loud motor = happy motor?

[Clarence L.Snyder]

PMDRACER at aol.com wrote:
> 
> In a message dated 11/3/98 1:41:07 AM Pacific Standard Time,
> am018 at post.almac.co.uk writes:
> 
> << As a general rule as taught to me by my grandfather who was setting
>  ignitions by ear at the start of this century an over advanced ignition
>  always sounds more powerful -- this could be partially explained (I think)
>  by the fact that it will pick up revs more quickly when reved out of gear.
>  On few cars I have come across (Lotus Elans which had only 20 crank
>  degrees of mechanical advance) retarded ignition has caused pinking ---- I
>  suspect due to hot spots forming from excess rejected heat.
>   >>
> Well, to be truthful, you will never see full advance curves on a motor revved
> out of gear. You simply cannot achieve any sort of vacuum to run the advance,

I have to jump in here.
You will NEVER see full advance on a LOADED engine at WOT, because under
load you have HIGH manifold pressure, which translates to low
vacuum.Under no load conditions, manifold pressure is low (high vacuum)
and advance is on full.
> so in reality, you are revving the motor with retarded timing. Ignition timing
> is a factor dictated by today's gasoline. You simply cannot run the amount of
> ignition advance today that you used to 10 to 20 years ago.
Again, I have to disagree. Under certain conditions you can run a WHOLE
LOT more advance than you used to, because todays engines can retard it
WHEN NECESSARY. This is, to a large degree, what allows today's engines
to be so much more efficient than the engines of yesteryear. Yes, the
octane has dropped, but today's engines are getting more power out of
unleaded regular than you used to get out of leaded super premium, like
Sunoco 260.
 The "more is
> better" rule also does not apply. You can easily go too far, and lose
> performance (and the motor, under extreme conditions). The idea of ignition
> timing is to start the ignited fuel's flame front early enough so that the
> largest explosive force occurs when the piston/rod combination is on it's way
> down on the combustion stroke.
Actually, you want peak pressure at the point where the crankpin is
moving closest to parallel with the piston - in otherwords down, not out
or in.
 If ignition timing is retarded, (closer to Top
> Dead Center),
Retarded makes the spark closer to BOTTOM dead center.( I know, you mean
just a LITTLE retarded, but still before TDC - but you have to be a
little clearer)
 the maximum flame front will occur too late, and a loss of
> potential power will occur. If the ignition timing is too far advanced,
> (farther before TDC), the maximum flame front will occur too early, and the
> piston will actually fight the flame front on it's travel upward, causing a
> pressure spike, and that pressure causing the actual secondary ignition (and
> flame front) of the remaining fuel. As the two flame fronts meet in the
> cylinder, a harmonic clashing occurs (audible ping), and instead of the one
> flame front propagating throughout the cylinder, and creating power, both
> flame fronts collapse, and power diminishes, along with the real possibility
> of extensive engine damage!
> You must also keep in mind that all engines are different. For example, a
> stock Chevy small block will run with a static timing of 4 deg. advance, and a
> total of 40 to 44 deg advance at full power. A Pontiac engine, on the other
> hand, runs with a static timing of 12 to 16 degrees, and 36 to 38 deg of
> advance at full power. Also keep in mind that if you change an engine's
> combination of parts (a new cam, heads, etc.) the ignition timing demands will
> change. Other things that will change an engine's demand for more or less
> timing is ambient air temp. and density, altitude, humidity, gas quality, load
> (towing, etc.), and state of tune.
> Hope this answers your question!
> PMDRACER at aol.com