Why not just remove thermostat?

[KILLSHOTS]

I've seen colder thermostats for the LT5 discussed and they're apparently extremely desirable but tough - if not impossible - to find. I live in Phoenix and my car is just a weekend toy. We all know that a cooler engine produces more power. We also know that thermostats are basically only designed for 2 things: allow the engine to run "efficiently" (read: please the EPA) and to produce heat for the cockpit. I don't care about either. So can anybody think of a COMPELLING reason for me to retain my thermostat? Less heat soak, less wear on the engine, more power. Opinions?

Thanks! :cheers:

[mike100]

The car runs rich until it warms up and it will wash down your cylinders in short order if you take it on short drives with no thermostat.

I once thought I'd be smart and ran a 160 'stat in Flagstaff on a carb'd muscle car. It got to 15 deg that night. I never could get my windows defrosted. You should always try to get your water and oil temp up as soon as possible, the engine will last much longer.

[Vetman]

Thermostats when open let the correct amount of water flow to optimize cooling. I understand removal will allow the water to flow too rapidly through the radiator before it is cooled. Guess there may be other reasons too with water flow too fast.

[tccrab]

I've got to guess that emissions control are a big reason why the engineers design engines to run within certain temperature ranges.

I'm also guessing that the thermostat provides some restriction to water flow as well. The volume and pressure of coolant the water pump pushes when the engine is at 7500rpms is vastly different than at idle.

'Crabs

[efnfast]

I asked Marc H about a 160 thermostat. He said it may gain as much as 10 hp, but was concerned that the oil and gas are engineered to run at higher temps. Not that I mean to put words in his mouth, but that is what I heard. -Steve

[XfireZ51]

ECM doesn't go Closed Loop/Learn mode till 81C or 178F. So you pretty much lose any fuel trim from the O2 sensors. The motor is really designed to run better at a warmer temp than 160F.

[GOLDCYLON]

Chris I run a 160 Degree T-stat on my Daily runner. For Phoenix it works well as the days are now in the Century range. Even in the brutal winter season when it gets into the 30s I have zero issues with defrost and heat as well as we all know very well the car heats up rapidly. Keep in mind my car is highly modified engine wise and I run a larger Dewitts radiator and SPAL fans. So your mileage may vary. I do not recommed running without a T-stat GC

[XfireZ51]

GC,

What temp does your motor run at?

[Bob Eyres]

Remember, 160deg. is where a 160deg thermostat is designed to open, and not that the thermostat keeps the engine at that temp.

The LT5 is a lot stronger with cool intake temp, but that's another issue.

I have run a 160deg. thermostat for 17 yrs. in my ZR-1 with no ill effects. It has helped keep temps down in the hot Florida environment.

I would think that it would be ill advised to remove the thermostat entirely.

[Paul Workman]

Well, for starters:

Engines are expected to become hot.
Parts are expected to expand.
Parts work together best within certain tolerances.
Heat is controlled to keep parts tolerances in the range to assure longevity.
Lubricants are designed to specification that they meet certain characteristics over a range of certain temperatures.
Fuel (gasoline) must be completely vaporized to mix with oxygen before it will burn. (liquid gasoline droplets will only burn at the surface where oxygen is present)
Operating the LT5 (or any) motor at WOT below a certain minimum temp can result in damage (refer to #s 2, 3 & 5)
Operating (any) motor where gasoline is not being vaporized completely results in carbon buildup in combustion chambers and on valves, washing the cylinder walls of needed oil, and reducing the viscosity of the oil resulting in accelerated wear of cylinder walls, bearings, and rings.

And, last, but every bit as important, in the case of the LT5, certain steps are taken in the thermostat housing (with the thermostat in place) to control coolant over-pressurization resulting from high rpm operation.


These LT5s are a magnificent engineering achievement. They are kinda rare, parts are expensive, and provide a rare experience not felt in any other Corvettes before or since. And, when operating within their "window" they are nearly "bullet proof". If you operate this or any motor outside the design window, as some always will, you're "off the chart", and serendipity becomes your tutor. (But, NOT on my dime!)

[Bob Eyres]

#9 is the most relevant here Paul.

I don't know for sure, but I think an LT5 without a thermostat would blow the plastic components of the stock radiator apart.

[Paul Workman]

#9 is the most relevant here Paul.

I don't know for sure, but I think an LT5 without a thermostat would blow the plastic components of the stock radiator apart.

Ah, YES. I wrote about those plastic tanks, but musta inadvertently deleted that point when I edited. Good catch!

[Dynomite]

Well, for starters:

Engines are expected to become hot.
Parts are expected to expand.
Parts work together best within certain tolerances.
Heat is controlled to keep parts tolerances in the range to assure longevity.
Lubricants are designed to specification that they meet certain characteristics over a range of certain temperatures.
Fuel (gasoline) must be completely vaporized to mix with oxygen before it will burn. (liquid gasoline droplets will only burn at the surface where oxygen is present)
Operating the LT5 (or any) motor at WOT below a certain minimum temp can result in damage (refer to #s 2, 3 & 5)
Operating (any) motor where gasoline is not being vaporized completely results in carbon buildup in combustion chambers and on valves, washing the cylinder walls of needed oil, and reducing the viscosity of the oil resulting in accelerated wear of cylinder walls, bearings, and rings.

And, last, but every bit as important, in the case of the LT5, certain steps are taken in the thermostat housing (with the thermostat in place) to control coolant over-pressurization resulting from high rpm operation.


These LT5s are a magnificent engineering achievement. They are kinda rare, parts are expensive, and provide a rare experience not felt in any other Corvettes before or since. And, when operating within their "window" they are nearly "bullet proof". If you operate this or any motor outside the design window, as some always will, you're "off the chart", and serendipity becomes your tutor. (But, NOT on my dime!)

Why not just remove thermostat? NO...NO...NO!!!!

I run 180 deg thermostats in ALL ZR-1s.

1. At a coolant temperature of say 190 deg a 160 deg thermostat is open....so is my 180 deg thermostat. So from that point on our coolant system flow rates are identical at the same rpm. And so is the cooling.

2. Using a 160 deg thermostat in cooler weather drops the engine coolant temperature below the designed engine temperature with the 180 deg thermostat. The PVC (at the cooler engine temperatures) is working at less than optimum temperatures as well as your oil and fuel functioning at less than optimum temperatures.

Also see Defective Stant Thermostats (http://www.zr1specialist.com/HAT%20Web/facts%20and%20failures/thermostat.htm)

Oh....almost forgot.....my fans come on a bit sooner controlled by Marc Haibeck chip to help with engine temperatures when idling at a traffic light on a hot day (On at 205 deg F and Off at 200 deg F). But again....my 180 deg thermostat and the 160 deg thermostat are both open in that condition :D

But MUCH MORE as you can see as the LT5 thermostat has several functions LT5 Thermostats (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070558)

2. Thermostat Multiple Functions.

The LT5 thermostat sits in two cavities and is located on the outlet side of the radiator. On one end of the thermostat is the first valve [pressure relief) that expands and opens to excessive radiator pressure (but only relative pressure over and above that normal thermal expansion radiator pressure). That valve is in the first cavity which is exposed to coolant outlet flow. In the second cavity is the second thermostat valve (temperature relief) which controls coolant inlet flow depending on engine temperature.

