Rob,

Thanks, I feel better now.

Scott Krueger

In a message dated 8/8/2005 3:50:18 P.M. Central Standard Time,=20 REHBINC@aol.com writes:

<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>

1. In the carburated engines I am familiar with, over half of the=20 vaporization takes place in the cylinder. I'm referring to normal operatin= g=20 speed here, not idle.

2. The primary advantage of finer atomization is enhanced droplet=20 suspension into the cylinder. The larger droplets tend to fall out of=20 suspension and also run into the intake runners at turns. This results in=20= a=20 river of fuel running along the floor of the runner. Large droplets and=20 puddles in the combustion chamber absorb heat slower and hence don't vapor= ize=20 and burn as well. Thus excess fuel is consumed, displacing working fluid a= nd=20 increasing hydrocarbon polution.

One of the ways I used to tune the fuel distribution on carburated ra= ce=20 engines was to glue small dams made from slivers of tongue depressors = ;to=20 the floor of the intake runners of the richest cylinders. This would reduc= e=20 the liquid fuel flow on the runner floor yet had negligable effect on the=20= air=20 flow because it was well down into the boundary layer.

Port fuel injection gets around these problems.

3. Assuming all of the fuel can still be vaporized and combusted, it=20= is=20 prefferable to vaporize all of the fuel in the cylinder. The density of=20 Gasoline is about 700 Kg/cm (kilograms per cubic meter) in the liquid phas= e=20 and about 3.5 kg/cm in the vapor phase. Using the 70 deg. F change in air=20 temperature given by Gary for vaporization temperature drop of the ai= r=20 and the ideal gas equation and assuming intitial air temperature of 350 Ke= lvin=20 and a 14 to 1 air fuel ratio, we get the following equations:

Specific volume liquid fuel mixture =3D (1 / 700 + 14 / 0.968)=20= / 15 =3D=20 0.9643 cm/kg

Specific volume gaseous fuel mixture =3D ( 1 / 3.5 + 14 / 1.092)= / 15=20 =3D 0.8714 cm/kg

Thus, 10.7 % more fuel mixture will fit into the cylinder if the fuel= is=20 in liquid form.

4. With respect to detonation margin, the vaporization of fuel in the= =20 intake of a carburated engine has no benefit compared to that of an inject= ed=20 engine, since the fuel must still be voprized before the combustion event=20= can=20 be completed. (If anything, a lower temperature in the intake runner will=20 absorb additional heat from the runner wall on the way to the cylinder,=20 resulting in nominally higher combustion chamber temperatures) Therefore,=20= a=20 given mass of fuel mixture results in essentially the same peak combustion= =20 temperature whether vaporized in the runner or the cylinder. The differenc= e in=20 the temperature curves around the time of ignition are=20 minimal.