[DeTomaso] Radiator Caps

[michael@michaelshortt.com]

>From Super Street Magazine

Michael


It’s Friday afternoon.and you and your jobless friends are bored. Such
mindless activity arouses the proposal of a road trip and, three pairs of
eyes fixate on you for silent nomination as the driver. After all, you’ve
spent the past year squeezing your parents’ credit cards for those mods to
your Integra. The turbocharged B18 and an engine-management system were
completely justifiable expenses in your quest to be the toast of the
show-car scene.

Two hours later, the tiny coupe crawls along a clogged freeway, enjoying
the inti-macy of Friday-night traffic. As the
car<http://www.superstreetonline.com/techarticles/61718_cooling_systems/#>
inches
up a congested interchange ramp, the engine begins to run a little
rough—then a thin plume of steam rises from under the corner of the hood.
No one noticed the temperature needle peg itself deep into the “doom” zone.
Nice work, sport—this completely unnecessary trip may have just cost you
your motor.

The modified engine under your faux–carbon-fiber hood is an air pump that
uses a spark to release the potential energy of gasoline. At peak
efficiency<http://www.superstreetonline.com/techarticles/61718_cooling_systems/#>,
only about 30 percent of your fuel’s energy is used to create reciprocating
power. The remaining 70 percent of the fuel’s potential energy escapes
through the tailpipe or is converted into heat that’s absorbed by the
cooling system. This absorption of heat is vital to proper engine
performance. Yet important as they are, cooling systems have a tendency to
get overlooked. Sure, they rate low on the scale of sexiness, especially
when compared to the likes of turbocharging but remember: Engines tweaked
to rev higher or handle forced induction to create more power also create
additional heat as a byproduct. In these instances, a stock cooling system
may not be able to handle the extra load.

Knowledge, in this instance, is your best defense. Understanding how the
cooling system works, how to improve it, and how to identify possible
problems can save you from making potentially wallet-devastating mistakes
as well as help you to maximize performance. So learn well, grasshopper,
and don’t forget to flush.

*Coolant and Pressure*
If an engine ran without coolant, even for a brief period, the temperatures
could soar high enough to melt a piston and fuse it to the cylinder wall.
Metal surface temperatures in the cylinder head and combustion chamber can
rise higher than 500 degrees F, so the cooling of these surfaces becomes a
vital engine-design element for power and longevity.

Honda blocks use aluminum, open-deck construction with iron sleeve inserts
as friction surfaces. Most of the areas inside the cylinder head that are
not of structural significance are filled with a coolant passage. The
coolant—in most cases a mixture of antifreeze (ethylene glycol) and
water—absorbs heat from such hot spots as combustion chambers and the
backside of cylinder walls. While water absorbs heat effectively, it also
freezes at a high temperature (32 degrees F) and boils at too low a
temperature (212 degrees F) for use in
cars<http://www.superstreetonline.com/techarticles/61718_cooling_systems/#>
in
certain climates. Mixing water with antifreeze yields a solution that
benefits from a lower freezing point of -35 degrees F (for a 50/50 mixture
of water to antifreeze) and a higher boiling point. It also adds
anticorrosion properties.

The effectiveness of the coolant—its ability to resist boiling and transfer
heat—can be helped with Redline’s Water Wetter, which reduces the surface
tension of the coolant. Another option would be Evans’ NPG coolant, which
is designed for use without water, allowing you to run a zero-pressure
cooling system. At zero pressure, this waterless coolant has a boiling
point of 360 degrees F.

