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

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