vehicle cooling system part 1 

   I will introduce the function of the engine radiator in the vehicle and the cooling topology for a specific model, so that everyone can have a deeper understanding of the radiator technically, so that when customizing the production of the radiator, you can know which is the key.

   The following are the chapters introduced.

1. Basic information of the vehicle

2. Basic information of engine and electric motor

3. Cooling topology

4. Cooling system

5. Air conditioning system

6. Air intake system

7. Exhaust system

8. Thermal insulation to components

Vehicle nameHonda 2019 CRV Hybrid 2.0L
Vehicle sizeLength, width and height [mm]4585*1855*1679
Wheelbase [mm]2660
Body style5-door 5-seater SUV
Energy typeHybrid
Engine2.0L, horsepower 146PS, L4
Electric motorFront single motor
Power BatteryLi-Ion 1.411Kwh
Vehicle nameHonda 2019 CRV Hybrid 2.0L
Other configurationEngine start-stop technologyNO
Skylight typePanoramic skylight
Active closed air intake grilleWith upper active grille, without lower active grille
Battery preheatingNO
AC SystemAutomatic air conditioning/with rear seat air outlet/with temperature zone control
SunshadeSunshade with rear side window/sunshade without rear windshield
 Vehicle nameHonda 2019 CRV Hybrid 2.0L 
 Engine informationEngine InstallationHorizontal 
 Engine Capacity2.0L 
 Engine configuration in-line engine 
 Number of cylinders4 
 Compression Ratio13 
 Max Horsepower (PS)146 
 Max Power (KW)107 
 Max output (rpm)6200 
 Max. torque (Nm)175 
 Max. torque (rpm)4000 
 Cylinder block/cylinder head materialAluminum alloy 
Vehicle nameHonda 2019 CRV Hybrid 2.0L
Electric motorTotal motor power135KW
Total motor torque315Nm

Cooling system topology:

Engine cooling (red circuit): At the beginning of the engine start, if the engine water temperature is low, the thermostat will be closed, and the engine cooling circuit takes a small cycle, water pump B to engine block to cylinder header to heater to water pumpB , the engine’s heat makes the water warm up. When the water temperature is higher than a certain value (such as 90℃), the engine cooling takes a large cycle, RAD to Thermostat to water pumpA to engine block to cylinder head to RAD. We can see that the EGR cooler is also on the engine cooling circuit. At the same time, the circuit is equipped with an expansion tank. For the specific functions and functions of the expansion tank, please refer to this blog.

PCU cooling circuit (green circuit): Because hybrid models have electric motor, motor controller and IPS, an additional radiator is needed to cool them. You may ask, why is the auxiliary radiator not connected in series with the engine cooling circuit, but a radiator is required independently? The reason is that the inlet temperature of the coolant required for motor and motor controller is generally lower than 60°C, which is much lower than the temperature of the engine coolant, and the temperature of the engine water outlet is generally higher than 90°C, so the same radiator cannot be shared. Due to this reason, the auxiliary radiator is generally arranged in front of the engine radiator。Auxiliary radiator to expansion tank to water pumpC to PCU(including motor, motor controller and IPS) to  Auxiliary radiator.

Air-conditioning circuit (yellow circuit): The air-conditioning circuit is mainly used for air-conditioning and cooling of the passenger compartment. Note that the air-conditioning circuit takes the refrigerant R134a or R1234yf not Ethylene glycol coolant, and the Condensing temperature for condenser is generally 50-60°C, so the condenser also needs to be arranged in front of the engine radiator.

CDS to Expansion valve to Evaporator to compressor to CDS.

The figure above shows the gearbox cooling circuit and the power battery cooling circuit.

gearbox cooling circuit:Oil cooler to oil pump to E-CVT to oil cooler,oil cooler for gearbox.

Power battery cooling circuit:Cabin to blower to power battery to cabin,air cooling for battery. General power battery cooling has three cooling methods: air cooling, liquid cooling and direct refrigerant cooling.

The following table shows the size of various heat exchangers of CRV models for your reference.

Heat exchangerSize(mm)
Auxiliary radiator550*125*21
Engine radiator745*420*16
Oil cooler200*288*32.5
Engine cooling fanSingle fan


1. Electronic water pump A is used for engine cooling;

2. The heating system adopts electronic water pump B;

3. The EGR cooler is connected in series in the high temperature circuit;

4. The expansion tank does not participate in the circulation of the coolant;

5. E-CVT adopts oil cooling, PCU adopts water cooling, separate separately;

6. The power battery is air-cooled.

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