Idea for recovering Energy from Idling engine
 

Hi everybody, I am wondering if if would be possible to fool the computer so that it has a strong bias on kicking on the alternator while at idle.

If I know where the voltage reading that controls the alternator is, then I could add and subract a bias voltage depending on whether the engine is idling or not idling.

Suppose normally the voltage reading of V is taken

V= Vbatt

If this were to be changed to

V= Vbatt - Vbias where Vbias -0.5V for engine at idle and +0.5 V for engine not at idle .....

then there alternator should likelier kick on at idle.

Any idea how hard it would be to do this?? :confused: Not sure if it makes a difference, but my car is OBD1.

Combined with an HHO system, that can turn battery energy into mechanical energy, I think this might gain significant mpg's

Re: Idea for recovering Energy from Idling engine
 

Having the alternator increase output when its not required, will result in overcharging your battery and decreased life. Also, the alternator is not capable of full output at idle, so if you were to significantly increase the load at idle you will deplete the battery.

Re: Idea for recovering Energy from Idling engine
 

Yeah, yours being an older vehicle (you said OBD1) I am not sure but in newer vehicles the charging output is controlled by the PCM.

Re: Idea for recovering Energy from Idling engine
 

The way I read it, eee understands how the computer controls the alternator and wants to try changing that.

It shouldn't be too hard to monkey around with, but I don't think that trying to kick it on during idle will help anything. When idling, it's not using any more fuel than is necessary to idle; adding drag will just increase fuel consumption. At best it is a zero sum game.

Barking up a similar tree, here's an idea that might work: Get a higher-output alternator and run it full-strength during DFCO.

Re: Idea for recovering Energy from Idling engine
 

But the HHO is certainly a winner! :thumbup:

Re: Idea for recovering Energy from Idling engine
 

Well, as I understand it, at idle the typical engine (anything aside from diesel and direct injection) is running at minimal efficiency while being choked off of air; the purpose is only to keep the engine spinning, and, for the given (engine displacement) * (idle rpm) * (air density), throw in enough fuel to avoid a lean burn condition. That is why most gas engines on the road use ridiculous amounts of fuel, on the order of typically 1/3 gallon per hour (more like over 1/2 gph for V6's and higher) to idle. You're running essentially a vacuum pump.

I usually turn off the engine when I expect to be sitting over a minute or so. But it gets tiresome, and some say, wearing on the starter motor. It would be nice to have an automated system for all these shorter traffic light idles.

My though is that it isn't a zero sum game. I'll increase the efficiency of idle by letting a tiny bit more air (raising the manifold pressure) into the cylinders, and using a tiny bit more fuel to charge the battery. What tiny bit I loose in fuel at idle I expect to more than offset during driving, as the alternator will kick in less frequently while driving.

I'm not so concerned about battery life and willing to an old sacrifice battery for this experiment. The bias voltage can always be adjusted to smaller voltage if that becomes a concern.

Anyways, I have no idea yet where the circuit is that controls the alternator.

Thanks all, for any help and input so far :) .

Re: Idea for recovering Energy from Idling engine
 

I know for a fact BMW and Honda have developed "smart alternator controllers" that relieve the alt at accel and cruise and work it harder on decel and idle. Claimed fe benefit is a couple percent.

Re: Idea for recovering Energy from Idling engine
 

I think you'd have a much higher benefit reducing alternator load during acceleration than increasing it at idle. idle also is going to have the lowest BSFC so doing your charging there is going to use more gas per watt/hr into the battery than while driving. Right idea though. makes me wonder if I can rig something up with my megasquirt...

Re: Idea for recovering Energy from Idling engine
 

It has the lowest BSFC because there is no load and the throttle is choking off the air as there is no load. As soon as the load of the alternator is applied the throttle will open up. If you look at the chart and extrapolate to an idle rpm of ~1000, then you'll see the consumption is going to be around 230 versus the theoretical optimum of 206 (for whatever typical engine was used in producing the chart). Anyways, I'd consider that pretty much near optimum. Even if the alternator load were too light, and it was chugging up 300, that's still close enough to the peak that it'd be worth it imo. Point is, the throttle position has much more to do with BSFC than the rpm.

Re: Idea for recovering Energy from Idling engine
 

Oops that may have made little sense, as I totally forgot to provide the link; https://upload.wikimedia.org/wikipedi...mption.svg.png

See first figure in:
https://en.wikipedia.org/wiki/Brake_s...el_consumption