[Diy_efi] Link for greenfire spark plugs...

[Mike]

At 08:59 AM 9/06/05, Adam Wade <espresso_doppio at yahoo.com> wrote:
>--- 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?

As I mentioned in an earlier response to you the pressure
changes are enough to cause flow and correct me if I'm wrong
aren't the exhaust gases in the combustion chamber removed
by normal operation. Why would those exhaust gases somehow
stay in the plug gap and not be exhausted due to pressure changes
that occur during intake and exhaust  ?

btw: I repeat, I never said the plug design was optimum, I have
been offering a mechanism how it can function perhaps "well enough"...

>> since 'dynamic pressure effectively equals flow',
>
>Flow to where?  There is no outlet near the
>electrodes.

They come out the holes into the chamber and out the
exhaust valve, granted its not going to be perfect, though
nothing is perfect in the chamber  anyway,  but
what makes you think there wont be flow,  is it because
you think its somehow  really 'small'  there wont be ?

Its not a critical orifice, its way big enough to have flow
as a result of ordinary pressure changes.

>> 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.

Thats right, there is nothing to prevent the flow out of
the spark plug region into the chamber during exhaust
and nothing to prevent flow into the plug gap region
upon compression. Just because one end is closed
doesnt mean there isnt going to be flow into the region
as a result of pressure changes compounded by turbulence.

>> 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.

The gases dont know your assessment of long and narrow
and blind (!) , they will flow due to pressure change, just because
it appears *to you* to be a bit small doesnt mean the gases
wont flow. Big, small, long, short, narrow,  are your subjective
assessments, gases dont stop moving as a result of your
interpretations of relative dimension.

>> your implication there isnt enough time is sheer
>> speculation
>
>What implication?  I never said anything about time,
>as I recall.

<groan> Here is an extract from your earlier email:-

"...despite the compression of the end gases inside the
"empty space", I doubt very much that by the time
combustion occurs, especially at higher engine speeds,..."

Here you spoke about '...by the time...' which is a pretty
clear implication you interpret there isnt enough time
in that context.


>> and borders on a ludicrous over-simplification to
>> save thinking,
>
>Another insult.  :(  And one without any apparent
>basis in my posting, to boot.

Because you are hung up on the over simplified notion
that diffusion can be the only means for gases and ignore
totally pressure providing the mechanism for flow is
why I am responding that its ludicrous. If thats a insult,
then thats your emotional response, try thinking about it
and exercising imagination and remove your fixation on size ;-)

>> 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.

No, because you brought up the issue of not being
enough time, if that proposition was extended then
the sorts of speeds in F1 couldn't be reached. its
an extrapolation based on your limited view it can
only be diffusion albeit my subjective in response ;)

>> 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?

Flow comes about due to pressure change both out
of and into. And you'd appreciate its not laminar flow,
there is a huge amount of turbulence. You seem to
be fixed on a view the passage is too long and there isnt
enough time for the flow, this is a static view not
ameliorated by the huge dynamics going on or your
imagination for that matter.

>> turbulence generated by asymmetrical combustion
>> effects also occur from mixture in state of motion
>> and not homogenous.
>
>I cannot parse this sentence at all.

There is turbulence...

The chamber is not symmetrical...

There is considerable motion... (read that as momentum)

There is no homogeneity

Taking these combinatorial concepts together provides,
I would have thought, a more helpful basis to appreciate
that flow into the region of the plug as a result of the
above would assist your understanding.

>> 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?

Pressure results in flow, it doesnt stop because one end
of a tube is closed, it doesnt stop because *you* think its
too long or because *you* think its too narrow. 

>For the cheap seats:  Long, blind hole.

Your static view, gases dont see it that way, they move
into and out of passages all the time due to *pressure*.

Do you get it now ?

Or are you saying there is no pressure change and as a
consequence it must *only* be diffusion ?

>> 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.

As this is a technical group, talking about a technical
subject then its appropriate to talk technical, why
dont you see that <sigh> ?

Sure it would be ideal to have the means and interest
to set up a physical experiment and often its easy to
see something happen when it cant be thought about
beforehand, we have brains to think ahead, hopefully
and we can imagine, just open it up a little more...

Its clear to me now you've never seen the high speed films
of turbulence and flow in a combustion chamber, such
films are around and most mech students get to see them
during their studies, me included, if they are not on the
net then a visit to your old school might suffice.

In the absence of that, I'd suggest defining a thought
experiment, in respect of a tube with a plunger, pair
of differently coloured gases etc as an interim aid.

>> 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.

Well try turbo charging your  imagination then.

If a tube or chamber is perfectly symmetrical and
there wasnt any combustion then you have little opportunity
for anything except laminar flow then you 'might'  be
able to claim the only means for exhaust and entry
is diffusion. Clearly there is no symmetry and there is
combustion therefore laminar flow is destroyed therefore
diffusion is not the only mechanism for flow, in any case,
as I've said earlier and it still hasnt sunk in for you,
pressure is enough to cause flow.

