If you will go to stewartequipment.com, they measured the shaft HP of a mechanical water pump requiring 2.2 HP at 4000 rpm. Now if you can completely eliminate the hp requirement of the engine to turn any kind of water pump, then you will gain only 2.2 HP. Will you please explain where the additional 10 HP at the rear wheels comes from that you are claiming for electric water pumps (you claim 12 RWHP).Furthermore, I would once again like to put to bed forever the completely wrong notion that speeding up the water flow decreases the ability to transfer heat. No matter how fast water flows (until cavitation starts), heat is transfered into the coolant based on the difference of temperature between the heat source and the coolant. As a matter of heat transfer physics, heat is transferred at a higher rate when the coolant speed is increased. This is also confirmed by Stewart at their website.
The electric water pump you talk about replaces the mechanical pump, so it must weigh about the same, and you have the additional weight of the electric motor. Now you have added weight to your car and you still are consuming HP to operate the electric motor. Where are the advantages to an electric water pump? I don't see any.

 

"The fact is that your alternator pulls a constant drag on the engine, so does an engine driven water pump. "

Wrong.

"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. "

How about something that actually draws a decent load...

"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."

I think we came up with the fact that an alt only produces what the system needs, so there is no waste.

"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."

Where is the research for this one??? Have you measured drag on a mechanical pump vs an alternator?

"They show stock and competing mechanical water pumps as only flowing 35 gpm when they get up to 5700 rpm, that's only 100 rpm away from the redline!!! The Meziere unit flow 35 gpm all the time."

As we have already said, the Meziere is rated at zero pressure, so it will not pump 35 GPM all the time!

"Read carefully. I only pick arguments that I can win."

I think we have proven this wrong also.

Again, not tyring to pick fights. Quoting from you:
"I'm sorry if I offend you and if you thought me to be a little arrogant, but when my knowledge gets insulted by somebody who doesn't do any research just because they don't like what I have to say? That puts a person in the mood to prove themselves correct and make the other person look like the fool they are."

Please take my comments as merely a suggestion from someone. Follow them or don't. That is your choice.
Lastly, this is not really public forum material here. You can email me at ChrisK@SpeedDemonMotorsports.Com if you would like to continue this.
Sorry to the forum.
Chris

 

Added weight, 3.5 pounds for 9 dyno proven hp. You add more weight than that if you don't take a crap before you drag race.

 

Wow, you even crap big too! 3.5lbs is a LOT of crap, but you do not seem to be short on it.

[This message has been edited by TheAdmiral (edited 07-19-2001).]

 

wanna read some more inputs??
just my opinion...
Mechanical water pump is not regulated, but must be designed to carry away maximum heat load of the engine (worst case).
If engine operates under normal conditon - partial load - the machanical water pump pumps more than actually needed. This causes more power loss and energie loss than needed under these circumstances.
An electrical water pump will be regulated some way. At least it's switched ON if needed and OFF if not needed.
In off condition there is "no" power loss and no waste of energy. In ON condition the efficiency of the whole electric system is lower than the mechanical systen - THEN there could be a higher power loss than with mechanical system.

In average engines operate maybe 25% in maximum load condition. In the rest 75% where the electical water pump does not need to work full time there will be power and energy savings.

Does that make sense?

 

Klaus,
Unfortunately, the electric pump at hand is not regulated in any way.

Thanks,

 

Not even switched in relation to coolant temperature, like the thermostat opens the way to radiator???? ---> my conclusion would be ... be happy with the mechanical one

 

Alright people, think old school here.

Picture an engine with a radiator fan on the front. Nothing fancy, no clutches, just driven straight off the water pump like they used to be. Drag increases with with engine RPM and let's just say for the sake of argument that it produces a CONSTANT drag of 10 hp, regardless of RPM. Eliminate the fan and you suddenly have 10 more hp.

What some people, who shall remain nameless, are trying to say is this:

If you removed the fan and replaced it with an electric fan that moved the same amount of air as the engine mounted fan operating at the redline you would not see any horsepower increase. The reasoning is that the increased power demand would be such that it would increase the rotating resistance of the alternator so much that it would drag down that 10 hp right off the motor.

We all know this is false, why you ask? An alternator can only produce a maximum of so much power, and with that max power it only creates so much drag on the engine. That drag may be variable, but it does have an upper limit. So what happens if you draw more current than the alternator can put out? Then current is pulled from the battery, remember it is a storage of energy that is just sitting there, not being otherwise used when the motor is running. The result is an absolute worse case scenario of draining your battery as if the alternator was not charging it.