A major component of coolant-system maintenance is the periodic flushing of
the system. Old antifreeze/water mixtures can actually become corrosive to
metals after extended use, but they must be disposed of responsibly, as the
mixture is toxic. Sealing the radiator’s filler neck on modern cooling
systems is a rubber-gasketed cap with a spring-loaded valve that
pressurizes the system and increases the coolant’s boiling point. Factory
radiator caps typically increase the cooling-system pressure by 14 or 15
psi and raise the boiling point about 43 degrees F. As the engine warms up,
the coolant heats up and expands, causing pressure to build up; the cap’s
valve is the only place where this pressure can escape. When the system
pressure reaches the cap’s pressure rating, the cap’s spring is compressed,
forcing the valve open and allowing coolant to escape through the overflow
tube to the expansion tank. This also permits air to escape the cooling
system; as the radiator cools down, the vacuum created by the cooling
system contracting pulls down another spring- loaded valve, returning
coolant to the radiator. Due to the pressure contained by the radiator cap,
and the fact that boiling liquid can lead to Darkman-like disfiguring
burns, it’s never a good idea to open a radiator cap while the engine is
still hot—and certainly never when you’re in the nude.

*The Pump and the Thermostat*
Coolant must flow through the block and head in such a way that it can
absorb and transport heat without boiling. When coolant boils, its
capability to absorb heat is diminished, causing temperatures to rise
dramatically.

Coolant makes its way from the bottom of the block and out of the cylinder
head to the radiator by a mechanically driven centrifugal pump. The water
pump also draws coolant from the radiator and forces it through the engine
at a higher pressure.

A thermostat regulates the flow of coolant from the block to the radiator.
By varying the size of its aperture, the thermostat slows coolant flow to
ensure that the coolant will spend enough time in the block and cylinder
head to absorb heat. On a cold engine, the thermostat completely restricts
flow to the radiator block outlet. The thermostat uses a wax-filled
cylinder to open at the prescribed temperature. A rod connected to the
spring-loaded valve in the cylinder presses against the wax. As the wax
heats up, melts, and expands, the rod is pushed out of the cylinder and
opens the valve. The thermostat is located at the top of the engine at the
coolant outlet, where coolant temperatures are highest.

Typically, a car runs most efficiently when the coolant temperature is kept
around 200 degrees F. At this temperature, the combustion chamber is warm
enough to vaporize the fuel mixture for improved combustion, and the oil’s
viscosity has lowered sufficiently to reduce parasitic drag.

*The Radiator: Heat Transfer and Airflow*
The modern radiator is constructed of densely finned, aluminum cores
usually with plastic tanks. Aluminum has a very
efficient<http://www.superstreetonline.com/techarticles/61718_cooling_systems/#>
rate
of heat transfer and the structural strength to withstand higher system
pressures.

>From the factory, most radiators are designed to match the heat output of a
stock motor. The radiator sits behind the grille opening in the path of air
that rushes in when the vehicle is in motion. When super-heated coolant is
pumped from the top of the engine into the radiator, it flows through a
structure of tubes. Folded aluminum fins connect the tubes, and the metal
absorbs the heat of the coolant. Air entering through the grille moves
across the tubes and fins, and cools them by transferring the heat to the
ambient air.

The fins-per-inch measurement gives an indication as to how effectively the
unit will transfer heat. More fins of folded metal result in greater
surface area for air to flow over and increased heat transfer. After-
market aluminum radiators, such as those offered by Fluidyne, not only have
a high density of fins, but they also have wider aluminum cores to provide
greater cooling surface area and coolant capacity.

The rugged, all-metal, welded or epoxied construction of such radiators can
also handle higher coolant-system pressure, and it maximizes the
temperature differential between the coolant entering the engine and the
super-heated fluid entering the radiator. A high-pressure radiator cap
(such as a 24-psi unit) is available from many aftermarket-radiator
suppliers, but such pressure puts greater stress on the rest of the system
(clamps, hoses, gasket surfaces, and so on). When a vehicle is at rest, or
moving slowly, the airflow must be maintained through the radiator so it
can continue dissipating heat. A fan provides constant airflow through the
radiator; the fan is electric in most front-wheel-drive cars, since the
engine’s power output is oriented toward the side of the car.
Thermostatically controlled pusher or puller electric fans (aka “blow” or
“suck” fans) draw air through the radiator core once the coolant reaches a
predetermined temperature.

