Honda engineers provided the Civic with an economical plastic and aluminum/copper/brass radiator that keeps the engine cool while still being lightweight. But over time, dirt, corrosion, and even bits of rubber from hose breakdown can lodge themselves in the radiator, causing the unit to become less efficient and eventually overheat. Equipped with the D-series engine, the Honda Civic uses a half-width, single-core, 16mm (5/8-inch) thick radiator-sufficient for the 102hp DX and 125hp EX, but less than ideal on Civics with engine swaps or turbochargers. Using the factory half-width radiator on a high-output engine at the track can be catastrophic if the radiator isn't efficient enough to dissipate heat. Constant heat being built up in the radiator can cause coolant temperature to skyrocket and the engine to overheat.
Some Civic owners prefer using a half-width radiator to reduce weight, save money, or make space for a custom turbo setup or equal-length header. Upgrading to an aluminum radiator like the Koyo R-Core, with its 53mm (2.08-inch) dual core, allows for better efficiency in dissipating heat from its larger coolant capacity. The Koyo radiator's tubes, fins, end tanks, and brackets are brazed in a state-of-the-art Nocolok furnace, bonding all components to resist damage from vibration, oxidation, and road debris. Road-raced Civics require a much more stout cooling system, due to the extended periods of time spent under hard driving as opposed to the quick spurts of hard street driving or drag racing. For endurance drivers who require the best in cooling, we recommend upgrading the half-width unit to a properly engineered, full-sized radiator that offers more flow capacity and improved efficiency.
Nissan R35 GT-R
On the track, the R35 GT-R is infamous for overheating issues with its twin-clutch transmission. When driven under extreme conditions, high temperatures switch the trans into auto mode, automatically up-shifting to Sixth gear until it has cooled off. After numerous laps around Japan's Fuji Speedway, HKS engineers data-logged the factory R35 GT-R's transmission oil temperature as it triggered a "fail safe" mode at 140-145 degrees Celsius (284 to 293 degrees Fahrenheit). Elevated clutch temperatures also caused the vehicle to automatically switch from all-wheel drive to two-wheel drive, even when the transmission oil temperatures were recorded below 140 degree Celsius (284 degree Fahrenheit).
HKS' recently released DCT (Dual Clutch Transmission) Cooler Kit effectively cools the transmission and keeps oil temperatures low even during prolonged circuit use. Integrated with the factory water-cooled transmission cooler, the DCT Cooler Kit also assists in reducing the GT-R's overall engine coolant temperature.
HKS designed the DCT cooler core to fit within the car's front left fender, and sit enshrouded in a specially designed Fiber Reinforced Polymer (FRP) air duct which directs airflow into it. The transmission's stock heat exchanger and HKS thermostat are integrated into the DCT Cooler, along with a specially designed oil outlet attachment that allows the cooler to stabilize oil temperature in a shorter amount of time than the OE unit. A set of -10 AN oil lines replace smaller factory lines to reduce resistance and increase flow, ensuring proper oil supply to and from the transmission. During testing at Fuji Speedway, water temperature was reduced by an average of five degrees Celsius (41 degrees Fahrenheit), enabling the GT-R to make continuous laps around the circuit while maintaining a constant oil temperature of 127 degrees Celsius (260 degrees Fahrenheit).