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thermostat, restrictor

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thermostat, restrictor

Postby DCK » Fri Oct 02, 2009 9:12 pm

When one isn't running a thermostat, why do you run a restrictor and what does it do?

Keep some pressure in the block side of the cooling system? :oops:
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Postby Larry Sockwell » Fri Oct 02, 2009 9:18 pm

It helps keep the water pump from cavitating and raises the pressure in the block just a bit more than what you see in the radiator.



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Postby DCK » Fri Oct 02, 2009 9:22 pm

Larry Sockwell wrote:It helps keep the water pump from cavitating and raises the pressure in the block just a bit more than what you see in the radiator.



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Ok, that's the direction I was leaning. Didn't think about the cavitation in the pump. I was thinking hot spots/air pockets in the block from boiling due to less system pressure.
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Postby Dodge Freak » Fri Oct 02, 2009 9:23 pm

I had a belt throwing problem with my SBM at around 6500 rpms when running a flex fan which seemed to help back up my electric fan. So I got a smaller crank pulley from March but then motor did not like stop lights anymore, lol

I looked at a high flowing water pump but just spent $100 for that darn pulley, so out went the T stat (with no restrictor ) and down went my engine temps.

Work really nice during Michigan summer, still warmed up to 150 to 160 pretty quick (5 mins) and never went higher than 200 while stop, with most times staying around 170 to 180 driving around.

But summer is over here and in went a T stat..but next summer its coming back out.

Just try it with nothing and see what happens, I was going to try a high flowing water pump if taking the T stat out didn't work but it did.
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Postby Dodge Freak » Fri Oct 02, 2009 9:25 pm

System had great pressure too that built up quick.
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Postby DCK » Fri Oct 02, 2009 9:42 pm

I want to see if I can squeeze a little more out of what I have now and , of course, runs great colder. Not too cold though. It takes about 15 secs for my datalogger to connect with my pcm while running, then burnout/stage and thus warmer than I would like. Especially if your staging lane is going, then they throw someone in front of you after you've already been running for a little bit. All that time to cool down for not.
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Postby d64falcon » Fri Oct 02, 2009 11:26 pm

Im no Expert but when i raced my street car as a kid tried no thermostat. It got hot and pushed half the water out on the drive to track. Took a old thermostat cut the center out and no more over heating.

My conclusion was simple. the restrictor slowed the water down instead of getting thru the rad before it had time to cool
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Postby Abbottracingheads » Sat Oct 03, 2009 10:14 am

On my drag race car the restrictor slows the circulation of water so it can cool in the radiator. Without the restrictor it would not cool off quick enough. Of course we are using electric water pumps.
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Postby redcorvette » Sat Oct 03, 2009 12:17 pm

A couple of years ago I worked as a tech on a thermal hydraulics test loop for a company doing safety research for a nuclear reactor manufacturer. I asked the engineer in charge if it was possible to run water so fast through a radiator that the water would not have time to cool before returning to the engine. His answer was, well it involved way more math than I ever wanted to know. I think what he told me was that even though each pound of water you put through the radiator has less time to exchange heat, you are putting more pounds of water through in the same time period so the overall effect is the same. You have to consider the dynamics of the whole system. Putting in a restrictor changes many other conditions throughout the system (including conditions inside the radiator) that effects overall heat exchange. So putting in a restrictor works a lot of the time, but probably not for what appears to be the obvious reason. I think this is a lot like arguing when something is blown to bits whether it was an explosion or rapid combustion. At the end of the day there is a pile of rubble and a cool motor.
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Postby John Wallace » Sat Oct 03, 2009 12:45 pm

But did the nuclear reactor manufacturer have a limited/closed loop water supply?

Most reactors would have an abundant cool water supply.
Like a lake or stream.

:)
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Postby jpankey » Sat Oct 03, 2009 12:49 pm

we just cut a piece of metal and played around with the hole size . 1/2 to 5/8 usually works. slows the water down so it has sufficient time to pick up some heat . Kinda like my engines water temp runs 5 degrees warmer on the hand with water than it does with antifreeze that has to do with the boiling points and heat transfer. water by the way has the best heat transfer properties.
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Postby NewTune » Sat Oct 03, 2009 1:08 pm

Consider the way a typical air conditioning system works. The high pressure gas passes through an orifice tube or an expansion valve to the low pressure side where it sheds latent heat in the evaporator. I think the same thing takes place in a cars cooling system, however on a much smaller scale.
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Postby Tuner » Sat Oct 03, 2009 1:13 pm

http://www.motorsportsvillage.com/forum ... 904#p46904

The deal with water pumps, electric or engine driven, and thermostats or restrictors, is less mysterious if you know the information Howard Stewart and Edelbrock published in magazine articles in “Stock Car Racing” and “Circle Track” magazines about 15 or 20 years ago. They made water pump dynos and measured flow and pressure vs. RPM and power required with different restrictions of thermostats or restrictor discs and different radiator designs.

The ‘ah-ha moment’ was in understanding that the OE type engine driven pumps pressurize the system several lbs. per 1000 RPM. I recall 10lbs per 1000RPM when the pump is 1 to 1 with the crank, but that seems like a lot, it’s been a long time since I read the information. Put a pressure gauge on your cooling system and see. The caveat in this is you must have a pump with matching volute and impeller shapes and the clearance must be tight, just a few thousandths like a jet boat pump. The stamped sheet metal impellers won’t geturdun.

