Effective cooling?

[Warp Speed]

getting the coolant cooler is removing the heat from the engine.the why do some people run restrictors ?

To increase pressure in the block to raise the local boiling point. Radiator cap pressure is just radiator pressure, the block pressure is going to be much higher than that. And you need that boiling point increase, local metal temperatures at the spark plugs and exhaust valves is going to be WAY over 212F. I have SAE papers showing metal temperatures near the spark plugs of over 400F on some engines.

If all you care about is making the coolant cooler, don't pump the water at all. The coolant in the radiator will never get hot.

If you want to move BTUs out of the engine, run the coolant as fast as possible. The radiator efficiency goes up as it gets hotter than the air, and if the coolant moves slowly then the radiator gets less efficient as you get towards the bottom (or outlet side). So fast moving coolant uses the whole radiator. Likewise, if it moves slowly through the engine, the engine is going to be thermally irregular. Move the coolant as fast as the water pump will let you.

Notice that the OEMs are moving away from belt driven water pumps. They don't want the cooling system to be tied to engine RPM anymore. If you do that you either have a water pump that stalls before redline or you have an insufficient cooling system at low RPM. This is especially important when everything is turbocharged and is expected to make boatloads of torque (and heat) at low RPM.

This^^^^^

[Steve.k]

So how does the restrictor plates increase flow?i thought the diameter of the orifice is what allows a certain amount of flow similar to stat being fully open or partially closed. Why would you not just put electric pump with no stat or orifice to keep cool?If you want to move coolant as fast as possible?

[jake197000]

i think they got away from belt drives for simplicity mainly not going to argue with ase papers but belt drives worked fine for decades.but they would kill for 1/2 mpg and probably have.

[jake197000]

people run under drive pulleys all the time with no ill effects.but it certainly matters what application we are talking about.

[Kevin Johnson]

Re running higher pressure in a cooling system by design or happenstance.

It matters what particular equipment you are using and any variations in castings etc.

viewtopic.php?f=1&t=55036&start=15

... I'm going to declare the patient cured. Or at least, I feel comfortable that its cooling system is not going to overpressure. (One of the hoses that ruptured had a burst rating of 250psi!!)

[peejay]

So how does the restrictor plates increase flow?

They dont increase flow, they increase block pressure. Running the pump faster increases flow. But there is a limit to that, spin the pump too fast and it will cavitate. The impeller pulls enough of a vacuum on the backsides of the blades that the coolant boils there. Boiling point goes up with higher pressure and down with lower pressure. Vapor takes up a lot more volume than a liquid, and it's also compressible/expandable, so the flow stalls. So, to keep that from happening, you on run the pump as fast as won't cavitate at high RPM. And run more radiator pressure to assist in keeping cavitation from happening in the first place.

OEMs generally sized their water pumps so they were super efficient at lower RPM and didn't care if it cavitated at high RPM because the engines wouldn't normally live over 4000 or so for more than a few seconds. In a racing environment, the pump will basically be stalled all the time with those pulleys, so you need to change the pulley ratios so the pump works at high engine RPM. Likewise if you remove the thermostat, the engine might boil over because now the coolant is boiling in the heads because there isn't enough pressure to keep that from happening.

It is interesting that both of these effects lead to the idea that the coolant can "move too fast".

[peejay]

Re running higher pressure in a cooling system by design or happenstance.

It matters what particular equipment you are using and any variations in castings etc.

viewtopic.php?f=1&t=55036&start=15

... I'm going to declare the patient cured. Or at least, I feel comfortable that its cooling system is not going to overpressure. (One of the hoses that ruptured had a burst rating of 250psi!!)

Yeah, that engine was a bitch and a half, but we couldn't resize the pulleys because the project was basically married to the March pulley set. I'm told it's a right handful on the street (something like high 500s horsepower at the wheels at an easy to get to RPM, through the mufflers) but it's a reliable handful at least.

[Steve.k]

So how does the restrictor plates increase flow?

They dont increase flow, they increase block pressure. Running the pump faster increases flow. But there is a limit to that, spin the pump too fast and it will cavitate. The impeller pulls enough of a vacuum on the backsides of the blades that the coolant boils there. Boiling point goes up with higher pressure and down with lower pressure. Vapor takes up a lot more volume than a liquid, and it's also compressible/expandable, so the flow stalls. So, to keep that from happening, you on run the pump as fast as won't cavitate at high RPM. And run more radiator pressure to assist in keeping cavitation from happening in the first place.