GM found at high rpm and high coolant flow, excessive pressure in the radiator, due to it's restriction, would blow the rubber seals between the side tanks and the core. GM did not want to design a specific LT5 radiator, so the solution was the radiator bypass which opens when the pressure differential across the radiator reaches a certain level. This bypass valve is part of the thermostat and, when open, allows coolant to recirculate within the engine.
LT5 Coolant System Discussion (http://forums.corvetteforum.com/c4-zr-1-discussion/259664-thermostat-cooling-discussion-pic-included.html)

ZR1 provided this photo in the LT5 Coolant System Discussion :thumbs:
http://i287.photobucket.com/albums/ll142/dynomite007/91%20ZR1/A-THERM1-1.jpg
http://i287.photobucket.com/albums/ll142/dynomite007/A%20Engine%20LT5/zr1waterflowcrop-1.jpg

3. Lets simplify......the discussion of the 160 deg thermostat cooling better than the 180 deg thermostat.

1. Let us say we have identical radiators, identical rpm, steady state coolant temperature, and both fans on and we are cruising at same speed.
2. Lets say coolant temperature is 190 deg in both your Z and my Z given everything identical in item #1.
3. Your 160 deg thermostat is full open with same flow rate as fully open 180 deg thermostat.
4. My 180 deg thermostat is full open with same flow rate as fully open 160 deg thermostat.
5. In other words...we both have been driving our Zs for say at least 30 minutes and have reached a steady coolant state.

Now......lets say the day gets hotter. The coolant temperatures should rise the same in both your Z and my Z given EVERYTHING else is the same :yesnod:

If it gets REAL HOT......both our Zs coolant will reach 230 deg at the same time.

The maximum temperature reached (given it is over 190 deg) will be no different for you than me even though you have a 160 deg thermostat and I have a 180 deg thermostat.

I am saying that my thermostat just maintains a minimum temperature higher than yours.
I am also saying your thermostat does not maintain a lower higher temperature than mine. Once both thermostats are fully open, the coolant temperatures are controlled by everything else mentioned in item #1 and not the thermostats (yours or mine).

4. Fans and Radiators.

Same goes for fans......once your fan is on and my fan which may be on at lower temperatures is on.......we have identical radiator cooling no matter how hot it gets outside.

Now if we change radiators.....you run stock radiator and I run Ron Davis....DIFFERENT STORY as I have greater dissipation of heat than you at all rpms (water pump speed dependent) and ZR-1 speeds (air flow dependent).

5. Engine RPM.

1. Fans turn on at 205 deg F and OFF at 200 deg F (Haibeck Chip)
2. I use 180 deg Thermostats.
3. Ron Davis, Dewitt, and Fluidyne multi core Aluminum Radiators.

My experience in all ambient temperatures.

A. In sixth gear running 65 mph (less than 2,000 rpm) the Coolant always gets a bit over 200 deg F. On Hot days the coolant will get a bit over 213 deg F.
The key is the Water Pump is not pushing enough flow through the fully open thermostat to cool the engine to a Temperature where the Thermostat takes over (180 deg F).

B. If I shift to 5th gear at 65 mph (more than 2,000 rpm) the coolant temperature drops to Thermostat control (180 deg F) on cool days and drops to near 200 deg F on Hot days.

6. The Summary is simple.....

The Thermostat is fully open at all coolant temperatures over 180 deg F (no need to use cooler thermostat unless you want to run at temperatures below 180 deg F).

The Water Pump does not provide enough flow to cool the engine at rpms less than 2,000 rpm. This is not an issue at ambient environmental temperatures on cool days. This is a problem on HOT days. The Aluminum Multi Core Radiators DO provide better Heat Dissipation and offer cooler Coolant at ALL Temperatures for which the 180 deg F Thermostat Controls the Flow (above 180 deg F Coolant temperatures the Thermostat is fully open). The Cooling effects then being dependent on Water Pump Flow Rate and Air Flow Rate through the Radiator.

Having the Fans come on at 205 deg F DOES provide for COOLER Coolant in the radiator once sufficient coolant flow rate is provided above 2,000 rpm. Using Aluminum Multi Core Radiators ALSO provides for COOLER Coolant Temperatures in conjunction with the Air Flow provided by Fans and Vehicle Speed. The Heat Removal Rate from the Radiator is greater as the Air Flow Increases and as the Aluminum exposed to that Air Movement increases.

It DOES make a difference if you are moving at speed in conjunction with Fans PULLING Air Flow as the additional Air Pressure Up Front does add to the TOTAL AIR FLOW through the Radiator at any ambient environmental temperatures.

Using 180 deg Thermostats insures that the engine will not run cooler than that temperature since the Thermostat is in control and controls the Coolant flow rate through the engine at all Coolant Temperatures less than 180 deg F.

There has been some suggestions to drill 1/8 inch holes in the thermostat flange to allow better cooling.
Just tested several 180 deg F Thermostats for opening temperatures and found the Stants 180 deg Thermostat will start opening at 175 deg F with complete opening at 185 deg F. Marc suggested at one time the older Stants will deteriorate (Decrease in FUll Open Area) by up to 15% as they age. The Stants tested would be fully open with a flow area of approximately .785 square inches at 185 deg F.

Thermostat opening at 175 deg F....................................Thermostat opening at 185 deg F (Full Open)
http://i287.photobucket.com/albums/ll142/dynomite007/Dynomite21/2c0d5927-b56a-4e41-85ff-21541858daf1.jpghttp://i287.photobucket.com/albums/ll142/dynomite007/Dynomite21/e4d4f2ae-9950-4ecd-a40e-b545bbae5c78.jpg

A 1/8 inch diameter hole in the flange will 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.

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.

Given the LT5 runs Hotter idling at a stop sign than at 2,000 rpm as cited in Item #5 in the link above a much better focus regarding engine Heating would be engine RPM (which relates directly to pressure on the coolant flow through the Stant Thermostat) and not the Stant Thermostat (Old or New).

See item #7 The 180 deg versus the 160 deg thermostat or no thermostat (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-6.html#post1584987828)

[KILLSHOTS]

This is some great input and I appreciate it, guys. Of everything that's been said, the thing that truly alarms me is the pressure issue. I guess I had never considered that. Even without an engineering background, I can see that such a high-compression engine running at high RPM could put serious stress on the non-metal parts of the cooling system without a stat. In this case, the stat makes a more compelling case as a water baffle than a temperature regulator.

Yep, not worth the risk. Thanks guys!

[GOLDCYLON]

GC,

What temp does your motor run at?

About 80% of top band is the highest Ive ever seen it go in winter it never goes above 50%

[Dynomite]

Chris I run a 160 Degree T-stat on my Daily runner. For Phoenix it works well as the days are now in the Century range. Even in the brutal winter season when it gets into the 30s I have zero issues with defrost and heat as well as we all know very well the car heats up rapidly. Keep in mind my car is highly modified engine wise and I run a larger Dewitts radiator and SPAL fans. So your mileage may vary. I do not recommed running without a T-stat GC

Now Daryll :p

Here is my theory......about thermostats in your ZR-1 with LT5 modified or not and with Ron Davis Radiator or not...I have experimented with it all in 4 ZR-1s ;)

I run 180 deg thermostats in ALL ZR-1s :cheers:

1. At a coolant temperature of say 190 deg your 160 deg thermostat is open....so is my 180 deg thermostat. So from that point on our coolant system flow rates are identical at the same rpm. And so is the cooling.

2. You in cooler weather are running around with an engine coolant temperature less than my designed engine temperature with the 180 deg thermostat. Your PVC is working at less than optimum temperatures as well as your oil and fuel as Paul explained correctly.

3. See item #1 and item #2 above :D

Also see Defective Stant Thermostats (http://www.zr1specialist.com/HAT%20Web/facts%20and%20failures/thermostat.htm)

Oh....almost forgot.....my fans come on a bit sooner controlled by Marc Haibeck chip to help with engine temperatures when idling at a traffic light on a hot day. But again....my 180 deg thermostat and your 160 deg thermostat are both open in that condition :D

Cliff

[Bob Eyres]

1. At a coolant temperature of say 190 deg your 160 deg thermostat is open....so is my 180 deg thermostat. So from that point on our coolant system flow rates are identical at the same rpm. And so is the cooling.
Cliff

True enough. But as I mentioned before, though the 160deg. thermostat is designed to OPEN at that temp, that doesn't mean that it keeps the engine at that temp. Do we know if there is an average temp. differential between these thermostats? Not just during the warmup cycle.

