Mixture--science vs witchcraft?

"Douglas Paterson" wrote in message
...
"Matt Barrow" wrote in message
...

http://www.avweb.com/news/pelican/list.html (Start with #18 and go
through the entire "Engine-Related Columns" series)



Matt, that was a great series, thanks for the pointer. I found #63,
"Where Should I Run My Engine? (Part 1)," to most closely address my
question. http://www.avweb.com/news/pelican/182179-1.html

However, I'm still disappointed. Deakin's advice still falls on the
"witchcraft" side of the equation, in my book, boiling down to "put the
mixture where it feels right. From that article:

The books are full of various techniques for this, but I find the
simplest and most effective is just add full throttle,
full RPM, then grab the mixture knob and move it aggressively from
full rich to whatever feels like "more power"
on the takeoff roll. You can't hurt the engine with momentary
mixture settings like this on normally aspirated
engines! Saw that mixture knob back and forth, and feel the power
change in the seat of your pants! At some
point as you pull the mixture out from full rich, you'll feel the
power first increase, then for a large part of the
movement you'll feel no power change at all, because the "best
power" mixture setting is very flat in that area. (In
other words, "best power" occurs over a fairly wide range of rich
settings, but not at full rich.) Go ahead, pull it a
bit too far, and you'll feel the power drop off from being not rich
enough. Push it back in to the point where you
first felt the best power, and forget it. It's quick, simple, and
very effective, and pinpoint accuracy is not necessary.

However well this may work (??), it hardly qualifies as "science." Anyone
have any suggestions on what "books" he may be referring to when he says
"the books are full of various techniques"?

The old P&W series from the 40's and 50s.

I think, though, you're confusing his method of getting from rich to lean.
Given his copious charts and lengthy explanations of each, and discussion of
the "Danger Zone", lingering in the peak areas is, his points are in fact,
well documented. The part you mention above is, IIRC, how to do it without
proper instrumentation.


A big take-away from these articles is that I'm probably wasting my time
tweaking for max power (rpm) during the runup. Also, reading between the
lines seems to indicate that using the climb fuel flow chart from the POH
is probably a decent starting point--though I'm not yet really convinced
of that. Thanks again for the discussion--I appreciate any & all
insights!

Read his articles about the lunacy in most POHs.

You might find it helpful to print out his entire engine series and read
them slowly, trying to integrate all that he has to say. There is certainly
a load of information there and it's more difficult to grasp in that so much
of it goes contrary to what most all of us have been taught over the past
couple generations. (Think of the Enlightenment and Renaissance after the
Inquisition).

Good luck with your new bird!!


--
Matt Barrow
Performance Homes, LLC.
Cheyenne, WY