Since it seems like all the OEMs are doing this, I thought I should ask, has anyone here done this yet?

Doesn't seem like it would be too hard to implement, re-arrange some code so that the alternator charges only under certain conditions.
Just was reading about this topic and figured I would ask since a lot of guys do some neat stuff here.

Edit
on second thought it's starting to look a lot less worth it after further research

 

idk about changing the code to control the alternator,(my alt is not connected to the computer) but what i did to help keep my et's close for bracket races,(bat condition can change a lot. plus we all like a few more HP) is to place a micro switch on the throttle body to basically turn off the alt at WOT, via a relay. works very nice, smokey Yunick talked about something like this in one of his books.

 

Right, it's not connected to the computer, but it wouldn't be too hard to connect it to a relay that is grounded by the ecm under certain conditions. After looking into it some more, I'm not sure that it's worth it due to alternator wear and batteries not designed for it (maybe a deep cycle would work). What would also be neat would be one of those new alternators that doubles as a motor to give a few extra hp in acceleration. But the costs of the above would probably outweigh the benefit. Might be fun just as a science project.

 

you need to put a switch between the red wire on the connector with the brown and red wire.
disconnect the red wire and the alternator will stop loading. reconnect in and it will load again.
only thing you need now is somekind of TPS sensor switch/relay.

 

well it depends on the type of alt you use SI or CS, but it is vary easy to do and it helps quite a bit. i believe for any1 just looking for a few cheap hp it's a great idea.
but you always want to make sure the relay has to be energized in order for it to shut off the alt, that way if the relay fails you wont be left without it charging. as for it being hard on the alt i have been doing it for 2 years same alt same bat, it should not be any harder on it then when you start your car on a cold day.
on the SI alt's just switch the sense wire (mostly red) with the relay
on CS it can very a bit if you have the CS-144 and up but the most common is the CS-130d it does not have a sense wire cuz that is also the bat wire do not switch the bat wire it will work but it will kill the regulator, there is a lamp wire normally brown and if it is unhooked it will shut off the field, switch that one with the relay, sometimes it is the only wire in the connector, makes it easy to ID

 

I think you made the same mis-read that I originally did. This is when in deceleration, not acceleration.

Not sure why some car makers do this. To me it doesn't make sense, unless it is to help prevent the engine from stalling during DFCO.

RBob.

 

I'm confused now. To clarify, my original post was in reference to allowing the car to just run off the battery under most conditions in order to conserve fuel. Then when it is sensed that you are decelerating, the code enables the alternator to charge.
Of course this places more load on your alternator and batteries. Since the battery is frequently being discharged more than normal, and the alternator has to provide more amperage than normal to catch up.
I think things get a little tricky in that you'd probably want a transformer to boost the voltage on battery power so you don't get dimming lights and whatnot. And obviously, you'd have a lower voltage limit and other conditions that would enable the charging regardless of acceleration/cruise/decel.

They have also worked in using the alternator as a small helper motor during heavy acceleration demands. You could probably find a good balance of decel charging and accel power augmentation that would increase fuel mileage.

Sort of like hybrid technology on a much smaller scale. The OEMs are playing around with this on some new cars. Of course I suspect their alternators are far more robust along with their batteries.

I'd be interested to see how much power one of our alt's would put out if used as a motor

I was just thinking of ways to conserve fuel.

 

indeed i did misread this post, worst part is i read it a few times. yep i'm a bright one.

interesting idea Pablo there is not much parasitic loss from the alt to make that big of a differance in MPG but i guess over a long drive it would make a difference, i think the power steering would have more affect. and the alt as a small motor that is almost crazy enough to work, i wonder if i could experiment with this using my tractor, it has a starter generator idk it does intrigue me. worth looking into.

 

BAS is not only interesting, it looks to be fairly low-investment, at least if GM MSRPs are anything to go by. controlling it, that may be a different story.

well, if you're decelerating, you might as well have the alternator going full bore, since it should add a bit of drag to the engine by increasing the amount of power it makes, helping with engine braking. that and whatever power the engine is making in those conditions isn't really being used to move the vehicle, so it's almost free power.



me..... i'm not so certain if i would attempt something like this, i'd much rather know my battery is fully charged and have full voltage at all times than risk being in a situation where the battery is too discharged to start the engine on it's own.

