So Al how well does this work? Does it keep the mixture constant
   as you change altitude? As you change prop pitch?

   Paul Lamar

   Paul, I am wondering here why you are concerned about mixture
   change
   vs. pitch? Any carb system will change mixture slightly until you return
   to a steady state. In the Holley carbs they use a secondary system to
   maintain the mixture in a WOT low RPM state. (power valves) I'm sure
   you know this. A vacuum slide carb works better, but isn't instant.
   The Alpha-N FI systems will usually still outperform carbs in this
   situation.
   There may be some variance but it will be slight. If you run a O2
   sensor
   it will be better than carbs by far. Just curious what the buzz is
   about?
   Bill Jepson

A carb has a mass airflow sensor and throttle position sensor built in
so to speak. It also senses the rate of change of throttle opening.
That is done by the acceleration pump.

Tracy is using manifold air pressure, RPM  and air temperature
sensors only.

It does not appear to work on a dyno where the load changes
widely at any RPM. I attempted to tune the system and gave up
after a day or too. It was getting too expensive at $650 a day.
We stuck the Weber on there and had it tuned in five minutes.

A fixed pitch prop has only one load for each RPM.
A variable pitch prop and engine dyno has many loads for the same RPM.
What ever is going on I could not get it to run well
on the dyno for what ever reason.

The O2 sensor will work for awhile to set up the  look up
table in the computer but will deteriorate with the use of 100LL.

BTW this is another  interesting EFI system  I just discovered.

http://www.dtafast.co.uk/
http://www.zetecinside.com/xr2/injection.htm
http://dtaforum.psycode.com/index.php

BTW --------------------------------------------------------------
People spend a lot of timing tuning Tracy's system. Tracy original
concept was not to use a personal computer or lap top as it would
not fit in his RV4 cockpit. I think that handicaps the system when
it comes to ease of tuning. With a PC interface such as a USB it is
possible to easily change values in the fuel injection lookup tables
in the computer. It is also easy to save and store many look up tables,
swap them in and out of the engine computer in the aircraft
on a trial basis. Also the program itself can be easily upgraded.
Not to mention the real time engine parameter monitoring
and data acquisition advantages of a personal computer interface.

Lap top computers are getting smaller and smaller therefore I would prefer
an EFI system like Megasquirt (http://www.megasquirt.info/) or PICAXE
(http://www.rev-ed.co.uk/picaxe/) that took full advantage of the tremendous
computing power and hi rez graphic user interface inherent in a PC
to tune my system.

http://www.mobiletechreview.com/sony_ux180/Sony-Vaio-UX180P.htm
http://www.samsung.com/uk/products/mobilecomputing/ultramobile/np_q1_v000suk.asp

Paul Lamar ...No rotor no motor.

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