Ok this may sound like a dumb question, but has anyone ever tried to put an electric clutch (sort of like an A/C clutch) on an alternator?

A 115 amp alternator will draw a little over 2hp from the engine when charging at capacity. Why not have an electric clutch that disengages whenever the car accelerates (or based upon throttle position, like 3/4 to WOT)?

You could even put an algorithm in the computer that would override this function if the battery starts to become undercharged, as a safety feature protecting your battery.

Hey, its only 2 ponies max, but you would think the factory would have thought of this.

They use an electric power steering pump - and it only saves a couple hp.

Every little bit helps, right?

 

i guess, but it seems like it would be needlessly complex... also, if there is no power at all, the clutch wouldn't engage and it wouldn't start...

i'm thinking that it's one of those things that just gives you one more thing to break

 

Get an underdrive pulley,

 

totally not worth the gains. the computers need the alternator to run. if u took that link off at full throatle the car woudl prob die

 

Really? I didn't know the Cobalt's ECM/TCM used AC power. I thought that they ran off of DC from the battery.

Why then does disconnecting then reconnecting the car's battery reset the computer?

 

yeah

14v > 12v

 

ROFL

alternators dont putout ac, they output dc

knowledge > u

 

it would run fine on the battery for a few mintues, but there really is no point to it.

 

id also like to metnion its only under full loan when you got a system running

 

it doesn't require MORE engine to drive it when you're drawing more power... it's pretty constant... some drag cars run without one in order to save power... but then again, some run without a battery to save weight.... best bet, don't worry about it.

 

Alternators put out a/c power. The rectifier converts a/c power to d/c to charge the battery.

Only generators put out d/c power.

 

^^(2 post up)ur wrong i just dont know how to explain it. the more load on the alternator, the harder it is to spin

 

then y does the alternator directly connect to the battery?!!? you cant hook ac up to dc. alternators put out dc

 

Modern day car charging systems use an AC alternator because the field coils can be adjusted for current depending on engine speed, and give a constant voltage output. This is then rectified, and the battery serves as a filter.

 

thank you. the alternator isn't intelligent enought to adjust for voltage. it puts out it's amount of power based on RPM.

 

ok u were correct that alternators create ac current but not in the sense you t hink. the actual output from the alternator that goes to the battery is dc.

 

You are correct. I was just being a dick.

My point was that the car's computer runs off of d/c so it can run without an alternator present. If you doubt it, just disconnect the alternator or pop the alt. fuse briefly - just for kicks and giggles.

The alternator has a built in regulator/rectifier so it's only apparent output is d/c - not so on motorcycle alternators which usually use a seperate rectifier.

I guess the 1hp or so saved wouldn't be enough to worry about unless you're building a dragster.


But what about reducing the rotating mass of the alternator, wouldn't that be the same as a light weight flywheel, or pully? J/K

 

I wonder if you could reduce the resistance of the alternator electronically by not energizing the field coils when accelerating hard. No magnetism = less resistance to spin?

 

Let's break out the math again.

Let's say your system is at full power draw from the alternator.

Let's assume it's a 150A alternator.

150A * 12V = 1800W

1 hp = 746W.

1800W = 2.41 hp

That's at 100% draw and 100% efficiency, the first is highly unlikely and the second is impossible.

So worst case scenario, you lose like 3-4 hp from the crank.

 

We have a 115 amp alt. and it produces 13.88V. The rectifier regulator loses about 20% to heat. But it never runs at full output, only about 50%

So it's really only 1-2hp loss from electrical load, plus whatever angular momentum loss from rotating the mass - about the same effect as the electrical load.

Just an mental exercise really.

 

Are you absolutely sure it runs at 13.88 volts???

I have a Voltmeter in my trunk, and when the car is running it shows well over 14v

 

It's supposed to be regulated to 13.88 volts with a fully charged battery, but I never measured it myself. The voltage will fluctuate depending on the condition of the battery. If your battery is very low, or has a bad cell it could go over 14.5 volts. If you're running much over 14v you should have your battery checked. Where are you measuring the voltage, across the battery terminals?

 

Yup

Im not saying that it always runs over 14, but I have seen it do it quite a few times

 

Your battery acts as a buffer to filter out voltage spikes. Frequent spikes over 14v at the batt are normal, especially during or immediately following heavy use like: lights, stereo, defroster, and don't forget the fog lamps, steering, TB and computer load (with all the sensors) - I guess our car does put a fairly heavy drain on the electrical system. It should settle at just under 14v most of the time. The point is that our charging system is a dynamic system, responding to load and adjusting constantly. It if far from precise, and needs the battery as a stabilizer. Never try to remove the battery while running as this will cause the voltage to spike and will probably fry your computer. Running with a dead cell will also fry the regulator/rectifier portion of the alternator.

Right now, I notice my lights dim when my e-rams kick in (120amp load) so I'm going to try some additional grounding, either a red top Optima or a Odyssey pc925 battery, and possibly a 1mf audio capacitor to handle the surge of power needed.