PURPOSE-BUILT RACE CAR PRESSURIZED WATER SYSTEMS

 

RACING PRESSURIZED RACE CAR COOLING SYSTEMS can improve aerodynamics by allowing cars to run temperatures as high as 265 degrees.

How high can I run my water temperature?

What type of radiator can I use that will accept high pressures?

WARNING!: DO NOT PRESSURIZE THE SYSTEM TO RACING PRESSURE. ALLOW THE TEMPERATURE TO BUILD THE PRESSURE ON ITS OWN. INITIALLY ONLY ADD 5 TO 6 PSI OF PRESSURE!

By Jean Genibrel

 

Pressurized cooling systems are becoming ubiquitous in racing and off-roading.  Indy Cars, Formula Ones, NASCAR cars have used this type of cooling system for some time now with great success.Pressurized cooling systems are finding acceptance in off-road racing, short track, and road racing.

Properly designed pressurized cooling systems, such as those manufactured by C&R/PWR Racing, utilize an accumulator that is similar to a surge tank, but it is built to sustain higher pressures, and it acts as an air spring. Water accumulators contain a pressure relief valve and a sight gauge to help bleeding the system, a line from the suction side of the water pump and a return hose from the radiator. The tank comes with a Pressure Relief Valve (PRV). The PRV is adjustable, so it eliminates the pressurized radiator cap. The accumulator is also accompanied by a quick disconnect fitting for the operator to add pressure to check for any air trapped in the heads.

This drawing from Evans Waterless Engine Coolant identifies the areas most prone to boiling in the heads. These spots reside above the combustion chamber and the exhaust port. Once the water reaches Critical Heat Flux, the steam creates a barrier between the metal and the coolant. This condition can lead to preignition, detonation, pinging and severe engine damage. A system with an adjustable pressure valve will permit the pressure to increase to a preset level and to avoid boiling the water above the ports passages.

A water pressure gauge (and warning light) can give the driver an idea of the state of his car cooling system. The temperature should increase at the same rate as the cooling system pressure. When a hose blows or a leak begins, the driver can spot the problem before losing control of the car in the leaking coolant.

About Pressurized Cooling Racing Water Systems

From C&R Racing (now PWR Racing)

Pressurized water systems are relatively new to the short track and stock car world.  This technology has been around in F-1 and Indy Cars for many years.  C&R has been involved with the pressurized cooling systems through our Indy Car customers since its inception.  It’s more efficient and safer than the conventional closed cooling system that has been around for the last 80 years.  This is the future for cooling systems that will make its way into the stock car and short-track arenas over the next few years. (Since C&R published this piece, their pressurized cooling systems have made headways into off-road racing and drag racing. ed)

Pressure in a cooling system is vital for keeping water in contact with the metal surfaces of the cylinder heads and block.  Pressure keeps the air compressed and maintains the water-to-metal contact that is vital to prevent localized boiling or steam pockets in the combustion chamber areas of the cylinder heads.  When a situation occurs that causes temperatures to rise such as lean fuel mixture, too much ignition advance, or a clogged radiator, the air in the water will expand and form small steam pockets.  This will start in the combustion chamber area (hottest spot) and the steam pocket will be attached to the metal surface.  These spots get very hot, and since they are in the combustion chamber area, they will create a detonation problem.  Engines lose power when overheating occurs.  Once steam starts in the cooling system, the problem will magnify and worsen.

By keeping adequate pressure in the system, the boiling point will be high enough that this overheating situation can be prevented.  The higher the pressure, the higher the boiling point.  For instance, at sea level with a 30 lb. cap the boiling point would be around 265 degrees.  That’s why we always recommend a 30 lb cap for racing.  Our pressurized system uses an adjustable pressure relief valve instead of a radiator cap.  We do this because it will go higher than 30 psi.  The other components in this system are an accumulator and a tool to set the pressure in the system.  The accumulator is a can, similar to a header tank, that the air bleeds into from the cooling system and this can also has a controlled air space that acts as an air spring.  This air spring will compress under temperature expansion and keep water from going out the overflow.  It keeps the pressure in the system and is the place where the system pressure is set.

 The boiling point increases as the pressure in the system rises. The critical point to avoid is the nucleate state where the steam bubbles can explode and cause damage to the engine and create preignition. 

“If the heat flux of a boiling system is higher than the critical heat flux (CHF) of the system, the bulk fluid may boil, or in some cases, regions of the bulk fluid may boil where the fluid travels in small channels. Thus large bubbles form, sometimes blocking the passage of the liquid. This blockage results in a departure from nucleate boiling (DNB) in which steam bubbles no longer break away from the solid surface of the channel, bubbles dominate the channel or surface, and the heat flux dramatically decreases. Vapor substantially insulates the bulk liquid from the hot surface.

http://en.wikipedia.org/wiki/Critical_heat_flux

What are the advantages of a pressurized system?

