Direct Injection

[Howard Wilkinson]

Robert:
    I suspect that we are comparing apples to oranges here.  The
engines you are speaking of are extreme high performance supercharged
engines, and I suspect that direct injection was a strategy to help
combat detonation / as was the water injection system common on WW2
aircraft.  The problem with direct injection which resulted in the use
of two injectors (not the Orbital system) was atomization was not as
good as with port injection resulting in less max power output.
    I might add that as these systems of which you speak are
mechanical systems it is very likely that very high pressures are used
which results if far better atomization..... a well known principle.

    Nice flame!!..... however we are talking about a whole different
set of problems here.  In automotive applications a typical engine is
only operating at a small percentage of it's full output, and these
systems are designed with the intent of getting max efficiency in this
range.  You can't directly compare an engine designed with this in
mind to one designed to race...... it's a different world.  If you
wish to live in the past, or compare race cars with road cars that's
your problem.... None of the engines you speak of even approaches the
type of volumetric efficiency achieved by these modern engines at the
same percentages of max power output.  Efficiencies of as high as .3
lb per BHP/hr are frequently quoted (I'm not saying I believe it).
You're welcome to play with your Spitfires and Mercedes race cars....
I for one can't even come close to affording such toys.

    Furthermore this comment is utter nonsense:

>If you want Direct Injection without waiting for someone to get
around to
>re-inventing the wheel, you can directly adapt an automotive/light
truck
>diesel unit by running a little 100 to 1 synthetic 2 cycle oil with
your
>gasoline.

No doubt you could operate a diesel fuel injection system on a 100x1
oil mix, but how do you propose to regulate mixture??
     This I'm sure could be done in some way.... do you propose to
connect a servo of some sort to the fuel control to the injector pump
so that as the throttle is opened or closed the correct amount of fuel
is supplied?  These systems fire each injector every other revolution,
and the throttle only supplies more or less fuel to a diesel to
regulate power........ this doesn't work on a gas engine as the
mixture variation prevents ignition if too lean or too rich.
    To imply that this is a fairly simple project is to greatly
oversimplify things.  It is neither simple or practical.  I work with
these systems every day and am very familiar with them....... don't
try to feed me this load of nonsense.

H.W.


-----Original Message-----
From: Robert Harris <bob at bobthecomputerguy.com>
To: diy_efi at efi332.eng.ohio-state.edu
<diy_efi at efi332.eng.ohio-state.edu>
Date: Wednesday, April 28, 1999 6:47 AM
Subject: Direct Injection


>Detrimental to power output - tell that to the Spitfire pilots that
ate it big
>time when they met the Direct Fuel Injected Me109's etc.  Tell that
to the
>drivers of other makes who ran up against Mercedes Direct Injected
300's in
>the early fifties.  Bosch and Mercedes routinely used Direct
Injection thru
>the mid fifties.  Tis an old old idea laddies - and was making POWER
long
>before Orbital was a stain on daddies leg. Try like operational on
German
>aircraft engines in 1934.
>
>Some day, when you have nothing to do, you might enlighten yourself
about
>mixtures.  Like try inverting fuel air mixtures i.e. holding fuel
constant and
>changing air and plotting air to fuel vs power.  You will find that
the power
>varies far more with the amount of fuel than with the amount of air.
Then you
>will realize that max power is made with the fuel held equal in all
cylinders
>- the first major benefit.
>
>Then - re-read about the Bosch System - which Horror of Horrors was a
direct
>adaption of Bosch Diesel systems and shared most parts.  Since they
injected
>the fuel after the intake valve was closed - well into the
compression stroke
>and these old krauts knew all about "atomization" and vaporization
etc ad
>nauseum, they did not screw around with puffs of air or whatever -
but passed
>go, collected their 200 dollars and went to aiming the fuel spray
right onto
>the face of the exhaust valve - instantaneous fuel evaporation in a
CLOSED
>cylinder and heavens to murgitoid, actually cooling the exhaust
valve.
>
>Silly stupid german engineers didn't read the DIY_EFI archives on how
to get
>optimum fuel atomization or care about it.  They got instant
vaporization -
>screw atomization, they cooled the exhaust valve so they could get
even higher
>power outputs and by cooling the HOTTEST spot in the cylinder, they
were able
>to raise the compression ratio at least 2 whole ratios on the same
octane
>fuel.  With total vaporization, they were able to get incredible
throttle
>response, power and performance.
>
>But silly us didn't realize that all they wanted to do was stratify
the
>charge, get milage by sacrificing performance, and have poorer
mixture's than
>port injection.  Great Nazi propaganda apparatus must have covered
this up
>along with those stupid engineers at Bosch who forget to put the port
injector
>on the Messerschmits and Mercedes for high power usage.
>
>Further for the record, Bosch developed the timed port fuel injection
as a
>CHEAP almost as good replacement for the Direct Mechanical Injection
and then
>went on to develop the K "CIS" system as a more efficient
implementation of
>Fuel injection than the timed port injection and was only forced
backwards
>because of air pollution constraints - not power not economy - just
smog
>nazies.
>
>If you want Direct Injection without waiting for someone to get
around to
>re-inventing the wheel, you can directly adapt an automotive/light
truck
>diesel unit by running a little 100 to 1 synthetic 2 cycle oil with
your
>gasoline.
>
>Of course, then you would have to come over to the dark side and use

air
>control instead of fuel control because the high pressure ~1800 PSI
side
>doesn't let you do much.  But then why bother - we all know that fuel
shot
>thru a diffuser nozzle at 1800 psi is not going to be well atomized
without a
>puff of air or be as good as piss dribbles into the intake runner
timed to
>whizz into the cylinder when the valve is open.
>
>1963 Ford C-600 Prison Bus Conversion "Home"
>1971 Lincoln Continental 460 "Christine"
>1972 "Whale" Mustang awaiting transplant
>1978 Dodge Long Bed Peeek Up "Bundymobile"
>
>Habaneros - not just for breakfast anymore
>