I never figured out why the Spalding/Grant style dual coil ignitions were not more popular. The ones I used were excellent performers.
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