Tyler Townsley

Flow rate effect on temp drop.
http://www.achrnews.com/articles/128...ts-heat-output
As I read this as the flow rate increases the device transfers less heat to the outside air all other things being the same. IE at 2 gpm it drops the water flowing through the system by 55 degrees, at 8 gpm it only drops it 5 degrees.
OK. About 15 years ago I wanted my water temps to be 165-175 deg. I first installed a Ron Davis radiator capable of supporting 100+ gpm, no change. I tried a 160 deg thermostat. It took longer to get to 190 but it did not change the temperature once the car had been driven over a 20 mi loop. I then removed the thermostat, the temp at the end of the 20 mi loop was 210+ deg. I then cut the spring in the thermostat so it was always Full open and my water temps at the end of my 20 mi loop was 170 deg. I did this with the stock bypass and with a blocked bypass. The results were the same. From that experiment I concluded removing the t-stat allowed the 3+ gal of water to circulate through the radiator too quickly to be cooled. ( I limited my rpms to less than 5200).
Tonight I had a 2 hour conversation with my son who is a physics professor at the U of Alabama who started out with all the conclusions/arguments presented here. I was finally able to explain the above without having to get into the technical stuff.
I start at the water temperature coming out at the bottom of the radiator. I wanted that temp to be whatever it needed to be so that the water temperature on my gauge was 165 degrees. I started trying to get to that temp by changing the radiator to one that could handle 100 gpm. I changed the thermostat to a 160 deg hoping the better radiator would cool better. Even though it had a 160 thermostat the exit water at the bottom of the radiator did not drop to the temperature I wanted. I contacted a friend who was drag racing his ZR (Fastlane) and he was using a cut thermostat and getting down to the temps I wanted, he also tried running without a thermostat and the saw the same results I did. This was not some thought experiment; it was a real hands on done by 2 different people.
It took a while but my son and I finally concluded that a radiator can have ‘a sweet spot’ where it can remove enough heat to output the water at a temperature I want. That is the crux of this discussion, I have a closed system that generates x heat. I want the water coming in the water pump to be cool enough to see 165 deg on my gauge. With this system I did this by changing the flow rate through the radiator and in my testing of the changes in flow rate (removed thermostat) I discovered that the cooling was worse than that seen at lower flow rates.

Tyler

PS Does anyone have a thermostat housing out of the car? Could you check to see if the bypass closes down the flow from the radiator as it opens in the housing?

Tom400CFI

Tyler, you're only looking at "one dimension" in a multi dimensional system. I AGREE: If you fill the radiator w/200" coolant, then let that SIT for 10 minutes with air flowing through it, the water will cool more than if you pump that same 200* water through the radiator in 10 seconds, with the same air flow....your temp drop of the water would be greater, letting it sit in there for 10 minutes. "More heat will be extracted from water", meaning the water was cooled more *F. More heat wasn't extracted from the system though, b/c as the water cooled, heat tranfer slowed. What do you suppose happens to the engine, in that 10 minutes? It'll over heat! Additionally, what happens to the RATE of cooling to the water in the radiator as time passes? It slows. When the radiator is full of 200" water and the ambient air is 70* we have a 130" delta in temps, heat transferring out of the water to the air will be rapid. In 9 minutes, when the water in the radiator is 85* and ambient is 70* heat transfer is nearly non existent. But our engine is still heating up at the same rate! So we circulate the coolant faster, keeping the radiator as hot as possible (given our engine temp) and keeping heat transfer high, from the radiator.

Second, the link you posted: Tow problems w/this example;1. there is no airflow over the radiator (or very little). Had there been a fan on the exchanger, the temp drop would have been more profound, and increased water flow would have resulted in an increase in heat transfer. But even with out the fan, have a look at the graph from the link that you posted:



What happens to heat output of the exchanger as water flow increases? IT INCREASES!! This supports precisely what I'm saying! You're claiming that in your car, removal of the t-start increased your operating temps. For that to happen, your heat output of your radiator would HAVE to decrease. That is what you "concluded" (erroneously) happened. But this chart proves what I've been saying; increased flow increases heat exchange.
Now look at the second graph above, that shows an increase in temp drop across the exchanger w/increased flow....the very thing that you were/are seeking. The author is pointing out how the increase in flow doesn't provide a linear increase in heat transfer (which is in this case, b/c there is no air flow over the exchanger)...but according to his data, there is an INCREASE in heat transfer regardless. Mmore water flow = more heat transfer, Tyler.



I "get it" that you concluded that, but the test isn't complete. I ate cereal this morning and my car didn't overheat. I concluded that eating cereal prevents my car from overheating. As ridiculous as that is, you see what I did there? You see what you've done here? I'll ask again: If I go remove my t-stat from my car, and make a video of it running at what ever temps it runs at (will probably be around 100*F) will that help show you that the T-stat doesn't "slow coolant to provide better cooling"?



You need the "technical stuff", though, Tyler. You may have accurately convinced your son (who was originally right) that you can lower the temp of water in a heat exchanger more *F, (given time by letting it sit in there longer)....but that isn't an accurate representation of what's happening in the system!

\.

Tyler Townsley

I'll ask again: If I go remove my t-stat from my car, and make a video of it running at what ever temps it runs at (will probably be around 100*F) will that help show you that the T-stat doesn't "slow coolant to provide better cooling"?

OK do it. A 20 mi loop that allows the system to reach normal temperature. Two runs, one with thermo in the next with it out. While you are at it see if the bypass valve shuts down the water flow through the radiator as it opens by closing radiator path in the body of the housing.

If I make a change to the cooling system and it changes the temperature I see on the readout then I figure what I did resulted in the change. Eating cereal does not qualify.