Do we know what the average engine temp, (on a 70deg day), would be on two identical ZR-1's that had 160, and 180 deg. thermostats, after warm up?
And, what is the ideal engine temp, for performance, on the ZR-1.

This question does not apply to the intake plenum, where I think the ideal temp would be as cool as possible.

These questions are important on the LT5 because it seems to respond very noticeably to changes in temp. On a rare cool day here in Florida, after a short warm-up mine runs much stronger for a while until the plenum gets hot.

[Jim Nolan]

I have a 160 thermostat in mine and the fans programmed to come on at 185 and off at 180. In the summer months it normally runs 190, some times 200 in slow traffic. I never liked it stock running at 220-230 and on a really hot day in traffic 235.

[Dynomite]

Do we know if there is an average temp. differential between these thermostats? Not just during the warmup cycle.

Do we know what the average engine temp, (on a 70deg day), would be on two identical ZR-1's that had 160, and 180 deg. thermostats, after warm up?
And, what is the ideal engine temp, for performance, on the ZR-1.



Lets simplify....... You ask a lot of questions but are they relevant? :handshak:

1. Let us say we have identical radiators, identical rpm, steady state coolant temperature, and both fans on and we are cruising at same speed.
2. Lets say coolant temperature is 190 deg in both your Z and my Z given everything identical in item #1.
3. Your 160 deg thermostat is full open with same flow rate as fully open 180 deg thermostat.
4. My 180 deg thermostat is full open with same flow rate as fully open 160 deg thermostat.
5. In other words...we both have been driving our Zs for say at least 30 minutes and have reached a steady coolant state.

Now......lets say the day gets hotter. The coolant temperatures should rise the same in both your Z and my Z given EVERYTHING else is the same :p

If it gets REAL HOT......both our Zs coolant will reach 230 deg at the same time :D

The maximum temperature reached (given it is over 190 deg) will be no different for you than me even though you have a 160 deg thermostat and I have a 180 deg thermostat.

Or.....have I been on the tractor too long :sign10:

I am saying that my thermostat just maintains a minimum temperature higher than yours.
I am also saying your thermostat does not maintain a lower higher temperature than mine. Once both thermostats are fully open, the coolant temperatures are controlled by everything else mentioned in item #1 and not the thermostats (yours or mine).

Same goes for fans......once your fan is on and my fan which may be on at lower temperatures is on.......we have identical radiator cooling no matter how hot it gets outside.

Now if we change radiators.....you run stock radiator and I run Ron Davis....DIFFERENT STORY as I have greater dissipation of heat than you at all rpms (water pump speed dependent) and ZR-1 speeds (air flow dependent).

[Hog]

I agree with everything Dyno, makes sense. Just a tidbit, lets say your max. temp is going to be 210º no matter the temp of therostat used. If you have a 180º stat, and I have a 160º stat, my car will take longer to reach that 210º max than your 180º stat. Why? Because my stat has started to open at 160º and has been removong heat from teh system, while your car has NOT been removing heat from the system. Assuming all else equal of course.

Your arguements come across as sound to me, but whenever I have swapped from a stock OEM stat to a 160º stat, the engine coolant gauge has always been lower. SO much so, that I swap between my 160º stat for warm weather and the OEM stat for Winter as the interior heat is lacking with the lower rated stat.

There has to be something else at play here. (my experience with stats is not LT5 related-if that matters?)

[Dynomite]

I agree with everything Dyno, makes sense. Just a tidbit, lets say your max. temp is going to be 210º no matter the temp of therostat used. If you have a 180º stat, and I have a 160º stat, my car will take longer to reach that 210º max than your 180º stat. Why? Because my stat has started to open at 160º and has been removong heat from teh system, while your car has NOT been removing heat from the system. Assuming all else equal of course.

Your arguements come across as sound to me, but whenever I have swapped from a stock OEM stat to a 160º stat, the engine coolant gauge has always been lower. SO much so, that I swap between my 160º stat for warm weather and the OEM stat for Winter as the interior heat is lacking with the lower rated stat.

There has to be something else at play here. (my experience with stats is not LT5 related-if that matters?)

I concur with you on a non steady state (warming up or cooling down) but after driving for say 30 minutes we have a steady state which I compare.

Now on the experience part where many suggest a 160 deg Stat will run cooler in steady state.....I have no explanation :D

I am assuming a 160 deg Stat has the same flow rate as a 180 deg Stat when fully open.
I also assume both the 160 deg Stat and 180 deg Stat fully open relatively quickly as I experienced when placing them in a pot of water on the stove with thermometer. At least I thought they were fully opened ;)

[Schrade]

True enough. But as I mentioned before, though the 160deg. thermostat is designed to OPEN at that temp, that doesn't mean that it keeps the engine at that temp. Do we know if there is an average temp. differential between these thermostats? Not just during the warmup cycle.

Do we know what the average engine temp, (on a 70deg day), would be on two identical ZR-1's that had 160, and 180 deg. thermostats, after warm up?
And, what is the ideal engine temp, for performance, on the ZR-1.

This question does not apply to the intake plenum, where I think the ideal temp would be as cool as possible.

These questions are important on the LT5 because it seems to respond very noticeably to changes in temp. On a rare cool day here in Florida, after a short warm-up mine runs much stronger for a while until the plenum gets hot.

That should always be the end of discussions about lower-temp rated thermostats.

And if you have a 160', and LT5 Closed Loop starts @ 167 [?], or 176, that means your mill is going to spend more time in OL. MUCH longer in fact, because MUCH more of coolant is now cycling...


ed.:
Now if your chip was coded to make the fans come on @ 160, or 165, then the fans would do a pretty good job of staying neat that.

[Dynomite]

That should always be the end of discussions about lower-temp rated thermostats.

And if you have a 160', and LT5 Closed Loop starts @ 167 [?], or 176, that means your mill is going to spend more time in OL. MUCH longer in fact, because MUCH more of coolant is now cycling...

ed.:
Now if your chip was coded to make the fans come on @ 160, or 165, then the fans would do a pretty good job of staying neat that.

What did you just say ;)
Did you say your fans (or someones fans) come on at 160 deg F?

Seems to me I recall Secondary fan turns on at 228 deg F and Primary fan turns on at 219 deg F.
I also recall fans turn off with a drop of 11 deg F more or less.
With a chip....Marc sets the fans on at 205 deg F and off at 200 deg F.

I think lower temperature thermostats are a cheap way of trying to lower engine temperatures without having to spend money were it counts (get a Ron Davis Aluminum Radiator) :D
Or....blow more air through the radiator you have.

[Tyler Townsley]

I concur with you on a non steady state (warming up or cooling down) but after driving for say 30 minutes we have a steady state which I compare.

Now on the experience part where many suggest a 160 deg Stat will run cooler in steady state.....I have no explanation :D

I am assuming a 160 deg Stat has the same flow rate as a 180 deg Stat when fully open.
I also assume both the 160 deg Stat and 180 deg Stat fully open relatively quickly as I experienced when placing them in a pot of water on the stove with thermometer. At least I thought they were fully opened ;)

Check the code for fueling, it runs richer at the lower temp which will contribute to some cooling. I once asked Graham why they did not calibrate the car to run at the lower temps and the answer was emissions not power. The car can make more power at 165-175 than it can at 195-205 but it could not be made to comply with all EPA emission constraints at the lower temps.

Tyler

[KILLSHOTS]

Check the code for fueling, it runs richer at the lower temp which will contribute to some cooling. I once asked Graham why they did not calibrate the car to run at the lower temps and the answer was emissions not power. The car can make more power at 165-175 than it can at 195-205 but it could not be made to comply with all EPA emission constraints at the lower temps.