Without the restriction of a thermostat, the radiator core is the restriction in the system. The restriction of the thermostat or restrictor disc is necessary to isolate the pressure to the engine water jackets so as to not push open the radiator cap and blow the water out at high engine speed. This is where the old wives tale of “the water goes through the radiator too fast to cool” comes from. Remember, if it’s too fast through the radiator to cool, it’s too fast through the block to get hot, opposite sides of the same coin so to say. With old top-tank vertical flow radiators, when the core becomes the restriction because the thermostat isn’t there to do the job, the unrestricted pump pressure blows the water out the cap. If you look at cross flow radiators the cap is nearly always on the suction side of the core. Stewart mentions some of this on his website but the old magazine articles had more details.

Obviously, it’s desirable to have the coolant pressure high as practical to raise the boiling point. During a ‘Cup’ race on ESPN recently, I thought I heard the guy with the cut-away car mention a 45 lb. radiator cap. I can tell you from running a boat with a non pressurized cooling system, once the water boils in the heads you have to stop and wait for it to cool because all the water in the world won’t cool the vapor around the exhaust valve guides enough to cool them. Like water dancing on a hot griddle, the liquid doesn’t touch the metal until it’s below the local pressure’s boiling temperature.

I recall about 5 HP was necessary to turn one of the pumps 6000RPM. 1HP = 746Watts x 5HP = 3730W ÷ 12V = 310Amps, and that’s assuming 100% efficiency which isn’t possible. How many amps do the electric water pumps draw? Essentially, a starter motor is needed to power a water pump in any kind of continuous duty.

I guess it’s OK for drag racing to use a pump that’s incapable of pressurizing the engine when you could make a pass without water at all. Back in the day, there were stories of Grumpy dumping both the water and the oil for the money round. Pesky fluids just slow you down. Short attention span racing is over before it starts anyhow.

An engine is a sorry SOB if it hasn’t enough power to pump its own water (and fuel for that matter). What’s next, electric dry sump pumps? CNC Manufactured Billet Anodized Programmable Pulse Width Modulated Solar Wind and Wave Powered Dry Sump Systems, LLC. Get your order in early, avoid the Xmas rush.

That’s mine, what’s your opinion?
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Postby DCK » Sat Oct 03, 2009 6:08 pm

Tuner wrote:http://www.motorsportsvillage.com/forum/viewtopic.php?p=46904#p46904

The deal with water pumps, electric or engine driven, and thermostats or restrictors, is less mysterious if you know the information Howard Stewart and Edelbrock published in magazine articles in “Stock Car Racing” and “Circle Track” magazines about 15 or 20 years ago. They made water pump dynos and measured flow and pressure vs. RPM and power required with different restrictions of thermostats or restrictor discs and different radiator designs.

The ‘ah-ha moment’ was in understanding that the OE type engine driven pumps pressurize the system several lbs. per 1000 RPM. I recall 10lbs per 1000RPM when the pump is 1 to 1 with the crank, but that seems like a lot, it’s been a long time since I read the information. Put a pressure gauge on your cooling system and see. The caveat in this is you must have a pump with matching volute and impeller shapes and the clearance must be tight, just a few thousandths like a jet boat pump. The stamped sheet metal impellers won’t geturdun.

Without the restriction of a thermostat, the radiator core is the restriction in the system. The restriction of the thermostat or restrictor disc is necessary to isolate the pressure to the engine water jackets so as to not push open the radiator cap and blow the water out at high engine speed. This is where the old wives tale of “the water goes through the radiator too fast to cool” comes from. Remember, if it’s too fast through the radiator to cool, it’s too fast through the block to get hot, opposite sides of the same coin so to say. With old top-tank vertical flow radiators, when the core becomes the restriction because the thermostat isn’t there to do the job, the unrestricted pump pressure blows the water out the cap. If you look at cross flow radiators the cap is nearly always on the suction side of the core. Stewart mentions some of this on his website but the old magazine articles had more details.

Obviously, it’s desirable to have the coolant pressure high as practical to raise the boiling point. During a ‘Cup’ race on ESPN recently, I thought I heard the guy with the cut-away car mention a 45 lb. radiator cap. I can tell you from running a boat with a non pressurized cooling system, once the water boils in the heads you have to stop and wait for it to cool because all the water in the world won’t cool the vapor around the exhaust valve guides enough to cool them. Like water dancing on a hot griddle, the liquid doesn’t touch the metal until it’s below the local pressure’s boiling temperature.

I recall about 5 HP was necessary to turn one of the pumps 6000RPM. 1HP = 746Watts x 5HP = 3730W ÷ 12V = 310Amps, and that’s assuming 100% efficiency which isn’t possible. How many amps do the electric water pumps draw? Essentially, a starter motor is needed to power a water pump in any kind of continuous duty.

I guess it’s OK for drag racing to use a pump that’s incapable of pressurizing the engine when you could make a pass without water at all. Back in the day, there were stories of Grumpy dumping both the water and the oil for the money round. Pesky fluids just slow you down. Short attention span racing is over before it starts anyhow.

An engine is a sorry SOB if it hasn’t enough power to pump its own water (and fuel for that matter). What’s next, electric dry sump pumps? CNC Manufactured Billet Anodized Programmable Pulse Width Modulated Solar Wind and Wave Powered Dry Sump Systems, LLC. Get your order in early, avoid the Xmas rush.

That’s mine, what’s your opinion?
I appreciate the information and the link. I'll give it a read. I didn't expect I'd get these responses and your is interesting and colorful too. lol I was wondering if the restriction, at least, had something to do with the block/heads having hot spots, boiling, creating air pockets and the results of which. Thanks!
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Postby d64falcon » Sat Oct 03, 2009 7:45 pm

Tuner wrote: This is where the old wives tale of “the water goes through the radiator too fast to cool” comes from. Remember, if it’s too fast through the radiator to cool, it’s too fast through the block to get hot, opposite sides of the same coin so to say.


Then maybe the water is going thru the block to fast to cool the block ;)
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