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Disconnecting generator/alternator; How will this improve MPG?
Topic Started: Nov 21 2009, 02:25 PM (2,715 Views)
iamgeo
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Big League

Will someone explain in detail how disconnecting the generator(not by removing the belt) will reduce drag/load on the engine and increase MPG?
Edited by iamgeo, Nov 21 2009, 02:27 PM.
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mwebb
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FOG

it reduces calculated load
so Injector Pulse Width can be shorter
so less fuel is consumed

you can see it
connect your scan tool and turn on all the lights and heater blower while watching
the calculated load PID

how much will be saved ?
who knows ?
your results may vary

and if system voltage drops below 9.6 volts ....
maybe a higher number in your car ...
things like fuel pump and ECM and IGnition stop working .
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Cobb
BANNED

I had the same idea to use a deep cycle battery and upgrade the heat lights to hid so they do not dim.

A guy on another forum I read hooked a solonoid to it and the ac kill switch under hte gas petal, so when he floored it he got an extra 3hp from the alt being disconnected, but his lights dimmed.

What mwebb is saying is that the car conserves fuel if it doesnt have the full power it needs electrically. So, its a 2 fold save. 3hp from not having to spend the alt and the engine is further leaned out.

Not sure about the geo, but some hondas have a lean burn mode that if entered lets you get extreme fuel economy.
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billy508
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billy508

Be careful Some alts dont like having the load disconnected when they are running. Some times marine systems run into trouble when battery switches are turned to the off position and the engines are running. On The old Chevy one wire alts, you can switch the b+ wire going to the regulator. That way you can forget and run your battery down on a nice rainy night. :drivin :drivin :drivin Low voltage is not your friend. Mweb may correct me if I am wrong but most systems are looking for 13.5 to 13.8 to work correctly
Edited by billy508, Nov 21 2009, 10:55 PM.
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Metro Fanatic
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I'm experimenting with this right now. Check out my personal blog on this site. When I toggle the alternator 'off' (belt still attached)...you can hear the difference in workload on the engine. Right now I'm leaving the altenator on while coasting down hills and flip it off when I'm driving level or climbing. Here's a pic of my mod control panel. (silver switch is alternator disconnect) Batt voltage displayed on bottom right and solar input on top.
Posted Image
Edited by Metro Fanatic, Dec 27 2009, 09:04 PM.
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rmcelwee
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Do our alternators not already "disconnect" when not needed? I thought all modern vehicles did that. If ours do, the savings will be very minimal. I think a rack of batteries charged at home by solar power could give you a small amount of fuel savings but the investment would far outpace the savings.
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Woodie
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Yes, they do, and we've already had this discussion once. Any savings are going to be miniscule while the chance of screwing up the car are real.
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john.
Elite Member
[ *  *  *  *  * ]
Altenators output varies by demand. If you turn on wipers,heater, rear defrost, lights the amperage output of the altenator goes up to keep the voltage at around 14v.
I agree that running with less than ideal voltage to electrical items is not the way to go.
I'm not saying there isn't a gain to be had, but electronics and the battery work and last longest when proper
voltges are present.
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mwebb
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billy508
Nov 21 2009, 10:52 PM
Be careful Some alts dont like having the load disconnected when they are running. Some times marine systems run into trouble when battery switches are turned to the off position and the engines are running. On The old Chevy one wire alts, you can switch the b+ wire going to the regulator. That way you can forget and run your battery down on a nice rainy night. :drivin :drivin :drivin Low voltage is not your friend.
Mwebb may correct me if I am wrong but most systems are looking for 13.5 to 13.8 to work correctly
...."What mwebb is saying is that the car conserves fuel if it doesn't have the full power it needs electrically.
So,
its a 2 fold save. 3hp from not having to spend the alt and the engine is further leaned out. "....


..................
no ,
i am not saying that at all .

the system will
NOT OPERATE LEAN ever
as long as the 02 sensor is still functioning and the system is capable of fuel control

i am saying
at some point as system voltage falls
voltage will drop low enough that the system will stop working
ignition will not produce a strong enough spark to to what it has to do...
the fuel pump will stop pumping fuel ....

the system WILL NOT be running at peak efficiency when operating at voltages lower than it is designed to operate at.
how INefficient it will be depends on how low voltage is at the time .
=======================================================
having said that
some people seem to be getting increased FE values using deep cycle batteries that can hold system voltage ABOVE the minimum
needed for length of the trip .
while operating with the alternator switched off

but they must recharge the batteries often to keep voltage above the minimum .
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iamgeo
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Big League

I talked with a well known and trusted auto repair center owner in San Antonio about this subject. The thing that concerned him most was not the improvement in fuel mileage but the effect on the electrical system and computer. Turning the system back on while driving can create an electrical surge that can pretty much wreak havoc with the computer and/or other devices in the car.
If you do go this route be sure to keep generator off while driving and turn it back on when car is shut down.
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Cobb
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Did anyone else read the part about the second meter measuring power from the solar input?
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Murf 59
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Metro Fanatic
Dec 27 2009, 07:36 AM
I'm experimenting with this right now. Check out my personal blog on this site. When I toggle the alternator 'off' (belt still attached)...you can hear the difference in workload on the engine. Right now I'm leaving the altenator on while coasting down hills and flip it off when I'm driving level or climbing. Here's a pic of my mod control panel. (silver switch is alternator disconnect) Batt voltage displayed on bottom right and solar input on top.
Posted Image
There's a blog on this site??? I just reread this whole thread, I don't see it
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bogs
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Duct tape heals all wounds

If you click on MetroFanatics name, you get some information about that person, including the link to his blog http://geometroforum.com/blog/main/638548/ :)
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Metro Fanatic
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Murph, I must have mistyped. The blog is my personal blog that Bogs is talking about just above. I can't wait to see how/if this impacts FE and overall performance.
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Metro Fanatic
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Hot off the press. My first fill up since using my newly installed alternator/generator dissable switch set a new MPG record for Bullet. 62.93MPG. I only ran about 80 miles since the installation was complete so I'm hoping to get maybe another 1 or 1.5MPG that this in future tanks. I love this stuff!
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