Avtur has a somewhat lower calorific value than normal "kero", and cutting
it with engine oil in the correct ratio (it would be high i.e. lot's of oil)
would be OK. However, it would only be worth doing if you were getting both
the Avtur and the oil free I'd also suspect that in the long term it
would fuck the injector pump, the injectors and probably not do too much for
the combustion chambers either. Kero has no lubricity whatsoever and adding
it to an oil that does, dramatically reduces the lubrication qualities of
the base oil. In addition. as those poor demented bastards who own vintage
engines will tell you, the only way to reduce the octane rating of modern
petrol to the point where it is safe to use in old stationary engines, cars
and motorbikes is to cut it with kero. Your lubrication oil is quickly
contaminated and useless cause it don't burn that well and migrates past the
rings and into the sump
Stories your dad told you about running the family car on kero was using
stuff called "power kero", there's been none of that made in Australia for
about 20 years. The stuff we have now is what used to be called "lighting"
kero, good for lamps, heaters and stoves and not much else.
The cat has F'all do with it other than the fact it would be quickly ruined.
100LL (translation 100 octane Low Lead) Avgas still has about twice as much
lead in it than super ever did. It would quickly pollute the cat to
uselessness.
However, that has nothing to do with why you don't run Avgas in an
unprepared car engine.
That is a good idea, it slows the damage caused by detonation.
Where do you get this drivel?
Until a couple of years back the standard fuel for Touring cars, Sports
sedans and formula cars was avgas because of its greater performance
potential, of course none of these rev much past 7,000 to 8,000 RPM, so you
could have a point. Whoops, almost forgot the modified production motorbike
I used to race on avgas, it only revved to 11000 RPM so I guess it was safe
from them slow flames too.
The major difference between ULP and Avgas is that Avgas is 100 octane as
opposed to (I think) 90 octane for ULP. The second difference is the LEAD,
lot's and lot's of it. go back a few more years to when I started flying and
the avgas then (called purple petrol as opposed to modern 100LL which is
called "blue" petrol) had so much lead in it that if you got it on your hand
it left a grey stain and exhaust pipes in a well running engine were chalk
white inside. The lead is there to protect valve seats. Nowadays engines can
be designed so that they do not need this, hence ULP.
Avgas burns every bit as fast as ULP (in fact it has a significantly higher
calorific value) what it does not do is evaporate as fast or as easily as
ULP. The reason for this is that is mixed with some pretty spacey chemicals
so that it doesn't do nasty things like evaporate out of your tanks at low
ambient pressures, nor does it cause vapourlocks as easily as ULP.
A brief aside about learning this the hard way, I put red petrol (super)
into an aeroplane once as no Avgas was available and I didn't feel like
waiting 3 days for some to arrive. All seemed to go well until we got to
altitude and you could see the vapour plumes behind the aircraft as the high
order aromatics evaporated (or perhaps more correctly boiled out)(leaving
telltale red stains right down the wings that made it much easier for the
DCA "police" to ping me on arrival. Lower altitude solved that, but there
were also a few "interesting" vapour lock incidents that made me
sufficiently wary when I got to where I was going that those in attendance
swore it was the steepest approach they had ever seen in a PA28
Aircraft engines are low compression engines, the norm for piston engines
being around 6.5 to 8 to 1. (as opposed to around 9 to 1 being the norm for
modern car engines) Turbo normalised ones can be even lower as can the (now
rare) supercharged ones. They make their power from cubic inches and brute
force, not from finesse and advanced design. For example the 161 horsepower
engine fitted to your basic 4 place aircraft (your Piper Warrior or Cessna
172) does this with 4 cylinders and 350 cubic inches.
161 horsepower from 350 cubic inches is really a fairly soft level of
performance. Mind you, the torque produced is pretty good and it does do it
at around 2500 rpm.
Most aircraft piston engines (those produced by Lycoming or Teledyne
Continental) are redlined well before 3,000 RPM, if not for engineering
reasons at least for the fact that the tips of the props they are attached
to would go horribly supersonic before the engine got to 3,000 RPM.
Having said that, the idea of a 4 cylinder 350 cubic inch, aircooled engine
turning at 3,000 RPM is just a bit scary.
--
Tony Smith
Connected to the internet in Sunny Far North Queensland Australia
http://www.tonsyl.org
