Gee- I had overlooked the current draw for the injectors! It would
 seem that a 40 amp alternator is not sufficient for my application,
  and I have pretty minimal draw after accounting for fuel pump,
  injectors, and minimal avionics. This would explain why I'm getting
 good voltage on the ground at 1800 rpm, but not in the  air at 6400rpm.
 Anyone know what the injectors draw?

  There is a 45 amp alternator that fits my mounting application, but
 only bumping it up 5 amps is not enough. I might have to see about
 mounting a second alternator. Sort of a PITA. That Ammeter from
 Digikey looks good though.

 Brian Trubee

 Unplug one and use an ohmmeter to measure the coil resistance.

 The max current can be found by dividing the number of ohms found
 into the max voltage or 15V.

 Which injector are you using. Some of the older ones used peak and
 hold and the above scheme won't work. If it is around 10 or 12 ohms
 it is not peak and hold.

 If it is 12 ohms it is drawing 1.25 amps wide open max. However they
 never run wide open all the time so 80% of that is about right. Say
 1 amp. A larger alternator won't hurt.

 Paul Lamar

 Just ordered the ammeter and shunt. The bigger issue will be where
 to install the second alternator. Not an insurmountable problem.

 Brian Trubee

 Brian,
 Not a suggestion, but information.

 The standard alternator for the Renesis engine is  100A .

 The secondary alternator, gives you more backup, however.

 Rich

 I have the standard Mazda alternator on the standard location on the
 2nd gen.  My other alternator, a Kubuta, is mounted where the vacuum
 pump was originally mounted. The Kubuta is quite a bit smaller and I
 was able to use the vacuum mount as well with just a bit of
 modification to the alternator.  I have considered replacing the
 Mazda Alt due to weight, but it fits so nicely for now.

 Chris
 Houston

 As Brian is finding, light weight is not the only criteria to consider. You
have to have the balls to get the job done. A small second backup alternator
is a good idea.

Dale Davies



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