Use of 150 octane fuel in the Merlin (Xylidine additive etc etc)

"Tarver Engineering" wrote in message ...
"Gord Beaman" wrote in message
...
(Hildegrin) wrote:

Higher octane allows you to use higher boost pressures. It doesn't
create more boost, it just allows you to "overboost" the engine at
lower alts. Thus at rated alt and above, increased octane had no real
effect (it may have reduced power by a tiny amount, because the fuel
has a lower calorifc value, I think).


Yes, this is exactly right...some think that the higher the
Octane Rating the more "powerful" the fuel when actually high
Octane fuel is less 'powerful' that low Octane fuel. You get the
extra power because you can increase the Manifold Air Pressure
(boost) without causing DETONATION. This is the whole reason
behind high octane useage. Heavy detonation will trash an engine
in short order so you must prevent it.

Lead tetra ethyl is not short of energy, Gord.

The amount of TEL added makes little difference to the energy content
of a fuel becuase it is so small an amount. I don't even know how
much energy it releases upon combustion if it does so at all.

Ricardo, the great British engineer, developed the idea of using Tetra
Ehyle Lead (TEL) because he reasoned that the milky color of gasoline
was causing it to ignite due to to the transmision and absorbtion of
infra red radiation rather than burn smoothly. TEL acted as a
clarifying agent and this is how it increase the RON in a variable
displacement test engine. That was the theory at least.

Higher RON number do two things: First they eliminate pre-ignition due
to hot surfaces or the high temperatures caused by compression.
Second they prevent explosive combustion. Combustion should be a
controlled burn at subsonic velocities along a wavefront caused by
thermal conduction explosive combustion (not the technical term) means
that the combustion becomes supersonic and is propagated by infra red
radiation simultaneously in the mixture rather than smoothly along a
wavefront.



Water injection also results in higher engine power in a slightly
different manner.

No. Water injection only prevents the connecting rod bearings from being
destroyed by detonation. Much the same as an EGR valve on automobile
engines injecting exast gas into the manifold.

Water injection does two things:

1 It lowers the temperature of the charge thus preventing preignition.
2 It increase the density of the air and thus allows more air into the
combustion chambers and allows the supercharger to compress the same
amount of air for less work.

When engines are run rich the oversupply of fuel also cools the air in
the same way. Side effect is loss of efficiency and flames and smoke
from exhaust which your enemy can use to guage your intentions.