 

That is where careful implementation comes in, a lower voltage limit would most certainly be one of the parameters to enable charging regardless of conditions. Another consideration would be that all of its failure modes should result in standard charging operation.

The gains cited for GMs system are pretty substantial http://en.wikipedia.org/wiki/BAS_Hybrid

I don't expect anything approaching that, but it might be worth it even for single digit % gains. Admittedly I don't know how feasible it would be to use the alternator as a motor. I imagine you would need a brush-less controller for it but there are multiple sources for that. I also wonder what kind of rpm the alt would turn at 12 volts. Taking cues from the RC world, a brushless controller should not be hard to tie in to vary the speed, and if necessary, a transformer to optimize the voltage. This is all if you wanted to go to the next step of having it assist you in accel.

Some ecomodder guys have experimented with alternator delete and have seen 10% gains in economy, granted their engines produce a lot less torque so I would expect our gains to be less
http://ecomodder.com/forum/showthrea...g-gain-98.html

Moving to a country with close to 10 dollar a gallon gasoline got me thinking about it. People do some desperate things to save gas when it's this expensive. Fortunately I don't have to pay that price because of a military benefit, but it's still expensive nonetheless.

 

OK, totally confused now. The wiki article talks about hybrids, which uses regenerative braking to charge the batteries. This make sense as the vehicle is an electric/gas hybrid.

So now I'm back to my original post, which I deleted, that a gas powered engine when under WOT needs the full vehicle voltage. This is to improve both the fuel pump and ignition performance.

RBob.

 

As a science project it would be cool. Or 1/4 mile race car may see a tiny gain if it were switched off at WOT. But for a street driven car it's a waste of time and won't have any noticeable gains, just bad results.

There's just to much drain from car on battery to run properly without alternator. The battery's six cells and each puts out about 2.2 volts per cell. Fully charged battery in good condition measures 13.2 volts not 12... when running the system voltage is closer to 13.7 to 14.2 volts and starts to plummet without any input from alternator.

GM and other OEM go through great efforts to make EFI run under some varied voltages but running does not mean properly, look at injector voltage offsets written in to just keep car running. Then lower voltage lowers fuel pressure. Relays need certain amount just to stay on. Voltage readings on all sensors drop, readings are not correct and soon failure/engine dies

I have problems on older cars when doing EFI conversions just because of idle of older cars charging system not putting out enough voltage to keep battery charged. Depending on vehicle and condition of battery and alternator this can happen immediately at start up worst case, or best case start to deteriorate within minutes of idle with no accessories on. Add lights and A/C and effects on EFI system are almost immediate at idle because of loosing voltage. Only takes a minute or less in some cases to watch voltage drop to 10 volts and soon dies as I think relays just don't stay on anymore? Change out altenator to newer model with a good battrey and symptoms go away...

HTH!

 

Im not talking about wot performance. What my original post is about is essentially using regenerative braking to compensate for selective alternator use. This is not for racing. The point is to use the alternator in the same way that a parallel hybrid uses it's electric motor. as I am sure you know, an alternator should also be able to act as a motor. That said, there is no reason you couldn't skip the motor part and just implement regenerative braking. use energy stored by the battery to power the car until charging is required or when it makes the most sense from an economy standpoint,i.e decell. as far as voltage is concerned, an alternator isn't the only way to achieve full voltage. A transformer can give u the voltage you want. No alt. needed.

 

To reiterate, the point of this is not for wot performance. it is for fuel economy. whatever the car does in pe is not relevant to the efficacy of this system. Voltage is not a big deal, we are surrounded by transformers. what might be tough is determining whether or not even a deep cycle batt would be robust enough to make worthwhile. You could also toy with lithuim polymer batts and fortunately they have come down in price a lot. to have enough aH might really add up though. it's funny, seems like rc is ahead of everyone in technology in this arena of diy

 

In playing with RC cars with my son for 8 years till couple years ago when he got his license and a real truck and real rock crawler I understand.

