Another new lurker - question about shutting down alternator - Fuel Economy, Hypermiling, EcoModding News and Forum

Caelum Rex · 01-06-2008, 11:58 AM

Hi,
I am new to the forum too and I am very interested in ecomodding. I have a 90 Dodge Omni that I am going to be "experimenting" on.
I noticed in your article for beginners that you mention loosening the alternator belt to remove the alternator load from the engine. Wouldn't it be easier to just wire a switch into the wires that go to the field circuit of the alternator. It seems to me that if you turned the power to the field off the alternator would just rotate with little or no load and you could just turn it back on with the flip of a switch when you needed it.
I would appreciate any thoughts on this.
Also I have already used one mod on the Omni. My Omni does not have a passenger side rearview mirror and I was thinking of going to the junk yard to get one. After browsing the ecomodder forum I decided to put on an internal side mirror instead. While this did not decrease drag any (since I didn't have a mirror to begin with) at least it didn't increase drag at all thanks to the idea from the forum.

Thanks,

MetroMPG · 01-06-2008, 12:54 PM

Hi - welcome.

Quote:

Originally Posted by Caelum Rex

I noticed in your article for beginners that you mention loosening the alternator belt to remove the alternator load from the engine. Wouldn't it be easier to just wire a switch into the wires that go to the field circuit of the alternator.

Yes, that would be easier.

That said, running a vehicle off its battery alone is a pretty extreme mod. Yes it will save fuel. It will also destroy a regular starting battery in short order, since they're not designed to be deeply & repeatedly dis/charged.

This is a mod I often use in summer months. But I've got a supply of old deep cycle batteries which I can ruin at will.

paulwelkins · 01-06-2008, 01:19 PM

I just picked up a full length panoramic mirror from the local parts store for about 20 bucks. I lucked out. The mirror mounting holes matched to the old sun-visor mounts on my 88 honda crx. It's a bit scary as to how close it is to my head, but the full view is great. Side mirrors are coming off! Yay!

metroschultz · 01-07-2008, 11:31 AM

Greetings, Glad to have you with us.
I LOVE the "K" cars. I've owned too many to count(sold all of them)
I usually buy 'em cheap and fix 'em up. Got one in the garage right now. 1993 Dodge Shadow. Needs a crankshaft. Paid zilch for it. drove it home.
Actually planning on working on cleaning the garage this week so's I can get it running right again.
If you are not too far from the beach (Virginia Beach, that is) look me up. I think I may still have some parts in stock for your car. I know I've got a set of side mirrors, but I also know that you won't want those. (mirror delete= less drag).

heres a quick shot of the car and messy garage.
Not bad for a freebee.
Have fun. S.

What exactly is a "K" car? - see discussion in another thread.

Daox · 01-07-2008, 11:53 AM

Welcome to the board Caelum Rex. I look forward to seeing what you do with the Omni.

Caelum Rex · 01-13-2008, 08:47 PM

Thanks for the welcome guys. Too bad I am in Colorado or I would take you up on the parts for the Omni.
I have been quite busy so sorry for the dely in replying

AndrewJ · 01-13-2008, 11:50 PM

Aaaahh, the lovely and talented Dodge Omni.

I had an '87 once.

I beat the crap out of that thing.

Of course I had that car back when gas was less than $1/gallon. I don't really remember keeping track of the mileage.

Oh, and be nice to your doorhandles

Those were becoming a pain to replace every 6 months.

Stan · 01-14-2008, 01:28 AM

Quote:

Originally Posted by MetroMPG

That said, running a vehicle off its battery alone is a pretty extreme mod. Yes it will save fuel.

I don't mean to be rude...but no, it won't.

A study done more than 10 years ago and written up in Circle Track magazine showed that the typical carb'd 350 CID V-8 engine loses about 1 hp per minute with the alternator's field switch turned off (in other words...running on pure battery). That directly translates to modern EFI engines losing power with the alternator cut off...and hence, decreased FE.

So don't do it. The best way to maximize your engine's performance is to ensure the electrical circuit is operating at full capacity. Trying to increase FE by shutting off the alternator is false economy...just let it run. When the battery is full the alternator pulls just whatever the pulley and bearings require, and nothing more, so IMO this is one area that one needn't bother with. There are too many areas on any car where bigger gains are to be made to bother with this one...

MetroMPG · 01-14-2008, 01:37 AM

Quote:

Originally Posted by Stan

I don't mean to be rude...but no, it won't.

I've documented quite clearly that it will, and have corroboration from others who have done it as well (including a Jetta TDI owner).

It actually turned out to be the single most effective mod I've done to date. Most of my driving in the past 2 summers has been alternator-less (with a combination of solar/grid recharging).

There are significant caveats, however. See http://metrompg.com/posts/alternator-optional.htm

MetroMPG · 01-14-2008, 01:48 AM

I'll add: there are probably signficant differences in electrical consumption between the engine in the test you read, and my 3-cyl weed whacker motor.

As well, the magazine was probably testing at peak hp loads; I wasn't anywhere near that.

So let's say I wouldn't try to claim that it would definitely work to that extent on every vehicle. And I generally don't recommend it without a lot of warnings anyway