Author Topic: Hello and I have an electric water pump question  (Read 13506 times)

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Offline Jonny Hotnuts

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Hello and I have an electric water pump question
« on: March 17, 2007, 02:54:18 PM »
OK, here?s the deal.

I am putting together a busa powered LS car to compete in Mod-Sports class.

I have installed a Meziere electric water pump (needed the room for chain routing to the drive and the stock pump was in the way).

http://store.summitracing.com/partdetail.asp?autofilter=1&part=MEZ%2DWP136S&N=700+400027+115&autoview=sku

I have been getting conflicting info from very credible sources regarding the use of an electric pump.
The conflicting statements are as follows:

?If you use an electric water pump you must pre-pressurize your system as an electric water pump can not develop the necessary pressure to prevent water from boiling in your head. Water pressure is made behind the radiator and thermostat and while an electric pump can flow like a garden hose the fact is that for every pound of pressure you loose 2 degrees from boiling. The system needs about 15 pounds (will equal -30 degrees from boiling so your boiling temp will change from around 212 @ sea level to 242) and an electric pump can only make about 4. At 4 pounds the boiling temp will be about 220 and you will get boiling in the head and?.detonation.?


(Seems very plausible, and not a big deal to install a fitting in the radiator that I can pre pressurize the system with about 15 pounds of pressurized water (to avoid air in the system).

BUT I ALSO WAS TOLD:


?Once the temp of the motor starts to raise the heated water in your system will generate the pressure, and it is not because of the flow restrictions of the thermostat nor the radiator (argued that a system without a thermostat will make pressure anyway), so adding a way to pre pressurize the system is not needed.?


So who is correct?

Thanks
Jonny
jonny_hotnuts@hotmail.com

"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)

Offline RichFox

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Re: Hello and I have an electric water pump question
« Reply #1 on: March 17, 2007, 04:16:59 PM »
I'm no expert but I firmly believe that #2 was the right answer. As the water heats and expands pressure is built. Some restriction to the flow may be a good idea as in having a thermostat at the outlet, to insure the water is flowing everywhere is should. Dave may jump in here with the scientific answer.

Offline Dean Los Angeles

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Re: Hello and I have an electric water pump question
« Reply #2 on: March 17, 2007, 04:48:46 PM »
A pump is used to move water. Water is not compressible in this system. If you have an open system, like from one bucket to another, the pump can't achieve pressure because the system is open. If you restrict the system with a smaller opening, you can bring the pressure up, but the flow drops also. If you restrict the intake, the pump output will be less, and at some point will starve the pump and it will cavitate.

But this isn't an open system, it's a closed system. Everything that goes out the pump comes back through it. Unless there is a restriction in the system the pump can't achieve pressure, electric or engine driven. But there are restrictions.

To think of the cooling system as just a pressurized container for coolant is misleading. In a simple container, pressure is equal in all directions. Cooling system pressure, however, is average pressure, usually measured at the radiator return tank. Actual pressures vary throughout the system. Coolant circulation is vital to heat transfer and temperature control.

Pressures are highest at the water pump outlet and in the water jackets near the combustion chambers. System pressure is lowest at the water pump inlet. Pressure is generated by the water pump and controlled by variable restrictions, like the thermostat and valves in the radiator cap. The system also has fixed restrictions, such as orifices in the water jackets and passages in the radiator.

If you just sealed the system and ran it, the system would continue to create pressure until something let go. Using a radiator cap that bleeds pressure off at a certain pressure keeps that from happening.

The real pressure in the system comes from the heat of the engine. The system is pressurized to raise the boiling point of the water above 212 F. Raise the pressure to 15 psi and the boiling point goes up to 250 F. Add radiator coolant, like ethylene glycol and 15 psi gets you 265 F.

As the engine creates heat, the water flow and pressure have to remove enough heat to avoid steam. Steam will allow the spot temperature at that point to skyrocket. Air in the system will allow steam pockets even if everything else works just fine. The highest point in the system is where air will go, and you have to have a bleed there. High spots in the circulation path will also collect air. Avoid them if possible, if not, realize that you are going to run with some air in the system.

I can't see where pre-pressurizing will gain you anything. The system pressure is zero when you fire it up. The heat load is low because you aren't generating much heat at idle. The water pressure is coming up, but even at a low pressure, there isn't much heat because you have to get the engine up to temperature. As you accelerate in 1st gear or at some point in the curve, the engine will be near to as hot is it's going to get. During that temperature rise, the pressure in the system is rising along with it.

