[Diy_efi] Re: Burning Aluminium etc.

[Adam Wade]

--- Phil Lamovie <phil at injec.com> wrote:

> Of course all that is required is a set of scales.
> Perhaps someone who has a partially ventilated set
> might do the experiment and help enlighten the list.

I'd definitely be interested.  I've seen pistons where
visually it was obvious that they much have lost
material, and I certainly didn't find much in the
crankcase.  Wish I had a set around to weigh, since it
didn't occur to me to check last time I tore down an
engine.

> A quick check of the "blue bible" gives the boiling
> point of pure Al as 2467 Degrees C at STP. As no
> combustion could occur prior to vaporization I would
> posit that what is occurring is melting as a result
> of the pressure created during a detonation or two.

That was what I thought for a long time, but it
certainly appears that there is less aluminum than
there should be after all is said and done.  Could be
an "optical illusion" due to the hole itself.  Again,
interested to have more data on the subject.

*snip bit on pre-ignition*

> Detonation is on the other hand an extremely violent
> and unforgiving condition. It is the result of
> spontaneous combustion of the air fuel mixture.

Do you ever see situations where the mixture is
non-homogenous and detonation occurs fairly late in
the power stroke, such that some areas do not "light
off" during flashover?  I'd think that it would only
occur under a very narrow set of circumstances, but in
theory, you should be able to see such results.  Or
are modern engines too good at homogenizing the
mixture for this to occur?  I understand that
regardles of local variations in the mixture, a
typical detonation event will raise the temperature so
high and so quickly that all the available fuel and
air will combust, regardless of local variations in
mixture.

> Of course giving the operator (pilot) a manual
> air/fuel mixture control and reassuring them that
> Lambda A/F (not sure why this is the A/F target
> under these conditions) is denoted by peak exhaust
> temps may lead directly to the impact site.

Well, pilots only "know" EGT.  They don't use O2
sensors and don't really know what lambda they are
running at any given time.  Ignition timing, as John
noted in his emails to me, is often fixed for all
throttle positions, engine speeds, and mixture
settings.  In his last email to me, he indicated that
there was a company coming out with a feedback system
to best time the PPP automatically; sounds very much
like they must be using ion sensing for this, as it
would be the least expensive and most feasible method.
 That would help things a great deal, I'd say,
especially WRT setting mixtures that could cause
elevated EGTs.

| 82 Honda CX500 Turbo (Cassandra)  90 Kwak Zephyr 550 (Daphne) |
| "It was like an emergency ward after a great catastrophe; it  |
|   didn't matter what race or class the victims belonged to.   |
|  They were all given the same miracle drug, which was coffee. |
|   The catastrophe in this case, of course, was that the sun   |
|     had come up again."                    -Kurt Vonnegut     |
| M/C Fuel Inj. Hndbk. @ Amazon.com -  http://tinyurl.com/6o3ze |


		
__________________________________ 
Do you Yahoo!? 
Plan great trips with Yahoo! Travel: Now over 17,000 guides!
http://travel.yahoo.com/p-travelguide