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Temperature Management

Bob Chiras
Bob Chiras Distributing

Over the past two years the popularity of water-cooled motors has introduced many racers to new issues relative to tuning. The purpose of going to water cooled motors has been clear for years. Motorcycles made the transition in order to lighten motors. Air cooled motors needs fins and large surface areas to carry away heat. Water cooled motors rely on the principle of moving the heated liquid through a radiator that is placed into the air stream to cool the liquid and then deliver the cooled liquid back to the motor thereby taking away the heat generated during combustion.

Having water as a cooling agent causes racers to learn that water temperature is a metric that is tunable. We have all seen race teams in a variety of race series tuning their cooling by applying tape to radiators or changing how much air flows through cooling ducts We have also learned that in many forms of performance sports that there is a necessity to manage he flow rate of the coolant. Often we have to manage liquid flow to manage cooling. We do this with ratio changes at the drive of our water pumps. The issue being that the water has to have sufficient time to absorb the heat that we are asking the water to carry away from the motor. If water flows to fast and there is little heat transfer we may overheat a motor. If there the water flow is overly efficient and carries away to much heat we face a different issue of getting incomplete combustion and the motor running poorly much like your automobile on a cold morning.

All motors need to address temperature management but because of inherent design differences there are different techniques applied. Moto or motorcycle motors and ICC motors differ in that most moto motors have water pumps built into the motor while the ICC motors rely upon external water pumps that are driven by the rear axle. As you would expect each has its advantages and disadvantages.

First the advantages; Moto motors have water pumps built in to the motor and circulate water while the rear wheels are stationary. ICC motors have no built in water pump and are typically lighter and more compact.

Disadvantages; Moto motors are designed to run at lower and less constant RPM’s than is typically found in karting. This means that the water pump is likely turning at an incorrect speed and may be moving water at a rate that is different than the design engineers planned. ICC motors have no pump circulation until or unless the rear wheels are turning. This means the motor relies on natural convection to circulate coolant while the kart is on the grid waiting for the event to begin.

Both types of motors share the issue of needing to get the motor to the correct temperature and maintaining the correct temperature for the duration of a race event. The solution must be highly repeatable, increase reliability, increases performance and be elegantly simple. The solution was the introduction of a device being used in almost all other forms of motor sports, a thermostat designed for karts and motorcycles.

The thermostat is designed to address the needs of performance racing. The design manages the water path so that large rushes of cool water from the radiator never reach the water jacket of the motor and potentially cause a cold stick. The design addresses the convection heat transfer during start up of ICC motors with external water pumps as the design can open multiple paths to mix hot and cool water. With multi flow paths the thermostat always maintains sufficient water flow through the water jacket to carry away the heat generated by combustion.

Installation is simple but it does take some planning. The thermostat installs in the upper radiator hose for the purpose of controlling flow from the motor to the radiator. However there is a need to install a bypass hose that connects the bottom of the thermostat to the lower radiator hose. This provides the flow to allow the heat dissipation to occur during warm up and it also serves to prevent the to much flow from the radiator to the water jacket of the motor. As the water temperature begins to rise the thermostat opens at a rate that allows water flow without causing excessive changes to the running temperature of the motor. We found the thermostat to be very responsive to small changes in temperature with the thermostat opening and closing to maintain the proper motor temperature.

When we tested the thermostat we applied the thermostat to a Yamaha YZ125, a Honda RS125 and a TM125 and Aprilla 125. We tried the thermostat on karts that had over sized radiators and on karts with stock radiators. Our findings were astounding. First we learned that stock radiators were always sufficient to cool even very highest performance motors from Bill Price Racing. We also learned that large radiators were overkill when we applied the thermostat. We were able to reduce the size of the radiator by almost 50% and maintain a water temperature of 120 degrees on a day when the ambient temperature was 95 degrees. Being curious and living in New England we decided to replicate the testing on another day when the ambient temperature was only 50 degrees. We found less than one degree of operating temperature with the motors.

We used Digatron DT54K Max instruments to capture the water temperatures and to track the temperature of the motor from the start of the motor to the conclusion of the race. The temperature was exceptionally stable for all of the laps. We tried the same thermostat on a road racing motorcycle with a Digatron DT52K Max and achieved the exact same results that we found on the karts. Highly stable temperatures and no need for large or expansive radiators. We saw temperatures range from 120 degrees to 128 degrees with a great deal of consistency.

What is the secret? A design that manages water flow at all times. The thermostat opens and closes in response to very small temperature changes. We found a design reflects a device intended for high performance motor sports. It is lightweight, very modular with each fitting having the ability to be removed and or replaced as needed. There are fittings that allow is to utilize water temperature probes from Digatron, My Chron or any other data collection instrument. The thermostat and all of its parts are anodized to protect it from the corrosive nature of many of the water and water treatment chemicals used like water wetter. And we liked the fact that the dealer that showed us the device had a complete stock of product available for the racers. Each fitting had its own gasket that was provides so we were not using any Teflon tape and trying to tighten fittings with tape applied.

We purchased the thermostats from Rising Sun Cycles http://www.risingsuncycles.com . They have been a force in motorcycle racing for years and came to karting through the introduction of the Battle Shifter and their line of HRC/Honda OEM Parts that are without a doubt the highest quality parts available for your moto racing motors
Installation time was less than one half hour but as with all race accessories we suggest that you purchase the unit and do the installation at home or in the shop prior to getting to the track. This assures that you have the correct hoses needed to make the connections and that you are able to check all of the fittings and clamps to be sure that the installation is neat and attractive as well as functional.

Check out the two thermostats offered by  Rising Sun Cycles. The price of the thermostats are $199.95 to $250.00. If you need technical advice or want to discuss the application call Rising Sun Cycles at 860-916-3696. email Steve@rscycles.com  of write to them at Rising Sun Cycles, P.O. Box 122, Fall River, MA 02724-0122 Business hours are 9AM to 5 PM EST Mon-Fri. Steve can provide you with a list of events where he or his dealers will be supplying the thermostats. . Look for the karting section of the web site.

Get one soon and manage the temperature with one of the finest devices that we have found and get rid of that oversized radiator that is adding weight and slowing you down by putting too much draw into the air stream.