I also understand the new hybrid technoligy in using generators for brakes to charge batterys instead of just making heat from brake pads.

But I don't understand what it is your really trying to do? I just can't see turning on and off an altenater on any type of regular car and seeing any gains? You can make anything more complicated, I know guys who program ECMs to run their refridgerators, but I don't know why other than they can, mine runs fine without a computer. Really i'm not being sarcastic or anything, do you really think there is something to gain here?

 

It's not what I'm trying to do, it's what oems are already doing. At least GM and Mercedes do this and possibly others. Maybe you should tell GM and Mercedes they are wasting their time? The BAS system GM is implementing has very significant fuel economy gains. Read the link I posted.

Lets back up and make sure we are on the same page:
You turn on your lights, and lets say your cooling fans are on. Lets say your headlights are combined 100 watts (might be a low figure) and that your cooling fan is 240 watts (no, electric cooling fans do not use less hp than a mechanical fan moving the same amount of air). Total is 340 watts.
340 watts = 0.45594751 horsepower
Your alternator only sees load to meet demand, so if your lights and fan were off, it would not see this load.
Your alternator is only about 60% efficient at best so to produce 340 watts of energy it actually requires .75 hp. I am ignoring other loads placed on the alternator like ignition system, ecm, accessories. Let's stick with .75 hp for right now.
At 65 mph, a thirdgen with a cd of .37 and a frontal area of 24 sq feet requires just under 25 horsepower to maintain speed. .75 hp works out to 3% of the power the car is required to generate to just power the alternator. Now lets say that the car gets 25 mpg at this speed, that extra .75 hp at about 30% efficiency ballpark of what an I.C.E. will do actually requires about 2.25 mpg less at 65 mph.
Conveniently enough, that works out to an increase in MPG of 9% which is almost exactly what the geo metro eco-modder guy saw by disabling his alternator and running back to back tests.

Now what is running the fan and the headlights in this scenario? The battery. The battery has stored energy. Yes it will run out, so how do we charge it without incurring an mpg penalty? You wait until the car is in deceleration and then you enable the alternator to play catch up. This will provide more engine braking.

Now the BAS hybrid goes a step further and uses the alternator as a motor to assist the engine. Lets say you could get the alternator to contribute .75 hp at 65 mph. Well now you've close to doubled your mpg gain from earlier from 9% to around 18%. Where is the alternator getting the electricity to generate that .75 hp? The battery.

No, I don't believe the alternator could be used to generate hp at steady state, but under light acceleration, it could prove to be worthwhile.

Yes this can be tricky to implement. There must be a fine balance between the amount that is discharged from the battery and the power the alternator can generate under the conditions when you want it to charge. There are surely lower voltage limits and load limits that would enable the alternator to charge regardless of cruising or deceleration. It would need to be set up so that the alternator was able to keep the battery topped up for the amount of deceleration the car sees. Obviously the more time spent decelerating, the easier it would be to implement this system and have it be successful.

The problems in this lie in the alternator and battery. For just the decel alternator charging, I highly doubt a standard battery would work at all. Fortunately we have a lot of battery options. Maybe the alternator could handle the increased workload. Some kind of temperature safety strategy is probably built into modern alternators to really keep them out of danger. I don't know.
To use the motor assist, I do not know if our alternators could handle it or how much heat the alt would generate in doing so. This is why I posted about it, hoping someone had considered the implementation of this technology.

 

MOST OEM vehicles disable the alternator and charging system at WOT. For that matter most of the Nissan's run a pulley that has a magnetic field run clutch on the alternators stator. When the PCM shuts down the current that creates the alternators magnetic field, the rotor in uncouples from the pulley and the pulley freewheels, reducing parasitic loses at WOT. My Ram doesn't have the clutch, but shuts off the alternator and compressor at WOT. Doesn't seem like much, but then again simply installing a belt to bypass the p/s pulley and compressor pulley is worth over 1 tenth in the 1/8 mile every time I have done it, and worth more if you have to make any kind of steering input in the first 60 ft, which is practically every run on a 2wd truck on street tires that makes well over 400 hp.