white93vette

I'm confused as to how an electric water pump can save engine power. Seems to me that power is power. Does it really matter if you're getting that power directly from a pully/belt off the motor, or if you're getting it from an alternator producing the electricity from a pully/belt off the motor? Has it been documented that using an electric water pump gives you more power? Just curious.

87-ZZ4

The power is there from the alternator anyways, some of the excess floats the battery, the rest is lost.

I would say you would save HP, but how much I would guess would be low.

Rich

Nathan Plemons

YES! Something to the tune of 12 hp to the rear wheels.

The fact is that your alternator pulls a constant drag on the engine, so does an engine driven water pump. The alternator can however produce more power than is needed to power all of your accessories and it is wasted. It isn't all directed to the battery or you would boil it dry.

By eliminating the engine driven water pump you are reducing drag and taking advantage of the extra output of the alternator.

white93vette

I'm not so sure that is true Rich. The alternator has the ability to produce a certain amount of current, but it is only producing that when there is demand. The analogy I'd use is that of a centrifugal pump. If the pump is dead headed, and the impeller is just spinning but not actually moving any liquid, it is very easy to turn. The same is true of the alternator. If there is no current draw on the alternator, it is very easy to turn. If there is a large current draw, it is more difficult to turn.

white93vette

Nathan,
If all the power from the alternator isn't directed to your battery, where is it going?

Nathan Plemons

As far as I know the regulator inside the alternator dissipates it as heat. BTW I don't think your analogy is very accurate, it doesn't take a lot of force to push electricty. To prove this connect a hand generator to a light bulb with a switch in the circuit. Start turning the crank, it won't get harder to turn the crank when you flip the switch on.

white93vette

Nathan,
You point is well taken. Though I always thought that the regulator only regulated the voltage, and had little to do with the current draw. I used to drive a VW Golf. When I turned the lights on, there was a noticeable strain on the motor. But if the alternator did dissapate the extra power as heat somewhere, that would explain it to me.

Thanks!

white93vette

Nathan,
I just thought of another analogy that might make more sense. The commercial electrical generating station. The generator runs at a constant speed, day and night, to produce 60HZ power. It takes much less fuel to run the generator at night when few people are using electricity then it does to run it during the day when many people are using it. Just some food for though.

Nathan Plemons

I could be completely wrong on what/how a regulator does it's job. That's just a guess on my part that I thought makes pretty good sense. I'll ask my dad, he's the one retired from the electrical industry.

Chris@SD

This is a proven mod that produces on average 8 RWHP or close to it.
My guess is the gains will be had through efficiencies.
White93Vette is correct though. It takes energy to make energy. Nothing is free in this world.

Nathan Plemons

The man hath spoken.

The regulator keeps you from over-charging your battery. It basically measures the voltage of the battery and the output voltage of the alternator and will allow it to charge if the difference in voltage is great enough. Once the battery reaches a certain level it stops the alternator from charging the battery. Where exactly it directs the current after that he's not sure.

The electrical components basically draw off of the battery, so by adding accessories the alternator will simply have to charge the battery more. This is not a problem until you exceed the output rating of the alternator, in which case you will need a higher output alternator. Basically one that puts out more power at the same RPM, this will be harder to turn.

Makes sense if you think about it.

Nathan Plemons

Yes, but you are wasting some anyway, you are just taking advantage of it. That's what makes this mod so cool, if your electrical system has the capacity, this one really is free horsepower.

white93vette

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:[/color]<HR><font face="Verdana, Arial" size="2">This is a proven mod that produces on average 8 RWHP or close to it.
My guess is the gains will be had through efficiencies.
[/color][/QUOTE]

Chris,
That makes some sense. Perhaps the pully driven pump looses some effeciency in belt slip and heat loss. I'm not trying to be stubborn here. I'm just trying to make some sense of it! Thanks for helping me understand.

white93vette

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:[/color]<HR><font face="Verdana, Arial" size="2">Once the battery reaches a certain level it stops the alternator from charging the battery. Where exactly it directs the current after that he's not sure.....Makes sense if you think about it. [/color][/QUOTE]

That does make sense Nathan. The only part I'm still confused about is where the current would go when it's not directed at the battery. Seems like that would be a lot of extra current to disapate as heat.

