Test: Alternator vs. no alternator = 10% MPG gain @ 70 km/h

[vacationtime247]

Here's how I'm trying this mod, or at least tried it today. Took the serpentine belt off before going to work, during daylight hours. I work 2-10:30p. The drive to work really didn't use the battery hardly at all. Started with 13.07 volts by the time I was at work it read 12.7 volts. Hooked the belt back up once I was at work. Took 5 minutes. Have to drive home in the dark, when I'd be using the most volts to run the lights. I'm hopeful of some kind of gain not having to run the serpentine belt at all going in to work. The water pump is driven off the timing belt.
VT247

[steffen707]

As some have said, doing this will net worse mpg for you because the alternator is not very efficient at recharging your battery. So on the night time trip home the alternator is going to be working extra hard because the battery was already drained (not fully, but partially) on the way to work.

You might find better results in driving to work with belt on, then taking the belt off at night where the alternator works a lot harder.

I did a test with the alternator on and a full load of electrical (lights, defroster, blower, radio) and then another test with the same loads, but this time with my alternator in low charging mode and i got 13% better mpg on a flat road .5miles and cruising at 40mph.

The same test with no load was like a 1-3% difference.

[vacationtime247]

Here's my rational for why I'm trying this the way that I am. But, I could be wrong and it may not net any gain. Been wrong before, it was on a Wednesday in '89, lol

Taking off the serpentine belt before going to work. The engine won't have to turn the a/c, the idler pulley or the power steering, there is another belt from the ps to the alt. So none of them will be turning. Other than to charge the glow plugs, start and brake lights, the battery won't get much use except to keep the injector pump on. When I tried it yesterday, it still had what most would consider a full charge, 12.7 volts after getting to work. If for nothing else, I'm going to try this for one fill up or @ 350 miles. See what my mpg is then. No gain, I'll try something different. Would really like to use 2 deep cycle batteries for to and from work. Charge it once at home on the grid. But haven't got to that point yet.
VT247