Electric water pumps

[Dezertpilot]

I was looking through my Summit mag and saw a universal electric water pump. It has a bracket that sits off the side of your motor and has a small motor and from the motor and then a belt to your water pump. It says that it frees up to 17 HP and I was kind of thinking about putting one of these on my 4runner. I have a 1987 7m-ge motor that is swapped in. I know I would call and ask Summit if it would fit my app but lets say it does. Is it worth it? Its under $180 and looks nice. I do know its one more electrical accessory but if I can gain 10 HP or more I think I would be happy. What are you guys thoughts on this?

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[steveG]

I don't think its worth it. It's just one more thing to go wrong in the desert. Especially when the cooling system is concerned, simple and effective is the key. Besides that, most of the electric water pump drive kits are designed for short duration use like drag racing.

[TheWebWheeler]

Yeah do really want to have that be what bones you in the middle of no where?
I agree If your only drag racing or maybe running in a short corse at a track like ROR then it might be worth persuing But if your running out in the middle of nowhere I would'nt do it..

[Josh_K]

I dont think those things will build enough block pressure to cool a car that is ran continuisly. I think there nitch is in 1/4 mile cars.

It is typical for a v8 race engine to run 30 to 40 psi in the block of pressure. This reduces the ability of the coolant to boil. This is how cars can run temps or 265 and not boils the coolant off.

BTW, I am sure you know this but when you take the thermastat out and run a disk in it place, the smaller the hole in the disk and cooler the engine will run. The reasons are two fold. 1 more block pressure. 2 the coolent crosses the rad slower and has a more time to exchange the heat to the air making cooler water.

Josh

[Ramsey_ElWardani]

Josh, if that were the case, why wouldn't it blow all the coolant out of a 18 -22lb radiator cap, being that it is a closed system and pressures equalize in the whole system?

[Stephen]

I almost hate get this started but I guess I have to.

Slowing the water down through the radiator will only hurt your heat rejection through that radiator. The higher the flow rate, the higher the heat rejection rate. Reason is that heat is transferred best at high temperature differences. If your water comes out at 260 and the air is 100, you have a 160 degree difference and heat will fly out of the water since the air is so much cooler. If your water is only 200, you reject less heat because there is a lower temp difference.
If you slow the flow rate down in the radiator, the water at the inlet will be our theoretical 260 and the water at the outlet may only be 200. The water at the outlet of the radiator will be rejecting heat slower because it's so cool.
If you speed up the flow rate, the water at the inlet will still be 260 but the water at the outlet could be 240. The higher outlet temp will reject more heat to the air before it heads back to the motor for another load of heat.

Don't get hung up in trying to control temperatures with this example or even in real life, you're really trying to reject HEAT. If you get rid of lots of heat, temps will take care of themselves. I know it seems intuitively obvious that you would be better off putting that slower moving 200 degree water in the motor but it's not.

This same idea is why running high coolant temps is good for cooling. If have 100 degree air and try to regulate the block to 160 degrees, you have to have a huge cooling system because you only have a 60 degree temp difference to reject heat with. If you run a 260 block temp with the same air, you reject the same amount of heat with a smaller radiator.

[Chris_Wilson]

"being that it is a closed system and pressures equalize in the whole system?"

Sounds like you are thinking of a static system, not a dynamic system.
When fluids are flowing, a restriction to flow will result in a pressure
differential across the restriction.

An analogy would be a voltage drop due to current flowing through a resistor
(or a wire which has some resistance). When the current stops flowing then the
voltage becomes the same on both sides of the resistor.

Likewise, there are restrictions to the flow of coolant in your system. Some are
insignificant, others not. The pressure before and after the water pump is not
equal (except when the pump stops pumping!)

Or I could be wrong...

[Dezertpilot]

Ya Im not going to do it but this kinda brings up an interesting topic.

[Josh_K]

Stephen..... I don’t even know what you said? I couldnt get past you second of third sentence.

Ramsey, wait a moment and I will get to you.

Chris, I think we are on the same page.

O.K. I will type slowly for the thinking impaired. Please don’t read too fast.

First one given, the higher the pressure on a liquid the high the temp will need to be to make the fluid boil. Example, water at an elevation higher than sea level boils at less temp than water at sea level. Furthermore, we have all heard that if an astronaut’s space suite pops a leak that his blood will boil. Well that happens because the pressure drops so low that it gets to the point that the blood in his body will boil at 98.6 f thus killing him/her just as water boils at a lower temp in the mountains than at the beach. So, as water or blood boils at a low temp/low pressure water (and blood) will boil at a higher temp and pressure that we are accustom too when the pressure is raise above that of atmospheric pressure.

Now back at it.

In a running engine Pascals law doesn’t apply because the restrictor plate adds a resistance to the system and builds a pressure on the fore side of it which happens to be in the block. As I have said a block can run a pressure of 40 psi but there will be less that 24 psi in the rad because it is on the aft side of the restriction.

For instance, if your 8 truck is really hot 250+, and you keep the rpm’s up (3,500+) the water wont boil out of it because all the pressure that is in the block fore side of the restrictor plate is raising the boiling point of the water in the block to a point higher that the temp of the coolant. Now it you shut the engine off and Pascals law become effective and the water will pop the cap on the radiator.

Now I am sure some one will argue with me and thats fine, just be aware that I know this works because I have experienced all this stuff for my self so you’re not going to change my mind!

Josh

[Josh_K]

Now Stephan, I have tried to read your post again and I still don’t get your point. Now please explain how my 909 logic is wrong.

If a coolant flow slowly across a radiator than it has more time to transfer it heat into the surrounding (ambient) air.

BTW, what ever you come back with will most likely be wrong because I know smaller holes in restrictor disks = cooler water temps. It’s as simple as that.

Now you are right about the closens of the temp spread being less efficaint but we not taking about normal temps here. I am talking about temp that will cause the water to boil in a block and warp heads.

Josh

Oh one more thing, please don’t come back with, “if smaller is better than block the flow off”.