Fluidyne radiator question

[Dynomite]

The Bottom Line Question for any discussion regarding Effectiveness of LT5 Radiators/Cooling Fan Systems is How do the Radiator/Fans Cool the LT5 Engine with AC On at 100 deg F Ambient Temperatures while idling in traffic.

Using HVAC Display for Engine Coolant Temperature

Let us assume for simplicity that LT5 engine cooling is about the Radiator Air Flow and Radiator Coolant flow (as 5ABI VT and Goldcylon suggests). Lets further assume that the engine sensors, heat generation, spark advance, compression, load are identical between engines at a certain engine speed and ZR-1 speed in other words nothing to consider other than the air flow, coolant flow, and coolant temperature from the HVAC Display (AC ON and AC OFF).

I am going to do some testing to verify exactly how two ZR-1s here in CA (90' with stock radiator and 91' with Ron Davis radiator) behave at 100 deg ambient temperatures (stop and go and on freeway at various speeds). I will determine exactly what the coolant temperatures are at 60 mph and 2,000 engine rpm in 5th Gear (including the worst condition idling with ZR-1 not moving). The Conditions I have are a 180 deg F Thermostat and Fans ON at 205 deg F and OFF at 200 deg F running on 91 Octane Fuel (Marc Haibeck Chip).

Since this discussion was about Fluidyne Radiators, it would be interesting to see how the Fluidyne Radiators Cool the LT5 under the same conditions of 100 deg F Ambient Temperatures. That would then say something about the Stock Radiator, Ron Davis Radiator and Fluidyne Radiator effectiveness in cooling the LT5.

I am thinking ALL radiators function well at ambient temperatures around 90 deg F and lower.....it is the 100 deg F ambient temperatures that are of issue.

Using HVAC Display for Engine Coolant Temperature
Water Pump, Coolant Temperatures, and Coolant
Coolant Characteristics (Mix, Pressure, Elevation)

A. Experiment Number 1
1990 Fans On 205 deg F Fans Off 200 deg F
Stock Radiator
100 deg F Ambient
at least 50% Coolant Mix

AC On 72 deg AC Fan 7
Cruise 60 mph 5th HVAC temp 220 deg F (after exceeding that temperature during the idle test)
(this was interesting because once the temperature came down to 204 deg F with AC Off the temperature did not rise above 205 deg F with AC On)
AC Off 60 mph 5th HVAC temp 204 deg F and dropping slowly
Fans are Controlling Coolant Temperatures when AC is Off

AC On 72 deg AC Fan 7
Idle (not moving) HVAC 235 deg F and climbing (idle for 5 minutes)
Coolant Temperature would keep climbing if I did not turn AC Off within a few minutes

AC Off
Idle (not moving) HVAC 230 deg F and dropping slowly
Coolant Temperature CAN BE CONTROLLED by Turning AC Off

B. Experiment Number 2
1990 Fans On 205 deg F Fans Off 200 deg F
Stock Radiator
90 deg F Ambient
at least 50% Coolant Mix

AC On 72 deg AC Fan 7
Cruise 60 mph 5th HVAC temp 205 deg F

AC On 72 deg AC Fan 7
Idle (not moving) HVAC 228 deg F (idle for 10 minutes)
Coolant Temperature is stable at 228 deg F with AC On with Ambient Temperature 90 deg F

In Summary From this experiment at 100 deg F and 90 deg F Ambient Temperatures the 1990 ZR-1 with stock radiator and Marc Haibeck Chip controlling the fans On at 205 deg F and Off at 200 deg F the following results were obtained.........

1. The Fan thermal switching control the Coolant Temperature (100 deg Ambient) when moving with AC Off (With AC On the Fans are always On).

2. At 100 deg Ambient Temperatures the 180 deg thermostat is not a player staying open under ALL conditions.

3. At 100 deg Ambient Temperatures the Coolant System FAILS when idling in traffic or at stop lights for over 5 minutes with AC On.

4. Excessive Coolant Temperature at Idle with AC On can easily be controlled by turning the AC Off.

5. It also was determined that if the Ambient Temperature dropped to 90 deg F the 1990 ZR-1 can idle in traffic at a stop indefinitely with AC On.

(For those not having the Marc Haibeck Chip the Fan Controlled Coolant Temperatures in this experiment would be 234 deg F).