*Lost Coolant*
One of the most common causes of overheating is a low coolant level, which
reduces the system pressure and the coolant boiling point. Pressurized
systems with full coolant levels and functional expansion tanks are more
effective at maintaining temperatures.

Cracked hoses, faulty hose clamps, bad thermostat housing gaskets, radiator
pinhole leaks, leaky expansion tanks, and tired radiator caps are common
culprits of pressure loss. Leaks can often make slight hissing sounds and
can be identified visually after the car has been running. If a head gasket
is compromised, however, coolant can escape through a combustion chamber,
mixing oil with the coolant. Traces of exhaust gas and oil can be seen
floating in the coolant, and this means that the top of the engine must be
removed and resurfaced to replace the gasket.

Casting imperfections, such as hairline cracks or weeping freeze plugs,
relieve system pressure just as easily as pinhole cracks in the radiator
do. Temporary solutions for leaks include JB Weld (a “stronger than steel”
epoxy welding agent) applied to the crack or fissure, or such radiator
sealing agents as Alumnaseal or Bars Leak. These agents use a ceramic or
metallic medium that mixes with coolant or water to help seal leaks. Most
sealing agents are only temporary repairs at best, and ultimately, parts
will need to be replaced or welded.

While some radiators can be repaired, most shops will just replace the
whole unit. This plastic-tank/aluminum-core construction has proven to be
the weakness of the Honda radiator. A radiator passage can become clogged
with debris, reducing coolant flow through the core and fins and reducing
heat transfer. While debris can be removed with rods that clear the
radiator core, most shops will just opt to replace the radiator.

*How It Can All Go So Wrong*
If a cooling system maintains the correct pressure and fluid level, and yet
the engine still runs hot, then the problem has more to do with the fluid
flow rate or airflow/heat exchange rate. Coolant flow is managed by the
churning of the water pump and the variable restriction provided by the
thermostat, and the operation of these two components can be altered to
suit the engine’s cooling needs. Typically, water-pump failure is
accompanied by the squealing noise of cashed-out impeller-shaft bearings,
or the pump just leaks at the seals.

Water-pump impellers are designed to be most
efficient<http://www.superstreetonline.com/techarticles/61718_cooling_systems/#>
at
pushing water through the cooling system at the lower speeds at which
street engines tend to live. At very high rpm, however, temperatures can
rise because some water pumps pump more air than coolant. In such
instances, many racers increase water-pump pulley size to reduce the
water-pump impeller speed at higher rpm, therefore getting more effective
cooling during races.

A slipping belt is also an overlooked cause of high-rpm overheating. It
results in a pump impeller that spins more slowly relative to crankshaft
speed and thus can’t move coolant quickly enough.

*Thermostats*
If overheating persists after the operation of the thermostat has been
tested (using a pot of boiling water and a thermometer), consider that
switching to a lower-temperature thermostat will allow more coolant into
the engine sooner.

Thermostats that open sooner can help increase coolant flow, but the
coolant spends less time in the engine absorbing heat. Switching to a
lower-temperature thermostat is just a Band-Aid remedy, however; it’s also
necessary to increase the pressure of the cooling system with a stronger
radiator cap.

With an adequately pressurized system and an efficient radiator, a
higher-temperature thermostat (190 degree F instead of 180) will improve
engine cooling—it will slow the coolant and do a more thorough job of
absorbing heat. The larger temperature differential between the ambient air
and coolant temperature will need peak radiator efficiency to control
temperatures.

*Better, Stronger, Faster*
Unless you’re a sorcerer, not a whole lot can be done to control the
temperature of ambient air. You can, however, control the temperature
differential between the coolant and incoming ambient air. Ideally, you
want the coolant to absorb as much heat as possible before it turns into
vapor pockets, and then send the heat to the radiator for the most dramatic
temperature reduction possible. Typically, a 100-degree differential is the
desired target.

