If there is no differential pressure, there is no atomization.  The
fuel comes out in a stream, not a fog.  Having a slight differential
pressure is very helpful.  I must not understand your setup.  Is it NA
or TC'd?  If it is NA, then the upper deck pressure under the cowl is
higher than MP and that is the source of the differential pressure for
the injector.  If it's TC'd, the upper deck pressure comes through the
controller off of the turbo and is forced through the injector under a
3psi differential (above current MP), otherwise, the fuel wouldn't go
into the port without a  very high fuel pressure.  I have some pics of
this difference in fuel stream out of injectors if you'd like to see
them.

Walter,

 

1.  In the old days, my Lancair's Lyc IO 320 # 2 cylinder's injector was directly in the incoming path of the cooling air.  Unequal EGTs caused me to install a deflector in front of that injector (upstream) and, much to my delight, the first cylinder to lean changed and the intra-cylinder EGT spread was reduced. 

 

2. Currently, at WOT, my no-filter ram air induction system's pressure should be higher than the upper cowl pressure.  In the future I will have access to another MAP sensor which I will be able to place in various locations so that I might actually measure pressure differences using the same yardstick. In any event, I am neither NA (as defined by my Lyc engine manual which prints power/FF charts assuming no ram air) or TC.

 

3. A benefit of using shrouded injectors supplied by air from a common plenum is that each injector sees the same air pressure.  This theoretically should atomize each injector equally.

 

4.  In my case, I use a separate pitot to supply ram air to a wee plenum and thence to the shrouded injectors.  A more reasonable method for most folk would be to tap off of their ram air system.  Although I did not measure it, fuel distribution is much more even.   I am always weirdly different.

 

5. Effective ram air systems used on many Lancairs (especially hi-speed Legacies) can cause quite a bit of pressure in the induction system that is higher than pressure in parts of the upper cowl.  Perhaps even enough to cause fuel to come out of the injector air hole under certain conditions - the intake valve is closed and the induction pressure is high enough.......??? Maybe even leaving a tell-tale stain?

 

Yes, I would like to see the pictures you reference - send directly to me if no one else is interested.  Thanks. 

 

I sure would like to see pictures of Honda's 12 port electronic injector's output.