Bill,
   I re-read Bob Nuchol's Aeroelectic Connection last night looking for
some guidance on sizing of the alternator.  Tracy's EFI pulls a max of
about 21 amps and an average of about 11 amps.  The electrical load of a
Day VFR plane shouldn't be over a total of 17 - 18 amps average (is this
a true statement?).  What size alternator should be used to support this
load?  Is a 35 amp alternator to small?  I'm afraid that a 35 amp
alternator will overheat and that I need the stock Mazda 55 amp
alternator.  Note that the stock alternator weighs 10 lb 11 oz while a
35 amp / 1975 Honda alternator is said to weigh ~ 6 lbs.
   Also, we have talked about what fuel line to use on several occasions
but I do not remenber what type of hose we should use for the hose to
the oil cooler.  Is Aeroquip 303 OK?  The max operating temp for this
hose is 250 degrees, which doesn't seem like enough?

Thanks,
Ken Powell

If your only load will be the engine electronics, then 35 amps is clearly
more than enough.  Actually,  you need to do a detailed load plan.
You need to know exactly what each piece of equipment that will
be in the aircraft will draw (amps) and have an alternator that can
provide this.  Any alternator in good operation condition should be
able to put out the rated current indefinitely, assuming adequate
cooling air is available, which is normally the case.  Certainly a bit
of excess capacity is nice, in case you add something later.

I have been using a 55 amp NipponDenso ('85 Civic) for 11
yrs and 800+ hrs without problems.  I open it up and clean up
the brush dust every couple of years and check the brush
length.  These are good little alternators, but make sure you
have a 60 amp circuit breaker to protect everything if the
regulator fails, causing unlimited voltage and high current.
Bob Nuchols uses a nice fuse system and a "crowbar"
protection system. Check out his newsletter and ask him
directly, he is a real expert.  If I disagree with him, I'm
probably off base.

Aeroquip 303 is fine for fuel lines, make sure you use a fire
sleeve.   Replace it every 5 yrs or so.  Protect it from close
proximity to exhaust systems and the temps will be fine.  If
you make up your own be sure to check for rubber flaps being
made inside as you insert the end fitting.

Bill
Long EZ builder & pilot
mechanical engineer

 
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