OEMs generally sized their water pumps so they were super efficient at lower RPM and didn't care if it cavitated at high RPM because the engines wouldn't normally live over 4000 or so for more than a few seconds. In a racing environment, the pump will basically be stalled all the time with those pulleys, so you need to change the pulley ratios so the pump works at high engine RPM. Likewise if you remove the thermostat, the engine might boil over because now the coolant is boiling in the heads because there isn't enough pressure to keep that from happening.

It is interesting that both of these effects lead to the idea that the coolant can "move too fast".

That's interesting peejay. We have one car with the old school moroso 12volt motor on a edelbrock hi volume pump. I cannot beleive how cool this system keeps the engine even with a relatively small rad. A freind had same setup but switched to electric pump. He says the temp came up with the new pump so it may actually move less coolant.

[strokersix]

Thanks, peejay for the technical explanation so I don't have to. Persistent myth for sure.

The thought experiment I like to use is to consider how much heat comes out of the radiator. Hotter water means more heat out of the radiator which means more heat came out of the engine. This immediately debunks the "not enough time to cool the water" myth.

[midnightbluS10]

Maybe I missed the memo, but in my experience, 190-220F in almost all street or semi-street cars is not "running hot" but is actually about right for min. wear. "Hot" is when the thing upchucks green fluid all over the ground while stationary at idle. I also do not trust stock dash temp gauges to read right unless you've checked it with a calibrated source.

My wife's commuter Z-28 runs that temp most of the time and the gauge says 245F is 'warm' (around town speed and max AC in 100 F weather) while 260F is 'hot'. An IR gun verifies it runs in that range. Her '97 is stone-stock with 50,000 CA & Nevada miles- for some reason she won't let me touch it with tools in my hands....

It isn't considered running hot until 250* or higher in oem applications, AFAIK.

[Warp Speed]

Maybe I missed the memo, but in my experience, 190-220F in almost all street or semi-street cars is not "running hot" but is actually about right for min. wear. "Hot" is when the thing upchucks green fluid all over the ground while stationary at idle. I also do not trust stock dash temp gauges to read right unless you've checked it with a calibrated source.

My wife's commuter Z-28 runs that temp most of the time and the gauge says 245F is 'warm' (around town speed and max AC in 100 F weather) while 260F is 'hot'. An IR gun verifies it runs in that range. Her '97 is stone-stock with 50,000 CA & Nevada miles- for some reason she won't let me touch it with tools in my hands....

It isn't considered running hot until 250* or higher in oem applications, AFAIK.

That's fine for oem, but definatly not best for a performance application, unless the aero gains outweigh the performance loss.

[Steve.k]

It is thought in diesel engines especially the new style to run hotter. I own a fleet of heavy equipment and i can tell you we started seeing way less repairs and overhauls when we started concentrating on keeping temps well below 200. While this heat may aid fuel consumption and emissions it did zero for longevity and power. Im thinking neither most mfgs care less about.

[MadBill]

Maybe I missed the memo, but in my experience, 190-220F in almost all street or semi-street cars is not "running hot" but is actually about right for min. wear. "Hot" is when the thing upchucks green fluid all over the ground while stationary at idle. I also do not trust stock dash temp gauges to read right unless you've checked it with a calibrated source.

My wife's commuter Z-28 runs that temp most of the time and the gauge says 245F is 'warm' (around town speed and max AC in 100 F weather) while 260F is 'hot'. An IR gun verifies it runs in that range. Her '97 is stone-stock with 50,000 CA & Nevada miles- for some reason she won't let me touch it with tools in my hands....

It isn't considered running hot until 250* or higher in oem applications, AFAIK.

That's fine for oem, but definatly not best for a performance application, unless the aero gains outweigh the performance loss.

In the vast majority of modern non-performance vehicles, the coolant sensor reports to the computer, which uses the info for all the usual reasons: idle speed, fan control, spark and fuel table offsets, etc., including driving the temperature gauge. To avoid impossible-to-resolve customer complaints: ("My gauge reads a needle width higher than my neighbors; I insist on a new engine!") the computer provides a soothing "all quiet on the Western front" mid-gauge reading at anywhere from perhaps 170° to 240°actual engine temperature. Everyone lies...

[GARY C]

maybe your water pump is pumping too much so the coolant doesnt spend enough time in the radiator.

You want to coolant to flow AS FAST AS POSSIBLE.

The goal is not to make the coolant cooler, the goal is to remove heat from the engine.

I would like to see data results for flow in a specific cooling system as the pressure goes up, I would think as pressure increased the flow rate decreased??

I was listening to this podcast with Chris Smith of Elan Power Products and that was one of the subject, he said the BMW pump is one they have found that will actually move a decent amount of water at higher pressures.

[jake197000]

i stand corrected.but cooler water absorbs heat faster than hotter water up to a point and the temps cars run at today are above that point.