Cooler Thermostats, Thermostat Modifications and Engine RPM

[Dynomite]

Debate This

Cooler Thermostats, Thermostat Modifications, Engine RPM, and Fans

Here is what I have found regarding LT5 Stant Thermostats.

1. You want to run the engine at coolant Temperatures of 180 deg as the design requirement...……...Running cooler Thermostats only lowers coolant temperatures when running coolant below 180 deg F (which is too cold for the LT5 engine). Once the 180 deg Thermostat and 160 deg Thermostat are fully open at 180 deg, Coolant flow is the same through each Thermostat with equal cooling as directly dependent on coolant flow.
2. Drilling Holes in Thermostats offers minimal (non effective) additional Coolant Flow...….A 1/8 inch diameter hole in the flange will only offer additional flow area of .0123 square inches. Which one such hole will increase the total flow area by .016 or 1.6% (three 1/8 inch diameter holes would increase the flow area by 4.7%). This thinking does not address the change in coefficient of Discharge of such small holes. The Stants tested would be fully open with a flow area of approximately .785 square inches at 185 deg F.
3. The Stant Thermostat Opens a bit less with age......…...Marc suggests a 15% deterioration in Full opening area of the Thermostat over time as the Thermostat ages.
4. The LT5 Water Pump Flow is proportional to Engine RPM. ......The LT5 Water Pump Flow rate is insufficient at RPMs less than 2,000 RPM for adequate Coolant flow at the higher Ambient Temperatures. Larger Aluminum Radiators DO compensate for inadequate Coolant Flow at low RPMs. Fans Turning on at 205 deg F do help considerably. And KEEP The Radiator, Oil Cooler, AC Condenser CLEAN.
5. Fan Air Flow is inadequate when the ZR-1 is not moving...…..This was noticed when the ZR-1 coolant decreased in Temperature when shifting from 6th to 5th at 65 mph (going from 1,500 to 2,200 rpm) but while not moving increasing the rpm from 750 to 2,000 had the opposite effect actually increasing coolant temperature.

And I was thinking the issue was solved wherein it is TWO issues (Fan air flow at low speeds and water pump coolant flow at low rpms).

In regard to Item #2 and #3 above...…..Compared to the normal aging of the thermostat of 15% over several years of use one would be much better off installing a NEW Stant Thermostat gaining 15% flow area as compared to drilling three 1/8 inch holes in an older Stant Thermostat only gaining 4.7% flow area.

See Post 120 - Thermostats, Fans, Radiators and Coolant Filling

Post 286 - Cooler Thermostats, Thermostat Modifications, Engine RPM, and Fans

[Hib Halverson]

Originally Posted by Dynomite

Debate This

Cooler Thermostats, Thermostat Modifications and Engine RPM

Here is what I have found regarding LT5 Stant Thermostats.

1. You want to run the engine at coolant Temperatures of 180 deg as the design requirement...……...Running cooler Thermostats only lowers coolant temperatures when running coolant below 180 deg F (which is too cold for the LT5 engine). Once the 180 deg Thermostat and 160 deg Thermostat are fully open at 180 deg, Coolant flow is the same through each Thermostat with equal cooling as directly dependent on coolant flow.

Flow is only one variable which affects cooling. Others are: ability of the coolant to accept heat from the combustion chamber walls and the ability of the radiator to transfer heat to the atmosphere.

2. Drilling Holes in Thermostats offers minimal (non effective) additional Coolant Flow...….A 1/8 inch diameter hole in the flange will only offer additional flow area of .0123 square inches. Which one such hole will increase the total flow area by .016 or 1.6% (three 1/8 inch diameter holes would increase the flow area by 4.7%). This thinking does not address the change in coefficient of Discharge of such small holes. The Stants tested would be fully open with a flow area of approximately .785 square inches at 185 deg F.

Agreed. The practical value of "Drilling" 'stats is a myth.

The Stant Thermostat Opens a bit less with age......…...Marc suggests a 15% deterioration in Full opening area of the Thermostat over time as the Thermostat ages.

If Marc "suggests" that, barring any other test data, I'd sure be taking his suggestion as fact.

4. Lastly, The LT5 Water Pump Flow is proportional to Engine RPM. ......The LT5 Water Pump Flow rate is insufficient at RPMs less than 2,000 RPM for adequate Coolant flow at the higher Ambient Temperatures. Larger Aluminum Radiators DO compensate for inadequate Coolant Flow at low RPMs. Fans Turning on at 205 deg F do help considerably. And KEEP The Radiator, Oil Cooler, AC Condenser CLEAN.

The "bandwidth" of the water pump's flow is not wide enough. What GM should have done was give the LT5 an all-aluminum radiator and a higher system pressure. Then the coolant bypass could have been decreased which would have improved cooling at low engine speeds.

Now compared to the normal aging of the thermostat of 15% over several years of use one would be much better off installing a NEW Stant Thermostat gaining 15% flow area as compared to drilling three 1/8 inch holes in an older Stant Thermostat only gaining 4.7% flow area.

Well...duh!

