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Message
Hi Dale,
I was not arguing against the merits of
moving the injectors closer to the block. I also have tried the injectors
as far away as 24" and while I could determine no difference in power
produced, they did make starting on cold mornings very difficult. So I now
have them within 6" of the ports and like it much better.
My point was - that from a practical
standpoint, the main limitation we have in producing power is getting the engine
to ingest more air. We can always and easily inject more fuel - IF we only
have the air to combust it. And of course, getting more air is what the
forced induction (turbo/super) is all about.
If Rusty's "Power Problem" were simply due to some
of the fuel dropping out of suspension (which I agree likely happens),
then he could compensate by simply turning up the mixture control to enrich the
mixture. So if the lack of fuel in burnable condition (vapor) were the
problem, saturating the intake mixture with the mixture control would have shown
an increase in power. True, his gas mileage would likely be
terrible as he would be blowing all those large droplets through the combustion
chamber, but he would still get an increase in power from that increased amount
of fuel that did arrive in the proper state. The fact that did not happen
indicates to me that the limitation in producing power, in Rusty's case, is due
to insufficient airflow.
About the only time, I have seen lack of fuel be
the problem in producing power is when someone turbo/supercharges an engine
(thereby considerably increasing the airflow) and has a fuel system that is
incapable of providing the additional fuel needed to match it. However,
that situation rarely lasts long as it generally leads to detonation and damage
to the engine.
The airflow of an NA engine is theoretically
limited to the airflow its displacement at a specific rpm is capable of
producing. But, If you hit the tuning correctly you can get Volumetric
efficiencies of over 100%(this is that inertia/momentum and pulse tuning folks
are after). However, if you get it incorrect you can drop down to 85% Ve
or less. Many autos do little better than 85%. In any case, there is
a often a 15% or more increase in power waiting if you get the induction tuning
correct and capture that increased airflow.
It is always much easier to add fuel than produce
more airflow, most power problems are not due to lack of fuel but lack of
sufficient airflow. Limited airflow is the real practical limitation
on the power produced by any engine. So the induction tuning
thing is almost always focused on improving airflow and not fuel
flow.
FWIW
Ed
Ed Anderson
RV-6A N494BW Rotary
Powered
Matthews, NC
----- Original Message -----
Sent: Wednesday, May 12, 2004 12:31
PM
Subject: [FlyRotary] Re: Runner Length
Was Ref: injector relocation
Ed Anderson <eanderson@carolina.rr.com>
wrote:
> Rusty, I don't think anyone can answer that
question - depends on too many variables. You would think that even if
the fuel coated your long runners that eventually it ends up in the combustion
chamber.
Yes, but fuel that condenses on the sides
of the runners
finds its way into the combustion chamber as relatively
large, unburnable, droplets.
> My (admittedly limited)
experience with rotary intakes leads me to believe that the number one,
primary, uno, far outweighing all other factors, the key element, etc. etc.,
is AIR FLOW!
>
But you can't burn plain air, or
we'd all be flying for
free. There's that 14:1 thing. It not
only has to be
there, but but there needs to be enough ~vaporized~ fuel
to support combustion.
> If you DO have the
airflow then it is simple to dump in more fuel and get more power. If
you don't have the airflow in the induction system, then it don't make no
never mind how much fuel you pour into it, it won't produce more power.
That's so, and the extra fuel is not only wasted, but
will usually lower the combustion temperature enough to
reduce net
power output.
>Clearly, its not a simple matter to get great airflow
for a number of reason mentioned.
>
It will be a
while before I can prove it, but everything
I know about the process at
this point, suggests that Rusty
is on the correct track in moving the
injectors down close
to the housings.
Regards,
Dale
R.
COZY MkIV #1254
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