Summit - MSD box
TeamRush
Active Jeeper
Reluctor at dead even with pickup coil core is 'Zero Point'.
The magnetic load of the reluctor arm comes into the coil magnetic field and produces either a positive or negative pulse,
That pulse will stop at the Zero Point when magnetic load is dead even with the coil core.
No matter what the polarity of the pulse when load is moving through the magnetic field, the opposite polarity pulse will be induced when the load passes the zero point.
Negative-Zero-Positive, or Positive-Zero-Negative.
Depending on the module you use (MSD, HEI, DuraSpark, Etc) the module will ignore one half of the pulse and will trigger on the other half.
A 'Drifting' idle speed, moving up & down a little, will often be the wires (polarity) to the coil reversed, the module is getting triggered as the magnetic load is coming in and NOT right after the zero point.
(Guys with combined fuel injection should take note, an unstable idle speed might be as easy as flipping the trigger coil wires to fix)
.
Rotor Phasing fixes the multi-fire problem, firing more than one spark plug at a time.
By far the biggest cause of out of phase rotors is the distributor gear on backwards.
There are 13 teeth on the distributor gear, no 'Center Line' with an odd number, and when the gear is on backward, you are 1/2 space off on the rotor (between terminals).
This isn't a huge problem when the cross fire is firing both the cylinder on exhaust and the cylinder next in rotation, you probably won't notice.
You are losing some spark energy, but the point of an CDI unit is you have enough spark energy to get the correct plug fired.
When that multi-fire is the current plug in rotation,
AND the plug somewhere between 45 crank degrees and 90 crank degrees (plus advance) with a fuel charged cylinder you are hammering the cylinder that's coming up, not ready for spark yet.
You CAN hammer the cylinder so hard you break pistons, rods, etc.
Normally, you don't have enough compression to do huge damage, but it does accumulate over time.
It's good to correct, and we always check racing engines for the problem since they make a lot more power and self destruct much faster.
Hang a blower on that engine at about 28 psig boost and the Piston/rod will exit the rotating assembly immediately when it reaches peak pressure...
Just a slower failure when it's a low compression engine.
.
Now, some of you might know I worked for MSD about a 1,000 years ago, when it was family owned and every module did 24 hours of 'Burn In', active testing at full power as a QC test before they ship.
It's not family owned anymore, there are *Some* components made in China, and I can't recommend MSD the way I used to...
I understand they did away with the 24 hour burn in test on modules, and there was an instant increase in out of the box and shortly installed fails.
That's a shame because it was the single most reliable ignition you could buy...
.
As for plug gap,
If you go past about 0.045", you are going to work the ignition coil to death.
Internal insulation on MSD coils was about 125,000 volts, and that was the best insulation they could find.
Some factory coils, like the Ford TFI coils, could run with MSD... The reason I would snag factory Ford coils when I found them in the salvage yard and could recommend them.
(Ford had a module problem but thought it was a coil problem, made really good coils for years until the module problem was finally found)
When you open that plug gap WAY up, you drive the voltage in the coil WAY up to cross the spark gap.
This overheats the coil, and it breaks internal insulation down MUCH faster.
At about 0.045" you are getting PLENTY of voltage
To drive the voltage up any further is wasting the DURATION (Time) in the spark energy.
With smaller gap, you get a HOTTER spark (Amperage) and longer Duration (time the spark is in the gap) along with sufficient Voltage to ionize the gap so the spark can form properly.
While racers open the pug gaps to HUGE numbers, the coil/plug only has to last ONE race.
Exotic fuels are harder to get burning than standard pump gas, so they jack things WAY up.
The truth is, anywhere between 0.035" and 0.045" is sufficient and keeps the plugs/coil living longer, which IS a concern for us... Not wanting to be stranded without a pit crew and million dollar budget...
.
The coil is a TRANSFORMER...
The connected power, 12 volts in standard ignitions,
600 volts in MSD modules,
Voltage creates a magnetic field, and electromagnet in the PRIMARY windings of the coil.
When power is cut, that magnetic field collapses (moves) through the SECONDARY windings,
INDUCING (creating) an electrical current in the secondary windings, and that's the one connected to the plugs.
Since the power is cut (open circuit) and there is a Limited size/shape magnetic field, you only get SO MUCH magnetic energy to make electrical (spark) energy with.
It's Limited by the strength of the magnetic field, and the time it takes to collapse through the secondary windings...
So you can convert that magnetic energy into Amps or Volts (not both).
The idea is to balance the Amps & Volts,
Volts ionize the spark gap so the electrical arc can properly form,
The Amps are what sustains the full arc and determine how hot the spark will be.
Opening the gap so you get sufficient VOLTS to ionize the gap, initialize the arc in the gap,
Enough amps/heat to get the fire lit, all on that milli-seconds it takes the magnetic field to collapse is a balance that Nicola Tesla worked out over 100 years ago...
It's not as simple as a lot like to think, but it's not out of common man comprehension either...