Next the 1991 ZR-1 with Ron Davis Radiator
C. Experiment Number 3
1990 Fans On 205 deg F Fans Off 200 deg F
Ron Davis Radiator
100 deg F Ambient
at least 50% Coolant Mix



B. Experiment Number 4
1990 Fans On 205 deg F Fans Off 200 deg F
Ron Davis Radiator
90 deg F Ambient
at least 50% Coolant Mix

Notes:

1. When testing Coolant Temperatures at Idle, then increasing the rpm, the Coolant Temperatures rose.
This indicates the higher Coolant Temperatures at Idle are probably not caused by low pump flow.
2. The Water Pump Flow at 800 rpm is 15 gpm. The Water Pump actually gets more efficient as the rpm increases from idle to 2,000 rpm.
As Per Marc Haibeck graph provided to the ZR-1 Net email list by Graham Behan about ten years ago, the water pump flow rate is:
15 gpm at 800 rpm
18 gpm at 1,000 rpm,
44 gpm at 2,000 rpm,
65 gpm at 3,000 rpm,
90 gpm at 4.000 rpm,
120 gpm at 5,000 rpm at which time cavitation is starting.
3. Marc pointed out "the high flow rate design of the water pump assured high volume of coolant through the cylinder heads to wash away boiling bubbles that lead to hot spots around the exhaust valves". Another reason blocking TB Coolant works so well as any remaining air in the coolant system gets washed back to the top of the Radiator and out the pressure relief .
4. The Dual Thermostat Bypass pressure is apparently 5 psi and block resistance at 100 gpm is approximately 20 psi. I am not sure what the radiator Head Loss is at various flow rates but definitely depends on the radiator type.
5. It would seem that the Coolant Pressure Relief Cap on top of the Coolant Expansion Tank in front of passenger side set at 15 psi would assure the radiator maximum pressure would be 15 psi plus the Bypass Pressure of 5 psi or 20 psi.

[Hog]

Originally Posted by GOLDCYLON

It was 115 yesterday. Car Displayed 123 outside and it cooled down to 119 on the 101 freeway after leaving I-17 so much for averages Eh lol ?

More rows in your radiator buy you time as its a function of greater capacity only.

When I had my 4 row built the rad shop gave me a simplistic example. You take a one row he called it for argument's sake a glass of water on a hotplate vs a gallon of water on the same hot plate or a 4 row. You are buying time until the car can start moving again and cool down.

Yes, the averages are out the window for both of our areas. Ive got a cousin up from Phoenix and she said it cools down to 80-90º at night. Geez, thats warm. Ive been sleeping with the winbdows open with nightly lows of 50ºF. Weird weather for sure.

SInce you have a built 4 core rad, I would love to see the results of some water mist spraying on your rad, esp with your dry climate. It would work great.

You are correct, the extra coolant capacity, thus the extra heat carrying capacity of your rad buys you time before you reach criticality. Kinda like wearing thick gloves vs. thin gloves. Once you grab a cherry hot piece of metal, you will get burned with either pair eventually, but the thicker gloves buy you time to shake them off.

Once the air enters your rad, it can only take on so much heat. If the 1st core saturates the air with heat, the last 3 cores do nothing in regards to shedding heat.
However if you can force more air through quickly enough, you will see some some advantage. The more air molecules you force through the rad, the more heat can be removed from the rad. Of course there are many variables at play.

The packaging of the C4 is challenging. Anyone played with heat extractors to help get the underhood heat out?

[Dynomite]

Originally Posted by Hog

The packaging of the C4 is challenging. Anyone played with heat extractors to help get the underhood heat out?

Ya......after my experiment idling in 100 deg F .....with AC On and then AC Off....opening the hood did drop the temperature a couple degrees......With Headers I think it would be worse under the hood.

I have no clue how one would direct heat coming through the Oil Cooler, AC Condenser, and Radiator downward under the engine and somehow directing cool air above the engine except a new hood design with louvers.

The questions to be asked (specifically for those in the South West)......

1. How long can you sit at a stop light with AC On (AC Fans medium to high) when the outside air temperature is 100 deg F or higher?

2. Secondly, how high do you let your Coolant Temperature get under those conditions?

If you can sit indefinitely in 100 deg F Ambient Temperatures with the ZR-1 idling....what the hay do you have for radiator and fans?

Any one driving a ZR-1 around Phoenix, AZ the next ten days?

[5ABI VT]

The problem I see with raising rpm is I think of the heat generated by the cyinders being absorbed into the coolant through the heads and block.. when you raise the rpm say from 1000 rpm to 1500 rpm.. that's 50% more compression cycles and more heat generated. I think the only way to truly compare pump flow.. would be to overdrive it or swap for an ewp .