Quite a bit can be done to improve the flow of air through the radiator,
thus maximizing its heat-exchanging capabilities. The electric fans that
provide airflow for most front-wheel-drive cars are designed to draw air
through the radiator of a motor with a near-stock power level. The heat
generated by higher horsepower requires more aggressive airflow.
Aftermarket companies, such as Flex-a-Lite and SPAL, offer a range of
electrical fans that can move larger quantities of air than OE cooling
fans; these fans also provide different mounting possibilities. Whether it
be pusher or puller fans, such devices are crucial to help maintain airflow
when the vehicle is in traffic or just moving slowly.

A fan shroud fitted around the perimeter of the radiator also helps direct
airflow through the aluminum heat exchanger instead of around it. Radiator
airflow can also be improved on a moving vehicle by an air dam mounted
under the car’s front bumper, which forces air that would otherwise go
under the car up into the grille opening and through the radiator.

The majority of enthusiasts spend so much time combing ads for the next
great power-adding device or scheming of ways to make the larger engine
swap fit, that they never consider the extra heat that these modifications
will generate. Addressing a performance engine’s cooling needs as part of a
buildup will save you time and headaches on your dream car project.


Read more:
http://www.superstreetonline.com/techarticles/61718_cooling_systems/#ixzz2fGBK6AJJ


On Wed, Sep 18, 2013 at 11:33 AM, michael at michaelshortt.com <
michaelsavga at gmail.com> wrote:

