Charge
air cooling, or intercooling the intake air on a turbocharged
vehicle is essential to achieving maximum performance.
Project Sidewinder uses two intercooling systems to meet
the demands of both street and racing operation. On the
Bonneville Salt Flats, an air-to-water system was used,
but on the street a more conventional air-to-air system
does the job.
Bonneville
When
it comes to turbocharging, or supercharging for that
matter, compressing the intake air to high boost levels
raises the temperature of the intake air. On the Land
Speed Record attempts at Bonneville, our Project Sidewinder
utilized a unique air-to-water charge air cooling system
laid out by Bob Robe and Sheldon Tackett. The high-performance
Holset® HY55 variable geometry turbocharger used
on the Sidewinder for this endeavor heats the intake
air to approximately 480-500° F. while compressing
it to over 50 PSI boost. Such high intake temperatures
greatly reduce the charge density and maximum power
potential of the engine unless intercooling is used
to bring the temperature back to manageable levels
of 100-120° F. Cooling the intake air that much
is a challenge. It takes serious heat exchangers and
an adequate cooling medium to get the job done. The
only practical way to do it is with air-to-water intercoolers
using very cold water. And even then, the water flow
rate through the intercoolers must be substantial.
With
all of the above taken into consideration, Banks® engineered
a recirculating water system to intercool the compressed
intake air for the Sidewinder’s Bonneville runs.
The system uses twin Cummins® marine air-to-water
intercoolers fed by dual Stewart-E.M.P.® high-capacity
electric water pumps. The combined water flow rate
is an incredible 120 gallons per minute. The ice water,
taken from a custom 40-gallon tank designed by Gale
Banks Engineering™ and assembled by Glenn Lirhus,
is located at the rear of the pickup bed. Internal
vertical baffles divide the tank into four compartments
with alternating bottom and top crossovers to the next
compartment. Dual pickups, drawing from the bottom
of the fourth compartment, route ice water to the pumps,
which are mounted directly to the side of the tank.
A horizontal, expanded metal baffle inside the tank
prevents any ice chunks from being sucked into the
pumps. The water starts out at 33-35° F. and is
fed through dual 1-3/4-inch supply lines to the intercoolers.
The water, which exits the intercoolers an average
of 6° F. warmer than it entered, is returned through
2-inch lines to the tank where it is then forced to
flow through the four chambers in the tank to mix with
cooler tank water before being picked up and pumped
to the intercoolers again. Of course, during a run
the average temperature of the tank water rises. The
tank water was recooled to 33-35° before the start
of each run. The 300 pounds of water weight at the
rear of the Sidewinder also helped rear wheel traction
on the salt.
Street
Intercooling
for the street is less challenging. Because the boost
pressures are more conservative, the intake air is
not heated as much as in the full race setup. And full
throttle operation of the vehicle will be for shorter
periods of time. Consequently, a Banks Techni-Cooler™ air-to-air
intercooler, positioned in front of the radiator, is
used. The Techni-Cooler features a 4-inch inlet and
outlet. This is adequate to keep the intake air temperatures
to less than 150° F. Besides, on the street, utilizing
a recirculating water system, such as used at Bonneville,
would be both impractical and unnecessary. Using an
air-to-air intercooler also allows removal of 300+
pounds from the rear of the truck to improve both handling
and acceleration/braking performance. It also allows
the removal of the air-to-water intercoolers, electric
water pumps, and associated plumbing.
It
is, after all is said and done, a sport truck for the
street.
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