My thoughts on heat extraction would be to do it like the c7. Angle the rad forward, make a plate directing flow through the rad straight upwards and have a cutout in the hood.

[GOLDCYLON]

Originally Posted by Dynomite

Ya......after my experiment idling in 100 deg F .....with AC On and then AC Off....opening the hood did drop the temperature a couple degrees......With Headers I think it would be worse under the hood.

Cliff I would agree if the headers are not JET or SWAIN coated. Mine are and its amazing the difference in heat transfer. Jack your car up after stop. Wait 15 mins and grap the headers no problem. Grab any part of the engine during the same time period and waffle iron hot lol

Originally Posted by Dynomite

I have no clue how one would direct heat coming through the Oil Cooler, AC Condenser, and Radiator downward under the engine and somehow directing cool air above the engine except a new hood design with louvers.

YES other than hood louvers maybe on the sides and tops of the hood

Originally Posted by Dynomite

The questions to be asked (specifically for those in the South West)......

1. How long can you sit at a stop light with AC On (AC Fans medium to high) when the outside air temperature is 100 deg F or higher?

In my situtation till I run out of gas

Originally Posted by Dynomite

2. Secondly, how high do you let your Coolant Temperature get under those conditions?

I dont get concerned until after 240

If you can sit indefinitely in 100 deg F Ambient Temperatures with the ZR-1 idling....what the hay do you have for radiator and fans?

Any one driving a ZR-1 around Phoenix, AZ the next ten days? [/QUOTE]

[Dynomite]

Originally Posted by GOLDCYLON

Cliff I would agree if the headers are not JET or SWAIN coated. Mine are and its amazing the difference in heat transfer. Jack your car up after stop. Wait 15 mins and grap the headers no problem. Grab any part of the engine during the same time period and waffle iron hot lol
YES other than hood louvers maybe on the sides and tops of the hood

In my situtation till I run out of gas
I dont get concerned until after 240

My theory is simple regarding coating of the Headers......My Headers are NOT coated and are SOOOO HOT and all that heat goes into the Engine Compartment. Your Headers push ALL that Heat out the exhaust. Matter of fact.....I think Headers loose more heat into the Engine Compartment than the Stock Exhaust Manifolds given they are individual pipes.

Your situation regarding NOT overheating at idle in 100 deg F must be attributed to the Header Coating and your Higher Flow Rate Spal Fans I would say.

Thanks for the Information......

[Fully Vetted]

Originally Posted by GOLDCYLON

I dont get concerned until after 240

Thank you for that tidbit. I've been reading this and wondering at what point do I start looking for a place to park.

[tf95ZR1]

Originally Posted by Hog

Anyone played with heat extractors to help get the underhood heat out?

I know this is a radiator thread and don't want to hijack, but
"heat extractors" was brought up. A radiator is a heat extractor,
but I also found that my high rise hood helped reduce temps.
Not only more room above the engine, but vents in
front of the windshield.

[Hog]

Originally Posted by tf95ZR1

I know this is a radiator thread and don't want to hijack, but
"heat extractors" was brought up. A radiator is a heat extractor,
but I also found that my high rise hood helped reduce temps.
Not only more room above the engine, but vents in
front of the windshield.

On the 99-2002 SLP Firehawks, there were 2 vents at the corners of the hood at the windshield end. When the electric fans were running, you could place your hand over these "heat extractors" and feel warm air coming out of them.
I'm sure this would be more pronounced at speed.


Did you notice lower coolant temps or underhood temps?
Were your vents akin to a cowl induction hood?

My thoughs are that at a stop of slow speed, a "cowl induction" style of vent would work well, but at speed the high pressure area at the base of the windshield would lose its effectiveness. It seems that most guys have issues while idling around, so a hood like yours sound good.

While at speed, you dont even need fans as the natural airflow across the rad is more effective.

[Hog]

Originally Posted by Fully Vetted

Thank you for that tidbit. I've been reading this and wondering at what point do I start looking for a place to park.

Since the OEM calibration doesnt enable the 2nd fan until 234º you should be good.
My 98 STS had a similar very high 2nd fan enable temp, it was difficult to get that fan to engage from temps alone.

Thats the nervous point, do I drive faster and try to cool the engine?, or do I pull over in some shade? Pulling over and shutting down will not cool like I want it to.