Tyler

This is exactly what I thought. My car is emissions-exempt anyway, and I don't care about that. Obviously, a better radiator is the way to go but a cooler stat would help, too. And I don't understand the assertion that a 160-degree stat isn't meant to KEEP it at that temp; I think that's generally understood. The point is that it opens the coolant flow and STARTS the cooling 20 degrees earlier, which will keep the LT-5 from achieving such lofty temperatures in the first place. This is crucial, unless you like your ZR-1 feeling as though you'd misplaced its power key.

Took my car for a drive on surface streets in the 108-degree heat with the A/C on yesterday and it didn't like it one bit. Need to do something soon. A lot of you guys have to "put your cars up" for the winter. I don't want to have to "put mine up" for the summer!

[We Gone]

I run a stock thermostat with marc's chip and with AC on I see temps of 200-210 stopped and as soon as I start moving it stays 193-195. Outside temps 90s

[PhillipsLT5]

GC had luck running a stock radiator in Phx as a daily driver
With his new motor he went to a different radiator & fans
I have luck but running Marcs chip with fluidyne radiator, it really helped over stock radiator, but these cars need to be moving to keep cool in Phx
You can open it @ 160 or 180, but you will be lucky to run at 190-200
Sounds like you may have the typical blocked radiator due to fans sucking air thru along with dirt and blocking flow after years
Ron Davis is local/buy a new stocker/remove & clean 20yr old rad/Dewitts
You do not want to overheat & blow head gasket

[Schrade]

I agree with everything Dyno, makes sense. Just a tidbit, lets say your max. temp is going to be 210º no matter the temp of therostat used. If you have a 180º stat, and I have a 160º stat, my car will take longer to reach that 210º max than your 180º stat. Why? Because my stat has started to open at 160º and has been removong heat from teh system, while your car has NOT been removing heat from the system. Assuming all else equal of course.

Your arguements come across as sound to me, but whenever I have swapped from a stock OEM stat to a 160º stat, the engine coolant gauge has always been lower. SO much so, that I swap between my 160º stat for warm weather and the OEM stat for Winter as the interior heat is lacking with the lower rated stat.

There has to be something else at play here. (my experience with stats is not LT5 related-if that matters?)

Where is the guage temp signal coming from??? Is the temp sensor located where out-of-block [cooler] coolant is coming INTO the CTS???



I have a 160 thermostat in mine and the fans programmed to come on at 185 and off at 180. In the summer months it normally runs 190, some times 200 in slow traffic. I never liked it stock running at 220-230 and on a really hot day in traffic 235.
It's surprising to me that the fans don't take coolant temps back down to your shutoff temp...





This is exactly what I thought. My car is emissions-exempt anyway, and I don't care about that. Obviously, a better radiator is the way to go but a cooler stat would help, too. And I don't understand the assertion that a 160-degree stat isn't meant to KEEP it at that temp; I think that's generally understood. The point is that it opens the coolant flow and STARTS the cooling 20 degrees earlier, which will keep the LT-5 from achieving such lofty temperatures in the first place. This is crucial, unless you like your ZR-1 feeling as though you'd misplaced its power key.

Took my car for a drive on surface streets in the 108-degree heat with the A/C on yesterday and it didn't like it one bit. Need to do something soon. A lot of you guys have to "put your cars up" for the winter. I don't want to have to "put mine up" for the summer!

I disagree with this.

And it seems that Jim Nolan's ECM coding, above, points this out - he still had his fans coded to come on at a lower temp, because the coolant still will exceed the rated temperature of the stat - 160, and even then, his fans don't take temps down to that fan shutoff temp that he coded. THAT part is surprising to me...



What did you just say ;)
Did you say your fans (or someones fans) come on at 160 deg F?

Seems to me I recall Secondary fan turns on at 228 deg F and Primary fan turns on at 219 deg F.
I also recall fans turn off with a drop of 11 deg F more or less.
With a chip....Marc sets the fans on at 205 deg F and off at 200 deg F.

I think lower temperature thermostats are a cheap way of trying to lower engine temperatures without having to spend money were it counts (get a Ron Davis Aluminum Radiator) :D
Or....blow more air through the radiator you have.

I said IF...
ME
Now if your chip was coded to make the fans come on @ 160, or 165, then the fans would do a pretty good job of staying neat that.

And JN's chip is coded CLOSE to that...

[Dynomite]

I said IF...


OK :p

Now if anyone has a stock radiator with stock engine and say a 160 deg - 165 deg thermostat and fans coming on whenever.......and running stop and go with ambient temperature 100 deg F.....tell me what the temperature gauge reads.....and then go and read the temperature digitally using HVAC to confirm.

Press both Fan Up and Fan Down together waiting 3 seconds to enter HVAC diagnostics. Then press Fan Up to parameter #16 and then press Auto (between the two Fan Buttons) to read the Engine Coolant Temperature in deg C which Engine Coolant Temperature will be a real time continuous reading.

See Using HVAC Display for Engine Coolant Temperature (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070560)

Just interested ;)

[Schrade]

OK :p Ain't ya' got 20/20 hearing? http://www.franken-cruiser.com/community/images/smilies/blind.gif http://www.zr1.net/forum/images/icons/icon10.gif



Now if anyone has a stock radiator with stock engine and say a 160 deg thermostat and fans coming on whenever.......and running stop and go with ambient temperature 100 deg F.....tell me what the temperature gauge reads.....and then go and read the temperature digitally using HVAC to confirm.

Press both Fan Up and Fan Down together waiting 3 seconds to enter HVAC diagnostics. Then press Fan Up to parameter #16 and then press Auto (between the two Fan Buttons) to read the Engine Coolant Temperature in deg C which Engine Coolant Temperature will be a real time continuous reading.

See Using HVAC Display for Engine Coolant Temperature (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070560)

Just interested ;)

Me too here. Why does JN's temps not go back down with his lower fans kick-on temp coding???

And why does Hog's run a little cooler, with only a lower temp stat????????????

[WARP TEN]

FYI, Marc Haibeck's chip typically turns on both fans at 205 degrees. I don't recall my car showing anything higher than about 208 on a hot day, maybe 210. -- Bob

[Dynomite]

FYI, Marc Haibeck's chip typically turns on both fans at 205 degrees. I don't recall my car showing anything higher than about 208 on a hot day, maybe 210. -- Bob

Is that reading HVAC or analog (dash) gauge?

[Hog]

Where is the guage temp signal coming from??? Is the temp sensor located where out-of-block [cooler] coolant is coming INTO the CTS???




It's surprising to me that the fans don't take coolant temps back down to your shutoff temp...





I disagree with this.

And it seems that Jim Nolan's ECM coding, above, points this out - he still had his fans coded to come on at a lower temp, because the coolant still will exceed the rated temperature of the stat - 160, and even then, his fans don't take temps down to that fan shutoff temp that he coded. THAT part is surprising to me...





I said IF...


And JN's chip is coded CLOSE to that...

There is 2 CTS, 1 for the gauge located in the waterneck, and 1 for the PCM in the drivers side cylinder head.

OBD2 vehicle with clutch fan. The temp gauge is constantly moving in a steady state cruise, I', assuming the stat is opening and closing? The stock stat deos not show any cycling on the gauge.
Further evidence of a temp change is the lower heater output when the lower temp stat is installed.

Closed Loop Fueling enable has a stock setting of 56.25ºC or 133.25ºF. Much lower than the LT5's. In Tunercat's OBD2 I can adjust the Closed Loop Enable temp to whatever I wish.

There is a point where running an engine too cool increases cylinder wall and other wear.

[Hog]

This is exactly what I thought. My car is emissions-exempt anyway, and I don't care about that. Obviously, a better radiator is the way to go but a cooler stat would help, too. And I don't understand the assertion that a 160-degree stat isn't meant to KEEP it at that temp; I think that's generally understood. The point is that it opens the coolant flow and STARTS the cooling 20 degrees earlier, which will keep the LT-5 from achieving such lofty temperatures in the first place. This is crucial, unless you like your ZR-1 feeling as though you'd misplaced its power key.

