Ed,
I guess I left some stuff out of my original post.
<... I can think of no way to separate the temperature drop you
want from a certain quantity of fuel that must evaporate to give you that
temp drop ... on this manifold I place all 4 injectors in the throttle
body
area at the beginning to the tubes ...>
What I was postulating was TWO injectors in each runner - one at the
top near the TB and one at the bottom near the block. Implied, if
not specified, was an indication of intake temp and a way to adjust the
portion of fuel injected into a runner that passed through each
of these injectors.
Now let's suppose some stuff:
Suppose your intake runners were a little longer than they are.
Suppose you have a readout of intake temp.
Suppose you have injectors at both ends of the runners, and that the
total fuel flow through the injectors of a runner can be adjusted to inject
all at the block or all at the throttle body or anything between those
extremes.
Suppose you got DIE at some intake temp, say 30 F at 5500 rpm (injecting
at the block only). That's a data point. At some other intake
temp, you will get DIE at some other rpm. Now you have a chart.
Now, when you want to take off, and you anticipate your TO rpm to be
5500 you know you need 30 F intake temp. But on turn up it's actually
80 F (injecting at the block). So you adjust the knob to inject just
enough fuel at the top of the runner to lower the temp to 35F and viola'
your rpm jumps, you have DIE and life is good. Climbing to altitude,
it's cooler so you have to bias a little more to the top of the runner
to maintain DIE. You throttle back to cruise at 5000 rpm. You
need to bias more toward the TB to bring the DIE rpm down to 5000 which
occurs at 15 F. And so forth
You get my drift. With a chart of rpm v. Tr you know what temps
you need for DIE at TO, climb and cruise. You know how much you can
reduce intake temp by going to block only injection (highest temp) to TB
only injection (lowest temp). You pick your envelope and build your
runners to fit. Then, even though the OAT changes and rpm changes
(a little) you can adjust intake temp to get DIE at the rpm and OAT you
are at.
The key of course (more better we call it "detail devil") is coming
up with a way to bias fuel injected through each the two injectors while
maintaining the sum of the quantities injected at that needed for proper
combustion. That's one hell of a devil, but not nearly as difficult
as the original devising of a system that that figures out how much fuel
to inject and then delivers it. I would guess at this point that
it would be easier to adjust intake Temperature than intake Length.
Tracy, you listening??
Different folks desiring different flight regimes would need runner
lengths that bracketed the temps and rpm's they expected to be operating
at.
Just a theory ... Jim S.
Ed Anderson wrote:
Very interesting and novel idea, Jim.
There is no doubt that temperature does affect the
DIE RPM point. .... I can not reach that rpm with my engine
prop combination on the average OAT day such as 59F where my static is
around 5200 rpm ... However, on this manifold I place all 4 injectors in
the throttle body ...evaporation of the fuel does definitedly lower the
temperature in the manifold tubes ... the morning I flew down to
Shady Bend the OAT was approx 35F AND I saw 5800 rpm again ... not unreasonable
to assume the temp of the air in the tubes was approx 15F cooler or 20F.
So I think this supports the concept that you have postulated.
So here
again, the concept is fairly simple, but I think the devil is clearly
going
to rear its head in the details.
I can think of no way to separate the temperature drop you want
from a
certain quantity of fuel ... that fuel quantity might not be consistent
with the best air/fuel
mixture for power in the engine. On second thought, I suppose
a chemist
could figure it out, and it may be that less fuel evaporation is need
with
less airflow mass to bring the air temp down and more fuel evaporation
to
bring a larger quantity of air mass to a lower temperature. So
perhaps the
two conditions are not mutually incompatible.
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