With a pressurized system, the engine can operate safely at higher temperatures.  In the case of an Indy Car or F-1 car, it means that the air ducts to the radiators can be smaller and thus more aerodynamic.  On a Sprint Cup or road race cars, tape can be applied to the grill opening making the cars more aerodynamic by reducing the quantity of air that becomes trapped in the engine compartment.  There is a more significant safety margin for error such as clogging the radiator or running too lean on fuel mix.  You can run leaner for power and not be in the danger zone of overheating.  For example, most F-1 teams will run cooling system pressures as high as 50psi and race all day with temperatures at 265 degrees.

The accumulator should contain an air space above the water level to act as a spring when filled.

The air spring features additional capabilities. To ensure complete air bleeding, the system is filled with water, the engine runs at low to medium speeds for a few minutes, and the gauge is checked for any drop in the level, indicating the presence of air.

 FROM C&R RACING'S INSTRUCTIONS

 Fill cooling system with water and a water conditioner such as Safe Water Conditioner.  Remove –12 port plug from the top of the accumulator and top off with water.  Depress poppet on quick disconnect so that the air spring cavity will fill 75% with water, leaving the upper 25% as air space.  MAKE SURE THAT THE SCREEN ON THE –12 PORT BUNG IS CLEAN (Where Applicable)

 

When it comes to high-performance race cars, every component plays a crucial role in achieving optimal results on the track. The pressurized water system is one key system that often goes unnoticed but is essential for maintaining engine temperature and performance. Let's dive into the science behind purpose-built race car pressurized water systems.

What is a Pressurized Water System?

A pressurized water system in a race car is designed to cool the engine efficiently during intense racing conditions. By circulating water through the engine block and radiator, heat is transferred away from the engine, preventing overheating and ensuring consistent performance throughout the race.

How Does it Work?

The pressurized water system operates on a closed-loop principle, where a water pump circulates coolant through the engine and radiator. As the water absorbs heat from the engine, it is pumped to the radiator, which releases heat to the surrounding air. The pressurized system allows the coolant to reach higher temperatures without boiling, improving heat transfer efficiency.

Benefits of a Purpose-Built System

Compared to traditional cooling systems, purpose-built race car pressurized water systems offer several advantages. These systems are designed to withstand high temperatures and pressures, ensuring reliable performance under extreme racing conditions. Additionally, the pressurized nature of the system allows for more precise control over coolant flow and temperature regulation.

Efficiency and Performance

Efficiency is key in race car design, and the pressurized water system plays a critical role in maintaining optimal engine temperature for peak performance. By effectively managing heat dissipation, these systems help prevent engine overheating, which can lead to loss of power and potential mechanical failures on the track.

Conclusion

In the world of motorsports, every detail matters, and the pressurized water system is no exception. Purpose-built race car pressurized water systems are engineered to deliver reliable cooling performance, ensuring the engine operates at its best under the most demanding racing conditions. By understanding the science behind these systems, teams can fine-tune their setups for maximum efficiency and performance on the track.

 

Click on this video for more information

1. Run engine without –12 port plug until air is bled. Fill accumulator with water to top of –12 filler. Replace plug and warm engine to 180°F.

NOTE:  Using water circulator will help purge air from the system.

Connect the pressure filling tool to the quick disconnect fitting. Increase the pressure until water pushes through the PRV (approximately 35psi). Push water out until the level on the sight glass is at the halfway point. That point is the operating level.

 

NOTE: During setting the water/air spring level in the sight glass, you can see if any air is trapped in the cooling system.

If the level in the sight glass is at halfway and when adding pressure the water level drops substantially or even disappears, there is an air pocket somewhere in the cooling system.  Air will compress, causing the water level in the sight glass to drop.  The water level will return to the glass tube when you remove the pressure.

Circulate the water by running the engine or using the water circulator (Appliedspeed.com part number 60-00002 ) to bleed out the air.  When the system is properly bled, the level in the sight glass should only drop ½-inch or less upon applying pressure.

"Air will compress, water will not.”  This is an ideal way to test for trapped air. After setting the level in the sight glass halfway, bleed pressure down to 15psi.  15 psi is the starting pressure with a 180-degree engine temperature.

Qualifying

1. Fill the cooling system with water.  Plug in the water circulator and circulate to remove air.  Depress the poppet on quick disconnect to bleed air from air spring cavity and fill to top of sight Fill accumulator to the top and replace –12 port plug.
2. See step 3 under race day procedures.
3. After setting the level in the sight glass, bleed to 5-8psi.  This will be a starting point for qualifying with a cold engine and cooling system.  This number is based on starting with a “cooled off” temperature of 50°F.

ADVAMACS.com publishes this handy "Boiling Point Calculator":  http://www.trimen.pl/witek/calculators/wrzenie.html

 

SPECIAL NOTES

Do not attempt to run higher pressures than your radiator is designed. Purpose-built radiators from C&R/PWR Racing contain reinforced tubes, and they are welded with the proper techniques to hold high pressure.

Do not pre-pressurize your cooling system. Instead, allow the system pressure to build on its own from the engine heat. The C&R instruction video will guide you on how to check for air in the system by installing some initial pressure.