Took my car for a drive on surface streets in the 108-degree heat with the A/C on yesterday and it didn't like it one bit. Need to do something soon. A lot of you guys have to "put your cars up" for the winter. I don't want to have to "put mine up" for the summer!
I would ASSume that EPA testing for the ZR-1 is a bit more involved when testing a vehicle platform for EPA certification for manufacturer such as GM.
My point is that just because an OEM cant get a car to pass emmisions testing with lower temps, doesnt necessarily mean that a car with lower operating temps wont be able to pass a garden variety emissions test at the individual owners/driver level.
However, if a car had top be "sniffer tested" and the car was struggling to enter Closed Loop because the engine was running too cool, I can certainly see that causing issues in passing.

Graham Behan would have extensive experience with OEM and aftermarket emmisions testing as Lingenfelter PE had a couple LT5 emmissions compliant packages, and they even had an emissions compliant 550hp SAE net, 705 lb/ft torque from 605 cubes BBC engine package for their Suburban packages.
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/lpe605hp780.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/lpe605hp780.jpg.html)
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/605.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/605.jpg.html)
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/605cidLingenfelterburb.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/605cidLingenfelterburb.jpg.html)

If they can get a dirty BBC to comply with emmissions laws, and "tuned" LT5 shouldnt be too hard.



When we had the chassis dyno testing similar to California spec testing, I had 160º thermostat, longtube headers, aftermarket cats, EGR disconnected(but present to pass the visual) and the truck blew very clean.

[Paul Workman]

This is exactly what I thought. My car is emissions-exempt anyway, and I don't care about that. Obviously, a better radiator is the way to go but a cooler stat would help, too. And I don't understand the assertion that a 160-degree stat isn't meant to KEEP it at that temp; I think that's generally understood. The point is that it opens the coolant flow and STARTS the cooling 20 degrees earlier, which will keep the LT-5 from achieving such lofty temperatures in the first place. This is crucial, unless you like your ZR-1 feeling as though you'd misplaced its power key.

Took my car for a drive on surface streets in the 108-degree heat with the A/C on yesterday and it didn't like it one bit. Need to do something soon. A lot of you guys have to "put your cars up" for the winter. I don't want to have to "put mine up" for the summer!

I don't know that this will add anything useful to this interesting conversation. But, reading along, what gets written and what folks meant to say are not always the same. So, if that is the reason I got the impression that there was some confusion regarding some basic physics principals, I don't mean to be "speaking to the choir". :blahblah: But, for some perhaps majoring in sociology instead of science :p they might find something below worth using...maybe?

Anyway... It's easy. What it "boils" down to is simple physics:



HEAT (temperature, to be specific) generated in the engine/coolant will rise until heat escaping is equal to heat generated. (Temperature will stabilize at that level sans changes in the engine load, etc, for example)
HEAT transfer efficiency increases-

-with the relative difference in temperature between the heated medium, and the medium receiving that heat
-the amount of radiating surface area between the heated medium (aluminum in this case) and (air - also in this case).

Everything - the whole discussion about cooler or hotter thermostats circles around these two physical facts (1&2). Putting a 160º thermostat in for summer won't make any difference to the equilibrium temperature if conditions dictate that point to be closer to 230º. No matter if you have a 160 or a 200º stat, if the conditions dictate 230º, THAT is where temp will stabilize, regardless of the stat design.

Heat transfer efficiency for any given ambient air temperature can be increased by-

increasing the surface area between the radiator and the air, i.e., BIGGER radiator
increasing the differential temp between the (radiator) and (specifically) the air e.g, removing the heat-saturated air from the heated radiator surface.
proper coolant level and additive (e.g., antifreeze or whatever).


So, the facts are -

heat transfer gets better as (coolant) temps increase.
The lower the engineered equilibrium temp is to the ambient temp (of the air, in this case) the greater the need for increased radiant transfer area and exchange of heat soaked recipient medium (air) to maintain the highest differential temp difference between the source and the receiving medium).


The thermostat rating will prevent heat transfer until the designed temp is reached. At that point, the thermostat opens and physics takes over. There is either enough surface area in combination with the differential between the radiator and the (air) temp surrounding the core to result in the temperature stabilizing when the thermostat opens, or NOT. If, for example, ambient air temps are such that equilibrium will be 230º, then temps will rise w/o regard to the thermostat setting (beit a 160º* or a 200º or whatever), rising quickly at first, and stabilize at 230º (in this example) until and unless there are changes in engine load resulting in a change in the amount of heat being given off.

*The only difference in temperature rise on the way to say a 230º equilibrium between using a 160º stat and a 200º stat is the rate of temp rise in that window between 160º to 200º. That will be useful and desirable on a drag strip. But, on the street...not so much. A more practical temp, in terms of radiator size and cooling fan metrics, closed loop and fuel efficiencies, might be closer to 200º. AND, instead of bigger fans, having BOTH come on instead of the factory staggering arrangement is a better solution, I say from practical experience with that (Marc's calibration) arrangement.

Just sayin...

Paul.

[Dynomite]

Just sayin...
Paul.

:thumbsup:

What Paul Said :D

[Hog]

Good post Paul^^
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

I just wanted to add a tidbit about possible thermostats and the modern EFI vehcile. On the LT1 cars and L31 trucks, in the 90's there were ECM recalibration devices sold for these vehicles. Acommpanying these devices were 160º thermostats in order to help the engines and their 10.5:1 c/r produce full power with leaner WOT a/f ratios and advanced WOT timing curves these devices instilled into the ECM calibration.
If a lower temp thermostat only helped slow down rate of engine coolant temp increases(which they do after a cold startup) the lower temp thermostats these kits included, really would NOT help to prevent detonation/knock sensor counts by keeping engine coolant temps lower.

JET Performance and Hypertech were to companies that provided products in which they woudl suggest or include lower temp thermostats as part of their Level 2 (more agressive) ECM/PCM calibrations.

[XfireZ51]

I think you're better off cleaning your radiator, in and out, to gain maximum cooling efficiency.

[Dynomite]

I think you're better off cleaning your radiator, in and out, to gain maximum cooling efficiency.

And................installing a radiator Debris Screen :p

Radiator Debris Screens (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070563)

[XfireZ51]

And................installing a radiator Debris Screen :p

Radiator Debris Screens (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070563)

True, but there's lots of tiny dirt particles that over time clog the areas between the coils. For a vehicle, coming from the Southwest for example, that kind of dirt restricts airflow. Before swapping T-stats, I'd blow out the rad.
Look at what Chevy found by doing the "flo-tie" on the Z28. Increase airflow by 3%. just from that amount of increased area.

[Paul Workman]

And................installing a radiator Debris Screen :p

Radiator Debris Screens (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070563)

Oh, YEAH! I was just tutoring Ami in the do's n don't whether it be her 69 Vette or a Z: Avoid those grass clippings that some people spread out in the middle of the road (when mowing). Avoid - go around if possible, like it was a mud pit!

[A26B]

......................................

Heat transfer efficiency for any given ambient air temperature can be increased by-

increasing the surface area between the radiator and the air, i.e., BIGGER radiator
increasing the differential temp between the (radiator) and (specifically) the air e.g, removing the heat-saturated air from the heated radiator surface.
proper coolant level and additive (e.g., antifreeze or whatever).

I would add: Increased air flow through the heat exchanger, i.e. the radiator.
Increasing the surface area of the radiator in the LT5 can be accomplished only by adding additional cores. Adding additional cores increases the resistance to air flow. Compensation for reduced air flow due to the increased restriction of more cores can only occur with greater air flow.

So, the facts are -


heat transfer gets better as (coolant) temps increase.
The lower the engineered equilibrium temp is to the ambient temp (of the air, in this case) the greater the need for increased radiant transfer area and exchange of heat soaked recipient medium (air) to maintain the highest differential temp difference between the source and the receiving medium).

I might suggest "increases" in lieu of "gets better." The actual transfer of heat doesn't actually get any better with higher input.


