10/30/2003

Leaded Fuel

Poe, research director for His Majesties Royal Air Force, in the 30's stated
in his useless old non comic book that the location of the injection of fuel
did not matter as long as it all evaporated prior to entering the cylinder -
the final charge temperature would be identical.

Then, he goes on to say that with any compressor, the more fuel that is
evaporated ahead of the compressor, the higher the pressure ratio of the
compressor.

Then, consider that all fuel passing through a compressor is mechanically
carbureted and will have very small particles and generally burn much better.

The Rice Rats wear forced to run track side leaded fuel.  There is a large
body of leaded fuel, distribution of fuel, drozzling fuel draining into ports
( oops liquid flow ) etc ad nauseum.

Keep this in mind.  Leaded fuel has a molecular weight of ~325 for the lead
particles.  The lowest boiling point for the lead sleds is 228 degrees
fahrenheit.  Because of sensitively issues, very low grade, long length, and
low octane base fuel is used.  Not much better than the sixty octane swill of
the thirties - even when the final octane with lead ridiculous is 100+.  It is
also combined with high boiling point scavengers so that the lead residue will
not plug up the chamber in a few hours.  And do not forget the syntheses -
they work in conjunction will lead to raise the octane.  

The vapors of leaded fuel are very low in octane, and the slop that does not
boil at normal temperatures has all the octane.  Therefore, getting this slush
equally divided between cylinders is more important than any thing else.

Starting 30 years ago, the petroleum industry starting making unleaded fuel.
To confuse it with the leaded slop is a major mistake.  In lead-o-shitte free
fuel, the average molecular weight is around 110 - the same as iso-octane.
The boiling point is at least 100 degrees lower.  Light vapors such as MTBE or
Ethanol ( for oxygenates ), and benzene based aroma tics are lighter than the
average fuel weight.  The normal turbulence in an intake manifold at virtually
any throttle opening is sufficient to vaporize the entire mixture and at
worst, a minimum amount of heat is needed to be added.  At turbo pressure and
temperature without an inter cooler like bruce is using, you could piss into
the manifold and it would vaporize instantly.

An unleaded gasoline engine is not running on a liquid fuel for all practical
purposes. It is running on a homogenized ( less than 10 micron size ) gaseous
mix.  Bruce is pissing fuel onto the manifold floor below the level of the
ports.  Liquid drizzle into the ports is useful only with very high boiling
essentially non volatile leaded fuel.  The normal high and turbulence in the
manifold vaporize this extra fuel virtually instantly.

With unleaded fuel, equal air flow is paramount.  Above idle and very light
load, with a decent manifold, it makes no difference as far as power goes,
whether its sequential port, batch port or tbi injection.