Michael, many on this list do not monitor Paul's list.
Regarding the 555 injector.
The amount of fuel need to support combustion at a specific Air/Fuel
Ratio is dependent on two major factors. These two factors are the size of the
combustion chamber and the density of the air in the combustion chamber.
The role rpm plays is the number of times the chamber is filled and emptied per
unit time. Since the displacement (size) of the combustion chamber is
fixed that then means the fuel required (over time) is a function of both air
density and RPM. Air density can be inferred as a function of either air mass
flow or manifold pressure (the two most common approaches to determining engine
load).
But, in either case, air mass flow and/or manifold pressure is a
function of rpm AND engine Load. Lets not forget also it is also a function of
ambient pressure and air temperature as well.
The two most popular methods of controlling the fuel injected are based
on either a measurement of air flow (the method proposed in the article) or the
measurement of manifold pressure (reflecting air density). Either method
will work. One requires the air to flow fairly cleanly through an air
mass flow meter (such as one the Paul showed used to Lean the injector to more
closely match the airflow demands of the engine) the other approach normally
uses a pressure sensor to measure the manifold pressure. As I said
they both work. For example, instead of using an airflow meter, you could
simply use an appropriate range (10-30”Hg) manifold pressure sensor with
an output from 1 – 5 volts and hook it up the same way as Paul indicates
hooking up the air flow sensor to “lean” the fuel injector for
cruise.
Now when it comes to using one in an aircraft, I personally prefer the
air density (manifold pressure) approach. It does not require any mass
flow meter – you can use any throttle body you want. If your TB of
preference does not have an integrated mass flow meter then you will need to
place one in the air flow circuit after the TB. With the air density
approach, there is no sensing device in the airflow and the manifold sensor can
be attached to the manifold at any number of locations or a remote location
connected with a hose.
Then there is the question of redundancy. I personally had a
HALTECH EFI system with which I had flown approx 160 hours fail on me –
fortunately on the ground. That is one of the major reasons, I switched
to Tracy Crook’s EC2 – it has two independent controllers.
So, it really depends on what you are looking for. There is no
question that a unit like this could be put together rather inexpensively –
but, I personally prefer something a bit more sophisticated and with some
redundancy. Just my personal viewpoint.
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.dmack.net/mazda/index.html
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On Behalf Of Michael McMahon
Sent: Monday, January 19, 2009 5:07 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Paul Lamar's Simple Fuel Injection
I haven't seen any response on this list to the article that Paul Lamar
posted a couple days ago (below). I'm very interested in
objective
discussion of merits and flaws, and there hasn't been much on the
Rotary
Engines list. Has anyone read it? Any opinions?
Thanks, Michael
>>>> Not entirely done as I will be updating it from time
to time depending
on your questions.
>>>> http://www.rotaryeng.net/simple-cheap-555.html
>>>> Paul Lamar
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