I want to make absolutely sure you said it will run 100 deg F on the gauge when you remove your Thermostat.

Tyler

crowz

Wouldn't a more accurate test work with doing a few wot runs with the system as is and doing a few with a pair of long nose vise grips pinching the bypass line and seeing what the difference in temps are?

Of course exploding radiators might be in issue with this test method from what Ive seen bantered around in this thread.

Tom400CFI

What I actually said was:
I can run a test, but not with my car, today: I've had a bit of BAD LUCK, or bad timing, w/regard to this thread. I can run the test w/my Silverado though, if you'd accept that as evidence. Doesn't matter which car I do it with, as far as I'm concerned; the LORE of "fast coolant" should apply in any vehicle...

Tyler Townsley

Then you would be skinning an apple not pealing the orange.
Use the ZR when you get the time chance. No hurry.

Tyler

Tom400CFI

O.K. I'll be gone next week...hopefully the radiator will be here when I get back next weekend.

My car is not an ZR-1 (unfortunately)....it's "just" and LT1. Still think the test would be relevant and I'm keen to do it.

I agree with what you said earlier;
"Does anyone have a thermostat housing out of the car? Could you check to see if the bypass closes down the flow from the radiator as it opens in the housing?"
I think ^that^ is a fantastic idea.

z06scentair

I have a new housing somewhere around here, just can't find it. Whenn I do it will be posted as different angles. Until then here's a photo from Kurt's website.

Tom400CFI

Finally got my new radiator and installed it yesterday. Pulled the T-stat to run the test that we talked about but I ran into a problem; the LT1 stat looks very similar to the LT5 stat, the importance being that there are 4 ports in the T-stat housing where the T-stat sits. What this means is that if I remove the stat, I dont' think that coolant will flow through the radiator...I think it will (mostly) just loop in the engine/water pump.

I need a cooling system diagram before I can proceed, but I can not find one (on the 'net). This is partly why I wanted to run the test w/my truck; it's got a Gen I engine, so the t-stat is a simple open/closed valve. Removing it from that vehicle is straightforward, coolant will flow through the radiator 100%, unrestricted, and it should over heat or run hot....if the "coolant too fast" theory has any merit. If anyone knows where I can find an LT1 coolant flow diagram...let me know. Thanks.

Mr. Weed

I have to borrow from a Toby Keith song. But you're a fast once as you ever were!

WydGlydJim

Everything pushes......nothing sucks.........

Dominic Sorresso

They had a throttle stop at 70% throttle holding rpm at around 5500. And they used 3.08 gears for the run. Really was not a matter of engine reliability since the LT-5 had run 200hrs on an engine test stand. The problem w the cooling system is the water pump cavitation at 6000rpm.
That's not an issue for short bursts but would not play well for 24hours.
Reading Halverson's account of the run would be the best way of understanding the issues they faced.

GTB/ZR-1

Getting back to your original ask...

Going to be a tough road in B street. Some good shocks, maybe a front bar, Hawk HP+ pads, aftermarket axle-back--maybe Flowmaster if you can still find one & new BFG Rival-S tires, as wide as you can get & a LOT or rear toe-in.

I'm surprised glass slipper hasn't given you some tips. He's been AutoXing his car for ~20 years.
I didn't have much luck w/ my ZR a few decades ago in AutoX--so I made it just go fast in a straight line lol

Oh--and the older I get, the faster I was... (well, not really--yet lol)

Dynomite

Sucking is what causes cavitation or the formation of partial vacuums in a liquid by a swiftly moving solid body (as a propeller/impeller)

See Installing a Ron Davis Radiator and Testing

There are some parts of the technical discussion that confuses me

For example.....what is the difference between a 160 deg F thermostat and a 180 deg thermostat (both with the same Full Open Head Loss) once the coolant temperature has reached 190 deg F? I know the 190 deg F will be reached slower with a 160 deg F Thermostat but that is the only difference in that you reach the same Coolant Temperature at different rates of temperature increase. Kind of like using light weight pulleys to save HP which HP is only realized on acceleration as the rotational velocity of the pulley changes. Nothing is gained in a constant velocity (constant speed) situation.

See The 180 deg versus the 160 deg thermostat or no thermostat

I do understand removing the thermostat completely (and installing a plug in the bypass) changes the head loss of the flow through the thermostat housing considerably.

My thoughts here on the Bypass pressure of the thermostat which increases as the Bypass opening increases. The variable pressure (from spring loaded Bypass) the Radiator sees as it happens (except for the head loss in the hose length differences/flow rate differences to the Thermostat Bypass as compared to the hose length difference/flow rate difference to the Radiator Inlet).

That Thermostat Bypass Pressure (depending on opening of the Bypass since it is sprung) will be approximately equal to the total Head Loss of the flow through the Radiator. As the Bypass spring is compressed (By increased Water Pump Flow) so goes the increased head loss through the Radiator resulting in greater Radiator Coolant Flow (to create that greater Head Loss). We then have Greater Coolant Flow Bypassed and Greater Coolant Flow through the Radiator. The Bypass spring does not keep the head loss through the radiator constant but does keep the head loss through the radiator within limits.

Illustrations provided by others.......




ENGINE COOLING
Post 7 - LT5 Thermostats
Post 8 - LT5 Radiator and Initial Coolant Fill Tricks
Post 9 - Using HVAC Display for Engine Coolant Temperature
Post 10 - Water Pump, Coolant Temperatures, and Coolant
Post 11 - Radiator Debris Screens
Post 12 - Getting The Air Out of the Coolant System
Post 13 - TB Coolant Discussion
Post 14 - Coolant Characteristics (Mix, Pressure, Elevation)
Post - Eliminated TB Coolant Photos and Details