>
>
> Just found this at Stewart gauges website.
>
> Michael
>
> *Tech Tip #2 - Radiator Caps
>
> Radiator Caps*
> In a cooling system, a higher pressure equates to a higher boiling point
> for the coolant. Higher coolant pressures also transfer heat from the
> cylinder heads more efficiently. We recommend using a radiator cap with the
> highest pressure rating that the radiator is designed to accept. In
> general, performance radiators will accept 22-24 PSI, and professional
> racing radiators will accept a 29-31 PSI.
>
> The coolant will typically only build to 16-18 PSI, due to expansion up to
> 200°F. However, if the engine does overheat due to external factors, the
> pressure inside the cooling system could reach as high as 28 PSI. Once the
> radiator cap has opened and vented coolant, the engine will not cool down
> until it has been turned off. The radiator cap is basically a "safety
> valve", so always use the highest pressure radiator cap that the radiator
> will tolerate. If you are unsure of the pressure rating for your radiator,
> check with the manufacturer for the maximum recommended operating pressure.
>
>
> *Radiator Cap Location
> *The radiator cap should always be located at the highest point of the
> cooling system, and on the low pressure side (after the radiator
> core).Cross flow radiators mounted higher than the engine are ideal because
> the cap is on the tank that is connected to the water pump inlet. This
> configuration offers 3 advantages:
>
>   1.The cap is at the highest point of the system, allowing any air to
> migrate to the area just below the cap. In the event the cap vents due to
> excessive pressure, the air will escape first. 2. This area has the
> lowest velocity within the system, allowing air to separate from coolant
> even at high engine RPM. 3. The cap is located on the low pressure
> (suction) side of the system, so it is unaffected by the pressure generated
> by the water pump.
> For cooling systems NOT using a cross flow radiator, mounted higher than
> the engine, you must use a surge tank. A surge tank is typically a 1 quart
> tank mounted at the highest point of the system, with the radiator cap on
> top. The bottom of the tank is connected to the inlet side of the water
> pump with a 1/2" or 3/4" line. A 1/4" to 3/8" "bleed" line from the side of
> the surge tank is connected to the highest point of the low pressure side
> of the radiator. The bleed line allows some circulation through the tank
> while the engine is running. The surge tank is also large enough to allow
> the air to separate as the coolant flows through it. Air in the system will
> then migrate to the area just below the radiator cap, again so that it will
> forced out first if system pressure exceeds the radiator cap's rating.
>
> In street car applications, an upright radiator (top and bottom tanks,
> with the cap on the top tank) represents a compromise that will work, as
> long as the car is not operated at sustained high RPM, like those seen in
> racing.
>
> *Any aftermarket thermostat housing that mounts the radiator cap directly
> above the thermostat location, or that mount the radiator cap in the top
> coolant hose, are NOT recommended. Both of those housing styles are poorly
> designed, and will push coolant out of the cap at high RPM.
> *
>
>
> On Wed, Sep 18, 2013 at 11:28 AM, michael at michaelshortt.com <
> michaelsavga at gmail.com> wrote:
>
>> Every pound of pressure raises the boiling point of water 3 degrees. if
>> your system is designed for 10 psi and the cap is capable of holding that
>> you have increased the boiling point 30 degrees.
>>
>> So a 16 psi cap could stand a temp of  260 degrees, whereas 22 psi could
>> handle up to  278 degrees.
>>
>> I guess none of us want temps anywhere near 260 anyway, so perhaps the
>> lower rated cap is sufficient.
>>
>> The next point then becomes, if the cap fails to release the pressure,
>> then something else might, like a hose, gasket, etc.
>>
>> Michael
>>
>>
>> On Wed, Sep 18, 2013 at 11:20 AM, Larry Finch <fresnofinches at aol.com>wrote:
>>
>>> Overflow is zero pressure cap.
>>>
>>> But why so high - 22PSI - on the surge tank cap?
>>>
>>> Larry
>>> _______________________________________________
>>>
>>> Detomaso Forum Managed by POCA
>>>
>>> DeTomaso mailing list
>>> DeTomaso at poca.com
>>> http://poca.com/mailman/listinfo/detomaso
>>>
>>
>>
>>
>> --
>>
>>
>>
>>
>>
>>
>>
>> Michael L. Shortt
>> Savannah, Georgia
>> www.michaelshortt.com
>> michael at michaelshortt.com
>> 912-232-9390
>>
>>
>> This email is protected by the Electronic Communications Privacy
>> Act, 18 U.S.C. Sec. 2510-2521, is confidential and may be legally
>> privileged.  If you are not the intended recipient, you are hereby
>> notified
>> that any retention, dissemination, distribution or copying of this
>> communication is strictly prohibited.  Please reply to the sender that you
>> have received this message in error, then delete it.  Thank you
>>
>
>
>
> --
>
>
>
>
>
>
>
> Michael L. Shortt
> Savannah, Georgia
> www.michaelshortt.com
> michael at michaelshortt.com
> 912-232-9390
>
>
> This email is protected by the Electronic Communications Privacy
> Act, 18 U.S.C. Sec. 2510-2521, is confidential and may be legally
> privileged.  If you are not the intended recipient, you are hereby notified
> that any retention, dissemination, distribution or copying of this
> communication is strictly prohibited.  Please reply to the sender that you
> have received this message in error, then delete it.  Thank you
>
>
>
> --
>
>
>
>
>
>
>
> Michael L. Shortt
> Savannah, Georgia
> www.michaelshortt.com
> michael at michaelshortt.com
> 912-232-9390
>
>
> This email is protected by the Electronic Communications Privacy
> Act, 18 U.S.C. Sec. 2510-2521, is confidential and may be legally
> privileged.  If you are not the intended recipient, you are hereby notified
> that any retention, dissemination, distribution or copying of this
> communication is strictly prohibited.  Please reply to the sender that you
> have received this message in error, then delete it.  Thank you
>



-- 







Michael L. Shortt
Savannah, Georgia
www.michaelshortt.com
michael at michaelshortt.com
912-232-9390


This email is protected by the Electronic Communications Privacy
Act, 18 U.S.C. Sec. 2510-2521, is confidential and may be legally
privileged.  If you are not the intended recipient, you are hereby notified
that any retention, dissemination, distribution or copying of this
communication is strictly prohibited.  Please reply to the sender that you
have received this message in error, then delete it.  Thank you