Getting facts straight!! (2/2)

[Greg Hermann]

(continued from 1/2)

I have no hard numbers to back up this contention, YET, but I suspect that
if a port injected engine had MUCH BETTER fuel atomization than is
attainable with current art injectors, and a much quicker fuel squirt--one
timed with the high velocity flow of air in the port--that it would not
only make more power AND have a lower BSFC at WOT conditions, but would
ALSO want a mixture somewhat RICHER of stoich for maximum power than is the
case with current art port injected engines! WHY?? evaporatin fuel on the
back side of a hot intake valve allows fuel vapor to displace air--reducing
output, whereas--getting finely atomized fuel into the cylinder, and not
vaporizing much of it 'til after the I valve has closed not only avoids
displacement of inlet air by fuel vapor, but takes full advantage of the
heat absorbtion effect (as detailed above) during the compression stroke.
------------------------------------------

As to the best ECONOMY mixture--going lean of stoich tends to insure
burning every last bit of the fuel, and thus improves economy. The limit is
usually when one approaches a lean misfire condition. (Misfires waste
fuel.) Better fuel atomization and distribution BOTH work to push this
limit further out. Also--the basic  Otto cycle efficiency, even at WOT,
improves with a leaner mixture. Good chamber geometry and good mixture
turbulence during combustion push the lean limit further out, as well as
allowing better efficiency through higher compression ratio (by avoiding
pre-ignition and/or detonation). Furthermore-- leaner mixtures at part
throttle (with a spark ignition engine) reduce pumping losses, improving
economy even further at part throttle. SO--how far lean of stoich is best
for economy--the answer is--"As far as you can get away with!"--not some
set rule! It all depends on a large number of engine design factors.

So--what are we left with that is magical about stoich? The facts that a
stoich mixture is the point where a three way catalyst works best for
cleaning up tailpipe emissions and that it is also the point where a
standard EGO or HEGO exhaust oxygen sensor (as opposed to a UEGO WBO2
sensor) switches its output. Period.

In closing--I would like to say that this list will return to far better
health once it finally get put onto a different server, and can FINALLY get
off of the #$%^^&^*& digest mode--too many of the really knowlegeable
people here have been driven into the lurk mode by the digest format!

AND--the trick to getting good information off of the internet is the same
as it is anywhere else in life--one has to learn to sort useful information
out from BS!! There are always plenty of people in any field who are
willing to spread BS indiscriminately, usually without knowing any better,
but sometimes with premeditation and for profit! Good, old fashioned
fundamental education taken together with the ability and experience with
applying it is one of the most effective tools for accomplishing this
sorting process!

Unfortunately, high performance engines seem to attract more than their
proportionate share of the BS and the profiteers (particularly the ones who
feed on ignorance)!

Although I am NOT going to be so bold as to say where, I WILL promise that
there is a bunch of good information in this last series of posts--it's up
to all of you to figure out where!

Back to lurk mode, at least 'til we are off digest mode!

Regards, Greg