Alternatives to the alternator
 

We all know you can't run an SI engine very long without some sort of system for recharging the battery, but not all of us are sure to know all the options available. Therefore, I thought I'd open this thread to gather them all together in one place.

1. MetroMPG linked to the TIGER option. Very cool and sure to see actual production. :thumbup:

2. Then there is the tried and true underdrive pulley. For those not familiar with this option, here's how it works. In round numbers, the pulley on your car's alternator is sized relative to the crankshaft pulley to charge slightly at idle (or perhaps a little above idle), and to produce full rated power by about 1500 engine RPMs. The particulars differ from engine to engine, but that's the general idea.

An underdrive pulley is somewhat larger than the OEM alternator pulley, so slows the rotational speed of the alternator. By slowing the RPMs of the alternator the point at which it begins charging is delayed by several hundred RPMs to as much as a 1000 RPMs or more. That delay removes the alternator's electrical load on the engine at low engine speeds, and hence potentially permits better hypermiling in that same low engine speed range.

As an aside, underdrive pulleys are commonly used on water pumps, as well, and for the same reasons.

3. A somewhat more radical approach, but still very doable, is to move the alternator to a position that turns only when the car is rolling. Here is a photo of a (race) car with the alternator mounted above the transaxle and being driven by means of a conventional 'two pulleys and a belt' setup using a CV joint-mounted drive pulley. Again, sizing the pulleys to start charging at your desired speed is key. Oh, and sorry the photo doesn't show much detail, but I'm confident you get the idea.

http://bringatrailer.com/wp-content/...r_Engine_1.jpg

4. Field circuit switch. Most (but not all) alternators have a so-called 'field circuit' that uses a little juice from the battery to 'excite' the internal circuits of the alternator to make electricity. Without it the alternator will spin, but does not generate any charge. The wire feeding the juice attaches to a terminal on the alternator housing. Identify this wire and then wire in a dash-mounted toggle switch to cut the field whenever you wish.

There are a few options. Surely you guys can come up with some more! :thumbup:

I like Option 4 the best. Here is why:
A) It is the cheapest.
B) Totally reversible
C) Manually controllable so you can turn it off or on as needed or not.

One alternative for spark ignition is the old tried-n-true magneto.

I think that Tiger thing is pretty cool. With one of those, and an electrically driven power steering power steering pump, AC compressor, etc. you could potentially have no loads on the engine other than the drive shaft.

One thing I can surmise is that the alternater takes about 10% off a car's fuel efficiency. There are so many independent sources that claim up to 10% improvement after the conventional alternator is taken off-line. That's good to know. For me, a 10% improvement would be 3-4 mpg.

Tigers sounds great but...
 

That article is dated Sept. 2005, is ther a more current article?
Has an exhaust driven alternator been developed and marketed?

If it really works and is available I would be interested in acquiring
one for my own use. If not, then I can see a potential market
if I had the resources to work on this product.:)

just found this Permanent Magnet Alternators and Water Pumps

interrupt switch 4 engine loads?
 

For those of us out here who are "electrically challenged" ( I know not to stick anything into a wall socket ... except a plug) , would you elaborate a bit on the specifics of this "load switch"? I am in fear of burning up a very expensive alternator. It sounds great to me! The battery gets lots of charge time, anyhow....My Scangauge shows me great numbers of (downhill) "charge times" but who needs alternator drag while pulling a steep grade? -whitevette

I learned that when I was about 10 with a pair of tweezers OUCH they got real hot real fast.

On another note Option #4 the field wire would have to be killed before turning on ignition. Once you excite the alternator you don't need the field correct? Or not. That is what I thought they taught me in Mechanics class in HS.

TIGER sounds cool, but would need to be managed by a computer. Also, anything that resembles a turbo sees heat and requires maintainence <anyone have experience with the old Porche 924 T?)