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Here's more evidence that a restrictor in the cooling system is detrimental

22K views 24 replies 14 participants last post by  finn210 
#1 ·
So here's an actual test that some guy did on a Pontiac Tempest, under what appears to be very well controlled conditions. Among other tests, he tried a thermostat, a 1" restrictor, and a 5/8" restrictor in the upper radiator hose. The bottom line is that he proves that restricting coolant flow increased temperature of the engine. Read it and weep. :sign0020:

I agree with his conclusions, but his hypotheses in the first sentences below conflict with his test results. I think he proved them wrong with the test results.

http://www.ls1.com/forums/showthread.php?t=74945

Coolant Flow
Coolant that flows too fast through the system will not allow sufficient time for cooling by the air that passes through the radiator core. Conversely, coolant that flows too slowly spends more time in the engine block where more heat transfers through the water jackets into it.
To test whether the water pump was moving coolant too quickly through the radiator, the owner pulled out a vintage Moroso water outlet restrictor kit that consists of three restrictors, which range in size from 5/8-inch through 1 inch. The 5/8-inch restrictor will cut coolant flow approximately by half, while at the other end of the spectrum, the 1-inch restrictor is almost identically sized to the diameter of the thermostat. Rather than test all three sizes, just the largest and smallest sizes were utilized. To determine if the thermostat itself was causing a restriction, it was removed for the final coolant flow test.

5/8-inch Restrictor-After installing the 5/8-inch restrictor, it was apparent that restricting the water pump flow had a detrimental effect on overall cooling. Temperatures were elevated in low-speed testing, averaging 193 degrees. At the conclusion of high-speed testing, the gauge read 216.5 degrees and highway testing resulted in 230 degrees. The Tempest was within seconds of boiling over had it not been shut down and allowed to cool on the side of the road.

1-inch Restrictor-Once sufficiently cool, the Pontiac limped home and the restrictor was changed out to the smallest one (1 inch). Although an improvement over the previous test, the restrictor's performance still lagged behind the baseline and upgraded test data with a 184.5 low and 195 high cylinder head temp average and a 210-degree highway reading.

No Thermostat-The final test involved removing the thermostat entirely. Once again, the performance improved, but the overall results still weren't as good as when we began. The cylinder head average temp checked in at 176 degrees and 191.5 degrees, low and high respectively. Highway temp was 210 degrees.
According to Don Meziere, owner of Meziere Enterprises, "The Meziere water pump supports engines up to around 550 horsepower and has a free-flow rating of 40 gallons per minute. When measured in actual flow rate on an engine, it flows between 16-18 gpm, almost identical to what the stock-type pump does at higher rpm with far superior low-rpm flow ratings."
Having proved that restricting the water pump flow was detrimental to cooling system performance and the thermostat itself wasn't a restriction, it was time to focus our efforts on airflow through the radiator.

Conclusion
After examining and testing both coolant flow and airflow through the radiator, it was determined that any reduction in coolant flow brought with it increased coolant temps.

Airflow testing resulted in the addition of two key items that allowed significant improvements in cooling. The Ames Performance air conditioning seal kit allowed more air to be directed through the radiator and, although the PRC custom shroud was very attractive, it limited the volume of air passing through the radiator so the Tempest ultimately ran cooler on the highway without it. Fortunately, though low-speed performance without a shroud should have decreased, it didn't, showing just how strong the SPAL fan is in drawing air through the radiator. Performance at high-speed and on the highway showed the most dramatic improvements with a 20-degree reduction in coolant temperature.

In addition to significantly improving overall cooling system performance, we dispelled the rumor that electric water pumps are only appropriate for strip cars that see limited real-world usage. Anytime you can cruise the interstate for 50 miles at the posted speed limit and never exceed 190-degree coolant temps, you can be confident that you can hop in your Pontiac and drive to work or load up and travel a few states away to hit a national Pontiac event. With a rating of over 2,500 hours of continuous use, the water pump should last well over 75,000 miles and provide flexibility at the dragstrip to always be at or below your thermostat rating even if you are required to hot-lap your car for the next round of eliminations.
If your ride is in need of a cooling system upgrade, consider checking in with these vendors. In addition to quality parts at reasonable prices, they all provided timely and accurate technical support to make sure that the system was optimized.
Although the snow may be swirling and a football game is about to start, there's no better time than the present to prepare your Pontiac for next summer.


This test is consistent with what the physics and engineering would predict. Increased coolant flow through heat exchanger increases heat transfer. That's a fact. :tu
 
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#9 ·
Yeah, it's probably a lot like the early Greek astronomers trying to convince others that the earth is round, not flat as many believed..... :happy0030:

I posted the results of this test because we were accused on one of the other threads of not having any actual data or other empirical evidence showing that a restrictor inhibited cooling. It wasn't hard to find....the truth always prevails. :sign0020::tu

I'm done on this topic for now, unless someone wants to challenge or discuss the findings. :cool: :anim_25:
 
#13 ·
ok this is statement unbeatable!!! this is quote from the greatest!!!
"just make certain that there is a restrictor with an inside diameter about 11/16
inch in the single tube thats feeds into the radiator. This is important because there is no thermostat in the system, and overall flow volume will be controlled by the size of this orifice.If it is too large,the water will flow through the system too quickly ,and if it is too small,the water will flow too slowly!"
said by THE SMOKEY YUNICK! I rest my case your honor.:congrats:

Mikko
 
#15 ·
I dont have any "scientific" results but when a stock pump that is modified with a flow kooler disc (which improves pump efficiency and reduces cavitation) and it is then spun at about 7600 RPM it moves alot of water. My oil temps went up and coolant temps went down. Added a restrictor and the 2 temp readings on my Auto meter gauges leveled out and stayed steady instead of fluctuating. That said.........there is no 1 recipe for every different engine combination. I dont care if I have to shove 2 dead skunks in the radiator and pick my nose while driving to get the car cooled down then thats what Im going to do. I now have a CSR electric water pump and run it without a restrictor and it does fine.
 
#17 ·
Whoa !! Thank YOU Speedy !!! Finally, someone gets it !!

That said.........there is no 1 recipe for every different engine combination. I dont care if I have to shove 2 dead skunks in the radiator and pick my nose while driving to get the car cooled down then thats what Im going to do. I now have a CSR electric water pump and run it without a restrictor and it does fine.
...And that my friends is EXACTLY what I've been trying to say all along... just as Speedy said..."there is no 1 recipe for every different engine combination"

This is especially true if the combination is no longer Stock, i.e. Original OEM stuff, engine, radiator, etc. has been exchanged like many of us have dealt with who are part of this forum...

...and just as Speedy did, he discovered a coolant combination that WORKED to get him by, and at that time, it just happened to included the use of a Restrictor... However, now that he has altered that combination again, adding the CSR electric water pump, the Restrictor is NO LONGER Necessary !!! :congrats: so thanks Speedy for clarifying my point exactly with a REAL LIFE Experiance... I NEVER said a Restrictor was a FIX ALL....

In the meantime, Speedy, you have a good recomendation for a Skunk trap..? I need to get me a couple...:sign0020:

later, BDR...:cool:
 
#23 ·
So why Smokey want to slow down flow in radiator if it cools worser than higher
flow? (sa desing book smokey yunick´s power secrets) and my own experience
is that without thermostat engine runs hotter. It doesnt get simpler than that:)
 
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