Ancient History

[RD Rick]

RJ Harris wrote on diy_efi: 

>Am new to this mailing list, but have been thinking about this for 
years. >Several years ago I drove a 1966 Chevelle with a 350 V-8 that 
had>neck-snapping acceleration and excellent all-around drivablity. 
Belonged to>a young machinist I took an aluminum head in to have a 
crack welded on. >Asked his secret - and was amazed.
>
>Seems he took an older, off the shelf Hilborn mechanical fuel 
injection,>modified it slightly and put it on the engine.  Hold the 
objections, rumors>and myths till I finish.
>
>He drilled the heads so that the untimed variable flow injector 
sprayed>directly on the intake valve from the back side of the valve 
pocket.  What>was lacking in mechanical sophistication was made up in 
simple physics.
>
>Liquid fuel does not burn - period.  It must be vaporized before it 
burns.
>All forms of carboration - including fuel injection - atomize the fuel
>hoping enough vapor will be formed to start combustion so that the 
heat and>violence of combustion will finish the job.  Power and fuel 
efficiency are>directly related to how well that is done.
>
>Gasoline and air, when mixed has an broad range of combustion, from a 
12 to>one mixture for power to a 19 to one mixture for economy. The 
secret is how>well it is vaporized and atomized prior to combustion.
>
>From a vaporization point of view, gasoline has components that boil
>(vaporize) at temperatures from room temp to about 540 degrees F.  
Smokey>once built and patented an engine that heated the intake mixture 
to this>point and made amazing power and efficiency for NASCAR engines. 
 The fuel>-puddling on an intake valve has its temp raised several 
hundred degrees ->without heating the incoming air charge. More fuel 
vaporized probably than>even the most modern injectors achieve - by 
merely dumping it on the>hottest spot in the intake system. Plus fuel 
vaporizing had to cool the>valve - so even less heat added to the air 
mass - meaning a denser fuel air>charge to the cylinder.
>
>Next, from an atomization point of view,  the unvaporized gasoline
>components and fresh fuel were injected at the point where there is 
the>maximum turbulence and violence in the air flow - the seat of the 
intake>valve.  Cold dry air to the port, fuel in at the valve seat 
itself - no>drop out problems period. Not mechanically possible to mix 
it much finer.
>
>With simple tuning and good physics, this crude system worked very 
well>indeed. The extremely high quality fuel-air charge made up for 
much of the>mixture variations that this simple system had and made a 
very responsive,>decent fuel economy street engine.
>
>No moral to this story, just food for thought.  On my DIY conversion I 
am>thinking about, I plan to put my injectors in the valve pocket if at 
all>possible for all of the above.  Only thing better would be to steal 
a>diesel injector and squirt the fuel directly into the chamber against 
both>intake and exhaust.

Very good information there; thanks.

The Djet and Ljet EFI in the aircooled opposed VW and Porsche 914 
engines sprays directly at the intake valve from three inches away.

With the Djet, the fuel is squirted in at the beginning of the intake 
stroke two of the cyls, and at the beginning of the power stroke on the 
other two cyls, so its operation is compromised.  

People on the 914fans lists have been debating the injector timing 
question, so your post is being forwarded there.  Hope you don't mind.

RD