parasitic spark pre-ignition

[tjus]

just wound this video about parasitic spark pre-ignition from bundled spark wires.

he has neat test set up and explanations,

.

[Firedome8]

just wound this video about parasitic spark pre-ignition from bundled spark wires.

he has neat test set up and explanations,

.

A Service bulletin for small block chevys I believe identified this for cylinders 5 7 and and cautioned to keep the original wiring configuration that separated the wires and may have crossed them canceling out the induced voltage. If I recall the capatince effect was noted.

[ProPower engines]

While not new thinking the fact that wires run closely together has been an issue forever this just seems like a
different combination to deal with.

[MadBill]

just wound this video about parasitic spark pre-ignition from bundled spark wires.

he has neat test set up and explanations,

.

A Service bulletin for small block chevys I believe identified this for cylinders 5 7 and and cautioned to keep the original wiring configuration that separated the wires and may have crossed them canceling out the induced voltage. If I recall the capatince effect was noted.

The definition of preignition is the fuel/air mix igniting before the spark fires, so technically this is about inductive coupling causing cross fire.

I have some insider info re the Chevrolet 5/7 issue. Very early in the life of the SBC this problem (inductive firing of the #7 plug 90° early) was discovered and corrected by crossing those two leads at close to 90°. Years later, it resurfaced when some shiny new engineer, unaware of this history, 'tidied up' the wiring appearance by running the 5 & 7 wires closely in parallel, 're-inducing' the same problem. This was soon corrected by the same fix but about twenty years later, another shiny newbie followed the same path with the same result.

By the time the third generation arrived on the scene there were no distributors left to mess up...

[FredWinterburn]

I watched the first 15 minutes or so. Pre-ignition is the wrong word for it for sure. Cross fire due to capacitive coupling of the HT wires would be a better description. I believe he is correct in his statement that it is a capacitive effect that does it. If it were inductive, the free end of the other HT wire would have to make a closed circuit to ground and it is open-ended which makes it just like the plate of a capacitor. I've done exactly the same experiment to prove the CDI I build will not cause cross-fire to other cylinders on old cars that have the plug wires bundled in metal distribution tubes. With my experiments I used the variable spark gap on my test machine and a spark plug for the other gap. I found no difference between my CDI and the standard Kettering system using points/condenser when the same coil was used. Peak voltage plays a big role. Other than not bundling wires together over long lengths, the spark plug gaps should be fairly even to prevent cross-fire. With bundled wires, even if there is no spark on the low compression plug gap, there is still probably some energy lost as a corona discharge, but it will be very low energy and unable to ignite fuel. Fred

just wound this video about parasitic spark pre-ignition from bundled spark wires.

he has neat test set up and explanations,

.

A Service bulletin for small block chevys I believe identified this for cylinders 5 7 and and cautioned to keep the original wiring configuration that separated the wires and may have crossed them canceling out the induced voltage. If I recall the capatince effect was noted.

The definition of preignition is the fuel/air mix igniting before the spark fires, so technically this is about inductive coupling causing cross fire.

I have some insider info re the Chevrolet 5/7 issue. Very early in the life of the SBC this problem (inductive firing of the #7 plug 90° early) was discovered and corrected by crossing those two leads at close to 90°. Years later, it resurfaced when some shiny new engineer, unaware of this history, 'tidied up' the wiring appearance by running the 5 & 7 wires closely in parallel, 're-inducing' the same problem. This was soon corrected by the same fix but about twenty years later, another shiny newbie followed the same path with the same result.

By the time the third generation arrived on the scene there were no distributors left to mess up...

[AUTOMAN]

Actually capacitive coupling.

cliff

[Tuner]

I watched the first 15 minutes or so. Pre-ignition is the wrong word for it for sure. Cross fire due to capacitive coupling of the HT wires would be a better description. I believe he is correct in his statement that it is a capacitive effect that does it. If it were inductive, the free end of the other HT wire would have to make a closed circuit to ground and it is open-ended which makes it just like the plate of a capacitor. I've done exactly the same experiment to prove the CDI I build will not cause cross-fire to other cylinders on old cars that have the plug wires bundled in metal distribution tubes. With my experiments I used the variable spark gap on my test machine and a spark plug for the other gap. I found no difference between my CDI and the standard Kettering system using points/condenser when the same coil was used. Peak voltage plays a big role. Other than not bundling wires together over long lengths, the spark plug gaps should be fairly even to prevent cross-fire. With bundled wires, even if there is no spark on the low compression plug gap, there is still probably some energy lost as a corona discharge, but it will be very low energy and unable to ignite fuel. Fred

A Service bulletin for small block chevys I believe identified this for cylinders 5 7 and and cautioned to keep the original wiring configuration that separated the wires and may have crossed them canceling out the induced voltage. If I recall the capatince effect was noted.

The definition of preignition is the fuel/air mix igniting before the spark fires, so technically this is about inductive coupling causing cross fire.

I have some insider info re the Chevrolet 5/7 issue. Very early in the life of the SBC this problem (inductive firing of the #7 plug 90° early) was discovered and corrected by crossing those two leads at close to 90°. Years later, it resurfaced when some shiny new engineer, unaware of this history, 'tidied up' the wiring appearance by running the 5 & 7 wires closely in parallel, 're-inducing' the same problem. This was soon corrected by the same fix but about twenty years later, another shiny newbie followed the same path with the same result.

By the time the third generation arrived on the scene there were no distributors left to mess up...

Fred, how does this co-relate with your description of voltage/current ~ leading/lagging in your previous post in the "HEI or MSD box" thread? I'm still trying to wrap my head around that concept of ignition energy.
viewtopic.php?p=886086&sid=d914902cb4fc ... ef#p886086

You guys taking issue with the semantics or jargon of technical words used in the video need to cut some slack for the gentleman who created the video because his first language is not English, so in translation some nomenclature may not suit you semantically, although the expressed meaning should be understood.

[hoodeng]

Early development of the HEI as we know it.

https://www.youtube.com/watch?v=lBp5ag6SJH4

Enjoy!