Optimax (again?)

In Sean triped:

Knock is ignition related while O2 is fuel related.

Here's a very brief description of how fuel and ignition work....

Fuel - the basic requirement of a fuel injection system is to inject just
enough fuel to make the catalyst work at its most efficient; this occurs at
a air-fuel ratio of 14.7:1. So to determine fuel amount we need to know how
much air is going into the engine. This can be achieved by one of two
methods - either measure the flow directly or determine the amount from the
manifold pressure. The first relies on expensive (but accurate) sensors, the
second relies on the basic gas equation, i.e. PV = nRT (P=pressure, V=volume
of cylinder [constant], n = number of moles of gas [i.e. amount], R = Gas
constant, T = air temperature [in deg K]); this calculation can, believe it
or not, be carried out relatively straight-forwardly even on an old Intel
8096 8-bit processor. Once you know the mass of air, the mass of fuel
calculation is a doddle, and this can be used to determine the injector
pulse-width.

Ignition - the basic function of ignition is to set fire to the fuel we have
so carefully injected in the preceding paragraph! This is done by creating a
spark, however the timing of this spark is critical - too late and no power
is the result; too early and we have the dreaded knock. The spark is timed
such that peak pressure from the combustion process is achieved just as the
piston hits Top-Dead-Centre (TDC). The combustion time is constant, so as
the engine speed increases the spark will need to be triggered earlier with
respect to he angle of rotation, hence the term ignition advance. The load
of the engine also affects the combustion time, so the basic ignition timing
is determined form a matrix of speed and engine load. Knock is detected by
means of a sensor tuned to the resonant frequency of the engine block
usually mounted between cylinders 2 & 3 (on a 4 cylinder car). When knock is
detected the ignition is retarded, i.e. fired later, which reduces the
damaging effects of this phenomenon. BTW, I understand that during the
testing of the K-Series engine in the late 1980s, early 90s (my era) the
engine proved extremely difficult to break and was not susceptible to
destructive knock no matter how hard the engineers tried. Also a standard
production unit was takne off the line and revved to its maximum which was
recorded as somewhere in the region of 13000.

Cheers

 

Yeah yeah. We did this one already!

I was quite happy to get a '98 Blackbird with <4000 miles on it for the
price I did, and TBH I don't think my riding is sufficiently professional
that I would be bothered about the benefits of FI.