DFI, Batch Fire, and other myths

[andy quaas]

Doesn't a venturi atomize fuel very well in any case?  As stupid as it
sounds, why not make an intake that has a venturi for each port and
feed the fuel to the venturi at each intake port.  You'd have a lota
throttle shafts and such, but it would atomize the fuel better, no? 
What mechanical devices atomize fuel well?  How well does a mechanical
injection atomize fuel?  

Andy

p.s. what does IR stand for?  


---Greg Hermann <bearbvd at sni.net> wrote:
>
> Hi--
> 
> I just couldn't resist jumping beck into this one!!
> 
> Yes, Andy, you are right. Problems for most efi are:
> 
> 1. Most injectors  do not have enough dynamic range to be able to
inject
> all the fuel for WOT power during just 80 to 100 degrees of crank
rotation
> AND be able to turn down far enough (Can't go to a short enough pulse
> width) to inject a small enough quantity of fuel for proper fueling at
> idle.
> 
> 2. Most efi injectors do not atomize the fuel very well at all,
period. So
> tricks such as squirting fuel against the back side of a closed, hot
intake
> valve are used to get the fuel vaporized. (Vaporized is distinctly
> different from atomized, this is not just a semantic point.)
> 
> There are OBVIOUS benefits to timing a squirt of WELL ATOMIZED fuel
with
> high inhale velocity in the intake ports. Anybody who doubts this
> statement, get back to me after perusing some dyno data for an
engine, any
> properly tuned engine, equipped with an IR intake manifold with Weber,
> Delorto, or Mikuni/Solex IR carbs. Pay particular attention to how
LOW the
> bsfc numbers are when it is tuned properly. Try the same engine with
either
> a standard carb and wet manifold or TPI. When running the TPI test,
> restrict the Manifold runners with a choke the same size as whatever
> venturis were used in the IR carbs, so that air flow is equal. We
all know
> that the IR carbs will seriously outperform the wet manifold. What
is not
> so obvious to all is that:
> 
>  1. The IR carbs will give lower bsfc at part throttle than the TPI,
> because they atomize the fuel so much better.
> 
> 2. The IR carbs will geve significantly more power, together with
lower
> bsfc,  (remember, air flow has been equalized) at WOT both because
they
> atomize the fuel very well, and because they time the shot of fuel
with
> high inhale velocity in the port.
> 
> There would be a lot less debate about this if anybody had ever
bothered to
> set up a true, change only one variable at a time, test of it. (I
don't
> know of any such tests.)
> 
> There are several very clear performance, economy, durability, and
> thermodynamic benefits to getting well atomized, but not vaporized,
fuel
> inside the cylinder and getting the intake valve closed before much
> vaporization takes place. The finer the atomization, the better, and
the
> less vaporization, the better. Good IR carbs do this pretty well. Efi,
> (meaning TPI) despite all of its obvious airflow and metering accuracy
> benefits does not do these two things very well at all with current
> injector technology.
> 
> There are lots of folks in the industry working on developing ways
to make
> efi do these things better. I am working on the same thing as a
hobby. When
> I get an engine built, and get some test results, I will share them.
But
> some money is definitely going where my mouth is!!! That is so
because I
> believe that the above outline of the situation is sound
> engineering/science and I want a better performing engine(s).
> 
> Regards, Greg
> 
> 
> 
> >Is it true that none of the firing methods actually time the injector
> >to the intake stroke of that cylinder?  I would think that injecting
> >fuel on the other strokes would be a waste.
> >
> >Andy
> >
> >
> >---Sandy <sganz at wgn.net> wrote:
> >>
> >> I think that injection of all the fuel during a period has some
> >SMOG/Econ
> >> bennifits, but can't remember if any power was gained (anyone?).
> >Others
> >> have stated that the evaporation of the fuel sitting on the closed
> >valve is
> >> better then squirting raw liquid fuel (hard to burn) into a
> >cylinder.  I
> >> think that is why you don't see much power difference between SFI
> >and BATCH
> >> systems.
> >>
> >> Sandy
> >>
> >> At 10:17 PM 1/20/99 -0600, you wrote:
> >> >
> >> >
> >> >Ward Spoonemore wrote:
> >> >
> >> >> Tom
> >> >> Your Edelbrock ProFlo is typical on several other EFI system's
> >> >> actualy the tests I have run show little on no differace between
> >L/R and
> >> >> other systems.
> >> >> In fact all EFI are on almost 100% at or near WOT.
> >> >> Ward
> >> >
> >> >There is an ongoing discussion about the need to inject all (or
> >most) of the
> >> >fuel while the intake valve is open, probably starting before the
> >valve
> >> >opens and ending before it is closed. It would require large P&H
> >injectors
> >> >and lotta of pressure.
> >> >
> >> >Any ideas or comments (or experiences).     Regards  Tom
> >> >
> >> >
> >>
> >>
> >
> >_________________________________________________________
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> 
> 
> 

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