See Post 120 - Thermostats, Fans, Radiators and Coolant Filling

[Dynomite]

Originally Posted by Hib Halverson

Flow is only one variable which affects cooling. Others are: ability of the coolant to accept heat from the combustion chamber walls and the ability of the radiator to transfer heat to the atmosphere. Yes......I agree with you on the other variables but on this one variable of thinking a cooler thermostat will run the engine cooler at ALL temperatures is a myth since both the 160 deg thermostat and 180 deg thermostat function the same at engine temperatures over 185 deg F. (It will just take a bit longer to get there using the 160 deg Thermostat).



Agreed. The practical value of "Drilling" 'stats is a myth. Thank you for confirmation



If Marc "suggests" that, barring any other test data, I'd sure be taking his suggestion as fact. Concur completely

The "bandwidth" of the water pump's flow is not wide enough. What GM should have done was give the LT5 an all-aluminum radiator and a higher system pressure. Then the coolant bypass could have been decreased which would have improved cooling at low engine speeds. Yes again but the engine rpm up to 8,000 and the resulting Head Loss in plastic radiators were an issue.....thanks for confirmation again





Well...duh! I would not use the word "duh" as it may be obvious to some but not so obvious to ALL



See Post 120 - Thermostats, Fans, Radiators and Coolant Filling

Thank You Hib......



Keep the mice, leaves, plastic bags out of the Radiator area between Radiator, Oil Cooler, and AC Condenser using a debree screen with maximum 1/4 inch spacings. Do install a new Stant 180 deg Thermostat to make sure of maximum functionality of the Thermostat temperature control.



Also......Do install a Marc Haibeck Chip lowering Cooling Fan Operation to 205 deg ON and 200 deg OFF.



And many in HOT climates DO install Fluidyne, Dewitt or other brand Aluminunm multi core Radiators for greater cooling at the higher Engine RPMs.



(Run in sixth gear at 55 mph for a while on a relatively warm day, then shift to fifth and watch the Temperature gage drop)

See Post 120 - Thermostats, Fans, Radiators and Coolant Filling

[5ABI VT]

What bothers me most is if the oem stat is losing 15% opening area due to age. There aren’t any thermostats available so that’s why I was looking into options for lower stats. By the sounds of it 170 is what I would want since it wouldn’t actually keep temps at 170 but more like 180-185 which seems to be the temps everyone says the LT5 likes or is tuned for.

There are several cars out there that use thermostat housings similar to the ZR-1. I’m hoping I can find one similar to the LT5 and has all the fittings for the heater hoses etc that will house a widely available thermostat with a choice of temps. I plan to run an electric wp I’m not a fan of the bypass bandaid solution to prevent exploding radiators.

[HAWAIIZR-1]

Hey Cliff,

No debate here and I pretty much agree with your findings. My car started running in the mid 230s so I tried to clean out the radiator. No debris, but it had a bunch of sand in fins after some banging on it. That did not help so I replaced original radiator 31K miles on a 95 with DeWitts two core (love the fit and ease of installation) AC Delco 180 (did not drill holes) thermostat and Jerry’s silicone hoses/clamps while I was at it. Marc’s chip already installed.

To my surprise, the thermostat that came out from precious owner was a AC Delco 180 with eight 1/8” holes drilled. [emoji33]. I’ll send it to you if you want it....LOL.

In high 60s degree weather a few weeks ago, it ran in high 190s in various traffic conditions and got to 208 highest in stop and go traffic. I am very pleased and comfortable with that. I am mostly curious how it will do in the summer heat next year. You probably remember I consulted with you about this while I was gathering the parts and decided drilling holes was a no go. Thanks!


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[Dynomite]

Hi Craig.....You can hang on to the "holy" thermostat

I have found my coolant stays in the 190s and maybe up around 208 like yours on the warmer days as long as I keep the rpms above 2,000 while driving. Keeping the engine rpm above 2,000 at idle actually will raise the coolant temperature unless you have installed greater flow rate fans. It is amazing to watch that temperature gauge go up and down at 65 mph as I shift back and forth between 5th and 6th.

Have a great Christmas Craig

[HAWAIIZR-1]

Originally Posted by Dynomite

Hi Craig.....You can hang on to the "holy" thermostat



I have found my coolant stays in the 190s and maybe up around 208 like yours on the warmer days as long as I keep the rpms above 2,000. It is amazing to watch that temperature gauge go up and down at 65 mph as I shift back and forth between 5th and 6th.



Have a great Christmas Craig

Hey Cliff,

Ha, ha.....I should have just popped it in the mail for your trophy case...LOL!!!

Nice to hear the confirmation of similar temps. I’ll remember if stuck in traffic (which happens a lot here in Japan) to keep those revs up over 2K rpm if it gets too high. On the freeway it really cools down nicely. I have a different front bumper and a BMAD behind it so hard to compare to stock.

Take care and have a Merry Christmas to you too.

Aloha,
Craig



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[dredgeguy]

Wazoo replaced my plugged original radiator last year and put in a new DeWitts but I still saw the temps in the 235-240 range when I hit DC/Northern VA traffic. I was crawling along for almost 2 hours with fuel on reserve so keeping RPM's up was not an option. Now looking at possibility of DeWitts new fan box with two 11" Spal electric fans. Traffic is not getting any better and very stressful watching the temp gauge going up when stopped and then back down to 190-195 when moving.

[lfalzarano]

Did you install one of Marc’s chips that turn on the fans sooner?


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[dredgeguy]

Sure did, one of the first things I did 5 years ago along with new injectors.