The distributor is a lot more complicated than most think, but most can work it out with a little education and some experimentation....
The magnetic load of the reluctor arm comes into the coil magnetic field and produces either a positive or negative pulse,
That pulse will stop at the Zero Point when magnetic load is dead even with the coil core.
No matter what the polarity of the pulse when load is moving through the magnetic field, the opposite polarity pulse will be induced when the load passes the zero point.
Negative-Zero-Positive, or Positive-Zero-Negative.
Depending on the module you use (MSD, HEI, DuraSpark, Etc) the module will ignore one half of the pulse and will trigger on the other half.
A 'Drifting' idle speed, moving up & down a little, will often be the wires (polarity) to the coil reversed, the module is getting triggered as the magnetic load is coming in and NOT right after the zero point.
(Guys with combined fuel injection should take note, an unstable idle speed might be as easy as flipping the trigger coil wires to fix)
.
Rotor Phasing fixes the multi-fire problem, firing more than one spark plug at a time.
By far the biggest cause of out of phase rotors is the distributor gear on backwards.
There are 13 teeth on the distributor gear, no 'Center Line' with an odd number, and when the gear is on backward, you are 1/2 space off on the rotor (between terminals).
This isn't a huge problem when the cross fire is firing both the cylinder on exhaust and the cylinder next in rotation, you probably won't notice.
You are losing some spark energy, but the point of an CDI unit is you have enough spark energy to get the correct plug fired.
When that multi-fire is the current plug in rotation,
AND the plug somewhere between 45 crank degrees and 90 crank degrees (plus advance) with a fuel charged cylinder you are hammering the cylinder that's coming up, not ready for spark yet.
You CAN hammer the cylinder so hard you break pistons, rods, etc.
Normally, you don't have enough compression to do huge damage, but it does accumulate over time.
It's good to correct, and we always check racing engines for the problem since they make a lot more power and self destruct much faster.
Hang a blower on that engine at about 28 psig boost and the Piston/rod will exit the rotating assembly immediately when it reaches peak pressure...
Just a slower failure when it's a low compression engine.
.
Now, some of you might know I worked for MSD about a 1,000 years ago, when it was family owned and every module did 24 hours of 'Burn In', active testing at full power as a QC test before they ship.
It's not family owned anymore, there are *Some* components made in China, and I can't recommend MSD the way I used to...
I understand they did away with the 24 hour burn in test on modules, and there was an instant increase in out of the box and shortly installed fails.
That's a shame because it was the single most reliable ignition you could buy...
.
As for plug gap,
If you go past about 0.045", you are going to work the ignition coil to death.
Internal insulation on MSD coils was about 125,000 volts, and that was the best insulation they could find.
Some factory coils, like the Ford TFI coils, could run with MSD... The reason I would snag factory Ford coils when I found them in the salvage yard and could recommend them.
(Ford had a module problem but thought it was a coil problem, made really good coils for years until the module problem was finally found)
When you open that plug gap WAY up, you drive the voltage in the coil WAY up to cross the spark gap.
This overheats the coil, and it breaks internal insulation down MUCH faster.
At about 0.045" you are getting PLENTY of voltage
To drive the voltage up any further is wasting the DURATION (Time) in the spark energy.
With smaller gap, you get a HOTTER spark (Amperage) and longer Duration (time the spark is in the gap) along with sufficient Voltage to ionize the gap so the spark can form properly.
While racers open the pug gaps to HUGE numbers, the coil/plug only has to last ONE race.
Exotic fuels are harder to get burning than standard pump gas, so they jack things WAY up.
The truth is, anywhere between 0.035" and 0.045" is sufficient and keeps the plugs/coil living longer, which IS a concern for us... Not wanting to be stranded without a pit crew and million dollar budget...
.
The coil is a TRANSFORMER...
The connected power, 12 volts in standard ignitions,
600 volts in MSD modules,
Voltage creates a magnetic field, and electromagnet in the PRIMARY windings of the coil.
When power is cut, that magnetic field collapses (moves) through the SECONDARY windings,
INDUCING (creating) an electrical current in the secondary windings, and that's the one connected to the plugs.
Since the power is cut (open circuit) and there is a Limited size/shape magnetic field, you only get SO MUCH magnetic energy to make electrical (spark) energy with.
It's Limited by the strength of the magnetic field, and the time it takes to collapse through the secondary windings...
So you can convert that magnetic energy into Amps or Volts (not both).
The idea is to balance the Amps & Volts,
Volts ionize the spark gap so the electrical arc can properly form,
The Amps are what sustains the full arc and determine how hot the spark will be.
Opening the gap so you get sufficient VOLTS to ionize the gap, initialize the arc in the gap,
Enough amps/heat to get the fire lit, all on that milli-seconds it takes the magnetic field to collapse is a balance that Nicola Tesla worked out over 100 years ago...
It's not as simple as a lot like to think, but it's not out of common man comprehension either...
The distributor is a lot more complicated than most think, but most can work it out with a little education and some experimentation....
