Spark plug overgap-- effect on ignition system?

I've seen severely opened plugs which never caused any ignition problems. I don't think there is a acute relationship.

Hmmm. Higher resistance on the secondary side of a transformer. I think the voltage is determined by the number of turns, so the current must be reduced. That implies reduced current in the primary, so I don't see any problem.

When the plug fires the gap resistance of the conducting plasma is orders of magnitude smaller than the HT wire resistance, the built in plug resistance a the coil winding resistance its leakage inductance regardless of the gap. Larger gap will stress all HV components more because the larger gap will require the ignition voltage to build up to higher potential before it fires.

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs

When there is higher atmospheric pressure, there needs to be more electrical energy to spark. If the ignition still has a enough power to jump the larger gap, it won't miss. But in many cases, it won't have enough power and thus a missing engine.

chuck

ps: It seems strange that if there are more molecules >

Spark fires slightly later (retarded timing). That should cause reduced power and use more gas, but I never heard of it damaging the engine.

Extra stress (=heat) on the coil, extra wear of the cap and rotor and, to a lesser degree, of the ignition cables.

Fortunately none of those parts is expensive or difficult to replace.

DS

| Extra stress (=heat) on the coil, extra wear of the cap and rotor and, to | a lesser degree, of the ignition cables.

Nonsense ; a bigger gap just requires a higher voltage ( & more amps too, I believe ) to produce a spark, you can see in books under " dielectric breakdown". Users can use bigger gaps without any damage, only torque will drop & noise rises fast with rpm when voltage / ampere is inadequate.

My plugs ( fed by high efficiency *cables, 2 ohm/ft, in a honda F20A )' gaps are 3mm, to get a 3mm long spark to burn petrol vapour fstr = more torque. This must not be done on any 4 cylinder engine with just a small built-in coil & plain carbon-core cables ; a 1mm gap needs just 4.46kv, but a 3mm gap needs 12kv ( my estimate ) to produce a spark.

• can feed enough voltage & ampere to my 3mm gaps without any fast drop in torque, or noise rise, up to 3350 rpm ( no chance / need to spin fstr ; legal speed limit = 110kph ).

My mitsubishi 4G15P engine has a set of Sparko 3 core cables ( 240 ohm /ft, medium efficiency ), my plug gaps here are 2mm.

Congratulations, your post wins the most contradictions of the month award, and considering that the month just started, you should be proud.

chuck smoko wrote in rec.autos.tech

That is because air, gas and oil are not good conductors. More molecules of a conductive material will allow more current to flow, and that is why circuits with a lot of current use big wires. Also, if air and gas were good conductors it would be hard to get them to ignite, because heat is generated by the resistance of a circuit. The spark plug gap has to be wide enough for enough heat to be generated by the spark to ignite the fuel. Too wide, of course, and the spark cannot jump the gap. Too narrow, and not enough heat is generated, combined with not enough fuel in the area immediately surrounding the gap.

None. About the only way to damage SOME ignition systems is to leave a wire un-plugged and hanging in midair, but even that won't damage most of them.

Daniel J. Stern wrote in rec.autos.tech

Not really, at least the extra stress is so miniscule that in most cases no damage is caused at all. With no current flow because the spark plug gap is too large, there is no damage to any of the components. The voltage going through the coil is limited by simple fact that car only generates 12-14 volts, and whatever current the car can put into the coil. And it will pretty much be maxed out current wise under normal conditions.

And strangly enough, coils rarely go out. And the other parts you mentioned will have the same wear due to mechanical reasons whether there is a spark or not. But a spark will generate more wear on the items, because of the heat due to the current flowing through it. With the higher voltage coils most cars use today, spark plug wires need to be replaced more often than they used to. A miss does not put extra strain on the system, except possibly for some special High Energy electronic systems. What it does do is cause poorer gas mileage, and damage to the catalytic converter because of the raw fuel going into it.

Unless you have direct ignition (coils on plugs). In that case use the manufacturers spec'ed plug and gap. DI coils are expensive to replace and don't typically have that long a life to start with (e.g. less than 100K miles).

Yes, really.

We're not talking about "no current flow".

Primary-side voltage remains constant. Secondary-side voltage rises with increased total series arc gap (includes the rotor-to-cap gap and the spark plug gap) and with increased combustion chamber pressure (this is why the Caprice in question with the too-wide plug gaps would idle and rev just fine, but would begin to misfire when driven under road load), and with increased arc endpoint site surface area (new sharp-edged vs. worn rounded electrodes).

Your first sentence above contradicts your second sentence. The second sentence is correct.

DS

the computer should advance the timing to compensate. this is an '89 and by that year the computer probably controls the spark advance in closed loop mode. I don't know the details of this make and model car.

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The ECM has some control over ignition timing in the subject vehicle, but it is *NOT* adaptive and will not advance the timing to compensate for the (minuscule, BTW) spark retard caused by overgapped spark plugs. It will also not retard the timing to eliminate ping; it is not equipped with a knock sensor.

DS

Jimmy wrote in rec.autos.tech

replace.

Even at that, they do not go out that often, considering how many of them are around. But I am sure the frequency is higher.

| your post wins the most contradictions of the month award Where's my prize then ? I like a solar battery charger, pls.

| you should be proud. Thank you. I wonder why some men like to post about things they have no theoretical knowledge / experience of, & mislead others.

Who said there was a prize?

Don't know, you tell me...

First you reply "nonsense" to the problems someone else listed that could be expected, then you post "This must not be done on any 4 cylinder engine with just a small built-in coil & plain carbon-core cables."

So, which is it?

| which is it?

My high efficiency cables ( 2 ohm/ft ) are not plain carbon-core cables ( e.g. honda's original Sumitomo cables have 6323 ohm/ft ) . Carbon cannot possibly have just 2 ohm/ft, only metals can.