I don't see anything wrong with pre-pressurizing either. You start with a system that has a 265 F boiling point. But I don't see that it would make a difference if it is an electric pump or engine driven. Only if the electric pump is under the flow capacity of the engine at some point, and I wouldn't run something like that.

The amount of flow has to match the ability of the radiator to remove heat. All the flow in the world won't help if the radiator won't handle the load.
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Offline Glen

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Re: Hello and I have an electric water pump question
« Reply #3 on: March 17, 2007, 05:24:33 PM »
Read the Mod.Sports rules very carefully, there are restrictions on the class. What  type of production body etc. How many were made of that vehicle body. It's a little tricky.
Glen
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Offline Jonny Hotnuts

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Re: Hello and I have an electric water pump question
« Reply #4 on: March 17, 2007, 06:05:35 PM »
Wow, thanks for the answers they have definitely made this come to light.

Glen, I am surprised that you would say that, the modified sports class (as with all the mod classes) is IMO one of the most liberal classes to compete in openly allowing things that I, even as a car builder, think are pushing what the class should be.
It is however an important thing to say to someone given that I am new to this forum and unknown here but I am not unknown to the salt and have been at regular attendance for a "few" years now.
This is MY first car and I am working in conjunction with the advice of Jim Miller who as been very helpful in clearing up the "Grey" areas that is the blood of the SCTA-BNI rule book. I do appreciate the concern, and hopefully tech wont be too hard on me (wishfull thinking!).

Here is a pic of me:



And a few pics of the car in progress (not current photos but an idea).
jonny_hotnuts@hotmail.com

"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)

Offline Glen

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Re: Hello and I have an electric water pump question
« Reply #5 on: March 17, 2007, 06:37:04 PM »
Jonny
Not trying to discourage you. You didn't say any thing up front on what you were planning to run. It looks like a neat little project car and light enough to have some fun with. One thing is I hate to see anyone get caught short when building a new vehicle. It's generally a long way to tow. Jim Miller is a good source to go to. Oh, BTW, welcome to the forum, it's a great place to land and make new friends. What area  do you live in, is some cases there are others that can help if you are somewhat close. Keep sending pictures they help.
Glen
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South West, Utah

Offline Jonny Hotnuts

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Re: Hello and I have an electric water pump question
« Reply #6 on: March 17, 2007, 07:51:22 PM »
Glen, I did not take that as something discouraging.
I think its important to let someone know what is expected in building a car and even with a fairly good knowledge of the current rules the fact remains that the rules change or can be interpreted differently and it is a long way.....not to mention the hotels, fees etc.

I am concerned about the weight, but thankfully the motor is over the drive wheels. I will do some testing on a dry lake before august but I think I have the COP far enough back that it will drive straight. I dont want to add ballast if I can solve it with a nose!


Portland Oregon.


jonny_hotnuts@hotmail.com

"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)

Offline Glen

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Re: Hello and I have an electric water pump question
« Reply #7 on: March 17, 2007, 10:10:40 PM »
There are a lot of LSR people in Portland including Marlo Triet, we just last month had the NWLSR banquet, to bad you didn't know about it. It is at the Airport Shilo Inn every February . Hooking up with any of the racers would be a good thing.
Glen
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Offline Sumner

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Re: Hello and I have an electric water pump question
« Reply #8 on: March 17, 2007, 11:08:03 PM »
OK, here?s the deal.

I am putting together a busa powered LS car to compete in Mod-Sports class.

I have installed a Meziere electric water pump (needed the room for chain routing to the drive and the stock pump was in the way).

http://store.summitracing.com/partdetail.asp?autofilter=1&part=MEZ%2DWP136S&N=700+400027+115&autoview=sku

I have been getting conflicting info from very credible sources regarding the use of an electric pump.
The conflicting statements are as follows:

?If you use an electric water pump you must pre-pressurize your system as an electric water pump can not develop the necessary pressure to prevent water from boiling in your head. Water pressure is made behind the radiator and thermostat and while an electric pump can flow like a garden hose the fact is that for every pound of pressure you loose 2 degrees from boiling. The system needs about 15 pounds (will equal -30 degrees from boiling so your boiling temp will change from around 212 @ sea level to 242) and an electric pump can only make about 4. At 4 pounds the boiling temp will be about 220 and you will get boiling in the head and?.detonation.?


(Seems very plausible, and not a big deal to install a fitting in the radiator that I can pre pressurize the system with about 15 pounds of pressurized water (to avoid air in the system).

