Hi, Daniel...
Basically I believe you are absolutely
right on this "way" of seeing it but it's
interesting 'cause if you look at the old
Leyland Special Tuning Sheets, when
the modifications and compression ratios
really got up there, the recommended
static setting on their recommended competition mechanical advance dizzy
actually did go to 2 degrees ATDC for the "later" Stages of recommended
factory
"tunes".
And of course, the needle or amount
of fuel you are putting in has a great deal
to do with combustion temperatures at
any given ignition advance setting.
Now, for competition, we don't really
much care about the advance "rate"
'cause we're basically "up there" running
total advance all the time, so only the total
advance figure is really important to us.
On a street car, "torque" or max hp per
500-1000rpm is the name of the game...
considering we'll be spending a great
deal of time below max advance and
rpms, alternating between acceleration.
deceleration and part-throttle cruise, normally in higher gears at more
or less "street legal" speeds.
Herein "the game" becomes a matter for
someone who knows what they're doing
in terms of "reasonable" lb. per hour of
fuel consumed per hp with "reasonable"
advance "rate".
It can also be seen why vacuum advance
"cans" simply aren't a requirement for
competition and why for fuel economy,
we'd want same on the street application, so as to run leaner mixtures
and more
efficiently in terms of fuel consumption considering the lower
combustion chamber temps. produced by the lower
dynamic compression ratios which are
a result of "partial" rather than WOT
throttle settings, WOT normally used
in "dialing in" fuel/ignition advance curves.
Usually it will get to a point in the street
application where we are dumping so much fuel in there to stay "cool"
that the
bottom end goes all "soggy" as you attempt more agressive timing rates
and
numbers for every 1,000 rpm in a WOT
dyno run ("pull") as EGT or combustion
temps. begin to soar, "colder" plug not-
withstandings. I mean they can only be
so cold before they begin to foul in
slow-running (on the street) due to
excessivley rich mixtures. Actually, CO
and EGT readouts pretty much tell the
story in the chassis dyno I used in setting
up my PO'd '74 Vizardized Spridget.
But as you said, Aldon has about every
timing curve for about every Series A
application one can think of, including
"boosted" operation. And APT is right
there along side them, only a phone
call or email away....and I am quite
sure Dave Anton knows exactly who
to talk to "over there" in that rare instance
wherein he might require assistance in
this respect.
For my planned Judson application I went directly to Aldon (via Bill
Perry) for a
curve matched to engine spec/low pressure supercharging on today's
relatively lower octane premium unleadeds.
The foregoing having been said,
I know I had a ball in the dyno
shop...watching CO
and EGT change with various jets,
ignition settings, etc. Not inexpensive
but well worth the investment, most
definitely so in terms of education.
It's one thing to read about it so us to
understand in theory...but there
is nothing like being there and being a
part of the process to really reinforce
in a 'gut' way what you understand
intellectually.
Cap'n. Bob
'60 :{)
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