[Diy_efi] Link for greenfire spark plugs...

[Adam Wade]

--- Mike <niche at iinet.net.au> wrote:

> heh ? Why cant the mixture be pushed through/into
> this space

Where would the gases already in the gap go?

> since 'dynamic pressure effectively equals flow',

Flow to where?  There is no outlet near the
electrodes.

> There are many situations where plug electrodes dont
> extend that much into the chamber and are very close
> to the chamber edge or below with negligible effect,

So what?  There's nothing there to prevent flow into
the combustion chamber.

> Surely most people who have been on this list for
> more than a few years and/or who have an engine
> background would have likely seen some of those high
> speed flow videos at school, shows just how
> turbulent the inside of a chamber actually is
> or had occasion to understand flow in the chamber is
> not simple,

Again, so what?  You're talking about a long, narrow
blind passage.

> your implication there isnt enough time is sheer
> speculation

What implication?  I never said anything about time,
as I recall.

> and borders on a ludicrous over-simplification to
> save thinking,

Another insult.  :(  And one without any apparent
basis in my posting, to boot.

> If your logic was even partly true then the IC
> engines in F1 would have great trouble managing
> 18,000 rpm

Why?  Are there long, narrow, blind holes involved in
combustion on F1 engines?  Never heard anything about
that in Racecar Engineering magazine.

> In any case the end gases wont stay compacted for
> long, most of them disperse during a large part of
> the exhaust stroke

How do they "disperse" from this long, blind hole?

> turbulence generated by asymmetrical combustion
> effects also occur from mixture in state of motion
> and not homogenous.

I cannot parse this sentence at all.

> You seem to be fixated on the paradigm that the
> compressed end gases from the last combustion cycle
> wont be able to exit through the 5 or so peripheral
> holes of the spark plug cap,

What would cause them to exit?  With what would they
be replaced, and how would the replacement arrive?

For the cheap seats:  Long, blind hole.

> with the huge pressure fluctuations they will be
> exhausted pretty damn quickly

Since you seem to speak in such technical terms all
the time, perhaps you have access to a laboratory
where it should be easy enough to test your claim that
gases will pass as freely in and out of the length of
a small, long blind hole as easily as through an open
combustion chamber in a SI engine.

> It could be you believe the apparent symmetry of the
> plug means they wont get in because the previous
> cycle didnt get them out etc.

What on earth are you talking about?  What does
"symmetry" have to do with anything?  I can't imagine
why you bring it up at all.

> I think you are grasping at straws here, the mixing
> of the end gases and charge occurs already before
> most reaches the plug.

I'm wondering now if you are being deliberately
obtuse.  How can the end gases INSIDE THE BLIND HOLE
mix with fresh intake charge "before most reaches the
plug"?

> if we followed your interpretation and logic the
> region at the top or near the top or in fact
> anywhere not too distant from a wall of the chamber
> might also be interpreted as a "blind" hole

Not based on anything *I* said, I assure you.  I would
strong argue against your contention that this was the
case.

> I'm inferring from your grammar above that you may
> believe the gases need to mix in that little virtual
> pre-chamber in the plug

Well, that is specifically what I said, yes.

> (and that they arent mixed at all before they get
> there..)

How can gases not there yet mix with gases inside? 
You're not making any sense.

> Um yeah sorry about that, I was having a bit of a
> sarcastic dig, because it would be obvious to me
> diffusion has occurred some time before the mixed
> gases are pushed into the end regions

What are "end regions"?

> I'm actually surprised you are attached to the
> notion of a static gas containment scenario

Well, since the blind section of the "plug" seems to
be perhaps a few mm in diameter, and on the order of
40-60 mm long, what would you propose the scenario
should be?  And I haven't argued "static gas
containment"; I argued that diffusion would be the
only significant method for mixing fresh mixture with
end gases deep inside the blind hole.

> hence my purile attempt to get you to snap out of it

Ah, I see.  You just need to grow up, is all. 
Understood.

> as its easy to see how your logic has import
> for you as you seem attached to it as a huge over
> simplification.

Then be so good as to explain what goes on, and show
me how you experimentally verified it.

> the net effect was the plug electrodes were
> significantly recessed into the head - did this
> make a difference (?), none readily discernable -

For starters, I doubt the electrode was any deeper
than the diameter of the plug hole; further, you
should have seen effects similar to retarding ignition
timing, unless you were running EFI with an ECU that
was running knock-limited mixtures under load; such an
ECU would simply advance ignition timing to
compensate, and thus would make no discernible
difference when run with a reasonable AFR.

Second, I doubt the plug hole was so narrow that
turbulent flow couldn't penetrate almost
instantaneously.  This differs markedly from a blind
hole such as found on the plug in question.

> If your logic were actualised in that scenario the
> effect would have been noticeable with somewhat
> poorer performance.

No, as I just explained.  It should be slight but
measurable if spark timing remains unchanged.

> what I am doing is offering a scenario that allows
> it to operate at least in terms of firing the
> mixture reliably and countering your notion that it
> shouldnt operate

You've tried to claim my "scenario" was impossible,
ridiculous, and "puerile", but you seem to have a
fundamental misunderstanding of fluid flow and the
design of the plug.

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