SLEV89

Marc,
you are correct in your analogies.
If you completely removed all electrical load from the alternator, the alternator would provide very little rotational load to the engine (when there's no current demand, the electricity isn't "going" anywhere).
as current flow (demand) increases in the alternator, an induction (magnetism) is built up in the windings/core of the alternator (ie. the alternator is now 'working'). it's this induction that the engine sees. induction by definition is a tendency to resist any change in current. since an alternator is providing Alternating Current (diodes and Regulator give the DC) you can see how increasing the amperage draw, and thus the induction, will increase the mechanical load.
Like a Honda Generator or a Gas driven Electric Arc Welder, when they're 'working' the Gas engine has to compensate by increasing its throttle.

It's a good question as to Electric Water Pump vs Mechanical; one would almost think it was more inefficient, since there's more devices involved. but then, the electrical unit is probably pretty much 'mono-speed' whereas the mechanical speed is varying with engine speed. at higher speeds, the water mechanical pump may be 'too fast' for what is required, and therefore absorbing too much engine power. the coolant's duty cycle would be the same in any case (% time in radiator vs % time in engine) so why not run it slow(er), so long as it doesn't go past it's extreme at the engine discharge.

sorry about the blah blah windbag thing
the first paragraph is kinda factual though sKetchy
the second is purely supposition

silver & red CE

re: how an alternator works:

Instead of permenent magnets and brushes in a generator, and alternator varies the current in an electro-magnet. By varying the current in the "field coil" the magnetic field is varied and the power output at a given RPM is controlled.

The alternator's voltage regulator modulates the magnetic field in the alternator to compensate for load and RPM variations.

The alternator only delivers the power required to drive the load, there is no extra power to be disipated. BTW, the power company's generator works with the same principal as the automotive alternator, except the field current is on the order of 6000A instead of 6A.

I think the main benefit of an electric H2O pump is that the power draw is constant where as a belt driven pump's power draw goes up as the RPM increases. At high revs the belt driven pump is a big draw compared with the alternator load (constant).

Eric

white93vette

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:[/color]<HR><font face="Verdana, Arial" size="2">as current flow (demand) increases in the alternator, an induction (magnetism) is built up in the windings/core of the alternator (ie. the alternator is now 'working'). it's this induction that the engine sees. induction by definition is a tendency to resist any change in current. [/color][/QUOTE]

SLEV89,
You certainly said it much more eloquently than I! I certainly belive, from the posts above, that it is an HP saver modification. But nobody's been able to explain why. But thanks for all the replies.

white93vette

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:[/color]<HR><font face="Verdana, Arial" size="2">I think the main benefit of an electric H2O pump is that the power draw is constant where as a belt driven pump's power draw goes up as the RPM increases. At high revs the belt driven pump is a big draw compared with the alternator load (constant).
[/color][/QUOTE]

Hey Eric! That sounds like it might be it. So in effect, you are consuming more power at low RPMs with the electric pump vs. the pully pump, but less power at high RPMs. I think I'm satisified with that answer.

Thanks!

Chris@SD

Let me throw a wrench into this. The HP gains that I have seen are across the whole RPM range, not just at higher RPM.
To me, the fact that the gain is across the whole RPM range is a pretty good indicator that we are talking about efficiencies.

I forgot to answer the above earlier and it has been said now, but the alternator will only produce what it needs. There is no extra energy to disapate. If it did produce a constant rate of power and need to disapate the extra, I immagine that the heat would be enough to melt the car down to nothing inside 30 minutes.

Nathan Plemons

You are right, about the heat thing. Like I said that was only a guess, and an incorrect one at that. Somebody said the alternator will only put out as much power as is needed, in this case we are just adding a little more to what is needed. It would appear that the alternator is just a much more efficient design than we are giving it credit for. It may become harder to turn under a higher load, but that is much less than the drag induced by a mechanical water pump.

As was also stated, the electric water pump will draw a constant current, regardless of engine RPM. Thus as the engine accelerates (in a generator situation) the power output potential would increase while the draw remained the same. Where as a mechanical pump would create more drag as rpm increases.

Another consideration is cavitation. Submarines use large propellors that move slowly, if they move too quickly the water can't fill in around the blades quickly enough, creating a vacuum and a line of steam on the trailing edge of the blade. This is not very efficient, and for a submarine makes a lot of noise as the steam bubbles collapse under the sea pressure. Obviously noise wouldn't be much of a problem (unless it was detected as false knock) but the effeciency is reduced. Therefore I would have to think that an electric pump that moved water at an optimal speed all the time would also provide the best cooling characteristics for the energy spent to turn the impeller.

As you can tell I'm interested in submarines, but I never thought I would use any of that knowledge and try to apply it to a car.