An electric water pump works on the same principal, it is just another source of current draw used to eliminate parasitic drag on the engine. What do you risk my eliminating everything engine driven and going electric? You risk a dead battery. The solution to which would be to install an alternator that can keep up with the demand, something like a 140 or 200 amp unit. These would create more drag on the engine, but again it would peak. That peak would still not come close to the power gained by going with electric water pumps and fans.

On a pseudo related matter, think about a supercharger, it uses engine power, to make more engine power. The gains are tremendous. Sure there are tradeoffs in any situation, but if your electrical system is slightly over-sized (which it is) then you'll be just fine with an electric water pump. Only when you exceed your alternator's output do you run into problems, and even those don't drain horsepower. It's the solution to that problem (ie, bigger alternator) that drains horsepower.

 

Electric H2O pumps, electric power steering, it's all coming soon, stock from the factory. A GM engineer told me there is ~1-2MPG gain on a small car by switching from a mechanical power steering pump to an electric power steering assist motor.

jfb,
I assume the mechanical drain due to belt drven H2O pump from 4000rpm to 600rpm isn't linear. If the drag is 2.2hp at 4000rpm, what is it at 6500rpm, 5-8HP? BTW, the electric H2O pump draws less than 20A, that's ~1/3HP plus the alternator loss, call the electric H2O pump a constant 0.5HP compared to the belt driven pump, which is ~6-7HP at 6500rpm, you have around a 5HP increase which is the number I see quoted for the electric H2O pump.

Eric

 

Finally another person who makes sense. It's just hard to make a point when everybody gangs up on you, nobody wants to go out on a limb and actually accept a different way of thought.

Now that we've all screamed and yelled and called each other names, can we all just get along? A vette is still d*mn fine car any way you mod it up, and that's what brings us together right?

 

Are you calling us all morons or am I just taking this wrong?!?!
Not much honey in your posts...lot of vinegar though. [img]http]//www.corvetteforum.cc/ubb/frown.gif[/img]
JMHO,
Chris

 

I was wondering who the other guy was (that makes sense) (I'm joking).

Eric

 

There is alot of good theory here, and I am definitley for theory - but I think the issue is being a little confused from lack of values.


1) Electric waterpump - mine (meziere, LT1) takes 6.8A @ 12.4 volts (juse measured it). That's 84.32Watts. Assume the alternator is 25% effecient with mechanical -> electrical power conversion = 337W of mechanical power = 0.45 HP. So the electric waterpump takes ~ 0.45 HP to turn, everything taken into consideration.

Now all the values I have seen for what it takes to turn a mechanical water pump are much greater than this - but regardless, .45 is really a negligible amount.

One factor I don't know if anyone has mentioned is impeller effeciency. Since the electric turns at a fairly constant rotational velocity, the design of it's impeller can be more specialized, and thus hopefully more effecient - while the stock pump has to work over a large range of speeds.

Regradless of the theory though, there are three reasons why I would go with an electric waterpump

1) Testing has borne out a 8-10rwhp gain with the pump (this has been repeatedly dyno verified and proven).
2) The weep hole is plugged up so your waterpump will never leak coolant on your opti-spark (compounding your problems)
3) An electric waterpump and 95+ opti allow the use of a double roller timing chain - which is MUCH stouter than any GM piece, and much cheaper. Personally I am more concerned about breaking a timing chain than I am gaining or loosing 10rwhp.

 

ChrisB, since you are very familiar with the M electric water pump. Did it make any excess noise? Is it true you won't have to pull the whole housing off if the motor break down? How is the 12 volt power connected.
I'm ready to pop a waterpump in soon because of the mileage and worry about the weep hole.
More facts if available please. Thanks.

 

[/B]

With the hood open and your head next to eat you most of the time can *discern* if it's running if you listen very keenly - assuming you don't have a loud exhaust/headers. With the hood open, stock manifolds, stock heads, cam etc. (no extra noise, stock NVH) you are straining the limits of your hearing to tell if it's on, and that's only if you know what to listen for. I would call it silent without qualms.


