Re: LT5 Info.., and 1228331 stuff in general/ KNOCKIN

["Jeff M" <tystorm@email.msn.com>]

> In a message dated 1/22/00 12:22:47 AM Eastern Standard Time,
> terryk@foothill.net writes:
>
> >
> >  > Most motors do not make best power right before they start knocking.
> >
> >  They make the best power when ...............
>
> They are knocking to death?
> Mike V

Knocking as interpreted by the ECM program and/or sub-system, or actual
occurring in the engine is a better question I am thinking here.  I know of
a few comrades who have done enough tests on dyno simulations for
combustion/power tuning while monitoring all important issues (cylinder
pressure, in cylinder combustion temperatures, etc) with different heads,
cams, turbos and electronic engine management parameters/tuning, found that
there is a window of knock and intensity of knock with and within all
cylinders.  We have to agree that intake and cylinder head air flow is NOT
the same for each port.  The onset of conditions for a new engine to knock
is not a cylinder wide issue, the first cylinder to start knocking is the
one that gets the most air, then followed by the next as condition for knock
are increased until the last cylinder knocks, and at that point the first
can be hammering hard.  Lets also leave out age and continue with a new
engine as done by an auto maker as a model here.  If it is desired to tune
this engine for safe running/long life, we have to consider that it may/will
actually be tuned for less than maximum power production, (now some, like
the LT1, live bouncing back and forth on the fine line of max power/proper
combustions).  This de-tuning is done for those nice (competitive) long and
optional longer drivetrain warranties.  Now the next phase here, lets puts
some age/miles on this engine; injectors are flowing different amounts of
fuel and with changing spray patterns (gumming up) this causes the
conditions for improper/less than optimum fueling to exist and with this,
sooner events of improper combustions/knock (this added to the already
un-even flow characteristics of an engine intake system).  Also then, knock
intensity can increase more rapidly in some cylinders than others so your
window of only one cylinder to all cylinders knocking is of far more of a
concern as now, those can vary from one only requiring 1 to 2 degrees of
timing retard to alleviate, to 10, 15 degrees or more.   Along with this
less than optimum combustion going on and now the ORI (octane requirement
increase) goes up as it does in all engines (hence those combustions chamber
cleaners like the original Duralt and now everyone else has to sell,
including some of it in the fuel of more expensive brand name gas stations).
Add some more age and you start to get more blow-by of oil, that because of
emissions, gets routed down the throttle body and we all know, oil in the
combustion mix makes knock happen faster than shit and no amount of fuel
will fix that problem!!  Knocking in a cylinder that is not on the (V6 or
V8) side of the block where the knock sensor is and you can push the limits
of detonation control, if you did not build in EXTRA detonation management
(de-tune again).  THIS is how the (we certainly hope ;-) auto makers work in
their minds with this portion of tuning i.e. worse case scenario, of course
this does not apply to this bunch of tech heads as we keep injectors clean
(and fuel system), combustion chambers clean, tune the chips better than
stock and, keep our ignition systems and such etc running at peak!!!  ;-)

So where does this take us in tuning, I have worked with a few who have
found that the stock ECM programs and/or sub-system parameters for knock
recognition activation (onset) and response (severity related) to be very
healthy and sometimes quite a bit more than detonation was and/or required
for control of the true severity.  This was confirmed with them by the "not
recommended for your car" method of unplugging or bypassing the knock sensor
or reducing the knock signal/reading with a couple of resistors, as their
ETs dropped quite a bit (repeatedly) and upon inspection of their spark
plugs, found no signs of any detonation enough to be concerned about.

Now, most engines have one knock sensor but the better ones have two, and
now the newer engines can even manage with programming, the ability to know
that the knock occurred in what cylinder and since the engine has separate
coil control for each cylinder, can manage each individually making for an
engine that CAN be tuned to the max without being overly conservative.

Jeff M






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