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

[Formula413]

Originally Posted by Nerys

I was wondering exactly that for a different reason.

I was wondering what it would take to replace the crank pully with a AC CLUTCH pulley.

this way I could simply turn it off and leave the belt etc.. intact and with the flip of a switch engage the clutch and engage the stock pump and alternator.

is that possible? how might I go about that?

Wouldn't controlling the power to the field coil accomplish basically the same thing?

[Nerys]

no because you would still have the drag from the water pump (rather significant) and you would still have the drag from the very act of spinning the pulleys and the belt itself.

I want to eliminate ALL of that 100%.

a clutch would get me REALLY close to 100% without having to actually remove anything.

thats why I want the clutch on the CRANK and not the pump or alt. I want to make them "STOP" no motion. the only drag would be the drag in the clutch assembly itself. then I could just push a button and resume normal operation (long trips or letting someone else drive the car etc..)

[Formula413]

Originally Posted by Nerys

no because you would still have the drag from the water pump (rather significant) and you would still have the drag from the very act of spinning the pulleys and the belt itself.

I want to eliminate ALL of that 100%.

a clutch would get me REALLY close to 100% without having to actually remove anything.

thats why I want the clutch on the CRANK and not the pump or alt. I want to make them "STOP" no motion. the only drag would be the drag in the clutch assembly itself. then I could just push a button and resume normal operation (long trips or letting someone else drive the car etc..)

Oh ok I gotcha, that's gonna be tricky to do, the crank pulley often doubles as the balancer

[Mario_Marques]

Its possible, but i dont know what exactly parts u need for your car, but there are cars with those systems on the street, vw's bmw....
There's available in the market for some cars, lightweight pulleys.

[MetroMPG]

Originally Posted by Mario_Marques

One important question, does your alternator has clutch assisted pulley?
Do you have hidrailic assisted steering?
Thanks.

My car (Geo Metro/Firefly) has no clutch on the alternator pulley. Steering is manual.

[steffen707]

Originally Posted by MetroMPG

Assuming it's turning at the same speed as when driven by the engine, it'll use the same amount of fuel regardless of hooking it up to a wheel or a turbine (which won't work - it would require a really big swept area). There's no free lunch.

The wheel-driven idea would cause it to be under-driven at low speeds, so battery voltage may drop and you may save fuel at those times, but the load on the alternator will be higher as the RPM increases and it puts the lost energy back into the battery, so fuel consumption will go up. I can't see any real savings from that approach.

Also worth emphasizing again: discharging a starting battery will dramatically shorten its life. Going alternator-less may be an effective efficiency mod, but it's definitely not a money saving mod unless you have a source of free or cheap batteries.

I thought if you had a deep cycle battery this wouldn't be a problem, because they are designed to be depleated and then recharged?

[steffen707]

Originally Posted by MetroMPG

Good stuff, thanks. That gives me some ideas of what to look for. I'm just headed out to see what's at the local auto parts store. I want a non-energized, manual switch / disconnect like some of those, rather than a relay/contactor setup. I won't be switching the thing on/off very often, so I don't need the convenience of a remote dash mounted solution. Opening the hood and flipping a simple switch is fine.

I promise to read all 20 pages, but I did read on the "plug in blackfly" website that the civic vx has parameters to shut off the alternator. Any idea where blackfly, or Randy, who he quoted got this info?

I have a civic vx engine (d15z1) in a 96 civic hatch and have noticed that when going slow at night the lights are dim, i take my foot off the gas and coast, lights get bright. I think his info about the VX alternator shut off is my "problem". Turns out it might be for better gas mileage.

What I was thinking is disconnecting the alternator whenever the brake isn't pressed with a relay. That way when you're coasting to a stop, it uses the alternator as a brake and charges the battery a little, but when you're going you don't have that drag. That in conjunction with charging the battery at home might net a nice gain overall, and give more distance per "home charge". Also it wouldn't drain your battery as much so you might gain more overall years of use per battery.

EDIT: I just realized 95% of the time I stop i just coast with car in gear, no foot on brake and then apply the brake 5 feet from the stop sign. Might need to use a microswitch that disconnects it when the throttle is all the way closed......YAY!

[steffen707]

Originally Posted by MetroMPG

For this approach to make sense financially, you would neither either (or both) of:

1) fuel that is much more expensive than it is now;

2) a supply of free or cheap batteries.

Fortunately, I've found (2).

Today, with two 6v "junk" batteries (from the forklift company) in series to make 12v, then in parallel with the existing 12v starting battery, I did a 46 mile / 74 km alternator-less round trip.

Starting voltage: 12.68
Ending voltage: 12.40 (batteries resting for 1 hour)

11.7v is "empty", so I used 26% pack capacity in that trip, with light accessory load: wipers occasionally; heater fan occasionally; lights; occasionally; plus engine overhead, turn signals & brake lights.

Assuming similar electrical loads, my total range to 100% depth of discharge is about 177 miles / 285 km.

I stumbled upon this site that contradicts some of your voltage numbers.
Deep Cycle Battery FAQ

They seem to say that zero is 10.5volts, 30% left is 11.75, 80% is 12.42.

I don't know what is right or wrong, but you might have a longer range than you think. I know discharging less is safer for the longevity of the batteries though.

[MetroMPG]

Originally Posted by steffen707

I stumbled upon this site that contradicts some of your voltage numbers.
Deep Cycle Battery FAQ

They seem to say that zero is 10.5volts, 30% left is 11.75, 80% is 12.42.

I don't know what is right

It's hard to say exactly, because it depends on the load you're putting on the battery.

You could take a battery resting at, say 11.75v (30% state of charge, says that page) and immediately drop it to 10.5 (empty) by connecting a big enough load to it - something like engaging the starter motor. (Below 10.5v, you risk cell reversal - permanent damage).

I must have taken my full-to-empty figures from some other chart that took a heavier load into account.

A better way for me to do this would have been to monitor voltage under load, right down to 10.5. Then I would have known my total "range" under those particular conditions / usage.

[steffen707]

Originally Posted by MetroMPG

A better way for me to do this would have been to monitor voltage under load, right down to 10.5. Then I would have known my total "range" under those particular conditions / usage.

Yeah but then you run the risk of hurting your batteries. I think i read that you took the belt completely off, or maybe you removed the whole alternator as well.

But that's why I'm going to try just disabling it, that way if I run into a situation where i'm going to not have enough range, I can just flip the alternator back on and finish the trip.

Have you maintained that 10% increase in mpg over the long term, compared to your previous long term numbers?

I'm sure if you did other mods to the car post, alternator delete it would be hard to pinpoint what savings is coming from which mod.