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Old 05-11-2018, 02:22 AM   #7 (permalink)
Wanting more for less
D.O.G.'s Avatar
Join Date: Jan 2011
Location: New South Wales, Australia
Posts: 307

Metric - '94 Honda Magna 250
90 day: 70.47 mpg (US)

RedCelica - '94 Toyota Celica ZR
90 day: 35.97 mpg (US)

i30 - '12 Hyundai i30 Elite
90 day: 39.56 mpg (US)
Thanks: 22
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Originally Posted by Stubby79 View Post
It's output is limited at lower RPMs. It will try to make up for it by boosting the field voltage, but it will hit a wall/limit and not be able to output any more without spinning faster. (as shown by cars with small alternators that can barely keep the voltage up at idle with a decent load put on)
Too true.
When I modded my Datsun to have a really tall overdrive, I didn't take into account the reduced engine rpm also meant reduced alternator rpm.
At 60kph, (with only 40A to start with), it couldn't keep the battery charged with lights, wipers and demister all going.

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