Or in respect of your fixation on "Blind Hole", the gases
are blind - they dont know there isnt a way out and
get pushed there by pressure and come out by pressure, doh  ;-)


>> 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"?

I'm not trying to be obtuse, its in relational context
with words I used in my same email, some of those
words you have removed in this email. No need to shout
about your fixation on a blind hole someone being a problem
for your conception, try exercising the imagination
and observe the pressure changes in your mind
as the piston goes down accepting new gas and
starts its way up compressing and *moving* gases
around due to *pressure* changes...

<chuckle>

>> 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.

Well its an issue of interpretation, you attach great
significance to the issue of a "blind hole" and it being
"narrow" and "long" - gases dont know these subjective
limitations your "narrow" imagination is putting on this issue...

>> 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.

I meant mixed in terms of a combustible mixture
before they get to the plug area, I used a contraction
assuming your imagination could get up to speed  ;)


>> 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"?

Any regions where there is a wall etc, The end point
where the gases are physically stopped by the metal,
its not my definition or universally accepted, call it
a discussion contraction.


>> 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.

Pressure causes flow, any 1st year mech eng student
should be able to see that, most high school students
see that, my son sees that. its not limited by issue
of tube having one end closed, pressure gives flow
*plus* there is huge turbulence - as well - bonus !

>> hence my purile attempt to get you to snap out of it
>
>Ah, I see.  You just need to grow up, is all. 
>Understood.

Not helpful, try using your imagination, I extended
a concession, and you retorted immaturely, what does
that make you ?


>> 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.

huh ? How did you experimentally verify diffusion is
the only means for gases to enter and exit a passage.

You would do well to be balanced, I never expected you
to be able to verify experimentally your claim that diffusion
is the only means allowing operation...

WHY is pressure not enough for your imagination and understanding ?


>> 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.

In that case with the Ford, no ECU, carb only.

>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.

Ah - I think we are getting to the nub of your problem,

You are saying your interpretation of the hole being narrow
means turbulence cant penetrate - yes - no ?

The relative difference between a chamber of say 100mm
across versus a hole of 2mm across, in comparison
with size of gas molecules is negligible and that may well
illuminate why your belief diffusion is the only mechanism.

Now maybe I understand the source of your imagination, I win ;-)

Difference between 100mm across and 2mm  isnt
something that greatly influences the gases when those
gas molecules are many orders of magnitude smaller...!

Yet it influences your imagination and your unwillingness
to concede that simple pressure and turbulence can
provide enough flow and mixing.... !



>> 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.

Now you are really being naughty here. tut tut...

1.  I never claimed your scenario was impossible, show
     me where you think I said that ?

     Obviously diffusion occurs, I never said if didnt.
     I am claiming its not the only mechanism, you seem
     to be fixated that it is.


2.  I never said you were purile, I conceded *I* was acting
     in a purile way to snap you out of your fixation.

     No need to lie to embellish your argument. I will accept
     your apology.

     Ah stuff it - I accept your apology in advance :o)


3.  You are saying I have a fundamental misunderstanding
     of fluid flow, really funny thing to say (!)... Its actually fluid
     dynamics we are talking about, that says something - lol :)

     You are the one who is fixed on the view it can only
     be diffusion and refuse to accept pressure results in flow.

     Who has a fundamental misunderstanding of fluid dynamics ?


4.   You are saying I have a fundamental misunderstanding
      of the design of the plug, I guess its an understandable
      accusation since you just cant imagine flow due to pressure.

      The plug is shown in cross section in the patent its clear.

Your problem is you are attached to the notion that because
it appears the plug electrode is recessed deeply that diffusion
is the only mechanism for mixing and flow,  compounded by
your subjective assessment of 'long' and 'narrow' being enough
to somehow influence the gas molecules etc

Clearly you are firm in excluding all other mechanisms, the
greater onus is therefore on you to prove there is not any other
mechanism, not really on me to prove there is - read on.

Because any person who has even a basic appreciation of
fluid dynamics accepts readily that pressure and turbulence
is really really impossible to remove from any dynamic system.

It appears you do not subscribe to this view possibly in combination
with your subjective assessment of 'long' and 'narrow' in respect of
the plug configuration and  this is what I think clouds your
judgement and limits your imagination creating your fixation.

Sort of makes you wonder who here has the superior
fundamental understanding of fluid dynamics.

<chuckle>


Mike
PS: If you want to take this discussion further, I think it mature
and professional you converge the argument and pursue the
design of a suitable thought experiment. Responding by retaliating
and accusing isnt your best or most subtle attribute but it might
well be the most easily recognisable paradigm in your posts.




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Regards from


Mike Massen
Perth, Western Australia
VL Commodore Fuse Rail that wont warp or melt !
http://niche.iinet.net.au