clare at snyder dot ontario dot canada wrote in message
...
On Sun, 13 Apr 2008 11:30:58 -0400, "Ed Huntress"
wrote:


clare at snyder dot ontario dot canada wrote in message
. ..
On Sat, 12 Apr 2008 19:08:43 -0400, "Ed Huntress"
wrote:


"RoyJ" wrote in message
...
After reading the other comments I think you have multiple issues
going
on
to switch from diesel to gasoline:
-the gasoline will have a MUCH lower viscosity, you are going to get
way
different (more)amounts of fuel through the injector. I'd think that
is
what causes the white smoke a lousy performance, it's too rich.
-at the same time, gasoline has lower fuel value per gallon or
milliliter,
same volume of fuel will cause the engine to go lean, never a good
thing

You raise an intriguing question there, Roy. How do you make a diesel
run
lean? g

-gasoline has a much higher flame front speed, ie it will detonate,
really
does bad things to the top of the piston.

It will detonate, but it's because of the *slower* flame front speed.
That's
the thing that's indirectly measured by the cetane rating: gasoline
around
25, diesel typically 45+.


It's not realy detonation, and it's not really the speed of the burn
that is involved (flame front). It is the speed at which the cyl
pressure goes up with gas vs diesel. You DO get a faster pressure
spike when burning gasoline than when burning deisel at high cyl
pressures.

Reference? You may be comparing a homogeneous mixture in a spark-ignition
engine with the timed spray in a diesel. If you create a homogeneous
mixture
with diesel alone, it burns faster than gasoline. That's what the
HCCI-engine research shows.


But what is the difference between timed spray of diesel vs timed
spray of gasoline. That was not, from what I saw, addressed.

It wasn't, in the papers from which I quoted. It was in some of the other
200 or so.

Diesel combustion is NOT a homogenous mixture under normal operating
conditions.

It is in an HCCI engine running on diesel, which is what I said.

You don't need HCCI to have diesel burning faster. It burns faster in a
conventional stratified charge diesel, as well. It just doesn't happen in a
way that you can compare it with a SI engine, which is what that paragraph
was about.

Running deisel fuel in a spark ignition engine, with more or less
homogenous mixtures, the burn speed of the deisel is DEFINITELY faster
than the burn speed of gasoline in a homogenous mixture, but NOT as
fast as the burn speed of decomposed endgas, which is involved in
detonation.

?? I'm not sure if we just got off on a siding, or what...

--
Ed Huntress