Vehicular climate control system

1. A vehicular climate control system comprising:

a coolant subsystem configured to circulate coolant between an engine, a thermal generator, and a cabin heat exchanger; and

a controller configured to, responsive to an air inlet temperature of the heat exchanger exceeding a threshold, retard engine spark timing to increase heat generation, wherein the threshold is defined by a quotient of (i) a difference between a discharge temperature target and the air inlet temperature and (ii) a thermal effectiveness parameter, and wherein the thermal effectiveness parameter is based on a difference between an air flow rate and a coolant flow rate.

2. The vehicular climate control system of claim 1 , wherein the controller is further configured to, responsive to a parameter proportional to the difference between the discharge temperature target and the air inlet temperature falling below the air inlet temperature, increase an idle rotational speed of the engine.

3. The vehicular climate control system of claim 1 , wherein the coolant flow rate is based on a configuration of the coolant subsystem including a thermostat position, a heater core isolation value position, a main pump speed, and a HVAC pump speed.

4. The vehicular climate control system of claim 1 , wherein the coolant flow rate is based on an output from a flowmeter.

5. The vehicular climate control system of claim 1 , wherein the thermal generator is an electric heater, and the controller is further configured to, responsive to a parameter proportional to the difference between the discharge temperature target and the air inlet temperature exceeding the air inlet temperature, reduce a current how to the electric heater.

6. The vehicular climate control system of claim 5 , wherein the electric heater is a resistive heater or a positive temperature coefficient (PTC) heater.

7. The vehicular climate control system of claim 1 , wherein the thermal generator is a thermal electric heat pump or a vapor compression heat pump configured to provide cabin heating or cooling, and the controller is further configured to, responsive to a parameter proportional to the difference between the discharge temperature target and the air inlet temperature exceeding the air inlet temperature, switch the thermal generator from a heating mode to a cooling mode.

8. A method of controlling a vehicular climate control system, comprising:

by a controller,

circulating coolant in a coolant subsystem to heat a heater core associated with a vehicular passenger compartment; and

responsive to output from an air inlet sensor arranged upstream the heater core exceeding a threshold, retarding engine spark timing to increase heat generation, wherein the threshold is defined by a quotient of (i) a difference between a discharge temperature target and an air inlet temperature and (ii) a thermal effectiveness parameter that is based on a difference between an air flow rate and a coolant flow rate.

9. The method of claim 8 further comprising, by the controller, responsive to a parameter proportional to the difference between the discharge temperature target and an air inlet temperature falling below the air inlet temperature, increasing an idle rotational speed of the engine.

10. The method of claim 8 further comprising, responsive to a parameter proportional to the difference between the discharge temperature target and the air inlet temperature exceeding the air inlet temperature, reducing a current flow to an electric heater.

11. The method of claim 10 , wherein the electric heater is a resistive heater or a positive temperature coefficient (PTC) heater.

12. The method of claim 8 further comprising, by the controller, responsive to a parameter proportional to the difference between the discharge temperature target and the air inlet temperature exceeding the air inlet temperature, transitioning a thermal generator from a heating mode to a cooling mode, wherein the thermal generator is a thermal electric heat pump or a vapor compression heat pump.

13. A climate control system comprising:

a coolant subsystem that circulates coolant between an engine and a heater core; and

a controller configured to, responsive to an air inlet temperature of the heater core exceeding, a threshold, increase an idle rotational speed of the engine, wherein the threshold is defined by a quotient of (i) a difference between a discharge temperature target and the air inlet temperature and (ii) a thermal effectiveness parameter that is based on an air flow rate and a coolant flow rate.

14. The climate control system of claim 13 , wherein the controller is further configured to, responsive to a parameter proportional to the difference between the discharge temperature target and the air inlet temperature falling below the air inlet temperature, increase an idle rotational speed of the engine.

15. The climate control system of claim 13 , wherein the coolant subsystem further includes an electric heater, and the controller is further configured to, responsive to a parameter proportional to the difference between the discharge temperature target and the air inlet temperature exceeding the air inlet temperature, reduce a current flow to the electric heater, wherein the electric heater is a resistive heater or a positive temperature coefficient (PTC) heater.

16. The climate control system of claim 13 , wherein the coolant subsystem further includes a thermal generator that is a thermal electric heat pump or a vapor compression heat pump configured to provide cabin heating or cooling, and the controller is further configured to, responsive to a parameter proportional to the difference between the discharge temperature target and the air inlet temperature exceeding the air inlet temperature, switch the thermal generator from a heating mode to a cooling mode.