There is 2 CTS, 1 for the gauge located in the waterneck, and 1 for the PCM in the drivers side cylinder head.

Here is the location for the LT5 sensors.
.http://jerrysgaskets.com/store2/root/images/Sensors,%20Cooling%20Temp.jpg


#9 is the most relevant here Paul.

I don't know for sure, but I think an LT5 without a thermostat would blow the plastic components of the stock radiator apart.

Although not a good idea to remove the thermostat, its removal would actually decrease flow resistance and would not cause the plastic tanks to blow off.

Damage to radiators has occurred from excessive restriction of the "bypass system" which was part of the LT5 cooling system, designed to prevent radiator damage.

I can see that such a high-compression engine running at high RPM could put serious stress on the non-metal parts of the cooling system without a stat. In this case, the stat makes a more compelling case as a water baffle than a temperature regulator.........


Not so with the LT5. Look at the coolant flow diagram. The thermostat is downstream of the radiator. It is actually a component of the resistance causing backpressure which is generally attributed to the radiator alone. The LT5 thermostat does not function as a baffle. The bypass system is proof of that.

........And I don't understand the assertion that a 160-degree stat isn't meant to KEEP it at that temp; I think that's generally understood. The point is that it opens the coolant flow and STARTS the cooling 20 degrees earlier, which will keep the LT-5 from achieving such lofty temperatures in the first place.

Paul, Dynomite & others have explained the function of the thermostat very well.
You need to understand that thermostats DO NOT regulate MAXIMUM temperatures, but only MINIMUM opening temperatures.



Maximum temperatures are limited by the capacity of the radiator. Efficiency of the stock radiator can be restricted by debris within the fins and in front of the radiator (as others have stated).
Efficiency of the stock radiator is improved by the stock cooling fans which can be "turned on" earlier at lower temperatures.
More air flow to further improve the capacity of the radiator, can be achieved by adding additional or higher capacity cooling fans.
Improved coolant flow rate through the radiator can be achieved by drilling two to four 1/8" holes in the flange of the stock, 180F thermostat. This increases the total flow capacity of coolant through the thermostat and thereby reduces restriction through the radiator. Originated by Lingenfelter and the biggest bang for the buck to make the LT5 run cooler.
Bigger is not always better when it comes to radiators for street driven ZR-1 Corvettes. Going from a 2 core stock radiator to a 5 core Ron Davis Racing Radiator. It's a beautiful & expensive piece. A 5 core radiator requires more air flow through it to function as designed. The key word in Ron Davis Racing Radiators is "Racing." They are designed for high speed which obviously means more air flow that street driven cars don't achieve.

In summary,


A 160F t-stat is not going to help your high operating temperatures
Remove your stock radiator and either (1) replace with a new one or (2)have yours thoroughly cleaned of debris in the fins & any trash in front of it.
Do have you prom programmed to turn the cooling fans on earlier
Drill three 1/8" holes in the stock 180F t-stat flange

[Schrade]

Good stuff there Jerry...

Colder-rated thermostat for cooler running temps is one of the biggest myths I know of.

But Hog said his twister DOES turn "so much so" cooler, with only the lower-rated stat.

I agree with everything Dyno, makes sense. Just a tidbit, lets say your max. temp is going to be 210º no matter the temp of therostat used. If you have a 180º stat, and I have a 160º stat, my car will take longer to reach that 210º max than your 180º stat. Why? Because my stat has started to open at 160º and has been removong heat from teh system, while your car has NOT been removing heat from the system. Assuming all else equal of course.

Your arguements come across as sound to me, but whenever I have swapped from a stock OEM stat to a 160º stat, the engine coolant gauge has always been lower. SO much so, that I swap between my 160º stat for warm weather and the OEM stat for Winter as the interior heat is lacking with the lower rated stat.

There has to be something else at play here. (my experience with stats is not LT5 related-if that matters?)

Is this only because the temp sensor is close to radiator flow???

And are you surprised that Jim Nolan's cooling system doesn't keep his mill running closer to 185', which his ECM is re-coded for?

I have a 160 thermostat in mine and the fans programmed to come on at 185 and off at 180. In the summer months it normally runs 190, some times 200 in slow traffic. I never liked it stock running at 220-230 and on a really hot day in traffic 235.

I would add: Increased air flow through the heat exchanger, i.e. the radiator.
Increasing the surface area of the radiator in the LT5 can be accomplished only by adding additional cores. Adding additional cores increases the resistance to air flow. Compensation for reduced air flow due to the increased restriction of more cores can only occur with greater air flow.

I might suggest "increases" in lieu of "gets better." The actual transfer of heat doesn't actually get any better with higher input.



Here is the location for the LT5 sensors.
.http://jerrysgaskets.com/store2/root/images/Sensors,%20Cooling%20Temp.jpg




Although not a good idea to remove the thermostat, its removal would actually decrease flow resistance and would not cause the plastic tanks to blow off.

Damage to radiators has occurred from excessive restriction of the "bypass system" which was part of the LT5 cooling system, designed to prevent radiator damage.



Not so with the LT5. Look at the coolant flow diagram. The thermostat is downstream of the radiator. It is actually a component of the resistance causing backpressure which is generally attributed to the radiator alone. The LT5 thermostat does not function as a baffle. The bypass system is proof of that.



Paul, Dynomite & others have explained the function of the thermostat very well.
You need to understand that thermostats DO NOT regulate MAXIMUM temperatures, but only MINIMUM opening temperatures.



Maximum temperatures are limited by the capacity of the radiator. Efficiency of the stock radiator can be restricted by debris within the fins and in front of the radiator (as others have stated).
Efficiency of the stock radiator is improved by the stock cooling fans which can be "turned on" earlier at lower temperatures.
More air flow to further improve the capacity of the radiator, can be achieved by adding additional or higher capacity cooling fans.
Improved coolant flow rate through the radiator can be achieved by drilling two to four 1/8" holes in the flange of the stock, 180F thermostat. This increases the total flow capacity of coolant through the thermostat and thereby reduces restriction through the radiator. Originated by Lingenfelter and the biggest bang for the buck to make the LT5 run cooler.
Bigger is not always better when it comes to radiators for street driven ZR-1 Corvettes. Going from a 2 core stock radiator to a 5 core Ron Davis Racing Radiator It's a beautiful & expensive piece. A 5 core radiator requires more air flow through it to function as designed. The key word in Ron Davis Racing Radiators is "Racing." The are designed for high speed which obviously means more air flow that street driven cars don't achieve.

In summary,


A 160F t-stat is not going to help your high operating temperatures
Remove your stock radiator and either (1) replace with a new one or (2)have yours thoroughly cleaned of debris in the fins & any trash in front of it.
Do have you prom programmed to turn the cooling fans on earlier
Drill three 1/8" holes in the stock 180F t-stat flange

[Dynomite]

I would add: Increased air flow through the heat exchanger, i.e. the radiator.

A 160F t-stat is not going to help your high operating temperatures
Remove your stock radiator and either (1) replace with a new one or (2)have yours thoroughly cleaned of debris in the fins & any trash in front of it.
Do have you prom programmed to turn the cooling fans on earlier
Drill three 1/8" holes in the stock 180F t-stat flange



Excellent Jerry :thumbsup:

I would add........

Turning the cooling fans on earlier has the same effect as opening your thermostat earlier (160 deg). After a steady state coolant temperature is reached where your fans and my fans are both on no matter when I turned my fans on the cooling effect is the same.

But then again ....if you are operating where the coolant temperature is 218 deg (just below the secondary fan normal operation) then turning on your fans at say 200 deg would be a definite advantage. Same goes for the coolant temperature at which the primary fans turn on at 228 deg. If you have coolant temperature of 227 deg then turning on your fans at a lower temperature will be an advantage. But if we both have a standard radiator and the coolant temperature is at least 228 deg where both your fans are on with my fans turning on at a lower temperature...there would be no advantage to me turning my fans on at the lower temperature in that situation.