BUT I ALSO WAS TOLD:


?Once the temp of the motor starts to raise the heated water in your system will generate the pressure, and it is not because of the flow restrictions of the thermostat nor the radiator (argued that a system without a thermostat will make pressure anyway), so adding a way to pre pressurize the system is not needed.?


So who is correct?

Thanks
Jonny

Maybe I missed it, or you going to run a water tank or a radiator?? 

Also how about some larger pictures??

Sum

Offline 1212FBGS

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Re: Hello and I have an electric water pump question
« Reply #9 on: March 17, 2007, 11:22:07 PM »
hey hotnuts
how big is your water tank? I have a 30 gal water tank in my liner for ballast and a meziere pump that feeds both zx1100 motors. I preheat my water to 180 then turn the pump on and warm my blocks up before i fire my motors. i can run the loing course and still be under 230 in the tank. my system is sealed and i do not pre-pressurize my systern at all. dont worry about it, it will work great, my suggestion would be to run about a 20 gal tank in the nose of the car for ballast and put a restrictor in line so you dont over flush your system... that meziere punp will move so much water that it wont let the water soak up and disipate the heat..... slow the flow down a little and go have some fun.
kent

dwarner

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Re: Hello and I have an electric water pump question
« Reply #10 on: March 17, 2007, 11:40:57 PM »
All the above aside Jonny xxxx will have to have some type of radiator in Mod Sports.

DW

Offline Jonny Hotnuts

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Re: Hello and I have an electric water pump question
« Reply #11 on: March 18, 2007, 01:47:23 AM »
Dwarner is correct, I am running the stock busa radiator but use 2 fans (stock uses 1).

1212FBGS: noted and will take under advisement.

Sumner, when I try to post the pic larger it somehow defaults to the smaller size....
here is the pic as it should be but its not posting:

http://hayabusa.org/iB_html/uploads/post-12-39123-multi.jpg

Glen, I did know about the NWLSR banquet but was unable to attend because of the nut-farm I call work.

jonny_hotnuts@hotmail.com

"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)

Offline Rex Schimmer

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Re: Hello and I have an electric water pump question
« Reply #12 on: March 18, 2007, 02:15:40 AM »
Interesting that we have another "water pump" thread, I was going to start one myself but this is a good one to add my thinking.

I was reading the latest "Racercar Engineering" and they had a very good article on the Cosworth F1 V8 engine in which  they gave some interesting numbers regarding it's cooling system. The engine AND the radiator only hold 4 liters of water! total! and the pump volume is 270 liters/minute!!! So Dan Warner's comment regarding slowing down the flow may not be what you should do. With extremely high rates of flow the water is very turbulent which means that each molecule of water is brought into contact with the hot parts of the engine and also with the cooling tubes of the radiator many times which allows for greater heat dissipation, also the very high flow rate through the engine helps eliminate any hot spots as they are literally sweep away by the high velocity water. This information also backs up the rule for water pump flow that Stu Van Dyne has always gone by, 10 gpm/100 hps.

Your car looks like it should be fun, going to make this year?

Rex
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Re: Hello and I have an electric water pump question
« Reply #13 on: March 18, 2007, 02:27:25 AM »
I don't recall my input as to water flow.

I do know that we have not used an electric water pump since the late 90s. Ed Pink told us that you MUST fill all possible heat pockets. We have used a JFK sprint car pump for the last few cars. Works swell.

We heeded Ed Pinks advice - it was free, how much would your attorney have charged for those minutes?

Results? An El Mirage Championship, a Bonneville record over 250 in only three miles, what else do you need to know?

DW

Offline ack

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Re: Hello and I have an electric water pump question
« Reply #14 on: March 18, 2007, 08:31:16 AM »
I could never understand why anyone would want to preheat water used for engine cooling or run without a thermostat if they had the ability to start it and warm it prior to a run.  The whole purpose of the water is to absorb Btu?s and remove heat from the engine.  Heating it just reduces the amount of Btu?s that can be absorbed by the water. The thermostat in modern engines does exactly what it is designed to do, regulate temperature of the engine within the limits for which it was designed.  If you start and run the engine for a short time prior to a run and then let it heat soak while you are waiting to run at high power it will be at the proper temperature by the time you are 1/4 mile down the track. The same thing goes for oil also unless you are running straight 50W and it is 10 degrees outside.   Oil absorbs Btu?s when it heats that?s why they make oil coolers.  Modern multi weight oils lubricate just fine at low temperatures.