So Al how well does this work? Does it keep the mixture constantÂ
  as you change altitude? As you change prop pitch?Â
Â
  Paul LamarÂ
Â
  Paul, I am wondering here why you are concerned about mixtureÂ
  changeÂ
  vs. pitch? Any carb system will change mixture slightly until you
returnÂ
  to a steady state. In the Holley carbs they use a secondary system toÂ
  maintain the mixture in a WOT low RPM state. (power valves) I'm sureÂ
  you know this. A vacuum slide carb works better, but isn't instant.Â
  The Alpha-N FI systems will usually still outperform carbs in thisÂ
  situation.Â
  There may be some variance but it will be slight. If you run a O2Â
  sensorÂ
  it will be better than carbs by far. Just curious what the buzz isÂ
  about?Â
  Bill JepsonÂ
Â
A carb has a mass airflow sensor and throttle position sensor built inÂ
so to speak. It also senses the rate of change of throttle opening.Â
That is done by the acceleration pump.Â
Â
Tracy is using manifold air pressure, RPM and air temperatureÂ
sensors only.Â
Â
It does not appear to work on a dyno where the load changesÂ
widely at any RPM. I attempted to tune the system and gave upÂ
after a day or too. It was getting too expensive at $650 a day.Â
We stuck the Weber on there and had it tuned in five minutes.Â
Â
A fixed pitch prop has only one load for each RPM.Â
A variable pitch prop and engine dyno has many loads for the same RPM.Â
What ever is going on I could not get it to run wellÂ
on the dyno for what ever reason.Â
Â
The O2 sensor will work for awhile to set up the look upÂ
table in the computer but will deteriorate with the use of 100LL.Â
Â
BTW this is another interesting EFI system I just discovered.Â
Â
http://www.dtafast.co.uk/Â
http://www.zetecinside.com/xr2/injection.htmÂ
http://dtaforum.psycode.com/index.phpÂ
Â
Paul Lamar ...No rotor no motor.Â
Â
Paul,
Looks like some interesting players in the EMS/FI stuff there. Did you
find prices anywhere? I've had the Jenvey site bookmarked for some
time, but I hadn't seen the DTA site. I wonder if they have a direct
rotary engine system.
The thing is the Alpha/N systems with MP sensors
shoud, provide good response to a load change. I think the dyno
problems you experienced may be due to the rather sudden load
changes seen only on the dyno. I did considerable dyno work on bike
engines and since there is so little flywheel affect it could be very hard
to smoothly accellerate. Even on the chassis dyno the accell/decel was
so sudden that missed shifts were common. We often just started the
bike in top gear witht the load turned off, (water brake dyno), ran theÂ
bike into the normal rev range and then loaded the engine up.
Bill JepsonÂ



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