Now having said that......There is a caveat ;)

My fans come on at 205 deg and off at 200 deg but then again I have a Ron Davis Radiator. Turning my fans on earlier (at a higher temperature than my 180 deg thermostat) will have a greater cooling effect (because of the Ron Davis Radiator). My coolant temperatures are actually less than the standard fan turn on temperature of 228 deg or 219 deg (I recall Secondary fan turns on at 228 deg F and Primary fan turns on at 219 deg F.
I also recall fans turn off with a drop of 11 deg F more or less). With a chip....Marc sets the fans on at 205 deg F and off at 200 deg F.

Both our fans are on at 205 deg (Programmed in the modified Chip) but my fans are pulling air through a Ron Davis Radiator and can take advantage of the lower coolant temperature operation fan turn on programmed by Marc.

In other words....because of my Ron Davis Radiator I would be normally running the ZR-1 with the fans OFF (because I am below the normal coolant temperatures that would normally turn the fans on). So....I turn my fans on sooner (Marc Chip) where the full advantage of the Ron Davis Radiator can be experienced.

Dynomite aka Cliff :p

I hope I made my self clear ;)
I know.....clear as mud :sign10:

[GOLDCYLON]

GC had luck running a stock radiator in Phx as a daily driver
With his new motor he went to a different radiator & fans
I have luck but running Marcs chip with fluidyne radiator, it really helped over stock radiator, but these cars need to be moving to keep cool in Phx
You can open it @ 160 or 180, but you will be lucky to run at 190-200
Sounds like you may have the typical blocked radiator due to fans sucking air thru along with dirt and blocking flow after years
Ron Davis is local/buy a new stocker/remove & clean 20yr old rad/Dewitts
You do not want to overheat & blow head gasket

I also am running the Big Mouth Air Dam with a debries screen and the SPAL Fans on early at the PROM. Mines a daily driver and a desert runner. Phil is right these cars like to run. On the freeway in 6th gear not a issue. Stop and go the temp will climb. For a stock LT5 the original radiator is fine.. as long as the front air dam system is in good shape and the fins are clean. Killshots (Chris) if you need another radiator I have a 6 month new stock delco replacement I used for 6 months up in the attic before I went to the larger radiator and fans. These older 20 plus year radiators swell at the plastic ends and some grit you cant get out of the fins.

[KILLSHOTS]

I also am running the Big Mouth Air Dam with a debries screen and the SPAL Fans on early at the PROM. Mines a daily driver and a desert runner. Phil is right these cars like to run. On the freeway in 6th gear not a issue. Stop and go the temp will climb. For a stock LT5 the original radiator is fine.. as long as the front air dam system is in good shape and the fins are clean. Killshots (Chris) if you need another radiator I have a 6 month new stock delco replacement I used for 6 months up in the attic before I went to the larger radiator and fans. These older 20 plus year radiators swell at the plastic ends and some grit you cant get out of the fins.
Thanks Daryll! Based on input from you and Phil and the other brothers, I actually decided that step 1 was cleaning my radiator. So I had it removed yesterday and WHAT A MESS!!! Probably a pound of crap came out of the cooling stack, the majority of which was on the rad itself. Only drove it a couple miles afterward, but it was about 110 out and with the A/C on it didn't seem to get much over 200. I'm confident that it's going to be MUCH better now. With only 16K on the car, my radiator looked pretty much new, after it was cleaned.

[PhillipsLT5]

I also am running the Big Mouth Air Dam with a debries screen and the SPAL Fans on early at the PROM. Mines a daily driver and a desert runner. Phil is right these cars like to run. On the freeway in 6th gear not a issue. Stop and go the temp will climb. For a stock LT5 the original radiator is fine.. as long as the front air dam system is in good shape and the fins are clean. Killshots (Chris) if you need another radiator I have a 6 month new stock delco replacement I used for 6 months up in the attic before I went to the larger radiator and fans. These older 20 plus year radiators swell at the plastic ends and some grit you cant get out of the fins.

GC parts bin to the rescue

[KILLSHOTS]

GC parts bin to the rescue
No kidding Phillip! Someday, Daryll, I PROMISE I'm going to buy something out of your attic!!

See you at C&C on Saturday, Phil? Daryll, can you make it?

[Dynomite]

True, but there's lots of tiny dirt particles that over time clog the areas between the coils. For a vehicle, coming from the Southwest for example, that kind of dirt restricts airflow. Before swapping T-stats, I'd blow out the rad.
Look at what Chevy found by doing the "flo-tie" on the Z28. Increase airflow by 3%. just from that amount of increased area.

Great point....yep...I delicately use a pressure washer connected to HOT water once in a while especially if there is any kind of previous oil that is contaminating the radiator cooling fins :thumbsup:

Especially on the passenger side where the oil cooler hoses are located.

[PhillipsLT5]

Thanks Daryll! Based on input from you and Phil and the other brothers, I actually decided that step 1 was cleaning my radiator. So I had it removed yesterday and WHAT A MESS!!! Probably a pound of crap came out of the cooling stack, the majority of which was on the rad itself. Only drove it a couple miles afterward, but it was about 110 out and with the A/C on it didn't seem to get much over 200. I'm confident that it's going to be MUCH better now. With only 16K on the car, my radiator looked pretty much new, after it was cleaned.

Yesterday hottest day of year so far @ 110, 200 is GREAT!, check coolant level after refill, do not use dexcool
http://zr1specialist.com/HAT%20Web/articles/Filling%20the%20LT5%20With%20Coolant.pdf

http://zr1specialist.com/HAT%20Web/articles/Evidence%20that%20DexCool%20Harms%20the%20Cylinder %20Head%20Gasket.pdf

[PhillipsLT5]

No kidding Phillip! Someday, Daryll, I PROMISE I'm going to buy something out of your attic!!

See you at C&C on Saturday, Phil? Daryll, can you make it?

I am planning on going early 6:30 or 7 & leaving early due to heat 9AM should be 90, maybe motor down scottsdale road to corvettes & caffeine for a water & donut

[KILLSHOTS]

I am planning on going early 6:30 or 7 & leaving early due to heat 9AM should be 90, maybe motor down scottsdale road to corvettes & caffeine for a water & donut
Yeah, I'll be leaving early too. Look forward to seeing you there.

[rkreigh]

Check the code for fueling, it runs richer at the lower temp which will contribute to some cooling. I once asked Graham why they did not calibrate the car to run at the lower temps and the answer was emissions not power. The car can make more power at 165-175 than it can at 195-205 but it could not be made to comply with all EPA emission constraints at the lower temps.

Tyler


the man speaks truth, you want warm oil and cool coolant to make power

the drag racers warm the oil in the pits and go beat on the engine right after the burnout.

and the lt5 loves cool temps

at 50 deg, the lsv puts down 525 vice 508 at 75 corrected

their ain't no dyno correction factor on the street

drive the car on a a cool dry day and report back

[Tyler Townsley]

I have posted this before but it warrants repeating. Read what everyone posts and decide what you feel is best for your situation. I have run a Ron Davis radiator and no thermostat, it ran hot. I ran a cut thermo so it was open all the time blocked the bypass and at 70 mph and 95 degree day it ran 175-185 degrees with air on. In traffic it ran 190-200 with air on. At below 65 outside the temps ran 158 just below going closed loop and any lower the heater did not put out hardly any heat. If you consistently race your car I highly recommend this setup.

Engine temperature calibration is a huge compromise to emissions. The calibration is designed to meet EPA mandated levels and this requires the engines to run at higher temperatures. The current stock system is designed to accomplish this goal.

I happen to believe engine temps should run 165-185 degrees, but that's me. I have not seen any posting that show how to get the ZR-1 to run those temps in traffic on a hot day, that includes me. I can only conclude that the airflow through the engine compartment/radiator is not sufficient enough to cool the engine to at the lower speeds.

