Date: Wed, 13 May 1998 08:11:45 -0700 (PDT)
From: Robert Harris
Subject: Fireball 2

Heisler again. I understand the fireball, and think we can steal it!

"4.6.4 Split Level (May Fireball) combustion chamber (Jaguar)

This combustion chamber has the exhaust valve head deeply recessed in a
circular chamber wheras the inlet valve head is sunk just below the flat
face of the cylinder head so that the valve head does not bump the
piston crown when it approaches TDC.  The walls of the deep exhaust
valve are steep.  However, a chamber groove merges the slightly sunken
inlet valve seat with the flat face of the cylinder head. This shallow
recess of the inlet valve head merges into the sidewall of the deep
exhaust valve chamber so that it forms a neck or a passage between the
valves when the piston is in the TDC region.  The sparking plug
intersects the steep sidewalls of the exhaust valve chamber, slightly to
one side of the shallow passage communicating between the two valve
heads.

When the piston approaches TDC the bump clearances reduces so that the
mixture is squeezed with great intensity through the offset recessed
passage into the deep exhaust valve chamber. This eccentric or
tangential entry from the large squish one into the deep chamber
therefore produces a highly intensified squish induced swirl about the
deep exhaust chamber's axis.

At the same time, the violent inward squish due to the reducing bump
clearance surrounding the exhaust chamber converts the mixture motion
into a highly turbulent swirl.

At the instant of ignition, the high swirl rate and the surrounding
inward squish produces a rapid and contolled propagation of the flame
front from the sparking plug to the furthest point in the chamber with
rich, stoichiometric and weak mixture strengths without hesitation and
misfiring. It is claimed that the combustion chamber  operates
satisfactorily with a 97 RON octane petrol with a 16:1 compression
ratio, and a 92 RON octane petrol with a 12:1 ratio, without detontation
due to the elimination of most end-gases before they become overheated."


Interested ?? I thought so.  What this does is create a column of very
rapidly rotating gases along the axis of the exhuast valve.  The plug is
at the edge of the column. Centri-whatever (not that thread again) moves
the fuel to the outside, so that whatever the actual mixture, the
sparking plug sees a very rich mixture, meaning fast, clean intitial
burn.  Everything about the chamber exists to create this column.  Its
downfall is that it has to have very high compression to work and that
would scare the crap out of most dweebies.

Picture the following.  A standard wedge chamber, angle milled to make
as flat as possible and lowver volume.  Recess the exhaust valve up as
high as you can ( In chevy head's vizard recommends a little so the
intake flows over the lip of the exhaust instead of out).

Now get the most overdomed piston you can stuff in.  Machine it so that
it completely fills the chamber with no clearance. Mill a valve pocket
such  that the intake valve has about 050 to 100 clearance and is no
wider than .100 + intake valve size. Everything still zip clearance.
Mill out the combustion chamber as a cylinder along the exhuast valve
axis to suit desired compression - modifing just enough so the sparking
valve has good access.  Cut the swirl inducing slot either on the plug
side or opposite, depending on the direction of the induction and
compression induced swirl. Minor clean up's and you have the basics
without the patent.

Goal was to get the swirling exhuast valve axis column going as fast as
possible with minimum clearance everywhere else.

Think about it - will try to pull a head and check it out later on a
V-6.

The plus's I think I see - mixture insensitive - centri whatever makes
all mixtures rich for sparking.  Very fast burn - because of high
velocity swirl - so less advance, less negative power and higher
efficiency of combustion.