1racerdude

Not true.

turbo_Z

Now c'mon that makes absolutely NO sense. Maybe the coolant doesnt stay in the radiator long enough to cool but its impossible for it to be moving too fast to absorb heat.

96camaroSS

It's absolutely true. I work on commercial heating and air conditioning equipment. If water is moved too quickly through a machine you will not get designed heating or cooling. For example. If water is moved through a chiller evaporator barrel at a gpm rate that exceeds design you will not get the intended temperature drop of the leaving vs. entering water.

The same temperature/flow relationship exists in an automotive cooling system. A thermostat is used to regulate engine temperature as well as regulate flow.

1racerdude

Agree
The water pump is NOT a positive displacement pump,it is just an agitator. It will only move the water as fast as the restriction in the radiator and system will let it.
When the T'stat is OPEN(like being removed)it don't circulate to fast so why if it's out would it circulate to fast?
The T'stat helps the engine warm up quicker for the heater and emissions and performance. When it's not there it takes longer to warm up and thus more emissions and bad running.

A/G

Because there is less restriction. Less restriction means it is moving a larger volume of liquid in a specific amount of time.In your case, the electric WP wouldn't flow as much as a mechanical at high RPM, so a problem may not surface.

1racerdude

There is no restriction when the T'stat is open and the pump I have will outflow a mech water pump except at very high RPM's(above 7000)
An OPEN T'stat has very little restriction.

km9v

Just get a fail safe t stat & be done w/ it.

turbo_Z

I think water absorbs heat easier than it gives it up.... I havent taken thermodynamics since high school so I could be wrong.

speedmiser

Sounds interesting - What size is the bypass hole, and how did you plug it. Also, which electric waterpump are you using?

Injuneer

The driving force is "delta T"... the difference between the the hot fluid and the cold fluid.... no matter which way the heat is moving. The specific heat (BTU/#/degF) of water is fairly constant. The difference in "delta T" is addressed by the heat transfer area. Since the combustion chamber might be 1,000+degF the heat moves easilly to the 180degF coolant, even though the heat transfer area it small. At the radiator, the delta T becomes smaller (coolant at 200+degF - air at ambient) and the heat transfer area is increased.

Think about this..... the head temps are very high around the combustuion chambers. Do you really think that it matters how fast the coolant is moving if the delta T is maybe 800degF? Yes, the water will not heat up at much, but the mass rate of flow is increasing, removing the same number of BTU's. Turbulence increases the heat transfer coefficient. I can't quite see how increaing the velocity of the coolant through the head can hurt heat transfer.

As far as the refrigeration system analogy (96camaroSS), its sort of an apples and oranges copmparison. The ability of the chiller to remove heat from the water is limited by the design capacity of the refrigeration system. There's a limit to the # of BTU's it can remove in a given period of time. Increase the mass of water passing through the exchanger, and your BTU removal, being limited by the capacity of the refrigeration machine will not cool the water as much. It will remove the same amount of heat, but the temperature delta per unit of water mass will be less.

That's not the same as an automotive cooling system. The radiator is not limited in its capacity. If the temperature of the water increases, the heat flow through the radiator to the surrounding air increases, because the coolant-air delta T increases. The capacity of the air to remove heat is not limited by any machine required to remove that heat. Increase the delta T and you remove more heat.

km9v

I don't think anyone has addressed the amount of flow restriction a t stat makes on a cooling system or what the max throughput is on a water pump @ 6K RPMs. Does a t stat actually restrict water flow in a noticable amount?

TripKidd

thanks... this is correct. I have experience with PC watercooling applications and have heard this debate played out before. For those who are interested, here ya go: http://www.overclockers.com/articles599/

GreenDemon

Well, that makes much more sense to me now. Added heat from overpumping could certainly be an issue, although I don't see how increasing the speed of coolant could lead to it no longer transferring heat. IMO increasing the speed of the coolant will continue to lower the difference in temperature until the coolant and the metal around it are the same temperature (at which point you would get a zero return from any further increases). If you want increased cooling capacity, getting a larger radiator is usually the better way to go, not increasing coolant flow- if you don't have enough radiator surface area to dissipate all that heat it's not going to matter how fast the coolant is going.

I would say run a thermostat. I ran without one for a while, when I put in a 160* the engine temp actually dropped in warm weather compared to no thermostat. I wouldn't run without one, or even with one modified to flow all the time, on a street engine. Cylinder wear increases significantly at temps of lower than 160*, as previously stated.

Josh'95Z28conv

Yes true. I said some engines, not all engines. I dont know about the LT1, but small Isuzu diesels, and I believe some Cummins diesels will overheat without a thermostat. Ive seen it happen, and talked to factory engineers about it. Some engines WILL overheat without the thermostat.

1racerdude

I have done a fair amount of work on 855T,and "N" series Cummings,Detroit,Cat and can't say it's true.(heavy crawler crane mech for 45 yr's)

Now a ZU ZU might be different but we are for the most part talking AMERICAN made here.

Don't work on overseas stuff. Eyes ain't built right, can't see it, HA Soooo