I have a 66 and for years saw high water temps at 85 until I installed a front spoiler, this change repositioned a low pressure area generated at that speed from inside the engine compartment to just below the pan which actually draws the air from the engine compartment. This allows the air to be placed in the underside airstream and drawn away from the car.

Tyler

[Hog]

Here is the location for the LT5 sensors.
.http://jerrysgaskets.com/store2/root/images/Sensors,%20Cooling%20Temp.jpg







Sorry I got my sensors backwards, the single wire CTS located in the cylinder head feeds the gauge, and the 2 wire CTS in the waterneck feeds the PCM of the L31.

The sensors you pictured are identical to the ones used in the L30/L31 305/350.

thanks for the pics, those 2 sensors should read the same temp all the time.

I'm surprised that an LT5 stat is only rated at 180º. Thats on the lower end of OEM stats.

I have to wonder if the differences between the LT5 and the L31 such as cooling capacity might be making a difference.
A 160º in my L31's trucks reads lower on the gauge and will not heat up as much as the stock 195º stat. I'm wondering if the limited cooling of the rad in the Vettes get hot and stay hot, whereas my truck will warm up letting coolant flwo through the rad and cool enough to cause the thermostat to close again?

The LT5 should ultimatley produce more BTU, but I wonder is the cooling system can transfer those BTU into the air as efficiently as an L31.
On another forum all persons who have installed a lower than stock stat are reporting similar reduction in gauge sweep visually, and via datalogging the PCM.

Looks like there isnt any advantage to using a lower temp stat in the LT5.

[Hog]

GM radiators part number and core measurements

52473260 1995 LT5-manual trans and LT1 auto/manual core size 23 9/16IN X 15IN X 1 5/16IN $224

89019344 1996+ L31 1500 core size 34IN X 17 1/2IN X 1 5/16IN
$409

Considerably more cooling capacity in the L31 rad.

[A26B]

...............
I have to wonder if the differences between the LT5 and the L31 such as cooling capacity might be making a difference.
A 160º in my L31's trucks reads lower on the gauge and will not heat up as much as the stock 195º stat. I'm wondering if the limited cooling of the rad in the Vettes get hot and stay hot, whereas my truck will warm up letting coolant flwo through the rad and cool enough to cause the thermostat to close again?............................[QUOTE]

Very possibly so. The Corvette radiator, angled vs perpendicular, and the fact that there are not one, but two heat exchangers in front of the radiator, combined with a very low air intake (i.e. right off the hot pavement), could all add up to more limited cooling, especially at low speeds. Add in the tendency of the Corvette to "vacuum clean" the road and collect all sorts of debris in front of the radiator and you have a pretty good recipe.


[quote]Looks like there isnt any advantage to using a lower temp stat in the LT5.

Considering the fact that the engine was designed to operate at 190F, I would say there is not an advantage to a 160F t-stat, UNLESS the engine was tuned and built for it.

LT5 engine clearances were designed for the higher temp which should also be considered. Considering thermal expansion, does 20F cooler operating temp have any detrimental effect on a stock engine with aluminum cylinders. What about a modified engine with iron cylinders and a lower coefficient of expansion? I don't profess to know the answers, but I do know from discussions with Graham Behan that the development of the LT5 was incredibly meticulous which is why no other production engine even comes close to the durability testing that the LT5 achieved. Even today, GM engineers are encountering problematic, dynamic engine issues that were noted and solved by the LT5 engineers 25 years ago.

Bob Eyers and others have made mention of cooler air intake benefits. I couldn't agree more. The increased power in cool ambient air at 40F is easily noticed in the seat of the pants. Considering the engine was designed for 190F operating temp, I would concentrate more on cooler air intake for increased Hp rather than 20F lower engine temperature.

I tend to agree with your statement, "Looks like there isn't any advantage to using a lower temp stat in the LT5." Air flow through the radiator is where the action is, not in the thermostat. Instead, concentrate on keeping the cooling system in tip-top condition. Drilling a couple of 1/8" holes in the 180F t-stat flange will help the t-stat to see direct coolant temp, increase flow through the radiator and reduce back-pressure which will retard the bypass by a corresponding amount. All good!

[XfireZ51]

I know people have made comment regarding how the motor feels stronger when cooler air is coming through the intake. I notice the same in early mornings or as fall comes to the midwest. I don't think that has anything to do with coolant temps. The motor has a MAT(Manifold Air Temp) sensor in the airhorn. The MAT sensor has a role in modifying the fuel delivery based on the manifold air temps. The warmer it is, the less fuel it can support due to density. However, one of the reasons tuners have moved the sensor and essentially "changed" the sensor to an IAT(Intake Air Temp) is that the MAT location is susceptible to heat soak and confusing the issue. By moving the sensor further forward in the intake track, the sensor is isolated from engine heat much more.
However, doing this also throws off the stock table that commands the ECM regarding how much attention it should give to air temp v coolant temps.
Part of the issue we experience with higher heat comes from this. By addressing the MAT tables, you are able to keep fueling much more consistent in spite of higher heat. When tuners move the sensor further forward, the ECM never sees the level of air temps that are assumed in the calibration. As a consequence, the motor runs richer even tho the coolant temps are higher unless the MAT table has been modified to compensate for the change. Unless you change that table, you'll never achieve a consistent tune and end up chasing the BLMs brought on by air temp change.

[SClarke1958]

I just found out about this web site yesterday and when talking to a couple ZR1 owners at the Myrtle Beach car show. Looks like a great site.

As far as whether to remove the thermostat or not, I would defiantly not. All the reasons have been mentioned in the replies already but I would emphasis a couple technical points.

1. The LT5 thermostat not only controls the temperature of the engine but limits the max pressure on the radiator inlet. When the radiator pressure is over a certain limit (about 25 psi at the radiator inlet), the bypass valve (spring disc on the thermostat) will open further and balance the amount of coolant flow to the radiator and engine.

2. The engine and thus associated controls for fuel and spark are designed to operate at thermostat control for the far majority of the engines life. So all the calibrations have been fine tuned to the thermostat control temp.

3. Coolant temp and oil temp have a relationship, so if the coolant temp is lowered, the oil temp goes down also and could cause longer term problems if too low.

Bottom line, the engine was designed to run with the thermostat and many many hours of testing went into the cooling system and engine at the design temps.

LT5 Cooling Engineer (retired)

[XfireZ51]

I just found out about this web site yesterday and when talking to a couple ZR1 owners at the Myrtle Beach car show. Looks like a great site.

As far as whether to remove the thermostat or not, I would defiantly not. All the reasons have been mentioned in the replies already but I would emphasis a couple technical points.

1. The LT5 thermostat not only controls the temperature of the engine but limits the max pressure on the radiator inlet. When the radiator pressure is over a certain limit (about 25 psi at the radiator inlet), the bypass valve (spring disc on the thermostat) will open further and balance the amount of coolant flow to the radiator and engine.

2. The engine and thus associated controls for fuel and spark are designed to operate at thermostat control for the far majority of the engines life. So all the calibrations have been fine tuned to the thermostat control temp.

3. Coolant temp and oil temp have a relationship, so if the coolant temp is lowered, the oil temp goes down also and could cause longer term problems if too low.

Bottom line, the engine was designed to run with the thermostat and many many hours of testing went into the cooling system and engine at the design temps.

LT5 Cooling Engineer (retired)

SC,

Welcome to the forum. Great to have resources like you available here. Any chance you know the ignition system engineer for the LT-5?

[Dynomite]

Bottom line, the engine was designed to run with the thermostat and many many hours of testing went into the cooling system and engine at the design temps.

LT5 Cooling Engineer (retired)

Welcome :cheers:

All great points.......appreciate the explanations :thumbsup:

Cliff

[SClarke1958]

Sorry, I do not know the name of the ignition system engineer, he would have been a person working at Lotus in England.