# How to determine values of VOLTS of spark gaps in series?

#### russwr

Joined Aug 29, 2017
66
Ignition coil Positive high voltage pulsing in series with 1st spark gap. 2nd spark gap is in series with 1st and to ground. The gaps are different mm spacing. Does first one determine the final voltage of second, if load is low 20 ohms to ground? Does voltage drop loss get involved?

#### crutschow

Joined Mar 14, 2008
34,719
The voltage is the sum of the two gap voltages, as if there were just on gap equal to the gap length of both added together.
Note that if one gap is under compression pressure, that will increase the voltage required to jump that gap.

#### russwr

Joined Aug 29, 2017
66
Yes, I understand that. But doesn't the greatly reduced load of 20 ohms under compression , get the voltage greatly reduced? ( Not air high ohms gap) Therefore, reflecting back to the first gap to make final say so as to spark plug voltage? The 1st gap requires its voltage level to meet ground also ,so as a minimum value. Such as similar to having a second gap as a near shorted plug.

#### crutschow

Joined Mar 14, 2008
34,719
Sorry, but can't really follow what you have from your description.
Please post a diagram of the connections.

#### LowQCab

Joined Nov 6, 2012
4,228
Placing an "Auxiliary-Gap" between the Coil and the Spark-Plug
is only advantageous when there is a definite propensity for Plug-Fowling.

Modern Engines with Electronic-Fuel-Controls never "foul" the Spark-Pugs,
the Spark-Plug-Gap-Materials simply "wear-out" over long periods of time,
which can lead to an increased Spark-Plug-Gap,
which will require a higher-Coil-Voltage to ionize the Gap,
which can lead to odd misfires under certain circumstances,
but this will occur only under maximum-Load conditions.

There is zero advantage
in raising the Spark-Voltage in a modern factory-stock Engine.

Modified Engines, with much higher Cylinder-Pressures,
such as with After-Market-Turbo-Charging,
may demonstrate some slight advantage from increased Ignition-Coil-Power and
adding a relatively high DC-Bias-Voltage to the Secondary of each Ignition-Coil,
( roughly ~500-Volts-DC is required to create any measurable effectiveness ).

Modern "Coil-On-Plug" Ignition-Systems are extremely powerful and reliable when
they are maintained in good working-order, ( clean and undamaged ).
You can't make any more Engine-Power by making the Ignition-System "better",
except maybe in the case of highly-modified Engines with
ridiculously high-Cylinder-Pressures being routinely generated.

Are You working with a an old antique Distributor-Ignition Engine ?
.
.
.

#### russwr

Joined Aug 29, 2017
66
Placing an "Auxiliary-Gap" between the Coil and the Spark-Plug
is only advantageous when there is a definite propensity for Plug-Fowling.

Modern Engines with Electronic-Fuel-Controls never "foul" the Spark-Pugs,
the Spark-Plug-Gap-Materials simply "wear-out" over long periods of time,
which can lead to an increased Spark-Plug-Gap,
which will require a higher-Coil-Voltage to ionize the Gap,
which can lead to odd misfires under certain circumstances,
but this will occur only under maximum-Load conditions.

There is zero advantage
in raising the Spark-Voltage in a modern factory-stock Engine.

Modified Engines, with much higher Cylinder-Pressures,
such as with After-Market-Turbo-Charging,
may demonstrate some slight advantage from increased Ignition-Coil-Power and
adding a relatively high DC-Bias-Voltage to the Secondary of each Ignition-Coil,
( roughly ~500-Volts-DC is required to create any measurable effectiveness ).

Modern "Coil-On-Plug" Ignition-Systems are extremely powerful and reliable when
they are maintained in good working-order, ( clean and undamaged ).
You can't make any more Engine-Power by making the Ignition-System "better",
except maybe in the case of highly-modified Engines with
ridiculously high-Cylinder-Pressures being routinely generated.

Are You working with a an old antique Distributor-Ignition Engine ?
.
.
.
Old style engines already have (2) spark gaps. The spark plug and the gap inside distributor of rotor TO the contacts inside distributor cap. If another is added in series , it may help the fouling of spark plug as assuring the spark goes through, for the ground of the added gap voltage. Non resistor spark plugs can also work better.

#### crutschow

Joined Mar 14, 2008
34,719
Plug fouling in a properly running engine was mainly caused by the use of leaded fuel, as the leaded deposit on the plugs was somewhat conductive and so the plugs had to be cleaned (sand blasted) or replaced after perhaps 10k miles or less.
With the use of unleaded fuel, plugs do not normally foul, and can last up to 100k miles.

#### nsaspook

Joined Aug 27, 2009
13,446
Plug fouling in a properly running engine was mainly caused by the use of leaded fuel, as the leaded deposit on the plugs was somewhat conductive and so the plugs had to be cleaned (sand blasted) or replaced after perhaps 10k miles or less.
With the use of unleaded fuel, plugs do not normally foul, and can last up to 100k miles.
I remember my first set of platinum plugs in a new car with unleaded fuel. Those original plugs lasted forever.

#### LowQCab

Joined Nov 6, 2012
4,228
That's the only reason for Platinum or Iridium-Tipped-Plugs, they last virtually forever,
but they are a definite liability in a modified-Engine because of the fact that they
create a "Hot-Spot" in the Combustion-Chamber which can
easily create, or at the very least aggravate, potential Detonation problems,
and Detonation is the number-one killer of High-Performance-Modified-Engines.

For the Hot-Rod-Community ..........

Just because they cost ~\$8.oo each, doesn't make them "the best" choice for a Modified-Engine.
Always use "Standard"-"Copper-Core"-"Resistor"-Spark-Plugs for Modified-Engines,
and install new Plugs every ~10,000 miles, no matter how perfect they may appear to look.

Never-Ever "clean" a Spark-Plug by any means or method,
ALWAYS REPLACE THEM WITH NEW ONES.

And, meticulously follow the manufacturer's instructions for Torquing the new Spark-Plugs.
You may have to go to the manufacturer's web-site for this information.
Proper Torquing is absolutely critical on many Engines.

And, always use "Anti-Seize-Compound" on the New-Plug-Threads,
( on Cast-Iron-Heads, this isn't a big issue, but it won't hurt anything to use it in any case ),
regardless of the manufacturer's claims that "none is required" because of "Special-Thread-Platings" etc.
It was nice of them to provide that extra bonus,
but You can't depend on any sort of "Metal-Plating" to