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:[/color]<HR><font face="Verdana, Arial" size="2"> Is it true you won't have to pull the whole housing off if the motor break down?[/color][/QUOTE]

It looks that way, though honestly I haven't had to replace my pump yet (2 years, 50k miles). It bolts into your stock housing - see that backing plate on the back of your pump - it attaches into those holes. So theoretically if the pump dies you can just unbolt those bolts and switch motor units. If mine ever dies that is certainly what I *plan* on doing.


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:[/color]<HR><font face="Verdana, Arial" size="2">
How is the 12 volt power connected.
[/color][/QUOTE]

I looked under the fuse box and found some un=used crimp connecetions (you have to lift box up). Probe through them and a few will be run=on, acc=off, crank=off. I used one of those and relayed it with a normal 30A relay. I also wired in a light that lights up if the pump ever stops drawing current (so I know if it dies.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:[/color]<HR><font face="Verdana, Arial" size="2">
I'm ready to pop a waterpump in soon because of the mileage and worry about the weep hole.
More facts if available please. Thanks. [img]http]//www.corvetteforum.cc/ubb/smile.gif[/img][/color][/QUOTE]


It's really a pretty simple setup. The only downside is if you have a custom radiator you may have clearance issues - I have an f-body and definitley would, but am not 100% on a vette, though I can go measure one tomorrow for you. If clearance is an issue do not get the heavy duty unit - it is significantly longer. I have the standard duty unit and am very happy with it.

The CSI pump is junk. The impellers are stamped steel, but of a quality 100* worse than the stock - it's hard to see how the blades/fins move water at all. Meziere is the way to go.

Another idea you might want to consider is hooking up an underhood switch to the pump/fans, so at the track you can flip a switch and have your fans/pump run - this should give you quicker cool downs and get your more laps at the track.

 

...when everybody gangs up on you...

did i miss something somewhere?
i think there was only one participant in this thread who questioned the HP claim. for the most part we all fully recognize that there ARE gains to be made by using the Electric Pump. it's just that the question was 'why'.

 

Thank you Chris B. for making the important features clear. I'm running a Mez. water pump for exactly the reasons you listed. Amps, alternator drag, load, blah, blah, doesn't matter, it works. One other thing, I've lost two GM water pumps in two years. I don't think that they can hold up to the revs that a modded motor turns. (This is only "my" opinion though)

 

lol, you people are killing me.. sorry i'm late to the party on this discussion..

for the record, my background is in vehicle electrical systems, my degree is BSEE (nobody was more deserving of a b.s. degree than me *smirk*) and i deal with this stuff all day long for military vehicle systems..

as i *think* everyone is accepting at this point, increasing electrical load does increase the mechanical load of the alternator on the engine.. what everybody wants to know is what's the trade off? for that you'd need to know for any specific alternator, how much engine hp it takes to spin it per 10A load or something generic like that.. nobody has those numbers in an easy to read format.. it depends on alternator design, pulley sizes, temperature.. if you have a lot of free dyno time, you could test it..

in general, the electrical loads created by removing mechanical pumps and adding electric pumps, will not be enough to outweigh the delta of the hp requirements required to spin the alternator harder instead of the mechanical pump..

now you have to consider the other factors.. is gaining 8hp on an engine that is spinning the tires thru 3 gears already really worth a couple hundred bucks????

 

Hot damn, I love both sides of this one. But, I've decided to go with a mechanical. Easy, Simple, Standard, Bolt on...-C4-

 

[/B]

You don't have to make it so complicated - we can just look at the general range

10A@12.5V = 125 watts. Say the alternator is 20 % effecient (lowww side, but let's keep this an overestimate). 125/.2 = 625 mechanical watts. There are 745 watts/hp, so 625/745 = 0.84 HP.
Even if you bump the voltage up to 14v, etc. you are still under 1hp total. And the pump doesn't pull 10A, and the alternator probably is a little better than 20% effecient. But regardless, we are talking less than 1 hp here (mine was under 1/2). Sure, if we want an excact precise figure with 5 significant digits it get's complicated, but let's accept a 25% confidence factor, and we are still under 1.5hp easy.


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:[/color]<HR><font face="Verdana, Arial" size="2">
now you have to consider the other factors.. is gaining 8hp on an engine that is spinning the tires thru 3 gears already really worth a couple hundred bucks????
[/color][/QUOTE]

If you can spin your tires through 3 gears you need better tires and a better suspension [img]http]//www.corvetteforum.cc/ubb/wink.gif[/img]